| If the <code>key</code> does not exist, a new key is created.</p><div class="tabs-container tabList__CuJ"><ul role="tablist" aria-orientation="horizontal" class="tabs"><li role="tab" tabindex="0" aria-selected="true" class="tabs__item tabItem_LNqP tabs__item--active">Java</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">Python</li></ul><div class="margin-top--md"><div role="tabpanel" class="tabItem_Ymn6"><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Increment the built-in distributed counter referred by key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key The name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param amount The amount to be incremented</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">void</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">incrCounter</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">long</span><span class="token plain"> amount</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>To asynchronously increment the counter, you can use <code>incrCounterAsync</code>.</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Increment the built-in distributed counter referred by key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * but dont wait for the completion of the increment operation</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key The name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param amount The amount to be incremented</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token class-name">CompletableFuture</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)"><</span><span class="token generics class-name">Void</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)">></span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">incrCounterAsync</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">long</span><span class="token plain"> amount</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">def</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">incr_counter</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">self</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> amount</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token triple-quoted-string string" style="color:rgb(255, 121, 198)">"""incr the counter of a given key in the managed state"""</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="retrieve-counter">Retrieve counter<a href="#retrieve-counter" class="hash-link" aria-label="Direct link to Retrieve counter" title="Direct link to Retrieve counter"></a></h3><p>You can use <code>getCounter</code> to retrieve the counter of a given <code>key</code> mutated by <code>incrCounter</code>.</p><div class="tabs-container tabList__CuJ"><ul role="tablist" aria-orientation="horizontal" class="tabs"><li role="tab" tabindex="0" aria-selected="true" class="tabs__item tabItem_LNqP tabs__item--active">Java</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">Python</li></ul><div class="margin-top--md"><div role="tabpanel" class="tabItem_Ymn6"><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Retrieve the counter value for the key.</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @return the amount of the counter value for this key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">long</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">getCounter</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>To asynchronously retrieve the counter mutated by <code>incrCounterAsync</code>, you can use <code>getCounterAsync</code>.</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Retrieve the counter value for the key, but don't wait</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * for the operation to be completed</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @return the amount of the counter value for this key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token class-name">CompletableFuture</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)"><</span><span class="token generics class-name">Long</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)">></span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">getCounterAsync</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">def</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">get_counter</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">self</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token triple-quoted-string string" style="color:rgb(255, 121, 198)">"""get the counter of a given key in the managed state"""</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="update-state">Update state<a href="#update-state" class="hash-link" aria-label="Direct link to Update state" title="Direct link to Update state"></a></h3><p>Besides the <code>counter</code> API, Pulsar also exposes a general key/value API for functions to store and update the state of a given <code>key</code>.</p><div class="tabs-container tabList__CuJ"><ul role="tablist" aria-orientation="horizontal" class="tabs"><li role="tab" tabindex="0" aria-selected="true" class="tabs__item tabItem_LNqP tabs__item--active">Java</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">Python</li></ul><div class="margin-top--md"><div role="tabpanel" class="tabItem_Ymn6"><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Update the state value for the key.</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param value state value of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">void</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">putState</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token class-name">ByteBuffer</span><span class="token plain"> value</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>To asynchronously update the state of a given <code>key</code>, you can use <code>putStateAsync</code>.</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Update the state value for the key, but don't wait for the operation to be completed</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param value state value of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token class-name">CompletableFuture</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)"><</span><span class="token generics class-name">Void</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)">></span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">putStateAsync</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token class-name">ByteBuffer</span><span class="token plain"> value</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">def</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">put_state</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">self</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> value</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token triple-quoted-string string" style="color:rgb(255, 121, 198)">"""update the value of a given key in the managed state"""</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="retrieve-state">Retrieve state<a href="#retrieve-state" class="hash-link" aria-label="Direct link to Retrieve state" title="Direct link to Retrieve state"></a></h3><p>You can use <code>getState</code> to retrieve the state of a given <code>key</code>.</p><div class="tabs-container tabList__CuJ"><ul role="tablist" aria-orientation="horizontal" class="tabs"><li role="tab" tabindex="0" aria-selected="true" class="tabs__item tabItem_LNqP tabs__item--active">Java</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">Python</li></ul><div class="margin-top--md"><div role="tabpanel" class="tabItem_Ymn6"><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Retrieve the state value for the key.</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @return the state value for the key.</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token class-name">ByteBuffer</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">getState</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>To asynchronously retrieve the state of a given <code>key</code>, you can use <code>getStateAsync</code>.</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Retrieve the state value for the key, but don't wait for the operation to be completed</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @return the state value for the key.</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token class-name">CompletableFuture</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)"><</span><span class="token generics class-name">ByteBuffer</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)">></span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">getStateAsync</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">def</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">get_state</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">self</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token triple-quoted-string string" style="color:rgb(255, 121, 198)">"""get the value of a given key in the managed state"""</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div></div></div><h3 class="anchor anchorWithStickyNavbar_LWe7" id="delete-state">Delete state<a href="#delete-state" class="hash-link" aria-label="Direct link to Delete state" title="Direct link to Delete state"></a></h3><div class="theme-admonition theme-admonition-note alert alert--secondary admonition_LlT9"><div class="admonitionHeading_tbUL"><span class="admonitionIcon_kALy"><svg viewBox="0 0 14 16"><path fill-rule="evenodd" d="M6.3 5.69a.942.942 0 0 1-.28-.7c0-.28.09-.52.28-.7.19-.18.42-.28.7-.28.28 0 .52.09.7.28.18.19.28.42.28.7 0 .28-.09.52-.28.7a1 1 0 0 1-.7.3c-.28 0-.52-.11-.7-.3zM8 7.99c-.02-.25-.11-.48-.31-.69-.2-.19-.42-.3-.69-.31H6c-.27.02-.48.13-.69.31-.2.2-.3.44-.31.69h1v3c.02.27.11.5.31.69.2.2.42.31.69.31h1c.27 0 .48-.11.69-.31.2-.19.3-.42.31-.69H8V7.98v.01zM7 2.3c-3.14 0-5.7 2.54-5.7 5.68 0 3.14 2.56 5.7 5.7 5.7s5.7-2.55 5.7-5.7c0-3.15-2.56-5.69-5.7-5.69v.01zM7 .98c3.86 0 7 3.14 7 7s-3.14 7-7 7-7-3.12-7-7 3.14-7 7-7z"></path></svg></span>note</div><div class="admonitionContent_S0QG"><p>Both counters and binary values share the same keyspace, so this API deletes either type.</p></div></div><div class="tabs-container tabList__CuJ"><ul role="tablist" aria-orientation="horizontal" class="tabs"><li role="tab" tabindex="0" aria-selected="true" class="tabs__item tabItem_LNqP tabs__item--active">Java</li></ul><div class="margin-top--md"><div role="tabpanel" class="tabItem_Ymn6"><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token comment" style="color:rgb(98, 114, 164)">/**</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * Delete the state value for the key.</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> *</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> * @param key name of the key</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token comment" style="color:rgb(98, 114, 164)"> */</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">void</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">deleteState</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> key</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></div></div></div><h2 class="anchor anchorWithStickyNavbar_LWe7" id="query-state-via-cli">Query state via CLI<a href="#query-state-via-cli" class="hash-link" aria-label="Direct link to Query state via CLI" title="Direct link to Query state via CLI"></a></h2><p>Besides using the <a href="#call-state-apis">State APIs</a> to store the state of functions in Pulsar's state storage and retrieve it back from the storage, you can use CLI commands to query the state of functions.</p><div class="language-bash codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-bash codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token plain">bin/pulsar-admin functions querystate </span><span class="token punctuation" style="color:rgb(248, 248, 242)">\</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> --tenant </span><span class="token operator"><</span><span class="token plain">tenant</span><span class="token operator">></span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">\</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> --namespace </span><span class="token operator"><</span><span class="token plain">namespace</span><span class="token operator">></span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">\</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> --name </span><span class="token operator"><</span><span class="token plain">function-name</span><span class="token operator">></span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">\</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> --state-storage-url </span><span class="token operator"><</span><span class="token plain">bookkeeper-service-url</span><span class="token operator">></span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">\</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> --key </span><span class="token operator"><</span><span class="token plain">state-key</span><span class="token operator">></span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">\</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">[</span><span class="token plain">---watch</span><span class="token punctuation" style="color:rgb(248, 248, 242)">]</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div><p>If <code>--watch</code> is specified, the CLI tool keeps running to get the latest value of the provided <code>state-key</code>.</p><h2 class="anchor anchorWithStickyNavbar_LWe7" id="example">Example<a href="#example" class="hash-link" aria-label="Direct link to Example" title="Direct link to Example"></a></h2><p>The example of <code>WordCountFunction</code> demonstrates how <code>state</code> is stored within Pulsar Functions.</p><div class="tabs-container tabList__CuJ"><ul role="tablist" aria-orientation="horizontal" class="tabs"><li role="tab" tabindex="0" aria-selected="true" class="tabs__item tabItem_LNqP tabs__item--active">Java</li><li role="tab" tabindex="-1" aria-selected="false" class="tabs__item tabItem_LNqP">Python</li></ul><div class="margin-top--md"><div role="tabpanel" class="tabItem_Ymn6"><p>The logic of <a href="https://github.com/apache/pulsar/tree/master//pulsar-functions/java-examples/src/main/java/org/apache/pulsar/functions/api/examples/WordCountFunction.java" target="_blank" rel="noopener noreferrer">WordCountFunction</a> is simple and straightforward:</p><ol><li><p>The function splits the received <code>String</code> into multiple words using regex <code>\\.</code>.</p></li><li><p>For each <code>word</code>, the function increments <code>counter</code> by 1 via <code>incrCounter(key, amount)</code>.</p><div class="language-java codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-java codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> </span><span class="token import namespace">org</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">apache</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">pulsar</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">functions</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">api</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import class-name">Context</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> </span><span class="token import namespace">org</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">apache</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">pulsar</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">functions</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">api</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import class-name">Function</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> </span><span class="token import namespace">java</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import namespace">util</span><span class="token import namespace punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token import class-name">Arrays</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">public</span><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">class</span><span class="token plain"> </span><span class="token class-name">WordCountFunction</span><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">implements</span><span class="token plain"> </span><span class="token class-name">Function</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)"><</span><span class="token generics class-name">String</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token generics"> </span><span class="token generics class-name">Void</span><span class="token generics punctuation" style="color:rgb(248, 248, 242)">></span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token annotation punctuation" style="color:rgb(248, 248, 242)">@Override</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">public</span><span class="token plain"> </span><span class="token class-name">Void</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">process</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token class-name">String</span><span class="token plain"> input</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token class-name">Context</span><span class="token plain"> context</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">throws</span><span class="token plain"> </span><span class="token class-name">Exception</span><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">{</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token class-name">Arrays</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">asList</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">input</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">split</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token string" style="color:rgb(255, 121, 198)">"\\."</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">forEach</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">word </span><span class="token operator">-></span><span class="token plain"> context</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token function" style="color:rgb(80, 250, 123)">incrCounter</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">word</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token number">1</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">return</span><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">null</span><span class="token punctuation" style="color:rgb(248, 248, 242)">;</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token punctuation" style="color:rgb(248, 248, 242)">}</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token punctuation" style="color:rgb(248, 248, 242)">}</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></li></ol></div><div role="tabpanel" class="tabItem_Ymn6" hidden=""><p>The logic of this <code>WordCount</code> function is simple and straightforward:</p><ol><li><p>The function first splits the received string into multiple words.</p></li><li><p>For each <code>word</code>, the function increments <code>counter</code> by 1 via <code>incr_counter(key, amount)</code>.</p><div class="language-python codeBlockContainer_Ckt0 theme-code-block" style="--prism-color:#F8F8F2;--prism-background-color:#282A36"><div class="codeBlockContent_biex"><pre tabindex="0" class="prism-code language-python codeBlock_bY9V thin-scrollbar"><code class="codeBlockLines_e6Vv"><span class="token-line" style="color:#F8F8F2"><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">from</span><span class="token plain"> pulsar </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">import</span><span class="token plain"> Function</span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain" style="display:inline-block"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"></span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">class</span><span class="token plain"> </span><span class="token class-name">WordCount</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">Function</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">def</span><span class="token plain"> </span><span class="token function" style="color:rgb(80, 250, 123)">process</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">self</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> item</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> context</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">for</span><span class="token plain"> word </span><span class="token keyword" style="color:rgb(189, 147, 249);font-style:italic">in</span><span class="token plain"> item</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">split</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><span class="token punctuation" style="color:rgb(248, 248, 242)">:</span><span class="token plain"></span><br></span><span class="token-line" style="color:#F8F8F2"><span class="token plain"> context</span><span class="token punctuation" style="color:rgb(248, 248, 242)">.</span><span class="token plain">incr_counter</span><span class="token punctuation" style="color:rgb(248, 248, 242)">(</span><span class="token plain">word</span><span class="token punctuation" style="color:rgb(248, 248, 242)">,</span><span class="token plain"> </span><span class="token number">1</span><span class="token punctuation" style="color:rgb(248, 248, 242)">)</span><br></span></code></pre><div class="buttonGroup__atx"><button type="button" aria-label="Copy code to clipboard" title="Copy" class="clean-btn"><span class="copyButtonIcons_eSgA" aria-hidden="true"><svg class="copyButtonIcon_y97N" viewBox="0 0 24 24"><path d="M19,21H8V7H19M19,5H8A2,2 0 0,0 6,7V21A2,2 0 0,0 8,23H19A2,2 0 0,0 21,21V7A2,2 0 0,0 19,5M16,1H4A2,2 0 0,0 2,3V17H4V3H16V1Z"></path></svg><svg class="copyButtonSuccessIcon_LjdS" viewBox="0 0 24 24"><path d="M21,7L9,19L3.5,13.5L4.91,12.09L9,16.17L19.59,5.59L21,7Z"></path></svg></span></button></div></div></div></li></ol></div></div></div></div><footer class="theme-doc-footer docusaurus-mt-lg"><div class="theme-doc-footer-edit-meta-row row"><div class="col"><a href="https://github.com/apache/pulsar-site/edit/main/versioned_docs/version-3.0.x/functions-develop-state.md" target="_blank" rel="noreferrer noopener" class="theme-edit-this-page"><svg fill="currentColor" height="20" width="20" viewBox="0 0 40 40" class="iconEdit_Z9Sw" aria-hidden="true"><g><path d="m34.5 11.7l-3 3.1-6.3-6.3 3.1-3q0.5-0.5 1.2-0.5t1.1 0.5l3.9 3.9q0.5 0.4 0.5 1.1t-0.5 1.2z m-29.5 17.1l18.4-18.5 6.3 6.3-18.4 18.4h-6.3v-6.2z"></path></g></svg>Edit this page</a></div><div class="col lastUpdated_vwxv"></div></div></footer></article><nav class="pagination-nav docusaurus-mt-lg" aria-label="Docs pages navigation"><a class="pagination-nav__link pagination-nav__link--prev" href="/docs/3.0.x/functions-develop-security/"><div class="pagination-nav__sublabel">Previous</div><div class="pagination-nav__label">Enable security on functions</div></a><a class="pagination-nav__link pagination-nav__link--next" href="/docs/3.0.x/functions-develop-admin-api/"><div class="pagination-nav__sublabel">Next</div><div class="pagination-nav__label">Call Pulsar admin APIs</div></a></nav></div></div><div class="col col--3"><div class="tableOfContents_jeP5 thin-scrollbar theme-doc-toc-desktop"><div class="border"><div style="color:var(--ifm-toc-link-color)">Was this helpful?</div><div style="border-width:1px;padding:3px;display:flex"><div style="justify-content:center;display:flex;border-radius:99999px;width:2.5rem;height:2.5rem;cursor:pointer;background:;color:"><svg style="width:initial;height:initial" width="12" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M10.086 1.594A1 1 0 0 1 11 1a4 4 0 0 1 4 4v3h4.655a3 3 0 0 1 2.994 3.45l-1.38 9A3.002 3.002 0 0 1 18.275 23H4a3 3 0 0 1-3-3v-7a3 3 0 0 1 3-3h2.35l3.736-8.406ZM8 11.212l3.608-8.117A2 2 0 0 1 13 5v4a1 1 0 0 0 1 1h5.671a1 1 0 0 1 1 1.15l-1.38 9a1 1 0 0 1-1 .85H8v-9.788ZM6 21v-9H4a1 1 0 0 0-1 1v7a1 1 0 0 0 1 1h2Z" fill="currentColor"></path></svg></div><div style="justify-content:center;display:flex;border-radius:99999px;width:2.5rem;height:2.5rem;cursor:pointer;background:;color:"><svg style="width:initial;height:initial" width="12" height="24" viewBox="0 0 24 24" fill="none" xmlns="http://www.w3.org/2000/svg"><path fill-rule="evenodd" clip-rule="evenodd" d="M20.563 3.316A1.31 1.31 0 0 0 19.687 3h-1.688v9h1.688a1.31 1.31 0 0 0 1.312-1.077V4.077a1.31 1.31 0 0 0-.436-.761ZM16 12.788l-3.608 8.117A1.999 1.999 0 0 1 11 19v-4a1 1 0 0 0-1-1H4.328a1.002 1.002 0 0 1-1-1.15l1.38-9a1 1 0 0 1 1-.85h10.291v9.788ZM19.661 1a3.31 3.31 0 0 1 3.329 2.866c.006.044.01.09.01.134v7c0 .045-.004.09-.01.134A3.31 3.31 0 0 1 19.661 14h-2.012l-3.736 8.406a1 1 0 0 1-.914.594 4 4 0 0 1-4-4v-3H4.344a3 3 0 0 1-2.994-3.45l1.38-9A3.002 3.002 0 0 1 5.724 1h13.937Z" fill="currentColor"></path></svg></div></div><div class="Actions_uugI"><a target="_blank" class="Action_iBHd" href="https://github.com/apache/pulsar/issues/new?assignees=&labels=doc-required&projects=&template=doc.yml&title=%5BDoc%5D+">💡 Suggest changes</a><a target="_blank" class="Action_iBHd" href="https://github.com/apache/pulsar/discussions/new?category=q-a">🛟 Get support</a></div></div><ul class="table-of-contents table-of-contents__left-border"><li><a href="#call-state-apis" class="table-of-contents__link toc-highlight">Call state APIs</a></li><li><a href="#increment-counter" class="table-of-contents__link toc-highlight">Increment counter</a><ul><li><a href="#retrieve-counter" class="table-of-contents__link toc-highlight">Retrieve counter</a></li><li><a href="#update-state" class="table-of-contents__link toc-highlight">Update state</a></li><li><a href="#retrieve-state" class="table-of-contents__link toc-highlight">Retrieve state</a></li><li><a href="#delete-state" class="table-of-contents__link toc-highlight">Delete state</a></li></ul></li><li><a href="#query-state-via-cli" class="table-of-contents__link toc-highlight">Query state via CLI</a></li><li><a href="#example" class="table-of-contents__link toc-highlight">Example</a></li></ul></div></div></div></div></main></div></div><footer class="footer"><div class="container container-fluid"><div class="row footer__links"><div class="col footer__col"><div class="footer__title"></div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://www.apache.org/" target="_blank" rel="noopener noreferrer" class="footer__link-item">Foundation<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://www.apache.org/events/current-event.html" target="_blank" rel="noopener noreferrer" class="footer__link-item">Events<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li></ul></div><div class="col footer__col"><div class="footer__title"></div><ul class="footer__items clean-list"><li class="footer__item"><a href="https://www.apache.org/licenses/" target="_blank" rel="noopener noreferrer" class="footer__link-item">License<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://www.apache.org/foundation/thanks" target="_blank" rel="noopener noreferrer" class="footer__link-item">Thanks<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a href="https://www.apache.org/foundation/sponsorship" target="_blank" rel="noopener noreferrer" class="footer__link-item">Sponsorship<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li></ul></div><div class="col footer__col"><div class="footer__title"></div><ul class="footer__items clean-list"><li class="footer__item"><a class="footer__link-item" href="/security/">Security</a></li><li class="footer__item"><a href="https://www.apache.org/foundation/policies/privacy.html" target="_blank" rel="noopener noreferrer" class="footer__link-item">Privacy<svg width="13.5" height="13.5" aria-hidden="true" viewBox="0 0 24 24" class="iconExternalLink_nPIU"><path fill="currentColor" d="M21 13v10h-21v-19h12v2h-10v15h17v-8h2zm3-12h-10.988l4.035 4-6.977 7.07 2.828 2.828 6.977-7.07 4.125 4.172v-11z"></path></svg></a></li><li class="footer__item"><a class="footer__link-item" href="/contact/">Contact</a></li></ul></div><div class="col footer__col"><div class="footer__title"></div><ul class="footer__items clean-list"><li class="footer__item"> |