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| <div class="section" id="application-reset-tool"> |
| <span id="streams-developer-guide-app-reset"></span><h1>Application Reset Tool<a class="headerlink" href="#application-reset-tool" title="Permalink to this headline"></a></h1> |
| <p>You can reset an application and force it to reprocess its data from scratch by using the application reset tool. |
| This can be useful for development and testing, or when fixing bugs.</p> |
| <p>The application reset tool handles the Kafka Streams <a class="reference internal" href="manage-topics.html#streams-developer-guide-topics-user"><span class="std std-ref">user topics</span></a> (input, |
| output, and intermediate topics) and <a class="reference internal" href="manage-topics.html#streams-developer-guide-topics-internal"><span class="std std-ref">internal topics</span></a> differently |
| when resetting the application.</p> |
| <p>Here’s what the application reset tool does for each topic type:</p> |
| <ul class="simple"> |
| <li>Input topics: Reset offsets to specified position (by default to the beginning of the topic).</li> |
| <li>Intermediate topics: Skip to the end of the topic, i.e., set the application’s committed consumer offsets for all partitions to each partition’s <code class="docutils literal"><span class="pre">logSize</span></code> (for consumer group <code class="docutils literal"><span class="pre">application.id</span></code>).</li> |
| <li>Internal topics: Delete the internal topic (this automatically deletes any committed offsets).</li> |
| </ul> |
| <p>The application reset tool does not:</p> |
| <ul class="simple"> |
| <li>Reset output topics of an application. If any output (or intermediate) topics are consumed by downstream |
| applications, it is your responsibility to adjust those downstream applications as appropriate when you reset the |
| upstream application.</li> |
| <li>Reset the local environment of your application instances. It is your responsibility to delete the local |
| state on any machine on which an application instance was run. See the instructions in section |
| <a class="reference internal" href="#streams-developer-guide-reset-local-environment"><span class="std std-ref">Step 2: Reset the local environments of your application instances</span></a> on how to do this.</li> |
| </ul> |
| <dl class="docutils"> |
| <dt>Prerequisites</dt> |
| <dd><ul class="first last"> |
| <li><p class="first">All instances of your application must be stopped. Otherwise, the application may enter an invalid state, crash, or produce incorrect results. You can verify whether the consumer group with ID <code class="docutils literal"><span class="pre">application.id</span></code> is still active by using <code class="docutils literal"><span class="pre">bin/kafka-consumer-groups</span></code>. |
| When long session timeout has been configured, active members could take longer to get expired on the broker thus blocking the reset job to complete. Use the <code class="docutils literal"><span class="pre">--force</span></code> option could remove those left-over members immediately. Make sure to shut down all stream applications when this option is specified to avoid unexpected rebalances.</p> |
| </li> |
| <li><p class="first">Use this tool with care and double-check its parameters: If you provide wrong parameter values (e.g., typos in <code class="docutils literal"><span class="pre">application.id</span></code>) or specify parameters inconsistently (e.g., specify the wrong input topics for the application), this tool might invalidate the application’s state or even impact other applications, consumer groups, or your Kafka topics.</p> |
| </li> |
| <li><p class="first">You should manually delete and re-create any intermediate topics before running the application reset tool. This will free up disk space in Kafka brokers.</p> |
| </li> |
| <li><p class="first">You should delete and recreate intermediate topics before running the application reset tool, unless the following applies:</p> |
| <blockquote> |
| <div><ul class="simple"> |
| <li>You have external downstream consumers for the application’s intermediate topics.</li> |
| <li>You are in a development environment where manually deleting and re-creating intermediate topics is unnecessary.</li> |
| </ul> |
| </div></blockquote> |
| </li> |
| </ul> |
| </dd> |
| </dl> |
| <div class="section" id="step-1-run-the-application-reset-tool"> |
| <h2>Step 1: Run the application reset tool<a class="headerlink" href="#step-1-run-the-application-reset-tool" title="Permalink to this headline"></a></h2> |
| <p>Invoke the application reset tool from the command line</p> |
| <div class="highlight-bash"><div class="highlight"><pre><span></span><code><path-to-kafka>/bin/kafka-streams-application-reset</code></pre></div> |
| </div> |
| <p>The tool accepts the following parameters:</p> |
| <div class="highlight-bash"><div class="highlight"><pre><span>Option</span><code> <span class="o">(</span>* <span class="o">=</span> required<span class="o">)</span> Description |
| --------------------- ----------- |
| * --application-id <String: id> The Kafka Streams application ID |
| <span class="o">(</span>application.id<span class="o">)</span>. |
| --bootstrap-servers <String: urls> Comma-separated list of broker urls with |
| format: HOST1:PORT1,HOST2:PORT2 |
| <span class="o">(</span>default: localhost:9092<span class="o">)</span> |
| --by-duration <String: urls> Reset offsets to offset by duration from |
| current timestamp. Format: '<span>PnDTnHnMnS</span>' |
| --config-file <String: file name> Property file containing configs to be |
| passed to admin clients and embedded |
| consumer. |
| --dry-run Display the actions that would be |
| performed without executing the reset |
| commands. |
| --from-file <String: urls> Reset offsets to values defined in CSV |
| file. |
| --input-topics <String: list> Comma-separated list of user input |
| topics. For these topics, the tool will |
| reset the offset to the earliest |
| available offset. |
| --intermediate-topics <String: list> Comma-separated list of intermediate user |
| topics <span class="o">(</span>topics used in the through<span class="o">()</span> |
| method<span class="o">)</span>. For these topics, the tool |
| will skip to the end. |
| --shift-by <Long: number-of-offsets> Reset offsets shifting current offset by |
| 'n', where 'n' can be positive or |
| negative |
| --to-datetime <String> Reset offsets to offset from datetime. |
| Format: 'YYYY-MM-DDTHH:mm:SS.sss' |
| --to-earliest Reset offsets to earliest offset. |
| --to-latest Reset offsets to latest offset. |
| --to-offset <Long> Reset offsets to a specific offset. |
| --zookeeper Zookeeper option is deprecated by |
| bootstrap.servers, as the reset tool |
| would no longer access Zookeeper |
| directly. |
| --force Force removing members of the consumer group |
| (intended to remove left-over members if |
| long session timeout was configured).</code></pre></div> |
| </div> |
| <p>Consider the following as reset-offset scenarios for <code>input-topics</code>:</p> |
| <ul> |
| <li> by-duration</li> |
| <li> from-file</li> |
| <li> shift-by</li> |
| <li> to-datetime</li> |
| <li> to-earliest</li> |
| <li> to-latest</li> |
| <li> to-offset</li> |
| </ul> |
| <p>Only one of these scenarios can be defined. If not, <code>to-earliest</code> will be executed by default</p> |
| <p>All the other parameters can be combined as needed. For example, if you want to restart an application from an |
| empty internal state, but not reprocess previous data, simply omit the parameters <code class="docutils literal"><span class="pre">--input-topics</span></code> and |
| <code class="docutils literal"><span class="pre">--intermediate-topics</span></code>.</p> |
| </div> |
| <div class="section" id="step-2-reset-the-local-environments-of-your-application-instances"> |
| <span id="streams-developer-guide-reset-local-environment"></span><h2>Step 2: Reset the local environments of your application instances<a class="headerlink" href="#step-2-reset-the-local-environments-of-your-application-instances" title="Permalink to this headline"></a></h2> |
| <p>For a complete application reset, you must delete the application’s local state directory on any machines where the |
| application instance was run. You must do this before restarting an application instance on the same machine. You can |
| use either of these methods:</p> |
| <ul class="simple"> |
| <li>The API method <code class="docutils literal"><span class="pre">KafkaStreams#cleanUp()</span></code> in your application code.</li> |
| <li>Manually delete the corresponding local state directory (default location: <code class="docutils literal"><span class="pre">/tmp/kafka-streams/<application.id></span></code>). For more information, see <a href="/{{version}}/javadoc/org/apache/kafka/streams/StreamsConfig.html#STATE_DIR_CONFIG">Streams</a> javadocs.</li> |
| </ul> |
| </div> |
| </div> |
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