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| <h1 id="cached-lookup-module">Cached Lookup Module</h1> |
| |
| <div class="note info">Please note that this is an experimental module and the development/testing still at early stage. Feel free to try it and give us your feedback.</div> |
| |
| |
| <h2 id="description">Description</h2> |
| |
| <p>This Apache Druid (incubating) module provides a per-lookup caching mechanism for JDBC data sources. |
| The main goal of this cache is to speed up the access to a high latency lookup sources and to provide a caching isolation for every lookup source. |
| Thus user can define various caching strategies or and implementation per lookup, even if the source is the same. |
| This module can be used side to side with other lookup module like the global cached lookup module.</p> |
| |
| <p>To use this extension please make sure to <a href="../../operations/including-extensions.html">include</a> <code>druid-lookups-cached-single</code> as an extension.</p> |
| |
| <h2 id="architecture">Architecture</h2> |
| |
| <p>Generally speaking this module can be divided into two main component, namely, the data fetcher layer and caching layer.</p> |
| |
| <h3 id="data-fetcher-layer">Data Fetcher layer</h3> |
| |
| <p>First part is the data fetcher layer API <code>DataFetcher</code>, that exposes a set of fetch methods to fetch data from the actual Lookup dimension source. |
| For instance <code>JdbcDataFetcher</code> provides an implementation of <code>DataFetcher</code> that can be used to fetch key/value from a RDBMS via JDBC driver. |
| If you need new type of data fetcher, all you need to do, is to implement the interface <code>DataFetcher</code> and load it via another druid module.</p> |
| |
| <h3 id="caching-layer">Caching layer</h3> |
| |
| <p>This extension comes with two different caching strategies. First strategy is a poll based and the second is a load based.</p> |
| |
| <h4 id="poll-lookup-cache">Poll lookup cache</h4> |
| |
| <p>The poll strategy cache strategy will fetch and swap all the pair of key/values periodically from the lookup source. |
| Hence, user should make sure that the cache can fit all the data. |
| The current implementation provides 2 type of poll cache, the first is onheap (uses immutable map), while the second uses MapBD based offheap map. |
| User can also implement a different lookup polling cache by implementing <code>PollingCacheFactory</code> and <code>PollingCache</code> interfaces. </p> |
| |
| <h4 id="loading-lookup">Loading lookup</h4> |
| |
| <p>Loading cache strategy will load the key/value pair upon request on the key it self, the general algorithm is load key if absent. |
| Once the key/value pair is loaded eviction will occur according to the cache eviction policy. |
| This module comes with two loading lookup implementation, the first is onheap backed by a Guava cache implementation, the second is MapDB offheap implementation. |
| Both implementations offer various eviction strategies. |
| Same for Loading cache, developer can implement a new type of loading cache by implementing <code>LookupLoadingCache</code> interface.</p> |
| |
| <h2 id="configuration-and-operation">Configuration and Operation:</h2> |
| |
| <h3 id="polling-lookup">Polling Lookup</h3> |
| |
| <p><strong>Note that the current implementation of <code>offHeapPolling</code> and <code>onHeapPolling</code> will create two caches one to lookup value based on key and the other to reverse lookup the key from value</strong></p> |
| |
| <table><thead> |
| <tr> |
| <th>Field</th> |
| <th>Type</th> |
| <th>Description</th> |
| <th>Required</th> |
| <th>default</th> |
| </tr> |
| </thead><tbody> |
| <tr> |
| <td>dataFetcher</td> |
| <td>Json object</td> |
| <td>Specifies the lookup data fetcher type to use in order to fetch data</td> |
| <td>yes</td> |
| <td>null</td> |
| </tr> |
| <tr> |
| <td>cacheFactory</td> |
| <td>Json Object</td> |
| <td>Cache factory implementation</td> |
| <td>no</td> |
| <td>onHeapPolling</td> |
| </tr> |
| <tr> |
| <td>pollPeriod</td> |
| <td>Period</td> |
| <td>polling period</td> |
| <td>no</td> |
| <td>null (poll once)</td> |
| </tr> |
| </tbody></table> |
| |
| <h5 id="example-of-polling-on-heap-lookup">Example of Polling On-heap Lookup</h5> |
| |
| <p>This example demonstrates a polling cache that will update its on-heap cache every 10 minutes</p> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span><span class="p">{</span> |
| <span class="nt">"type"</span><span class="p">:</span><span class="s2">"pollingLookup"</span><span class="p">,</span> |
| <span class="nt">"pollPeriod"</span><span class="p">:</span><span class="s2">"PT10M"</span><span class="p">,</span> |
| <span class="nt">"dataFetcher"</span><span class="p">:{</span> <span class="nt">"type"</span><span class="p">:</span><span class="s2">"jdbcDataFetcher"</span><span class="p">,</span> <span class="nt">"connectorConfig"</span><span class="p">:</span><span class="s2">"jdbc://mysql://localhost:3306/my_data_base"</span><span class="p">,</span> <span class="nt">"table"</span><span class="p">:</span><span class="s2">"lookup_table_name"</span><span class="p">,</span> <span class="nt">"keyColumn"</span><span class="p">:</span><span class="s2">"key_column_name"</span><span class="p">,</span> <span class="nt">"valueColumn"</span><span class="p">:</span> <span class="s2">"value_column_name"</span><span class="p">},</span> |
| <span class="nt">"cacheFactory"</span><span class="p">:{</span><span class="nt">"type"</span><span class="p">:</span><span class="s2">"onHeapPolling"</span><span class="p">}</span> |
| <span class="p">}</span> |
| </code></pre></div> |
| <h5 id="example-polling-off-heap-lookup">Example Polling Off-heap Lookup</h5> |
| |
| <p>This example demonstrates an off-heap lookup that will be cached once and never swapped <code>(pollPeriod == null)</code></p> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span><span class="p">{</span> |
| <span class="nt">"type"</span><span class="p">:</span><span class="s2">"pollingLookup"</span><span class="p">,</span> |
| <span class="nt">"dataFetcher"</span><span class="p">:{</span> <span class="nt">"type"</span><span class="p">:</span><span class="s2">"jdbcDataFetcher"</span><span class="p">,</span> <span class="nt">"connectorConfig"</span><span class="p">:</span><span class="s2">"jdbc://mysql://localhost:3306/my_data_base"</span><span class="p">,</span> <span class="nt">"table"</span><span class="p">:</span><span class="s2">"lookup_table_name"</span><span class="p">,</span> <span class="nt">"keyColumn"</span><span class="p">:</span><span class="s2">"key_column_name"</span><span class="p">,</span> <span class="nt">"valueColumn"</span><span class="p">:</span> <span class="s2">"value_column_name"</span><span class="p">},</span> |
| <span class="nt">"cacheFactory"</span><span class="p">:{</span><span class="nt">"type"</span><span class="p">:</span><span class="s2">"offHeapPolling"</span><span class="p">}</span> |
| <span class="p">}</span> |
| </code></pre></div> |
| <h3 id="loading-lookup">Loading lookup</h3> |
| |
| <table><thead> |
| <tr> |
| <th>Field</th> |
| <th>Type</th> |
| <th>Description</th> |
| <th>Required</th> |
| <th>default</th> |
| </tr> |
| </thead><tbody> |
| <tr> |
| <td>dataFetcher</td> |
| <td>Json object</td> |
| <td>Specifies the lookup data fetcher type to use in order to fetch data</td> |
| <td>yes</td> |
| <td>null</td> |
| </tr> |
| <tr> |
| <td>loadingCacheSpec</td> |
| <td>Json Object</td> |
| <td>Lookup cache spec implementation</td> |
| <td>yes</td> |
| <td>null</td> |
| </tr> |
| <tr> |
| <td>reverseLoadingCacheSpec</td> |
| <td>Json Object</td> |
| <td>Reverse lookup cache implementation</td> |
| <td>yes</td> |
| <td>null</td> |
| </tr> |
| </tbody></table> |
| |
| <h5 id="example-loading-on-heap-guava">Example Loading On-heap Guava</h5> |
| |
| <p>Guava cache configuration spec. </p> |
| |
| <table><thead> |
| <tr> |
| <th>Field</th> |
| <th>Type</th> |
| <th>Description</th> |
| <th>Required</th> |
| <th>default</th> |
| </tr> |
| </thead><tbody> |
| <tr> |
| <td>concurrencyLevel</td> |
| <td>int</td> |
| <td>Allowed concurrency among update operations</td> |
| <td>no</td> |
| <td>4</td> |
| </tr> |
| <tr> |
| <td>initialCapacity</td> |
| <td>int</td> |
| <td>Initial capacity size</td> |
| <td>no</td> |
| <td>null</td> |
| </tr> |
| <tr> |
| <td>maximumSize</td> |
| <td>long</td> |
| <td>Specifies the maximum number of entries the cache may contain.</td> |
| <td>no</td> |
| <td>null (infinite capacity)</td> |
| </tr> |
| <tr> |
| <td>expireAfterAccess</td> |
| <td>long</td> |
| <td>Specifies the eviction time after last read in milliseconds.</td> |
| <td>no</td> |
| <td>null (No read-time-based eviction when set to null)</td> |
| </tr> |
| <tr> |
| <td>expireAfterWrite</td> |
| <td>long</td> |
| <td>Specifies the eviction time after last write in milliseconds.</td> |
| <td>no</td> |
| <td>null (No write-time-based eviction when set to null)</td> |
| </tr> |
| </tbody></table> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span><span class="p">{</span> |
| <span class="nt">"type"</span><span class="p">:</span><span class="s2">"loadingLookup"</span><span class="p">,</span> |
| <span class="nt">"dataFetcher"</span><span class="p">:{</span> <span class="nt">"type"</span><span class="p">:</span><span class="s2">"jdbcDataFetcher"</span><span class="p">,</span> <span class="nt">"connectorConfig"</span><span class="p">:</span><span class="s2">"jdbc://mysql://localhost:3306/my_data_base"</span><span class="p">,</span> <span class="nt">"table"</span><span class="p">:</span><span class="s2">"lookup_table_name"</span><span class="p">,</span> <span class="nt">"keyColumn"</span><span class="p">:</span><span class="s2">"key_column_name"</span><span class="p">,</span> <span class="nt">"valueColumn"</span><span class="p">:</span> <span class="s2">"value_column_name"</span><span class="p">},</span> |
| <span class="nt">"loadingCacheSpec"</span><span class="p">:{</span><span class="nt">"type"</span><span class="p">:</span><span class="s2">"guava"</span><span class="p">},</span> |
| <span class="nt">"reverseLoadingCacheSpec"</span><span class="p">:{</span><span class="nt">"type"</span><span class="p">:</span><span class="s2">"guava"</span><span class="p">,</span> <span class="nt">"maximumSize"</span><span class="p">:</span><span class="mi">500000</span><span class="p">,</span> <span class="nt">"expireAfterAccess"</span><span class="p">:</span><span class="mi">100000</span><span class="p">,</span> <span class="nt">"expireAfterAccess"</span><span class="p">:</span><span class="mi">10000</span><span class="p">}</span> |
| <span class="p">}</span> |
| </code></pre></div> |
| <h5 id="example-loading-off-heap-mapdb">Example Loading Off-heap MapDB</h5> |
| |
| <p>Off heap cache is backed by <a href="http://www.mapdb.org/">MapDB</a> implementation. MapDB is using direct memory as memory pool, please take that into account when limiting the JVM direct memory setup. </p> |
| |
| <table><thead> |
| <tr> |
| <th>Field</th> |
| <th>Type</th> |
| <th>Description</th> |
| <th>Required</th> |
| <th>default</th> |
| </tr> |
| </thead><tbody> |
| <tr> |
| <td>maxStoreSize</td> |
| <td>double</td> |
| <td>maximal size of store in GB, if store is larger entries will start expiring</td> |
| <td>no</td> |
| <td>0</td> |
| </tr> |
| <tr> |
| <td>maxEntriesSize</td> |
| <td>long</td> |
| <td>Specifies the maximum number of entries the cache may contain.</td> |
| <td>no</td> |
| <td>0 (infinite capacity)</td> |
| </tr> |
| <tr> |
| <td>expireAfterAccess</td> |
| <td>long</td> |
| <td>Specifies the eviction time after last read in milliseconds.</td> |
| <td>no</td> |
| <td>0 (No read-time-based eviction when set to null)</td> |
| </tr> |
| <tr> |
| <td>expireAfterWrite</td> |
| <td>long</td> |
| <td>Specifies the eviction time after last write in milliseconds.</td> |
| <td>no</td> |
| <td>0 (No write-time-based eviction when set to null)</td> |
| </tr> |
| </tbody></table> |
| <div class="highlight"><pre><code class="language-json" data-lang="json"><span></span><span class="p">{</span> |
| <span class="nt">"type"</span><span class="p">:</span><span class="s2">"loadingLookup"</span><span class="p">,</span> |
| <span class="nt">"dataFetcher"</span><span class="p">:{</span> <span class="nt">"type"</span><span class="p">:</span><span class="s2">"jdbcDataFetcher"</span><span class="p">,</span> <span class="nt">"connectorConfig"</span><span class="p">:</span><span class="s2">"jdbc://mysql://localhost:3306/my_data_base"</span><span class="p">,</span> <span class="nt">"table"</span><span class="p">:</span><span class="s2">"lookup_table_name"</span><span class="p">,</span> <span class="nt">"keyColumn"</span><span class="p">:</span><span class="s2">"key_column_name"</span><span class="p">,</span> <span class="nt">"valueColumn"</span><span class="p">:</span> <span class="s2">"value_column_name"</span><span class="p">},</span> |
| <span class="nt">"loadingCacheSpec"</span><span class="p">:{</span><span class="nt">"type"</span><span class="p">:</span><span class="s2">"mapDb"</span><span class="p">,</span> <span class="nt">"maxEntriesSize"</span><span class="p">:</span><span class="mi">100000</span><span class="p">},</span> |
| <span class="nt">"reverseLoadingCacheSpec"</span><span class="p">:{</span><span class="nt">"type"</span><span class="p">:</span><span class="s2">"mapDb"</span><span class="p">,</span> <span class="nt">"maxStoreSize"</span><span class="p">:</span><span class="mi">5</span><span class="p">,</span> <span class="nt">"expireAfterAccess"</span><span class="p">:</span><span class="mi">100000</span><span class="p">,</span> <span class="nt">"expireAfterAccess"</span><span class="p">:</span><span class="mi">10000</span><span class="p">}</span> |
| <span class="p">}</span> |
| </code></pre></div> |
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| tries++; |
| if (tries > 300) clearInterval(timer); |
| var searchInput = $('input.gsc-input'); |
| if (searchInput.length) { |
| searchInput.attr('placeholder', 'Search'); |
| clearInterval(timer); |
| } |
| }, 100); |
| }); |
| </script> |
| </body> |
| </html> |