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href=/documentation/io/built-in/sparkreceiver/>Spark Receiver I/O connector</a></li><li><a href=/documentation/io/built-in/singlestore/>SingleStoreDB I/O connector</a></li><li><a href=/documentation/io/built-in/webapis/>Web APIs I/O connector</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Developing new I/O connectors</span><ul class=section-nav-list><li><a href=/documentation/io/developing-io-overview/>Overview: Developing connectors</a></li><li><a href=/documentation/io/developing-io-java/>Developing connectors (Java)</a></li><li><a href=/documentation/io/developing-io-python/>Developing connectors (Python)</a></li><li><a href=/documentation/io/io-standards/>I/O Standards</a></li></ul></li><li><a href=/documentation/io/testing/>Testing I/O transforms</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Schemas</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#what-is-a-schema>What is a schema</a></li><li><a href=/documentation/programming-guide/#schemas-for-pl-types>Schemas for programming language types</a></li><li><a href=/documentation/programming-guide/#schema-definition>Schema definition</a></li><li><a href=/documentation/programming-guide/#logical-types>Logical types</a></li><li><a href=/documentation/programming-guide/#creating-schemas>Creating schemas</a></li><li><a href=/documentation/programming-guide/#using-schemas>Using schemas</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Data encoding and type safety</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#data-encoding-and-type-safety>Data encoding basics</a></li><li><a href=/documentation/programming-guide/#specifying-coders>Specifying coders</a></li><li><a href=/documentation/programming-guide/#default-coders-and-the-coderregistry>Default coders and the CoderRegistry</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Windowing</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#windowing>Windowing basics</a></li><li><a href=/documentation/programming-guide/#provided-windowing-functions>Provided windowing functions</a></li><li><a href=/documentation/programming-guide/#setting-your-pcollections-windowing-function>Setting your PCollection’s windowing function</a></li><li><a href=/documentation/programming-guide/#watermarks-and-late-data>Watermarks and late data</a></li><li><a href=/documentation/programming-guide/#adding-timestamps-to-a-pcollections-elements>Adding timestamps to a PCollection’s elements</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Triggers</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#triggers>Trigger basics</a></li><li><a href=/documentation/programming-guide/#event-time-triggers>Event time triggers and the default trigger</a></li><li><a href=/documentation/programming-guide/#processing-time-triggers>Processing time triggers</a></li><li><a href=/documentation/programming-guide/#data-driven-triggers>Data-driven triggers</a></li><li><a href=/documentation/programming-guide/#setting-a-trigger>Setting a trigger</a></li><li><a href=/documentation/programming-guide/#composite-triggers>Composite triggers</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Metrics</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#metrics>Metrics basics</a></li><li><a href=/documentation/programming-guide/#types-of-metrics>Types of metrics</a></li><li><a href=/documentation/programming-guide/#querying-metrics>Querying metrics</a></li><li><a href=/documentation/programming-guide/#using-metrics>Using metrics in pipeline</a></li><li><a href=/documentation/programming-guide/#export-metrics>Export metrics</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>State and Timers</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#types-of-state>Types of state</a></li><li><a href=/documentation/programming-guide/#deferred-state-reads>Deferred state reads</a></li><li><a href=/documentation/programming-guide/#timers>Timers</a></li><li><a href=/documentation/programming-guide/#garbage-collecting-state>Garbage collecting state</a></li><li><a href=/documentation/programming-guide/#state-timers-examples>State and timers examples</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Splittable DoFns</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#sdf-basics>Basics</a></li><li><a href=/documentation/programming-guide/#sizing-and-progress>Sizing and progress</a></li><li><a href=/documentation/programming-guide/#user-initiated-checkpoint>User-initiated checkpoint</a></li><li><a href=/documentation/programming-guide/#runner-initiated-split>Runner initiated split</a></li><li><a href=/documentation/programming-guide/#watermark-estimation>Watermark estimation</a></li><li><a href=/documentation/programming-guide/#truncating-during-drain>Truncating during drain</a></li><li><a href=/documentation/programming-guide/#bundle-finalization>Bundle finalization</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Multi-language Pipelines</span><ul class=section-nav-list><li><a href=/documentation/programming-guide/#create-x-lang-transforms>Creating cross-language transforms</a></li><li><a href=/documentation/programming-guide/#use-x-lang-transforms>Using cross-language transforms</a></li><li><a href=/documentation/programming-guide/#x-lang-transform-runner-support>Runner Support</a></li></ul></li><li><a href=/documentation/programming-guide/#batched-dofns>Batched DoFns</a></li><li><a href=/documentation/programming-guide/#transform-service>Transform service</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Pipeline development lifecycle</span><ul class=section-nav-list><li><a href=/documentation/pipelines/design-your-pipeline/>Design Your Pipeline</a></li><li><a href=/documentation/pipelines/create-your-pipeline/>Create Your Pipeline</a></li><li><a href=/documentation/pipelines/test-your-pipeline/>Test Your Pipeline</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Common pipeline patterns</span><ul class=section-nav-list><li><a href=/documentation/patterns/overview/>Overview</a></li><li><a href=/documentation/patterns/file-processing/>File processing</a></li><li><a href=/documentation/patterns/side-inputs/>Side inputs</a></li><li><a href=/documentation/patterns/pipeline-options/>Pipeline options</a></li><li><a href=/documentation/patterns/custom-io/>Custom I/O</a></li><li><a href=/documentation/patterns/custom-windows/>Custom windows</a></li><li><a href=/documentation/patterns/bigqueryio/>BigQueryIO</a></li><li><a href=/documentation/patterns/ai-platform/>AI Platform</a></li><li><a href=/documentation/patterns/schema/>Schema</a></li><li><a href=/documentation/patterns/bqml/>BigQuery ML</a></li><li><a href=/documentation/patterns/grouping-elements-for-efficient-external-service-calls/>Grouping elements for efficient external service calls</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>AI/ML pipelines</span><ul class=section-nav-list><li><a href=/documentation/ml/overview/>Get started with AI/ML</a></li><li><a href=/documentation/ml/about-ml/>About Beam ML</a></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Prediction and inference</span><ul class=section-nav-list><li><a href=/documentation/ml/inference-overview/>Overview</a></li><li><a href=/documentation/ml/multi-model-pipelines/>Build a pipeline with multiple models</a></li><li><a href=/documentation/ml/tensorrt-runinference>Build a custom model handler with TensorRT</a></li><li><a href=/documentation/ml/large-language-modeling>Use LLM inference</a></li><li><a href=/documentation/ml/multi-language-inference/>Build a multi-language inference pipeline</a></li><li><a href=/documentation/ml/side-input-updates/>Update your model in production</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Data processing</span><ul class=section-nav-list><li><a href=/documentation/ml/preprocess-data/>Preprocess data</a></li><li><a href=/documentation/ml/data-processing/>Explore your data</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Workflow orchestration</span><ul class=section-nav-list><li><a href=/documentation/ml/orchestration/>Use ML-OPS workflow orchestrators</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Model training</span><ul class=section-nav-list><li><a href=/documentation/ml/per-entity-training>Per-entity training</a></li><li><a href=/documentation/ml/online-clustering/>Online clustering</a></li><li><a href=/documentation/ml/model-evaluation/>ML model evaluation</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Use cases</span><ul class=section-nav-list><li><a href=/documentation/ml/anomaly-detection/>Build an anomaly detection pipeline</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Reference</span><ul class=section-nav-list><li><a href=/documentation/ml/runinference-metrics/>RunInference metrics</a></li><li><a href=/documentation/ml/model-evaluation/>Model validation</a></li></ul></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Runtime systems</span><ul class=section-nav-list><li><a href=/documentation/runtime/environments/>Container environments</a></li><li><a href=/documentation/runtime/resource-hints/>Resource hints</a></li><li><a href=/documentation/runtime/sdk-harness-config/>SDK Harness Configuration</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Transform catalog</span><ul class=section-nav-list><li class=section-nav-item--collapsible><span class=section-nav-list-title>Python</span><ul class=section-nav-list><li><a href=/documentation/transforms/python/overview/>Overview</a></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Element-wise</span><ul class=section-nav-list><li class=section-nav-item--collapsible><span class=section-nav-list-title>Enrichment</span><ul class=section-nav-list><li><a href=/documentation/transforms/python/elementwise/enrichment/>Overview</a></li><li><a href=/documentation/transforms/python/elementwise/enrichment-bigtable/>Bigtable example</a></li><li><a href=/documentation/transforms/python/elementwise/enrichment-vertexai/>Vertex AI Feature Store examples</a></li></ul></li><li><a href=/documentation/transforms/python/elementwise/filter/>Filter</a></li><li><a href=/documentation/transforms/python/elementwise/flatmap/>FlatMap</a></li><li><a href=/documentation/transforms/python/elementwise/keys/>Keys</a></li><li><a href=/documentation/transforms/python/elementwise/kvswap/>KvSwap</a></li><li><a href=/documentation/transforms/python/elementwise/map/>Map</a></li><li><a href=/documentation/transforms/python/elementwise/mltransform/>MLTransform</a></li><li><a href=/documentation/transforms/python/elementwise/pardo/>ParDo</a></li><li><a href=/documentation/transforms/python/elementwise/partition/>Partition</a></li><li><a href=/documentation/transforms/python/elementwise/regex/>Regex</a></li><li><a href=/documentation/transforms/python/elementwise/reify/>Reify</a></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>RunInference</span><ul class=section-nav-list><li><a href=/documentation/transforms/python/elementwise/runinference/>Overview</a></li><li><a href=/documentation/transforms/python/elementwise/runinference-pytorch/>PyTorch examples</a></li><li><a href=/documentation/transforms/python/elementwise/runinference-sklearn/>Sklearn examples</a></li></ul></li><li><a href=/documentation/transforms/python/elementwise/tostring/>ToString</a></li><li><a href=/documentation/transforms/python/elementwise/values/>Values</a></li><li><a href=/documentation/transforms/python/elementwise/withtimestamps/>WithTimestamps</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Aggregation</span><ul class=section-nav-list><li><a href=/documentation/transforms/python/aggregation/approximatequantiles/>ApproximateQuantiles</a></li><li><a href=/documentation/transforms/python/aggregation/approximateunique/>ApproximateUnique</a></li><li><a href=/documentation/transforms/python/aggregation/cogroupbykey/>CoGroupByKey</a></li><li><a href=/documentation/transforms/python/aggregation/combineglobally/>CombineGlobally</a></li><li><a href=/documentation/transforms/python/aggregation/combineperkey/>CombinePerKey</a></li><li><a href=/documentation/transforms/python/aggregation/combinevalues/>CombineValues</a></li><li><a href=/documentation/transforms/python/aggregation/count/>Count</a></li><li><a href=/documentation/transforms/python/aggregation/distinct/>Distinct</a></li><li><a href=/documentation/transforms/python/aggregation/groupby/>GroupBy</a></li><li><a href=/documentation/transforms/python/aggregation/groupbykey/>GroupByKey</a></li><li><a href=/documentation/transforms/python/aggregation/groupintobatches/>GroupIntoBatches</a></li><li><a href=/documentation/transforms/python/aggregation/latest/>Latest</a></li><li><a href=/documentation/transforms/python/aggregation/max/>Max</a></li><li><a href=/documentation/transforms/python/aggregation/mean/>Mean</a></li><li><a href=/documentation/transforms/python/aggregation/min/>Min</a></li><li><a href=/documentation/transforms/python/aggregation/sample/>Sample</a></li><li><a href=/documentation/transforms/python/aggregation/sum/>Sum</a></li><li><a href=/documentation/transforms/python/aggregation/top/>Top</a></li><li><a href=/documentation/transforms/python/aggregation/tolist/>ToList</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Other</span><ul class=section-nav-list><li><a href=/documentation/transforms/python/other/create/>Create</a></li><li><a href=/documentation/transforms/python/other/flatten/>Flatten</a></li><li><a href=/documentation/transforms/python/other/reshuffle/>Reshuffle</a></li><li><a href=/documentation/transforms/python/other/windowinto/>WindowInto</a></li></ul></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Java</span><ul class=section-nav-list><li><a href=/documentation/transforms/java/overview/>Overview</a></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Element-wise</span><ul class=section-nav-list><li><a href=/documentation/transforms/java/elementwise/filter/>Filter</a></li><li><a href=/documentation/transforms/java/elementwise/flatmapelements/>FlatMapElements</a></li><li><a href=/documentation/transforms/java/elementwise/keys/>Keys</a></li><li><a href=/documentation/transforms/java/elementwise/kvswap/>KvSwap</a></li><li><a href=/documentation/transforms/java/elementwise/mapelements/>MapElements</a></li><li><a href=/documentation/transforms/java/elementwise/pardo/>ParDo</a></li><li><a href=/documentation/transforms/java/elementwise/partition/>Partition</a></li><li><a href=/documentation/transforms/java/elementwise/regex/>Regex</a></li><li><a href=/documentation/transforms/java/elementwise/reify/>Reify</a></li><li><a href=/documentation/transforms/java/elementwise/tostring/>ToString</a></li><li><a href=/documentation/transforms/java/elementwise/values/>Values</a></li><li><a href=/documentation/transforms/java/elementwise/withkeys/>WithKeys</a></li><li><a href=/documentation/transforms/java/elementwise/withtimestamps/>WithTimestamps</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Aggregation</span><ul class=section-nav-list><li><a href=/documentation/transforms/java/aggregation/approximatequantiles/>ApproximateQuantiles</a></li><li><a href=/documentation/transforms/java/aggregation/approximateunique/>ApproximateUnique</a></li><li><a href=/documentation/transforms/java/aggregation/cogroupbykey/>CoGroupByKey</a></li><li><a href=/documentation/transforms/java/aggregation/combine/>Combine</a></li><li><a href=/documentation/transforms/java/aggregation/combinewithcontext/>CombineWithContext</a></li><li><a href=/documentation/transforms/java/aggregation/count/>Count</a></li><li><a href=/documentation/transforms/java/aggregation/distinct/>Distinct</a></li><li><a href=/documentation/transforms/java/aggregation/groupbykey/>GroupByKey</a></li><li><a href=/documentation/transforms/java/aggregation/groupintobatches/>GroupIntoBatches</a></li><li><a href=/documentation/transforms/java/aggregation/hllcount/>HllCount</a></li><li><a href=/documentation/transforms/java/aggregation/latest/>Latest</a></li><li><a href=/documentation/transforms/java/aggregation/max/>Max</a></li><li><a href=/documentation/transforms/java/aggregation/mean/>Mean</a></li><li><a href=/documentation/transforms/java/aggregation/min/>Min</a></li><li><a href=/documentation/transforms/java/aggregation/sample/>Sample</a></li><li><a href=/documentation/transforms/java/aggregation/sum/>Sum</a></li><li><a href=/documentation/transforms/java/aggregation/top/>Top</a></li></ul></li><li class=section-nav-item--collapsible><span class=section-nav-list-title>Other</span><ul class=section-nav-list><li><a href=/documentation/transforms/java/other/create/>Create</a></li><li><a href=/documentation/transforms/java/other/flatten/>Flatten</a></li><li><a href=/documentation/transforms/java/other/passert/>PAssert</a></li><li><a href=/documentation/transforms/java/other/view/>View</a></li><li><a href=/documentation/transforms/java/other/window/>Window</a></li></ul></li></ul></li></ul></li><li><a href=/documentation/glossary/>Glossary</a></li><li><a href=https://cwiki.apache.org/confluence/display/BEAM/Apache+Beam>Beam Wiki <img src=/images/external-link-icon.png width=14 height=14 alt="External link."></a></li></ul></nav></div><nav class="page-nav clearfix" data-offset-top=90 data-offset-bottom=500><nav id=TableOfContents><ul><li><a href=#using-data-to-dynamically-set-session-window-gaps>Using data to dynamically set session window gaps</a><ul><li><a href=#creating-data-driven-gaps>Creating data-driven gaps</a></li><li><a href=#windowing-messages-into-sessions>Windowing messages into sessions</a></li><li><a href=#example-data-and-windows>Example data and windows</a><ul><li><a href=#standard-sessions>Standard sessions</a></li><li><a href=#dynamic-sessions>Dynamic sessions</a></li></ul></li></ul></li></ul></nav></nav><div class="body__contained body__section-nav arrow-list arrow-list--no-mt"><h1 id=custom-window-patterns>Custom window patterns</h1><p>The samples on this page demonstrate common custom window patterns. You can create custom windows with <a href=/documentation/programming-guide/#provided-windowing-functions><code>WindowFn</code> functions</a>. For more information, see the <a href=/documentation/programming-guide/#windowing>programming guide section on windowing</a>.</p><p><strong>Note</strong>: Custom merging windows isn’t supported in Python (with fnapi).</p><h2 id=using-data-to-dynamically-set-session-window-gaps>Using data to dynamically set session window gaps</h2><p>You can modify the <a href=https://beam.apache.org/releases/javadoc/current/index.html?org/apache/beam/sdk/transforms/windowing/SlidingWindows.html><code>assignWindows</code></a> function to use data-driven gaps, then window incoming data into sessions.</p><p>Access the <code>assignWindows</code> function through <code>WindowFn.AssignContext.element()</code>. The original, fixed-duration <code>assignWindows</code> function is:</p><div class='language-java snippet'><div class="notebook-skip code-snippet"><a class=copy type=button data-bs-toggle=tooltip data-bs-placement=bottom title="Copy to clipboard"><img src=/images/copy-icon.svg></a><div class=highlight><pre tabindex=0 class=chroma><code class=language-java data-lang=java><span class=line><span class=cl> <span class=kd>public</span> <span class=n>Collection</span><span class=o><</span><span class=n>IntervalWindow</span><span class=o>></span> <span class=nf>assignWindows</span><span class=o>(</span><span class=n>WindowFn</span><span class=o>.</span><span class=na>AssignContext</span> <span class=n>c</span><span class=o>)</span> <span class=o>{</span> |
| </span></span><span class=line><span class=cl> |
| </span></span><span class=line><span class=cl> <span class=c1>// Assign each element into a window from its timestamp until gapDuration in the |
| </span></span></span><span class=line><span class=cl><span class=c1></span> <span class=c1>// future. Overlapping windows (representing elements within gapDuration of |
| </span></span></span><span class=line><span class=cl><span class=c1></span> <span class=c1>// each other) will be merged. |
| </span></span></span><span class=line><span class=cl><span class=c1></span> <span class=k>return</span> <span class=n>Arrays</span><span class=o>.</span><span class=na>asList</span><span class=o>(</span><span class=k>new</span> <span class=n>IntervalWindow</span><span class=o>(</span><span class=n>c</span><span class=o>.</span><span class=na>timestamp</span><span class=o>(),</span> <span class=n>gapDuration</span><span class=o>));</span> |
| </span></span><span class=line><span class=cl> <span class=o>}</span></span></span></code></pre></div></div></div><h3 id=creating-data-driven-gaps>Creating data-driven gaps</h3><p>To create data-driven gaps, add the following snippets to the <code>assignWindows</code> function:</p><ul><li>A default value for when the custom gap is not present in the data</li><li>A way to set the attribute from the main pipeline as a method of the custom windows</li></ul><p>For example, the following function assigns each element to a window between the timestamp and <code>gapDuration</code>:</p><div class='language-java snippet'><div class="notebook-skip code-snippet"><a class=copy type=button data-bs-toggle=tooltip data-bs-placement=bottom title="Copy to clipboard"><img src=/images/copy-icon.svg></a><div class=highlight><pre tabindex=0 class=chroma><code class=language-java data-lang=java><span class=line><span class=cl><span class=nd>@Override</span> |
| </span></span><span class=line><span class=cl><span class=kd>public</span> <span class=n>Collection</span><span class=o><</span><span class=n>IntervalWindow</span><span class=o>></span> <span class=nf>assignWindows</span><span class=o>(</span><span class=n>AssignContext</span> <span class=n>c</span><span class=o>)</span> <span class=o>{</span> |
| </span></span><span class=line><span class=cl> <span class=c1>// Assign each element into a window from its timestamp until gapDuration in the |
| </span></span></span><span class=line><span class=cl><span class=c1></span> <span class=c1>// future. Overlapping windows (representing elements within gapDuration of |
| </span></span></span><span class=line><span class=cl><span class=c1></span> <span class=c1>// each other) will be merged. |
| </span></span></span><span class=line><span class=cl><span class=c1></span> <span class=n>Duration</span> <span class=n>dataDrivenGap</span><span class=o>;</span> |
| </span></span><span class=line><span class=cl> <span class=n>TableRow</span> <span class=n>message</span> <span class=o>=</span> <span class=n>c</span><span class=o>.</span><span class=na>element</span><span class=o>();</span> |
| </span></span><span class=line><span class=cl> |
| </span></span><span class=line><span class=cl> <span class=k>try</span> <span class=o>{</span> |
| </span></span><span class=line><span class=cl> <span class=n>dataDrivenGap</span> <span class=o>=</span> <span class=n>Duration</span><span class=o>.</span><span class=na>standardSeconds</span><span class=o>(</span><span class=n>Long</span><span class=o>.</span><span class=na>parseLong</span><span class=o>(</span><span class=n>message</span><span class=o>.</span><span class=na>get</span><span class=o>(</span><span class=s>"gap"</span><span class=o>).</span><span class=na>toString</span><span class=o>()));</span> |
| </span></span><span class=line><span class=cl> <span class=o>}</span> <span class=k>catch</span> <span class=o>(</span><span class=n>Exception</span> <span class=n>e</span><span class=o>)</span> <span class=o>{</span> |
| </span></span><span class=line><span class=cl> <span class=n>dataDrivenGap</span> <span class=o>=</span> <span class=n>gapDuration</span><span class=o>;</span> |
| </span></span><span class=line><span class=cl> <span class=o>}</span> |
| </span></span><span class=line><span class=cl> <span class=k>return</span> <span class=n>Arrays</span><span class=o>.</span><span class=na>asList</span><span class=o>(</span><span class=k>new</span> <span class=n>IntervalWindow</span><span class=o>(</span><span class=n>c</span><span class=o>.</span><span class=na>timestamp</span><span class=o>(),</span> <span class=n>dataDrivenGap</span><span class=o>));</span> |
| </span></span><span class=line><span class=cl><span class=o>}</span></span></span></code></pre></div></div></div><p>Then, set the <code>gapDuration</code> field in a windowing function:</p><div class='language-java snippet'><div class="notebook-skip code-snippet"><a class=copy type=button data-bs-toggle=tooltip data-bs-placement=bottom title="Copy to clipboard"><img src=/images/copy-icon.svg></a><div class=highlight><pre tabindex=0 class=chroma><code class=language-java data-lang=java><span class=line><span class=cl><span class=kd>public</span> <span class=kd>static</span> <span class=kd>class</span> <span class=nc>DynamicSessions</span> <span class=kd>extends</span> <span class=n>WindowFn</span><span class=o><</span><span class=n>TableRow</span><span class=o>,</span> <span class=n>IntervalWindow</span><span class=o>></span> <span class=o>{</span> |
| </span></span><span class=line><span class=cl> <span class=cm>/** Duration of the gaps between sessions. */</span> |
| </span></span><span class=line><span class=cl> <span class=kd>private</span> <span class=kd>final</span> <span class=n>Duration</span> <span class=n>gapDuration</span><span class=o>;</span> |
| </span></span><span class=line><span class=cl> |
| </span></span><span class=line><span class=cl> <span class=cm>/** Creates a {@code DynamicSessions} {@link WindowFn} with the specified gap duration. */</span> |
| </span></span><span class=line><span class=cl> <span class=kd>private</span> <span class=nf>DynamicSessions</span><span class=o>(</span><span class=n>Duration</span> <span class=n>gapDuration</span><span class=o>)</span> <span class=o>{</span> |
| </span></span><span class=line><span class=cl> <span class=k>this</span><span class=o>.</span><span class=na>gapDuration</span> <span class=o>=</span> <span class=n>gapDuration</span><span class=o>;</span> |
| </span></span><span class=line><span class=cl> <span class=o>}</span></span></span></code></pre></div></div></div><h3 id=windowing-messages-into-sessions>Windowing messages into sessions</h3><p>After creating data-driven gaps, you can window incoming data into the new, custom sessions.</p><p>First, set the session length to the gap duration:</p><div class='language-java snippet'><div class="notebook-skip code-snippet"><a class=copy type=button data-bs-toggle=tooltip data-bs-placement=bottom title="Copy to clipboard"><img src=/images/copy-icon.svg></a><div class=highlight><pre tabindex=0 class=chroma><code class=language-java data-lang=java><span class=line><span class=cl><span class=cm>/** Creates a {@code DynamicSessions} {@link WindowFn} with the specified gap duration. */</span> |
| </span></span><span class=line><span class=cl><span class=kd>public</span> <span class=kd>static</span> <span class=n>DynamicSessions</span> <span class=nf>withDefaultGapDuration</span><span class=o>(</span><span class=n>Duration</span> <span class=n>gapDuration</span><span class=o>)</span> <span class=o>{</span> |
| </span></span><span class=line><span class=cl> <span class=k>return</span> <span class=k>new</span> <span class=n>DynamicSessions</span><span class=o>(</span><span class=n>gapDuration</span><span class=o>);</span> |
| </span></span><span class=line><span class=cl><span class=o>}</span></span></span></code></pre></div></div></div><p>Lastly, window data into sessions in your pipeline:</p><div class='language-java snippet'><div class="notebook-skip code-snippet"><a class=copy type=button data-bs-toggle=tooltip data-bs-placement=bottom title="Copy to clipboard"><img src=/images/copy-icon.svg></a><div class=highlight><pre tabindex=0 class=chroma><code class=language-java data-lang=java><span class=line><span class=cl><span class=n>p</span><span class=o>.</span><span class=na>apply</span><span class=o>(</span> |
| </span></span><span class=line><span class=cl> <span class=s>"Window into sessions"</span><span class=o>,</span> |
| </span></span><span class=line><span class=cl> <span class=n>Window</span><span class=o>.<</span><span class=n>TableRow</span><span class=o>></span><span class=n>into</span><span class=o>(</span> |
| </span></span><span class=line><span class=cl> <span class=n>DynamicSessions</span><span class=o>.</span><span class=na>withDefaultGapDuration</span><span class=o>(</span><span class=n>Duration</span><span class=o>.</span><span class=na>standardSeconds</span><span class=o>(</span><span class=n>10</span><span class=o>))));</span></span></span></code></pre></div></div></div><h3 id=example-data-and-windows>Example data and windows</h3><p>The following test data tallies two users’ scores with and without the <code>gap</code> attribute:</p><pre tabindex=0><code>.apply("Create data", Create.timestamped( |
| TimestampedValue.of("{\"user\":\"user-1\",\"score\":\"12\",\"gap\":\"5\"}", new Instant()), |
| TimestampedValue.of("{\"user\":\"user-2\",\"score\":\"4\"}", new Instant()), |
| TimestampedValue.of("{\"user\":\"user-1\",\"score\":\"-3\",\"gap\":\"5\"}", new Instant().plus(2000)), |
| TimestampedValue.of("{\"user\":\"user-1\",\"score\":\"2\",\"gap\":\"5\"}", new Instant().plus(9000)), |
| TimestampedValue.of("{\"user\":\"user-1\",\"score\":\"7\",\"gap\":\"5\"}", new Instant().plus(12000)), |
| TimestampedValue.of("{\"user\":\"user-2\",\"score\":\"10\"}", new Instant().plus(12000))) |
| .withCoder(StringUtf8Coder.of())) |
| </code></pre><p>The diagram below visualizes the test data:</p><p><img src=/images/standard-vs-dynamic-sessions.png alt="Two sets of data and the standard and dynamic sessions with which the data is windowed."></p><h4 id=standard-sessions>Standard sessions</h4><p>Standard sessions use the following windows and scores:</p><pre tabindex=0><code>user=user-2, score=4, window=[2019-05-26T13:28:49.122Z..2019-05-26T13:28:59.122Z) |
| user=user-1, score=18, window=[2019-05-26T13:28:48.582Z..2019-05-26T13:29:12.774Z) |
| user=user-2, score=10, window=[2019-05-26T13:29:03.367Z..2019-05-26T13:29:13.367Z) |
| </code></pre><p>User #1 sees two events separated by 12 seconds. With standard sessions, the gap defaults to 10 seconds; both scores are in different sessions, so the scores aren’t added.</p><p>User #2 sees four events, separated by two, seven, and three seconds, respectively. Since none of the gaps are greater than the default, the four events are in the same standard session and added together (18 points).</p><h4 id=dynamic-sessions>Dynamic sessions</h4><p>The dynamic sessions specify a five-second gap, so they use the following windows and scores:</p><pre tabindex=0><code>user=user-2, score=4, window=[2019-05-26T14:30:22.969Z..2019-05-26T14:30:32.969Z) |
| user=user-1, score=9, window=[2019-05-26T14:30:22.429Z..2019-05-26T14:30:30.553Z) |
| user=user-1, score=9, window=[2019-05-26T14:30:33.276Z..2019-05-26T14:30:41.849Z) |
| user=user-2, score=10, window=[2019-05-26T14:30:37.357Z..2019-05-26T14:30:47.357Z) |
| </code></pre><p>With dynamic sessions, User #2 gets different scores. The third messages arrives seven seconds after the second message, so it’s grouped into a different session. The large, 18-point session is split into two 9-point sessions.</p><div class=feedback><p class=update>Last updated on 2024/04/26</p><h3>Have you found everything you were looking for?</h3><p class=description>Was it all useful and clear? Is there anything that you would like to change? Let us know!</p><button class=load-button><a href="https://docs.google.com/forms/d/e/1FAIpQLSfID7abne3GE6k6RdJIyZhPz2Gef7UkpggUEhTIDjjplHuxSA/viewform?usp=header_link" target=_blank>SEND FEEDBACK</a></button></div></div></div><footer class=footer><div class=footer__contained><div class=footer__cols><div class="footer__cols__col footer__cols__col__logos"><div class=footer__cols__col__logo><img src=/images/beam_logo_circle.svg class=footer__logo alt="Beam logo"></div><div class=footer__cols__col__logo><img src=/images/apache_logo_circle.svg class=footer__logo alt="Apache logo"></div></div><div class=footer-wrapper><div class=wrapper-grid><div class=footer__cols__col><div class=footer__cols__col__title>Start</div><div class=footer__cols__col__link><a href=/get-started/beam-overview/>Overview</a></div><div class=footer__cols__col__link><a href=/get-started/quickstart-java/>Quickstart (Java)</a></div><div class=footer__cols__col__link><a href=/get-started/quickstart-py/>Quickstart (Python)</a></div><div class=footer__cols__col__link><a href=/get-started/quickstart-go/>Quickstart (Go)</a></div><div class=footer__cols__col__link><a href=/get-started/downloads/>Downloads</a></div></div><div class=footer__cols__col><div class=footer__cols__col__title>Docs</div><div class=footer__cols__col__link><a href=/documentation/programming-guide/>Concepts</a></div><div class=footer__cols__col__link><a href=/documentation/pipelines/design-your-pipeline/>Pipelines</a></div><div class=footer__cols__col__link><a href=/documentation/runners/capability-matrix/>Runners</a></div></div><div class=footer__cols__col><div class=footer__cols__col__title>Community</div><div class=footer__cols__col__link><a href=/contribute/>Contribute</a></div><div class=footer__cols__col__link><a href=https://projects.apache.org/committee.html?beam target=_blank>Team<img src=/images/external-link-icon.png width=14 height=14 alt="External link."></a></div><div class=footer__cols__col__link><a href=/community/presentation-materials/>Media</a></div><div class=footer__cols__col__link><a href=/community/in-person/>Events/Meetups</a></div><div class=footer__cols__col__link><a href=/community/contact-us/>Contact Us</a></div></div><div class=footer__cols__col><div class=footer__cols__col__title>Resources</div><div class=footer__cols__col__link><a href=/blog/>Blog</a></div><div class=footer__cols__col__link><a href=https://github.com/apache/beam>GitHub</a></div></div></div><div class=footer__bottom>© |
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