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| <li class="">Back Log Emitter Service</li> |
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| <li id="publishDate" class="pull-right">Last Published: 2018-03-12</li> <li class="divider pull-right">|</li> |
| <li id="projectVersion" class="pull-right">Version: 0.11</li> |
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| <h2>Back Log Emitter Service<a name="Back_Log_Emitter_Service"></a></h2> |
| <p>Back Log Emitter service keeps track of all the process which have missed an SLA for a particular time and calculates backlog. Once a notification comes that process has completed, it updates the backlog. This service keeps on sending data to Graphite for each process which is missing SLA.</p> |
| <p>The emission and calculation of backlog are controlled by the below properties in startup.properties :</p> |
| <div class="source"> |
| <pre> |
| *.falcon.backlog.metricservice.emit.interval.millisecs=60000 |
| *.falcon.backlog.metricservice.recheck.interval.millisecs=60000 |
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| </pre></div></div> |
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| <h2>How Backlog is Calculated<a name="How_Backlog_is_Calculated"></a></h2> |
| <p>Back Log Emitter Service is a listener to :</p> |
| <p></p> |
| <ol style="list-style-type: decimal"> |
| <li>EntitySLAAlertService</li> |
| <li>WorkflowExecutionListener</li></ol> |
| <p>EntitySLAListeners service notifies BacklogEmitter whenever a process misses its shouldEndIn sla.</p> |
| <p>WorkflowExecutionListener notifies BacklogEmitter service whenever a process get completed.</p> |
| <p><b>Back Log Calculation:</b></p> |
| <p>If two instances of hourly process p1 have missed SLA for 4th and 5th hour then in 6th hourbacklog for process p1 will be ((6-4) + (6-5))*60 = 180 mins. It is cumulative in nature.</p></div> |
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| <h2>Dependencies :<a name="Dependencies_:"></a></h2> |
| <p><b>Other Services :</b></p> |
| <p>Following services and listeners should be enabled for Backlog Emitter Service in startup.properties:</p> |
| <div class="source"> |
| <pre> |
| ##Add if you want to enable BacklogMetricService |
| # org.apache.falcon.service.FalconJPAService,\ |
| # org.apache.falcon.metrics.MetricNotificationService,\ |
| # org.apache.falcon.service.EntitySLAMonitoringService,\ |
| # org.apache.falcon.service.EntitySLAAlertService,\ |
| # org.apache.falcon.service.BacklogMetricEmitterService |
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| *.entityAlert.listeners=org.apache.falcon.service.BacklogMetricEmitterService |
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| *.workflow.execution.listeners=org.apache.falcon.handler.SLAMonitoringHandler |
| |
| </pre></div> |
| <p><b>Falcon Database :</b> Back Log Emitter Service maintains its state in the database. It needs one table <b>BACKLOG_METRIC</b> please have a look at <a href="./FalconDatabase.html">FalconDatabase</a> to know how to create it.</p></div> |
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