| ---+Back Log Emitter Service |
| |
| 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. |
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| The emission and calculation of backlog are controlled by the below properties in startup.properties : |
| |
| <verbatim> |
| *.falcon.backlog.metricservice.emit.interval.millisecs=60000 |
| *.falcon.backlog.metricservice.recheck.interval.millisecs=60000 |
| </verbatim> |
| |
| ---+How Backlog is Calculated |
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| Back Log Emitter Service is a listener to : |
| |
| 1. EntitySLAAlertService |
| 1. !WorkflowExecutionListener |
| |
| |
| EntitySLAListeners service notifies !BacklogEmitter whenever a process misses its shouldEndIn sla. |
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| !WorkflowExecutionListener notifies !BacklogEmitter service whenever a process get completed. |
| |
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| *Back Log Calculation:* |
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| 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. |
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| ---+Dependencies : |
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| *Other Services :* |
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| Following services and listeners should be enabled for Backlog Emitter Service in startup.properties: |
| |
| <verbatim> |
| ##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 |
| |
| *.entityAlert.listeners=org.apache.falcon.service.BacklogMetricEmitterService |
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| *.workflow.execution.listeners=org.apache.falcon.handler.SLAMonitoringHandler |
| </verbatim> |
| |
| |
| |
| *Falcon Database :* |
| Back Log Emitter Service maintains its state in the database. It needs one table *BACKLOG_METRIC* please have a look at [[FalconDatabase]] to know how to create it. |
| |
