Denny Hatzenbihler InfoSphere Streams - Runtime Stream connection health, blockage and congestion InfoSphere Streams Version 3.0 Denny Hatzenbihler InfoSphere Streams - Runtime

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Agenda Stream connection health - additional capabilities Ability to detect Stream blockage and measure congestion

Stream Connection Health Streams Version 2.0 User can determine the number of broken connections Streams Version 3.0 User can identify individual broken connections Has a particular connection ever been connected? Timely information about connection state User can identify connections that are broken because their destination PE has died PE 2 This feature enables the user to identify which connection is broken. The list of functionality updates consists of: Adding ability to report the health state of individual connections. Streams v2.0 only provides an aggregate summary of connection health inferred from the connection metrics. This feature will provide state information of individual PE-to-PE data connections. Adding ability to determine connection state changes in relation with the health of the connected PEs. Streams v2.0 lacks functionality to determine the health of connections under certain conditions: for example, when a PE crashes, the system continues to report all its inbound connections as being in a healthy state, although there is no longer any process consuming tuples. In regards to a Streams instance’s job workload, version 2.0 of Streams Console can display Jobs, PEs, Operators, and Application Streams (Imports/Exports). For application health, Streams Console v2.0 shows the health of Jobs and PEs. Streams Console v3.0 can display a list of current connections. The connection list supports filtering by connection state, as well as the “normal” list of console filters such as: Job ID, Job name, PE ID, and user. The console would enable the user to drill down from the PE to see connections for a PE which may be the cause of a PE being unhealthy. Note: this feature does not address any direct Operator to Operator connection conditions. PE 1 PE 3

Stream Connection Health – Streams Console

Stream Connection Health – streamtool capturestate streamtool capturestate –i <instance> --select jobs <job id="1" name="application::PersonDataApp" submitTime="1351526069" user="warrena" state="running" healthSummary="partiallyUnhealthy"> <pe id="10" host="d0701b01.pok.hpc-ng.ibm.com" processId="0" state="stopped" reasonCode="failure" requiredConnections="disconnected" optionalConnections="disconnected" healthSummary="unhealthy"> <operator name="File"> <outputPort index="0" name="File" streamName="File"/> </operator> <outputPort index="0"> <connection inputPeId="11" inputPortIndex="0" required="true" state="closed"/> </outputPort> </pe>

Stream Blockage and Congestion When a PE is slow in processing The sender PE blocks on transmit This can propagate up to the sources (backpressure) Blockage: Inability to make forward progress for a longer duration Caused e.g. by an operator stuck in infinite loop or doing long term I/O Congestion: Short term blockages Tuples are being sent faster than the destination operator can process them Congestion Metric Per PE output port congestion Range from 0 (no congestion) to 100 (blockage) This functionality enables the user to detect connection congestion.  Because the definition of congestion is subjective, Streams v3.0 provides a metric value that indicates the level of congestion for each PE output port connection.  This metric provides a value from zero to one hundred which represents the percentage ratio of time spent waiting to send data divided by total time to send the data. This allows users to determine if a flow is congested or not. The port congestion metrics will be reported to the customer interfaces (Console, streamtool, IDE) along with other PE metrics to allow appropriate display of PE connections that may be, or are about to be, congested.

Streams Congestion – Streams Console

Stream Congestion – streamtool capturestate streamtool capturestate –i <instance> --select jobs=all The following <connection> element is under <job>, <pe>, <outputport> <connection inputPeId="1" inputPortIndex="0" required="true" state="closed"> <metric name="congestionFactor" lastChangeObserved="1350587443" userDefined="false"> <metricValue xsi:type="streams:longType" value="0"/> </metric> <metric name="nTuplesFilteredOut" lastChangeObserved="1350587443" userDefined="false"> </connection>

Demo

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