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- Subagent Clusters present a logical view of the way a given number of Subagents co-operate for job execution.
- The Selection makes use of one or more Subagents.
- The Scheduling Mode is one of:
- active-passive: execute jobs with the first Subagent and switch to the next Subagent only if the first Subagent becomes unavailable (fixed-priority clustering).
- active-active: execute each next job on the next Subagent (round-robin clustering).
- metrics-based: execute each next job on the Subagent that best matches metrics such as number of parallel tasks, CPU and memory consumption.
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Metrics-based Subagent Cluster
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Metrics are used to identify the matching Subagent for execution of the next jobs. Metrics include to evaluate indicator values such as the number of processes, CPU load and memory consumption to decide which Subagent best matches for execution of the next job.
Indicators
- Director Agent
- The Director Agent receives indicator values from Subagents at an ongoing basis approx. every second.
- Additional indicators are provided by the Director Agent:
- number of jobs running in a Subagent Cluster.
- number of jobs running per Subagent in a Subagent Cluster
- The Director Agent will check indicators provided by Subagents to decide which Subagent should execute the next job. If a Subagent does not provide indicators then it is not considered for execution of the next job.
- Subagent Cluster
- The Subagent Cluster configuration allows specification of an expression for the priority attribute of each Subagent:
- An expression language is available that offers algebraic functions to be used for the priority.
- Indicators
- Indicators are made available from variables that can be used in a priority expression.
- The Subagent Cluster configuration allows specification of an expression for the priority attribute of each Subagent:
| Indicator Variable | Metric |
|---|---|
$js7SubagentProcessCount | Number of processes running with the Subagent. |
$js7ClusterSubagentProcessCount | Number of processes running with the Subagent for the given Subagent Cluster. |
The following indicators are available as explained with https://docs.oracle.com/en/java/javase/17/docs/api/jdk.management/com/sun/management/OperatingSystemMXBean.html | |
| Returns the "recent cpu usage" for the operating environment. This value is a double in the [0.0,1.0] interval. A value of 0.0 means that all CPUs were idle during the recent period of time observed, while a value of 1.0 means that all CPUs were actively running 100% of the time during the recent period being observed. All values betweens 0.0 and 1.0 are possible depending of the activities going on. If the recent cpu usage is not available, the method returns a negative value. A negative value is reported as missing. CPU Load is not available for MacOS and is reported as missing. |
| Returns the amount of virtual memory that is guaranteed to be available to the running process in bytes, or A negative value is reported as missing. |
| Returns the amount of free memory in bytes. |
| Returns the total amount of memory in bytes. |
Expressions
- Expressions are evaluated per Subagent & job and must return numeric values. Expressions can return a missing value indicating that the related Subagent should not be considered.
- The Subagent with the lowest priority value including negative numbers will be used for the next task.
- If the expression evaluates to missing values for all Subagents in the Subagent Cluster, then job execution will be deferred and evaluation of the expression will be repeatedly performed with a 1s interval.
Examples:
| Expression | Meaning |
|---|---|
$js7SubagentProcessCount | Example for consideration of the Subagent with the least number of tasks running for any Subagent Cluster that the Subagent is a member of. |
$js7ClusterSubagentProcessCount | Example for consideration of the Subagent with the least number of tasks running for the given Subagent Cluster. |
if $js7SubagentProcessCount == 0 then 1 else missing | Example for conditional use of a Subagent if it does not run any tasks. |
if $js7ClusterSubagentProcessCount == 0 then 1 else missing | Example for conditional use of a Subagent if it does not run any tasks in the given Subagent Cluster |
if $js7SubagentProcessCount =< 10 then $js7SubagentProcessCount else missing | Example for conditional use of a Subagent if it runs fewer than 10 tasks. |
if $js7ClusterSubagentProcessCount =< 10 then $js7ClusterSubagentProcessCount else missing | Example for conditional use of a Subagent if it runs fewer than 10 tasks for the given Subagent Cluster. |
-1 / ( $js7CpuLoad*2 - 1/$js7FreeMemorySize + $js7SubagentProcessCount*3 ) | Example for least consumption of CPU weighted by 2, free Memory and the least overall number of tasks running in the Subagent weighted by 3. |
Error Handling
- If a Subagent is shutdown or is unreachable then it is not considered for job execution. No error is raised, but the next Subagent matching metrics will be assigned the job.
- On normal termination the jobs in a Subagent will complete normally, no further jobs are accepted for execution.
- If the Subagent is crashed then running jobs will fail and orders for running jobs will be set to the failed state. Such jobs are restarted when restarting the Subagent. Alternatively, jobs can be restarted from a next Subagent when the crashed Subagent is reset. For details see JS7 - FAQ - How does JobScheduler terminate Jobs.
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