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https://issues.apache.org/jira/browse/CAMEL-26688?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Work on CAMEL-26688 started by shashank.
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> camel-core - step listener SPI for the exchange sanitizer
> ---------------------------------------------------------
>
> Key: CAMEL-26688
> URL: https://issues.apache.org/jira/browse/CAMEL-26688
> Project: Camel
> Issue Type: Improvement
> Components: camel-core
> Reporter: shashank
> Assignee: shashank
> Priority: Minor
>
> Step 1 of the order of work of the exchange sanitizer design (CAMEL-26630,
> design document in apache/camel#29296).
> *What it adds*
> * {{org.apache.camel.spi.StepListener}} in camel-api: a listener that
> observes each call of the processor of a step of a route: {{onStepCall}} (the
> call starts; returns a state for the call), {{onStepReturn}}, {{onStepThrow}}
> and {{onStepCallback}} (each time the callback of the call is called, before
> it continues the exchange). All methods have an empty default. A listener
> only observes; many can be installed, separate from the one {{StepHook}}.
> * {{ExtendedCamelContext.addStepListener}}, {{removeStepListener}} and
> {{getStepListeners}}, as default methods (the pattern of {{setStepHook}}).
> * The Javadoc of the contracts the routing engine relies on, which is not
> written down today: the callback of {{AsyncProcessor.process(exchange,
> callback)}} is called exactly once, {{process}} does not throw (it sets the
> exception and calls the callback), and the {{doneSync}} of the callback is
> the value {{process}} returns (except for a processor that hands its callback
> to the reactive executor, as the channel of each step does); and for
> {{Synchronization}}, that the commit of a consumer runs {{onComplete}} or
> {{onFailure}} once, where it is held at the end, and moves only by a handover.
> * When at least one step listener is installed when a route is created,
> {{DefaultChannel}} adds one small wrapper after the {{InterceptStrategy}}
> loop, around what the loop returns. The error handler of the step calls it
> for each attempt (also each redelivery), and the channel calls it for a step
> without such an error handler. The strategies still get the processor of the
> step as their target, and the {{StepHook}} is asked before the wrapper, so a
> step the hook fails is not a call the listeners see.
> With no listener installed the routes are built exactly as today: no wrapper,
> no check per step.
> A listener that throws cannot change the routing: each call of a listener is
> caught and logged at WARN once per listener, the processor is called whatever
> {{onStepCall}} did, the real callback is called in a {{finally}}, and what
> the processor throws is thrown on unchanged.
> Not in this issue: the on completion listener, the {{camel-sanitizer}} module
> and its rules, the JUnit extension and the dev console (later steps of
> CAMEL-26630). A JMH benchmark in camel-performance-tests will check, before
> the change is merged, that a step without a listener costs the same as before.
> _Filed with Claude Code on behalf of allthingssecurity._
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