[CONF] Apache Camel > Camel 2.3 - ThreadPool Configuration

[confluence]

Camel 2.3 - ThreadPool Configuration Page edited by Claus Ibsen Design Notes for ThreadPool Configuration CAMEL-1588 is the ticket for a new and improved thread pool configuration for Apache Camel. Its intended for Camel 2.3. Scope Camel uses thread pool in various places such as EIP patterns, Components, Async API and whatnot. The aim is to improved and allow easier to configure those thread pools in a more streamlined manner. The goal is to offer both a fine grained configuration where you can tweak individual pools and have more coarse grained configuration with fallback to global settings etc. Outside scope Some components provides their own thread pool configuration and management which Camel of course cannot and should not try to tailor with. For example Jetty is such an example. Usages of thread pools in Camel Currently Camel uses thread pools in camel-core in the following areas: DefaultComponent - Optional thread pool for components in need of such DefaultEndpoint - Optional thread pool for endpoints in need of such DefaultProducerTemplate - Used by the Async API of this template ScheduledPollConsumer - Needs a ScheduledExecutorService to schedule its tasks RecipientListDefinition - The Recipient List EIP pattern SplitDefinition - The Splitter EIP pattern ThreadsDefinition - The threads DSL ToDefinition - Used by the toAsync variation WireTapDefinition - The WireTap EIP pattern MulticastProcessor - The underlying thread pool OnCompletionProcessor - For sending async on completion routes SendAsyncProcessor - The toAsync processor variation ThreadsProcessor - The underlying thread pool WireTapProcessor - For sending async wire taps SedaConsumer - To support the concurrentConsumers and multipleConsumers options (uses separate pools) Existing configuration You can configure the thread pool using the setExecutorService setter methods that usually exists on those places where its in use. Some EIP patterns offer a executorServiceRef option to refer to some pool to be looked up in the Registry. Using default ThreadPools We should use CachedThreadPool from the JDK Core as its the best general purpose pool for many short lived tasks, which is what Camel really does. Processing many messages in a short live. DONE Only used SingleExecutorService for background tasks, and ScheduledExecutorService for scheduled tasks DONE ThreadPool scope It should be possible to configure a thread pool on either per CamelContext level or per Route level, such as you can do with AutoStartup and the likes. Then you can say, eg this route should use this pool, which have 20/50 in the pool size etc. The problem with shutdown and restarting pools The ExecutorService API does not allow to restart a thread pool, which is PITA. So we need to find a better strategy for stopping vs. shutdown. Currently when we stop we also terminate the threadpool, and then re-create it on start. This only works for default pools which we can create again. But for custom thread pools we have no way to create them again as the pool is already created when its given to us. We may have to only shutdown thread pools if CamelContext is stopping. And then if end user stop a route from JMX we can keep the thread pool around. Only issue is the scheduled pool should stop scheduling tasks, which may be a bit more trickier to avoid. The problem with Component, Endpoint The DefaultComponent and DefaultEndpoint exposes API to get an ExecutorService. We should retrofit this API a bit so it can get hold of any external configured more easily. Also it should be able to use if you configure a shared pool on a per route or per camel context basis. Managed thread pool Check whether the thread pools is managed by default and avail in JConsole. If not we should probably at least expose some read-only data about the pools. Spring Factory for creating custom pools Create a Spring XML DSL for defining thread pools using custom options such as corePoolSize, maxPoolSize, keepAlive, thread name etc. DONE Change Notification Preferences View Online | View Change | Add Comment