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[[library-execution,Execution Library]]
= Execution =

== @Retry ==
Any method can be annotated with the @Retry annotation, which means that if there is an exception thrown, then
the method should be called again, for a max number of times.

The value() defines how many times the method will be called, if retry is triggered by the on() and unless()
parameters.

The backoff() parameter is available to slow down the retries, which is useful for network operations or
external systems that may still need more time to become available. The default is no backoff is deployed and retries
are executed as fast as possible.

The on() parameter defines which Throwable and subclasses should be considered for retrying the method call. The
default is all Throwables.

The unless() parameter negates the on() parameter, and if a subclass of any Throwable listed in unless() is thrown
then the retry operation(s) will not take effect.

== ExecutionService ==
The =ExecutionService= is the =java.util.concurrent.ExecutorService= provided simply as a flexible assembler for
configuration of it.

=== Configuration Parameters ===
The Configuration parameters are available in the =ExecutionServiceAssembler= via a fluent API (DSL), with the
following methods

[snippet,java]
----
source=libraries/execution/src/main/java/org/apache/polygene/library/execution/assembly/ExecutionServiceAssembler.java
tag=configuration
----


== ScheduledExecutionService ==
The =ScheduledExecutionService= is the =java.util.concurrent.ScheduledExecutorService= provided simply as a flexible
assembler for configuration of it.


=== Configuration Parameters ===
The Configuration parameters are available in the =ScheduledExecutionService= via a fluent API (DSL), with the
following methods

[snippet,java]
----
source=libraries/execution/src/main/java/org/apache/polygene/library/execution/assembly/ScheduledExecutionService.java
tag=configuration
----