Claus Ibsen created CAMEL-10388:
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Summary: Dynamic update predicate/expression at runtime
Key: CAMEL-10388
URL: https://issues.apache.org/jira/browse/CAMEL-10388
Project: Camel
Issue Type: New Feature
Components: camel-core
Reporter: Claus Ibsen
Fix For: Future
When using expression and predicates in your routes, then they are created once
during startup of Camel.
It may be desirable to allow dynamic updating these at runtime based on a
configuration parameter change configured from a property placeholder.
For example
{code:xml}
<from ...>
<filter>
<simple>{{auditEnabled}}</simple>
<to uri="{{auditUrl}}"/>
</filter>
...
{code}
In this example the simple predicate in the filter should be automatic updated
if the property placeholder value changes.
This requires
1. Properties component to support notification of value changes (SPI hook)
2. Predicate/Expression Factory in camel-core
3. Creating all expression/predicates using the factory
4. Option to turn this feature on (off by default)
5. If the option is on, then the factory creates the expression/predicate with
a wrapper that hooks into the notification event and listen on changes. If a
change happens, then expression/predicate is re-created and swapped out with
the existing.
There should not be a global lock, so the changes happens as-is and they are
not atomic. So end users should just beware, that if you do multiple property
changes then depending on concurrency then at any given time some
predicates/expression may be updated while others are still using old values.
We can optimize so they only update if the property placeholder key is used by
the expression/predicate.
Notice that endpoints is not supported. For those to updates you would need to
restart/re-create the route. Or use dynamic-to.
For the consumer we could consider a way for it to allow to auto restart by
doing a route stop/update/start.
However this is a slipping stope. As having immutable containers and leaving
updates to be done by a platform is better/safer.
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