Spring/spring-integration
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

GH-3452: Warn Publisher.onError in NullChannel (#3453)

Browse Source 
* GH-3452: Warn Publisher.onError in NullChannel

Fixes https://github.com/spring-projects/spring-integration/issues/3452

The `NullChannel` can subscribe to the `Publisher` payload fully ignoring
the possible data according the `NullChannel` nature.
However an error thrown from the reactive stream processing is also ignored.

* Log WARN message from the `Subscriber.onError()` when `NullChannel`
subscribes to the `Publisher` produced to this channel.
* Mention the logic in the `NullChannel` docs; point to the
`ReactiveRequestHandlerAdvice` for further possible error handling in
the target application

**Cherry-pick to `5.4.x`**

* * Remove unused imports

* * Fix `PseudoTransactionalMessageSourceTests` for `LogAccessor`
from `NullChannel`
This commit is contained in:
Artem Bilan
2021-01-05 15:08:30 -05:00
committed by Gary Russell
parent 5ed8c11c58
commit ebe79aedfb
3 changed files with 21 additions and 15 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
src/reference/asciidoc/channel.adoc
View File

@@ -1145,6 +1145,8 @@ For example, you can use this technique to configure a test case to verify messa
Two special channels are defined within the application context by default: `errorChannel` and `nullChannel`.
The 'nullChannel' (an instance of `NullChannel`) acts like `/dev/null`, logging any message sent to it at the `DEBUG` level and returning immediately.
The special treatment is applied for an `org.reactivestreams.Publisher` payload of a sent message: it is subscribed to in this channel immediately, to initiate reactive stream processing, although the data is discarded.
An error thrown from a reactive stream processing (see `Subscriber.onError(Throwable)`) is logged under the warn level for possible investigation.
If there is need to do anything with such an error, the `<<./handler-advice.adoc#reactive-advice,ReactiveRequestHandlerAdvice>>` with a `Mono.doOnError()` customization can be applied to the message handler producing `Mono` reply into this `nullChannel`.
Any time you face channel resolution errors for a reply that you do not care about, you can set the affected component's `output-channel` attribute to 'nullChannel' (the name, 'nullChannel', is reserved within the application context).
The 'errorChannel' is used internally for sending error messages and may be overridden with a custom configuration.