GH-2744: ScatterGather: reinstate request headers #2750
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Fixes spring-projects#2744 When we get scattering results, there is no reason to keep internal headers any more. * Fix `ScatterGatherHandler` to modify scattering result messages to reinstate headers from original request message. This way we are able to re-throw an exception from the gatherer to the caller.
garyrussell
suggested changes
Feb 14, 2019
| } | ||
| MessageChannel gatherResultChannel = headers.get(GATHER_RESULT_CHANNEL, MessageChannel.class); | ||
| if (gatherResultChannel != null) { | ||
| this.messagingTemplate.send(gatherResultChannel, message); | ||
| } | ||
| else { | ||
| throw new MessageDeliveryException(message, | ||
| "The 'gatherResultChannel' header is required to delivery gather result."); |
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s/delivery/deliver the/
| @@ -206,3 +206,8 @@ public Message<?> processAsyncScatterError(MessagingException payload) { | |||
| To produce a proper reply, we have to copy headers (including `replyChannel` and `errorChannel`) from the `failedMessage` of the `MessagingException` that has been sent to the `scatterGatherErrorChannel` by the `MessagePublishingErrorHandler`. | |||
| This way the target exception is returned to the gatherer of the `ScatterGatherHandler` for reply messages group completion. | |||
| Such an exception `payload` can be filtered out in the `MessageGroupProcessor` of the gatherer or processed other way downstream, after the scatter-gather endpoint. | |||
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| NOTE: Before sending scattering results to the gatherer, `ScatterGatherHandler` reinstates the request message headers, including reply and error channels if any. | |||
| This way errors from the `AggregatingMessageHandler` are going to be propagated to the caller, even if async hand off is applied for scatter recipients. | |||
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s/if async/if an async/
s/applied for scatter recipients/applied in scatter recipient subflows/ ?
| NOTE: Before sending scattering results to the gatherer, `ScatterGatherHandler` reinstates the request message headers, including reply and error channels if any. | ||
| This way errors from the `AggregatingMessageHandler` are going to be propagated to the caller, even if async hand off is applied for scatter recipients. | ||
| In this case a reasonable, finite `gatherTimeout` must be configured for the `ScatterGatherHandler`. | ||
| Otherwise it is going to be blocked waiting for reply from the gatherer forever by default. |
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waiting for a reply ... forever, by default
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Gary, requested changes have been pushed. Thanks |
garyrussell
reviewed
Feb 14, 2019
| @@ -208,6 +208,6 @@ This way the target exception is returned to the gatherer of the `ScatterGatherH | |||
| Such an exception `payload` can be filtered out in the `MessageGroupProcessor` of the gatherer or processed other way downstream, after the scatter-gather endpoint. | |||
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| NOTE: Before sending scattering results to the gatherer, `ScatterGatherHandler` reinstates the request message headers, including reply and error channels if any. | |||
| This way errors from the `AggregatingMessageHandler` are going to be propagated to the caller, even if async hand off is applied for scatter recipients. | |||
| This way errors from the `AggregatingMessageHandler` are going to be propagated to the caller, even if async an hand off is applied in scatter recipient subflows. | |||
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an async - will fix on merge
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Merged as 0d37566 |
garyrussell
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Mar 16, 2022
Resolves spring-projects#3750 **5.5.x only; removed in 6.0**
artembilan
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Mar 16, 2022
Resolves #3750 **5.5.x only; removed in 6.0**
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Fixes #2744
When we get scattering results, there is no reason to keep internal
headers any more.
ScatterGatherHandlerto modify scattering result messages toreinstate headers from original request message.
This way we are able to re-throw an exception from the gatherer to
the caller