Set limit on serialized message size in Subscriptions.Postgres

[williamdenton]

Postgres has a max limit of 8000 bytes for the payload in pg_notify. Exceeding this limit will result in infinite retries as messages are requeued internally back on to the channel. Due to batching a single poison (over size) message can break delivery of all messages.

This mitigates the infinite loop by blocking the messages from being queued into the subscription system.

Summary of the changes (Less than 80 chars)

• Throw an ArgumentException when a message is sent that exceeds the byte limit for postgres pg_notify

Closes #6658

[williamdenton]

hey @PascalSenn or @michaelstaib, i was considering how to best approach this.

• In the issue i suggested discarding the message as it was being delivered to postgres. I felt this was a bit late and didn't give enough feedback to the user. It's probably unlikely that an end user would have the appropriate diagnostic event listener configured (maybe you would after you tracked down the missing messages and found this issue, but thats a bit late in my opinion).
• This approach will throw an exception to the user when they enqueue a message using ITopicSender.SendAsync() when using the package Postgres.Subscriptions
• There is "work" done in the constructor to serialize the message in order to discover its length. This is not additional work, it has just moved earlier in the pipeline. (some people don't line work like this in a constructor, let me know what you think)

I think the 8000 byte limit is constant in postgres, this documentation suggests its configurable (emphasis mine)

The “payload” string to be communicated along with the notification. This must be specified as a simple string literal. In the default configuration it must be shorter than 8000 bytes. (If binary data or large amounts of information need to be communicated, it's best to put it in a database table and send the key of the record.)

I can't see where to configure it in postgres, but I allowed for it to be configurable in the provider with the default value set.

[PascalSenn]

Thanks a lot for the pr!
This looks very good and makes sense.

There is only one thing, I personally prefere a public static factory method on the PostgresMessageEnvelope instead of the magic constructor.

But let see what @michaelstaib thinks about it.

[PascalSenn]

I personally would prefer a public static factory method that does the formatting and then passes topic and payload to the envelope ctor.

[williamdenton]

yeah, this is fair, i wasn't sure about doing that extra work in the constructor, a factory would be better. Ill make that change

[PascalSenn]

@williamdenton
I quickly aligned the PR with out code style rules. Otherwise no change. Great work. Let's get this in! Thanks again 🚀

[codecov]

Codecov Report

Attention: 7 lines in your changes are missing coverage. Please review.

Comparison is base (6965960) 78.98% compared to head (c580f50) 78.12%.
Report is 65 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #6678      +/-   ##
==========================================
- Coverage   78.98%   78.12%   -0.86%     
==========================================
  Files        2903     2541     -362     
  Lines      139771   127086   -12685     
==========================================
- Hits       110397    99285   -11112     
+ Misses      29374    27801    -1573     

Flag	Coverage Δ
unittests	78.12% <82.05%> (-0.86%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files	Coverage Δ
...e/src/CookieCrumble/Extensions/WriterExtensions.cs	100.00% <ø> (ø)
...CookieCrumble/src/CookieCrumble/TestEnvironment.cs	0.00% <ø> (ø)
...polloFederationRequestExecutorBuilderExtensions.cs	66.66% <100.00%> (ø)
...ensions/ApolloFederationSchemaBuilderExtensions.cs	86.66% <ø> (ø)
.../src/ApolloFederation/FederationTypeInterceptor.cs	100.00% <100.00%> (ø)
...ion/src/ApolloFederation/Helpers/ArgumentParser.cs	68.65% <100.00%> (+0.47%)	⬆️
...rc/AspNetCore.CommandLine/Command/ExportCommand.cs	100.00% <100.00%> (ø)
...tChocolateAspNetCoreServiceCollectionExtensions.cs	93.33% <ø> (+26.66%)	⬆️
...rc/AspNetCore/Extensions/HttpResponseExtensions.cs	26.31% <ø> (+4.57%)	⬆️
...pNetCore/src/AspNetCore/GraphQLRequestException.cs	25.00% <ø> (+5.00%)	⬆️
... and 13 more

... and 875 files with indirect coverage changes

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.