Potential Memory Leak

[garethparris]

Which version of Serilog.Sinks.Grafana.Loki are you using?

v8.1.0

Which version of .NET are you using?

net6.0

Describe the bug

I've created a simple Prometheus .NET Exporter using Serilog and the Serilog Grafana Loki library.

On start-up of the application I can see it uses approximately 30,000 k active private working set. If I leave it running and do nothing, no requests, the private working set memory increases slowly over time. I have seen this in the GBs on my production servers.

On searching and profiling the code I commented out the loggerConfiguration.WriteTo.GrafanaLoki(lokiUrl, labels) section and I observed that memory no longer increases over time.

To Reproduce

Create a simple ASP .NET 6 Application with a basic page. Leave it running and see memory increase over time.

Expected behavior

I expect the application to start up and when it is doing no work for its memory use to be stable and not increase over time.

Log/SelfLog output or exception with stacktrace

No response

Application or code sample, which could be used to reproduce a bug

No response

Additional context

Whilst I am using Prometheus .NET I am not calling any of the methods after the initial request.

I have read the documentation

• [X] I have read Common Problems section in project wiki

[mishamyte]

Hi @prime23-gareth,

Feels like your logs not being delivered to Loki and they are keeping storing in memory.

To investigate this problem I suggest using Serilog's SelfLog and check stdout for diagnostic info of this Sink as described in Common problems section.

Also it is reasonable to restrict queue limit with queueLimit parameter. Available parameters are described here.

But I suggest that SelfLog will give you useful info. So, please, if you would have a time, try out with this parameter and tell me would be there any additional info.

Thanks!

[garethparris]

Thank you for your quick response. I've added SelfLog but its showing no errors. I also tried adding queueLimit:1 as a test and that does seem to dramatically decrease the memory increment but it does not stop it.

[mishamyte]

@prime23-gareth, OK, got it.

Could you please share the test app with your configuration and give me some details about your environment? Because we running sink for 2+ years and seems like all works like a charm. Plus hadn't heard about problems like that from Sink users.

So I wondering where is the problem.

And also could you confirm pls that Loki receiving logs correctly?

[garethparris]

I'll need to remove some private code but ill rewrite when i get a chance.

[mishamyte]

Yes, sure. I will keep my eye on it

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