Recording metrics could cause errors in operational code

[ChristianLMI]

Motivation

I recently ran into an issue where an exception thrown in Micrometer caused my request to break. The actual issue I ran into is not in reactor although reactor was used. However as reactor uses Micrometer as well and e.g. [here|https://github.com/reactor/reactor-netty/blob/main/reactor-netty-core/src/main/java/reactor/netty/channel/AbstractChannelMetricsHandler.java] there also doesn't seem to be any protection of the main functionality against errors in metrics recording, this might be good to look at in reactor as well.

Desired solution

IMHO metrics should be of lower priority than production results. Therefor a failing metric registration should write a log entry but not abort the current operation.

Additional context

In my case a misconfigured a MeterFilter that caused NullPointerExceptions when recording a filtered metric.

[violetagg]

@ChristianLMI Would you like to provide a PR?

[ChristianLMI]

I'll try to find some time to at least get a first step done. However as I'm not too familiar with the project I might miss edges ;)

[violetagg]

@ChristianLMI It will be great if you can find time. If you decide to work on this please do the changes against 1.0.x branch.

The classes that need to have this enhancement are:
reactor-netty-core

• reactor.netty.channel.AbstractChannelMetricsHandler
• reactor.netty.channel.ChannelMetricsHandler
• reactor.netty.channel.ContextAwareChannelMetricsHandler
• reactor.netty.transport.AddressResolverGroupMetrics

reactor-netty-http

• reactor.netty.http.client.AbstractHttpClientMetricsHandler
• reactor.netty.http.client.ContextAwareHttpClientMetricsHandler
• reactor.netty.http.server.AbstractHttpServerMetricsHandler
• reactor.netty.http.server.ContextAwareHttpServerMetricsHandler

[ChristianLMI]

I created a PR. However now I need to figure out how to get an approval for the CLA.