feat: Experimental Trace Metric

[aldy505]

Important

This will never get merged. This is a proof of concept on my end, and it works. This should be reworked if this (#1107) got merged.

If you want to use this, go set this on your go.mod:

replace github.com/getsentry/sentry-go => github.com/aldy505/sentry-go v0.0.0-20251027094200-132f880a4c16

On your sentry.Init call:

	err := sentry.Init(sentry.ClientOptions{
		ExperimentalEnableTraceMetric: true,
	})

Then use it:

meter := sentry.NewMeter(ctx)
meter.Count("number_of_lines", 1, sentry.MeterOptions{})
meter.Distribution("processing_time_ms", float64(time.Since(startTime).Milliseconds()), sentry.MeterOptions{})

Description

Implement trace metric based on getsentry/sentry-docs#15178

This work is based on the batch logger made by Giannis. Minimal documentation to really emphasize how experimental this is.

Issues

Reminders

• Add GH Issue ID & Linear ID
• PR title should use conventional commit style (feat:, fix:, ref:, meta:)
• For external contributors: CONTRIBUTING.md, Sentry SDK development docs, Discord community

[codecov]

Codecov Report

❌ Patch coverage is 4.62633% with 268 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.91%. Comparing base (c982e6f) to head (132f880).

Files with missing lines	Patch %	Lines
metrics.go	0.00%	141 Missing ⚠️
batch_metrics.go	0.00%	78 Missing ⚠️
interfaces.go	38.46%	14 Missing and 2 partials ⚠️
transport.go	0.00%	16 Missing ⚠️
internal/protocol/envelope.go	0.00%	10 Missing ⚠️
client.go	16.66%	3 Missing and 2 partials ⚠️
internal/ratelimit/category.go	50.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #1116      +/-   ##
==========================================
- Coverage   86.67%   82.91%   -3.77%     
==========================================
  Files          60       63       +3     
  Lines        6964     5829    -1135     
==========================================
- Hits         6036     4833    -1203     
- Misses        743      806      +63     
- Partials      185      190       +5     

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[cursor]

Bug: Goroutine Leak in Client Close

The Client.Close() method doesn't call Shutdown() on batchMeter (or batchLogger), causing goroutine leaks. The BatchMeter.run() goroutine will continue running indefinitely even after the client is closed, as it only stops when the context is cancelled. The Shutdown() method should be called to properly cancel the context and wait for the goroutine to finish, similar to how Flush() calls both batchLogger.Flush() and batchMeter.Flush().