Add metrics API

[markushi]

📜 Description

Add metrics API to support delightful developer metrics. This PR intends to provide the basic functionality:

• Metrics API for counters, sets, gauges, distributions and timings
• A MetricAggregator to locally aggregate into 10s buckets
• Flush / Closing functionality
• Hub integration
• Sending over the aggregated metrics using the new statsd envelope type

❓ Open Topics / Missing items

✅ How should the API entrypoint look like?

The aggregator is part of the hub, so it's either IHub.getMetricsApi() and our typical convenience Sentry.getMetricsApi()shortcut. It should definitely be in a sub-space, as all the different metrics, like Sentry.increment() would just pollute our top level namespace.

After some discussion, let's go for Sentry.metrics().increment(...)
✅ Is it "Metric" or "Metrics"?
Let's go for metrics, as the aggregator actually deals with multiple of them.
✅ Rate Limiting / Caching
I need to check if we need special handling for metrics on this.
✅ Automatically add global tags (e.g. release, environment)
✅ Add more tests, especially for the aggregator
✅ Use CR32 for hashing Strings values for set metrics

Out of scope / Will be done with follow up PR

1. Recording and sending code locations for metrics
2. Any span handling / local span aggregation

💡 Motivation and Context

Implements first parts of #3190

💚 How did you test it?

Added unit tests, taking some inspiration from https://github.com/getsentry/sentry-python/blob/master/tests/test_metrics.py and .NET

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• No new PII added or SDK only sends newly added PII if sendDefaultPII is enabled.
• I updated the docs if needed.
• Review from the native team if needed.
• No breaking change or entry added to the changelog.
• No breaking change for hybrid SDKs or communicated to hybrid SDKs.

🔮 Next steps

[github-actions]

	Messages
📖	Do not forget to update Sentry-docs with your feature once the pull request gets approved.

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[github-actions]

Performance metrics 🚀

	Plain	With Sentry	Diff
Startup time	300.54 ms	361.31 ms	60.76 ms
Size	1.70 MiB	2.28 MiB	590.47 KiB

Baseline results on branch: main

Startup times

Revision	Plain	With Sentry	Diff
0810952	364.51 ms	468.08 ms	103.57 ms
2fad834	390.07 ms	470.80 ms	80.73 ms
2465853	422.61 ms	491.20 ms	68.58 ms
8ff8fd0	432.77 ms	495.18 ms	62.41 ms
2465853	400.64 ms	465.47 ms	64.83 ms
5e04ee8	365.26 ms	448.49 ms	83.23 ms
c554ca2	368.52 ms	430.74 ms	62.22 ms
4e29063	384.14 ms	447.74 ms	63.60 ms
0404ea3	394.73 ms	461.79 ms	67.06 ms
0404ea3	332.47 ms	401.12 ms	68.66 ms

App size

Revision	Plain	With Sentry	Diff
0810952	1.72 MiB	2.27 MiB	558.21 KiB
2fad834	1.72 MiB	2.29 MiB	577.53 KiB
2465853	1.70 MiB	2.27 MiB	583.82 KiB
8ff8fd0	1.72 MiB	2.27 MiB	558.15 KiB
2465853	1.70 MiB	2.27 MiB	583.82 KiB
5e04ee8	1.70 MiB	2.27 MiB	584.64 KiB
c554ca2	1.70 MiB	2.27 MiB	582.25 KiB
4e29063	1.72 MiB	2.29 MiB	578.38 KiB
0404ea3	1.72 MiB	2.29 MiB	577.52 KiB
0404ea3	1.72 MiB	2.29 MiB	577.52 KiB

Previous results on branch: feat/metrics

Startup times

Revision	Plain	With Sentry	Diff
67ad747	424.90 ms	467.60 ms	42.70 ms
ac0ecb9	425.69 ms	506.96 ms	81.27 ms
f5d47c0	300.14 ms	342.90 ms	42.76 ms
5254f26	411.85 ms	442.08 ms	30.23 ms
0140fbc	399.74 ms	470.37 ms	70.63 ms
f5aa57f	413.70 ms	552.20 ms	138.50 ms
0e0f3c4	385.67 ms	458.14 ms	72.47 ms
4edc1f3	371.24 ms	446.73 ms	75.49 ms
6dd67a4	381.21 ms	445.40 ms	64.19 ms
038e0ae	364.92 ms	446.39 ms	81.47 ms

App size

Revision	Plain	With Sentry	Diff
67ad747	1.70 MiB	2.28 MiB	592.10 KiB
ac0ecb9	1.70 MiB	2.28 MiB	590.22 KiB
f5d47c0	1.70 MiB	2.27 MiB	586.58 KiB
5254f26	1.70 MiB	2.28 MiB	592.06 KiB
0140fbc	1.70 MiB	2.27 MiB	587.40 KiB
f5aa57f	1.70 MiB	2.28 MiB	590.22 KiB
0e0f3c4	1.70 MiB	2.27 MiB	587.24 KiB
4edc1f3	1.70 MiB	2.27 MiB	586.13 KiB
6dd67a4	1.70 MiB	2.27 MiB	587.20 KiB
038e0ae	1.70 MiB	2.28 MiB	590.25 KiB

[stefanosiano]

@NotNull 😛

[stefanosiano]

Last minor things!

[stefanosiano]

Just fix the last test (MetricsHelperTest.sanitizeValue) and we're good to go!

[sysmat]

• when using Sentry.metrics().notifyAll(); I get error

IllegalMonitorStateException: current thread is not owner
    at java.lang.Object.notifyAll(Object.java)
    at sentry.SentryMain.main(SentryMain.java:33)

• java 21, sentry 7.5.0