feat: Use sentry-go

[AbhiPrasad]

Motivation

Now that getsentry/sentry-go#235 has been merged in, we should implement the transactions from sentry-go with the collector.

This PR aims to generate transactions from rootSpanTrees, and then attempt to send them to sentry using sentry-go's async transport.

Implementation.

Please view https://github.com/getsentry/opentelemetry-collector-contrib/blob/6cd4cc16f2807b9d187e950e9cb381537cbb1e52/exporter/sentryexporter/docs/transformation.md on more details on how we chose to generate rootSpanTrees.

A root span tree is a datastructure that represents a Sentry transactions. It is made up of the following fields:

type rootSpanTree struct {
	rootSpan       *sentry.Span
	childSpans     []*sentry.Span
	libraryName    string
	libraryVersion string
	resourceTags   map[string]string
}

From a rootSpanTree, a transaction can easily be generated. We then can take that transaction, and use the sentry-go HTTPTransport to send it to Sentry.

[rhcarvalho]

omg, it starts off with already 57 commits! Big baby.

[AbhiPrasad]

Yes, this is due to the fact that it's built on top of #5

[rhcarvalho]

A few comments. Still, the most important thing seems to be validating that pushTraceData does "the right thing" for certain variations of input. Right now that is still beyond my reasoning.

Do we have test cases that operate on that level? They would help document what we expect to work with the exporter, given the limitations that we need to group spans together into transactions.

[AbhiPrasad]

Update: Addressed PR Review comments:

• Now set library name/version and resource tags on span, instead of carrying it around in a spanCollection.
• Made IsRootSpan -> isRootSpan
• Added transport buffer size config option
• Make sure to flush transactions before they overflow the transport buffer

[rhcarvalho]

The "root span tree" concept feels like one more thing one needs to learn to deal with this code base.

Would it be possible to simply create Transaction values (possibly as sentry.Event actually) for things we think are transactions and then append spans to transactions as we go?

The answer might be related to the ergonomics of storing a tree as "node and pointers/child list" vs "flat list".

WDYT?

[AbhiPrasad]

Good idea. I refactored to replace root span tree with just transactions.

[rhcarvalho]

Note: this works around the transport's buffer, but doesn't deal with rate limits.
Maybe we've talked already about shaping the traffic with a leaky bucket / token bucket, but that would only work if you have a single point of ingestion for a given DSN.

As Bruno mentioned, we have to understand the bigger picture, how is the data flowing through the exporter, how are spans batched, ...

The current implementation might be good for starters, though still more complex than if we used sentry.HTTPSyncTransport (which I think you ruled out for bad performance?).

[rhcarvalho]

👍