Contributing to streamplace

Source: Dev.to

How I found the Project

Nowadays I’ve been reading and writing Go code regularly, and my Go journey started with A Tour of Go. While building my http-server-ts, I watched this video where Primeagen builds an HTTP server in Go, which showed me how Go handles network programming. After getting confident with the language specifics, I found streamplace. I tackled that issue and successfully made a PR that got merged. I’ll give you the details below.

The Issue Description

When the firehose is unavailable, the stream had error‑prone code that would crash the loop. After getting familiar with the codebase (without even setting it up, thanks to my C++ background), I commented on the issue saying I’d like to work on it. I mentioned that the issue was in the StartLabelerFirehose() function in labeler_firehose.go, and I was planning to replace the crash with a backoff mechanism. I got nice feedback from the maintainer saying my approach sounded reasonable and that it would be better to add a metric to spmetrics.go. Basically, my conversation with the maintainer reduced the back‑and‑forth in my pull request, which I recommend to everybody: communicate beforehand when tackling an issue.

Set Up

Even though the code structure was pretty niche, setting up this project was time‑consuming because of handling dependencies. I spent way too much time on this, which I should have done a long time ago if I wanted to contribute regularly. I dealt with sqlite3 version issues when following the documentation.

The Solution

I fixed the issue by adding a streamplace_labeler_firehoses_connected metric in spmetrics.go to track labeler connections:

var LabelerFirehosesConnected = promauto.NewGaugeVec(prometheus.GaugeOpts{
    Name: "streamplace_labeler_firehoses_connected",
    Help: "number of currently connected labeler firehoses",
}, []string{"labeler"})

Then I imported spmetrics.go and changed the log level at the retry threshold from Error to Warn:

log.Warn(ctx, "firehose failed 3 times within a minute, backing off", "err", err)
time.Sleep(5 * time.Second)
retryCount = 0
retryWindow = time.Now()

When fixing this bug, I initially introduced a race condition by changing cancel():

defer func() {
    spmetrics.LabelerFirehosesConnected.WithLabelValues(did).Set(0)
    cancel()
}()

The defer wouldn’t execute until the function returns, and I also had a separate defer cancel(), causing confusion. I decided to keep the original defer cancel() and not modify it.

Testing and Suggestion from Maintainer

I tested the change locally using Bluesky’s official moderation labeler. I verified that the metric reports 1 while the labeler firehose is connected and that the retry path backs off for 5 seconds after repeated failures instead of crashing.

Initially I wrote:

spmetrics.LabelerFirehosesConnected.WithLabelValues(did).Set(1)
defer spmetrics.LabelerFirehosesConnected.WithLabelValues(did).Set(0)

The maintainer suggested using Inc and Dec to support multiple labeler firehoses:

spmetrics.LabelerFirehosesConnected.WithLabelValues(did).Inc()
defer spmetrics.LabelerFirehosesConnected.WithLabelValues(did).Dec()

Eventually my pull request got merged.

Gained Knowledge

For the first time, I dealt with a well‑structured Go codebase. I learned about race conditions and reminded myself how important small details are. Also, as mentioned before, it’s better to keep code changes precise and stay in touch with maintainers. I’ll keep going and continue contributing to this codebase.