Hey folks, hoping for a second set of eyes here. I've just set up Traceloop to monitor a few Flask services in my home lab, and while the SDK seems to be sending... *something*... my dashboard is a ghost town. Zero traces. I've double-checked the API key, and the logs look cleaner than my desk after a spring cleaning (which is suspicious in itself).
Reminds me of the time I spent three hours debugging a Prometheus scrape config only to realize I'd forgotten to open the firewall port. Classic.
Here's my basic setup. The service runs, the endpoints work, but Traceloop just gives me the silent treatment.
```python
from traceloop.sdk import Traceloop
Traceloop.init(app_name="my-flask-app", api_key="tl_my_key_here")
@app.route("/test")
def test():
# some logic
return "ok"
```
I'm running this in a Docker container, and I've verified the key is present as an environment variable. No errors in the container logs, and nothing juicy in the Traceloop agent logs either. Has anyone else hit this? Could it be a networking thing from inside the container, or maybe an issue with the auto-instrumentation not hooking in properly? I'm using the standard `opentelemetry-instrument` wrapper to run the app.
Any debugging steps you'd recommend beyond the obvious? I'm about to start throwing `tcpdump` at it, but I thought I'd ask the hive mind first.
-- Dad
it worked on my machine
Ah, the classic silent dashboard. Been there. A couple things to check:
First, are you actually making calls to the instrumented Flask app? The auto-instrumentation only kicks in on request. I've made the mistake of watching an empty dashboard while my load tester was pointed at the wrong port.
Second, and this got me last week, double-check the OpenTelemetry SDK logs, not just Traceloop's. Sometimes the export fails silently unless you set `OTEL_LOG_LEVEL=DEBUG`. I added that to my Docker env and suddenly saw connection timeout errors - turns out my corporate proxy was blocking the outbound calls.
If you're in Docker, maybe do a quick curl from inside the container to the Traceloop collector endpoint, just to rule out network. Let us know what you find!
Benchmark or bust
Been down that road more times than I'd like to admit. Your snippet shows `Traceloop.init`, but for Flask, the auto-instrumentation often needs the `FlaskInstrumentor` to be explicitly enabled, especially in newer SDK versions. The `opentelemetry-instrument` wrapper should do it, but I've seen it be flaky inside containers.
Since you're in Docker, the network is prime suspect. The SDK failing to export traces often doesn't log unless you crank up the OpenTelemetry verbosity. Add `OTEL_LOG_LEVEL=DEBUG` and `OTEL_EXPORTER_OTLP_TRACES_HEADERS="api-key=YOUR_KEY"` to your container environment. Then watch the logs for a request to `/test`. You'll either see successful export logs or, more likely, a connection refused/timeout to Traceloop's endpoint.
Can you share your Dockerfile or compose setup? I've had issues where the default OTLP endpoint wasn't being overridden by Traceloop's init, requiring an explicit `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT` env var.
Extract, transform, trust
I've seen the FlaskInstrumentor step trip people up too. The instrumentation sometimes loads before Flask itself, so it misses the app instance entirely.
If you're running with gunicorn, it gets worse. You need to import and call `FlaskInstrumentor().instrument_app(app)` directly in your main.py, not just rely on init. Their docs gloss over that.
Also, check your default OTLP endpoint. Some SDK versions default to `localhost:4317`, ignoring Traceloop's collector. Setting `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT= https://api.traceloop.com` explicitly is a solid move.
Numbers don't lie.
Ah, the silent dashboard syndrome! That's so familiar from when I was testing Traceloop against another vendor last month. The others gave me some solid points, but I'd add one more angle: have you verified the SDK version?
I ran into a similar silent issue when my `opentelemetry-sdk` version was slightly behind what Traceloop's Python SDK expected. The instrumentation would load without error, but the spans just evaporated. A quick `pip list | grep opentelemetry` might show a mismatch. Upgrading to their recommended versions fixed it instantly for me.
Also, since you mentioned Docker, try a quick `docker exec` into your container and curl your own Flask endpoint a few times. Sometimes the auto-instrumentation needs a warm-up request before it starts hooking properly. If you see logs from the Flask app but still no traces, then it's definitely the export path. Let us know what you find!
Good catch on mentioning the `opentelemetry-instrument` wrapper - that's the exact spot where mine broke silently too. For me, the issue was that the wrapper wasn't picking up the Flask app because I was using a custom WSGI entry point.
Two things to try right now:
- Instead of just `opentelemetry-instrument`, try setting `OTEL_PYTHON_DISABLED_INSTRUMENTATIONS=""` explicitly. Sometimes other libs interfere.
- Can you temporarily add `print("Instrumented")` right after your `Traceloop.init`? If you don't see that in your logs, the import order might be off and the init is getting skipped.
Also, network from Docker is always suspect. Quick test: add `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT= http://localhost:4317` and run a lightweight OTel collector locally. If traces appear there, you know the issue is the outbound hop to Traceloop.
Good call on checking the OTLP endpoint default. That's bitten me before too. Since you're using `opentelemetry-instrument`, there's a chance it's overriding your init and defaulting to a local collector. Could you set `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT= https://api.traceloop.com/v1/traces` explicitly and try one more test request? That'll force the export path, regardless of wrapper defaults.
Oh yeah, the `FlaskInstrumentor` step is a sneaky one. The auto-import via `opentelemetry-instrument` feels like magic when it works, but it fails silently so often inside containers. I've started explicitly calling it in all my Flask apps now, just to be safe.
Adding to your point about Docker network, I've also found that the SDK sometimes respects the `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT` from the init, but only if it's set before the first span is created. If there's any async initialization, the default localhost endpoint can win. Always setting it as an environment variable in the Dockerfile is the only reliable way I've found 😅
What's the typical latency you see from span creation to Traceloop dashboard? I sometimes wonder if there's a batching delay that makes the dashboard look empty.
If it's not measurable, it's not marketing.