GOPS: Trace your Golang service with ease
GoPS is one alternative (also made by Google, other than pprof) to measure, trace or diagnose the performance and memory usage your Go-powered service/long-lived program. The usage is very easy, you just need to import and add 3 lines in your main (so the gops command line can communicate with your program):
If you don’t put those lines, you can still use gops limited to get list of programs running on your computer/server that made with Go with limited statistics information, using these commands:
$ go get -u -v github.com/google/gops
$ gops # show the list of running golang program
$ gops tree # show running process in tree
# PID can be replaced with GOPS host:port of that program
$ gops stack PID # get current stack trace of running PID
$ gops memstats PID # get memory statistics of running PID
$ gops gc PID # force garbage collection
$ gops pprof-cpu PID # get cpu profile graph
$ gops pprof-heap PID # get memory usage profile graph
profile saved at /tmp/heap_profile070676630
$ gops trace PID # get 5 sec execution trace
# you can install graphviz to visualize the cpu/memory profile
$ sudo apt install graphviz
# visualize the cpu/memory profile graph on the web browser
$ go tool pprof /tmp/heap_profile070676630
Next step is analyze the call graph for the memory leaks (which mostly just wrongly/forgot to defer body/sql rows or holding slice reference of huge buffer or certain framework’s cache trashing) or slow functions, whichever your mission are.
What if golang service you need to trace it inside Kubernetes pod that the GOPS address (host:port) not exposed to outside-world? Kubernetes is a popular solution for companies that manages bunch of servers/microservices or cloud like (GKE, AKS, Amazon EKS, ACK, DOKS, etc) but obviously overkill solution for small companies that doesn’t need to scale elastically (or the servers are less than 10 or not using microservice architecture).
First, you must compile gops statically so it can be run inside alpine container (which mostly what people use):
$ cd $GOPATH/go/src/github.com/google/gops
# copy gops to your kubernetes pod
$ kubectl cp ./gops $POD_NAME:/bin
$ kubectl exec -it $POD_NAME — sh
# for example you want to check heap profile for PID=1
# copy back trace file to local, then you can analyze the dump
kubectl cp $POD:/tmp/heap_profile070676630 out.dump
But if your address and port are exposed you can directly use gops from your computer to the pod or create a tunnel inside the pod if it doesn’t have public IP, for example using ngrok.
Btw if you know any companies migrating from/to certain language (especially Go), frameworks or database, you can contribute here.
Originally published at http://kokizzu.blogspot.com.