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Node.js

Node.js is a popular platform to write server-side applications. Profiling Node.js based application is supported out of the box with Polar Signals Cloud.

To see function names for Javascript code the --perf-basic-prof-only-functions flag must be passed to the node command. For better quality we also recommend to pass the --interpreted-frames-native-stack flag.

For example the full command might look like this:

node --perf-basic-prof-only-functions --interpreted-frames-native-stack main.js

Troubleshooting​

Below are some situations and how to troubleshoot them. If you've tried these and still haven't been able to resolve the issue, please contact support.

Only functions broken​

For a long time --perf-basic-prof-only-functions was broken and resulted in incomplete data, ensure you are using a new enough version that fixes it.

v16​

The fix is not being backported for v16. Use --perf-basic-prof instead.

v18​

Fixed in v18.19.0 (specifically commit 5f852cc) make sure to use v18.19.0 or newer of the v18 release series.

v20​

Fixed in 20.10.0 (specifically commit e63aef9) make sure to use v20.10.0 or newer of the v20 release series.

v21​

Fixed in v21.1.0 (specifically commit f4da308) make sure to use v21.1.0 or newer of the v21 release series.

All I can see is memory addresses​

First make sure the node process is started with the --perf-basic-prof-only-functions and --interpreted-frames-native-stack flags. Then check that the process is successfully writing a perfmap. By default, perfmaps are written to /tmp/perf-<PID>.map.

On Kubernetes for example this can be checked with:

kubectl exec --namespace <namespace-name> <pod-name> -- ls -la /tmp

For example:

$ kubectl exec -n default nodejs-demo -- ls -la /tmp
total 144
drwxrwxrwt 1 root root   4096 Jul 12 08:59 .
drwxr-xr-x 1 root root   4096 Jul 12 08:59 ..
-rw-r--r-- 1 root root 131811 Jul 12 08:59 perf-1.map
drwxr-xr-x 3 root root   4096 Jul  4 17:33 v8-compile-cache-0

In this example the file we're looking for is the perf-1.map. For you it should be called something similar.