capturing-profiles.md

# Capturing profiles ?> This feature was first made available in Testground v0.5.4 + sdk-go v0.2.8. Profiling is a powerful way to understand how the code under test behaves under the hood. Different programming languages support different types of profiles. For example, Go supports these types: * CPU profiles. * Heaps and allocs profiles. * Goroutine, threads, mutex and block profiles. Refer to the [`pprof` package godocs](https://golang.org/pkg/runtime/pprof/#Profile) for more information. Testground has first-class support for capturing profiles continuously throughout the test execution, and it's very versatile: * You can choose to profile all test run instances, or just a subset of them \(per group\). * You can choose which profile types to record. * You can set the sampling interval or frequency of capture for snapshot-type profiles \(e.g. goroutine, heap, etc. profiles in go\). ?> **Success** Because profiling is a language feature, Testground delegates the capture to the corresponding SDK by sending the profiling requirements for each instance inside the `TEST_CAPTURE_PROFILES` env variable. The profiles are written to the [output path for each instance](./#testground-outputs-structure), and **are available in the output bundle** generated by `testground collect` or the `testground run --collect` flag. ### Enabling profiles You can enable profiles by setting the profiling settings under the run configuration. **To enable profiling globally** ###### composition.toml ```toml ... [global.run] # this enables a continuous CPU profile, a heap profile every 5 seconds, # and an allocs profile every 10 seconds. profiles = { cpu = "true", heap = "5s", allocs = "10s" } ... ``` **To enable profiling in a single group** ###### composition.toml ```toml ... [[groups]] id = "low-latency" [groups.run] # same settings as above profiles = { cpu = "true", heap = "5s", allocs = "10s" } ... ```