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Contributing

Here you can learn how you can contribute to Inspektor Gadget. If you are looking to develop Gadgets, please check the Gadget Development documentation.

Getting started​

To better understand how the pieces fit together, we recommend reading the architecture documentation before starting to play with Inspektor Gadget.

Setup developer environment​

Building the code​

Inspektor Gadget is composed of a client executable that runs on the operator's machine, and a container image that runs in the Kubernetes cluster. They can be built together or independently.

Building the client executable​

You can compile the client executable for your platform by running make kubectl-gadget.

To cross compile for all supported platforms, you can run make kubectl-gadget-all or select a specific one with make kubectl-gadget-linux-amd64 or make kubectl-gadget-darwin-amd64.

Building the gadget container image​

You can build and push the container gadget image by running the following commands:

$ make gadget-container
$ make push-gadget-container

The eBPF code is built using a Docker container, so you don't have to worry installing the compilers to build it.

If you push the container images to another registry, you can use the --image argument when deploying to the Kubernetes cluster.

Notes​

  • Using a locally built container image requires pushing it to a container registry, either local or remote. The default registry can be overridden by changing the value of the CONTAINER_REPO env variable, which defaults to ghcr.io/inspektor-gadget/inspektor-gadget if not defined.
  • You can generate the required BTF information for some well known kernel versions by setting ENABLE_BTFGEN=true

Building the eBPF object files​

If you need to compile the eBPF code of the gadgets, the ebpf-objects target will help you in this task:

$ make ebpf-objects
...
go: downloading github.com/giantswarm/crd-docs-generator v0.7.1
...
Wrote /work/pkg/gadgettracermanager/containers-map/containersmap_bpfel.go

Building ig​

Inspektor Gadget also provides the ig tool to trace containers without Kubernetes. It can be built independently from the kubectl-gadget and the gadget container image.

$ make ig

Testing​

Development environment on minikube​

For faster iteration, it's possible to make changes to Inspektor Gadget and test them on minikube locally without pushing container images to any registry.

  • Follow the specific installation instructions for minikube or use make minikube-start to start it.
  • Deploy the locally modified version of Inspektor Gadget to an already running minikube cluster with make minikube-deploy.

Unit tests​

You can run the different unit tests with:

$ make test

Regenerating testdata​

Some unit tests depend on precompiled files on testdata. These files can be regenerated by running

$ make testdata

Integration tests​

The integration tests use a Kubernetes cluster to deploy and test Inspektor Gadget. Note that, Inspektor Gadget must be deployed on the Kubernetes cluster before running the tests. Be sure that you have a valid kubeconfig and run:

$ export KUBECONFIG=... # not needed if valid config in $HOME/.kube/config
$ make integration-tests

Integration tests for ig​

Kubernetes​

The integration tests for ig uses minikube for testing different container runtimes. The default minikube driver used for testing is docker. Currently supported container runtimes are docker, containerd and cri-o. You can start minikube using:

$ make minikube-start-all
# for single container runtime e.g containerd
$ make CONTAINER_RUNTIME=containerd minikube-start
# for minikube driver other than docker e.g kvm2
$ make MINIKUBE_DRIVER=kvm2 minikube-start

And run the test using:

$ make -C integration/k8s test-all
# for single container runtime e.g containerd
$ make -C integration/k8s CONTAINER_RUNTIME=containerd test

if no CONTAINER_RUNTIME is specified docker will be used as a default runtime.

Non-Kubernetes​

The ig integration tests for non-Kubernetes containers directly interact with container runtime. The tests assume that you already have the desired container runtime installed. Currently supported runtime is docker only, You can run the test using:

$ make -C integration/ig/non-k8s test-docker

Benchmarks​

You can run the different benchmark tests with:

$ make gadgets-benchmarks

Or you can run an individual test with:

$ go test -exec sudo \
    -bench='BenchmarkAllGadgetsWithContainers/container10$/trace-tcpconnect' \
    -run=Benchmark \
    ./internal/benchmarks/...

Records of previous benchmarks are available here. See details in the CI documentation (benchmarks).

Explaining performance improvements in a PR​

If you want to contribute a performance improvement, it is useful to use benchmarks to explain the impact on performances. I will use the example of an improvement on the networking gadgets from #1430:

  • Run the benchmarks both on the main and the feature branches and saving the output in two files.
$ git checkout main
$ go test -exec sudo \
    -bench='^BenchmarkAllGadgetsWithContainers$/^container100$/trace-(dns|sni)' \
    -run=Benchmark \
    ./internal/benchmarks/... \
    -count 10 | tee main.bench
$ git checkout myfeature
$ go test -exec sudo \
    -bench='^BenchmarkAllGadgetsWithContainers$/^container100$/trace-(dns|sni)' \
    -run=Benchmark \
    ./internal/benchmarks/... \
    -count 10 | tee patched.bench

Please use -count to gather a statistically significant sample of results. The benchstat's documentation recommends 10 times.

  • Compare the results with benchstat:
$ go install golang.org/x/perf/cmd/benchstat@latest # if not already installed
$ benchstat main.bench patched.bench
goos: linux
goarch: amd64
pkg: github.com/inspektor-gadget/inspektor-gadget/internal/benchmarks
cpu: Intel(R) Core(TM) i7-6500U CPU @ 2.50GHz
                                                  │ main.bench  │           patched.bench            │
                                                  │   sec/op    │   sec/op    vs base                │
AllGadgetsWithContainers/container100/trace-dns-4   2.941 ±  3%   1.489 ± 4%  -49.38% (p=0.000 n=10)
AllGadgetsWithContainers/container100/trace-sni-4   4.440 ± 19%   1.495 ± 6%  -66.34% (p=0.000 n=10)
geomean                                             3.613         1.492       -58.72%
  • Include the commands used and the output of benchstat in your pull request description

Profiling benchmarks​

You can run the different benchmark tests while using the bcc profile tool. To be able to see the symbols in the profile, you need to build the binary with -ldflags="-s=false".

$ go test -exec sudo \
    -ldflags="-s=false" \
    -bench='^BenchmarkAllGadgetsWithContainers$/^container100$/snapshot-socket' \
    -run=Benchmark \
    ./internal/benchmarks/... \
    -count 100

Example of output showing a stack trace including both the userspace and kernel parts:

$ sudo /usr/share/bcc/tools/profile -p $(pidof benchmarks.test)
    b'established_get_first'
    b'established_get_first'
    b'tcp_seek_last_pos'
    b'bpf_iter_tcp_batch'
    b'bpf_iter_tcp_seq_next'
    b'bpf_seq_read'
    b'vfs_read'
    b'ksys_read'
    b'do_syscall_64'
    b'entry_SYSCALL_64_after_hwframe'
    runtime/internal/syscall.Syscall6
    syscall.Syscall
    syscall.read
    internal/poll.(*FD).Read
    os.(*File).Read
    bufio.(*Scanner).Scan
    github.com/inspektor-gadget/inspektor-gadget/pkg/gadgets/snapshot/socket/tracer.(*Tracer).RunCollector.func1
    github.com/inspektor-gadget/inspektor-gadget/pkg/netnsenter.NetnsEnter
    github.com/inspektor-gadget/inspektor-gadget/pkg/gadgets/snapshot/socket/tracer.(*Tracer).RunCollector
    github.com/inspektor-gadget/inspektor-gadget/pkg/gadgets/snapshot/socket/tracer.(*Tracer).Run
    github.com/inspektor-gadget/inspektor-gadget/pkg/runtime/local.(*Runtime).RunGadget
    github.com/inspektor-gadget/inspektor-gadget/internal/benchmarks.BenchmarkAllGadgetsWithContainers.func1.1
    testing.(*B).runN
    testing.(*B).launch
    testing.(*B).doBench.func1
    runtime.goexit.abi0
    -                benchmarks.test (3452330)
        22

It is also possible to use pprof to profile the benchmarks with the -cpuprofile and -memprofile flags.

go test \
    -cpuprofile cpu.prof -memprofile mem.prof \
    -exec sudo \
    -ldflags="-s=false" \
    -bench='^BenchmarkAllGadgetsWithContainers$/^container100$/snapshot-socket' \
    -run=Benchmark ./internal/benchmarks/... \
    -count 5
$ go tool pprof -top cpu.prof
$ go tool pprof -top mem.prof

Continuous Integration​

Inspektor Gadget uses GitHub Actions as CI. Please check dedicated CI documentation for more details.

Some integration tests (like AKS and ARO) are only run when a commit is pushed to the main branch or a new tag is pushed. It's also possible to run those by pusing a branch named citest/.... Please notice that the container images will be pushed to https://github.com/inspektor-gadget/inspektor-gadget/pkgs/container/inspektor-gadget and those should be manually cleaned up.

Documentation​

We kindly request that any contributions to the project also include updates to the respective portions of the documentation. This ensures that members of the community can easily learn about and utilize newly developed features.

Getting Help​

If you are having any issues with your contribution, or want to discuss anything about it, feel free to reach out to us on Slack or on our community meeting

Contribution Guidelines​

Code of Conduct​

Inspektor Gadget follows the CNCF Code of Conduct.

Authoring PRs​

For making PRs/commits consistent and easier to review, please check out Kinvolk's contribution guidelines on git.

We require all commits on a PR to be signed off certifying the Developer Certificate of Origin:

Developer Certificate of Origin
Version 1.1

Copyright (C) 2004, 2006 The Linux Foundation and its contributors.

Everyone is permitted to copy and distribute verbatim copies of this
license document, but changing it is not allowed.


Developer's Certificate of Origin 1.1

By making a contribution to this project, I certify that:

(a) The contribution was created in whole or in part by me and I
    have the right to submit it under the open source license
    indicated in the file; or

(b) The contribution is based upon previous work that, to the best
    of my knowledge, is covered under an appropriate open source
    license and I have the right under that license to submit that
    work with modifications, whether created in whole or in part
    by me, under the same open source license (unless I am
    permitted to submit under a different license), as indicated
    in the file; or

(c) The contribution was provided directly to me by some other
    person who certified (a), (b) or (c) and I have not modified
    it.

(d) I understand and agree that this project and the contribution
    are public and that a record of the contribution (including all
    personal information I submit with it, including my sign-off) is
    maintained indefinitely and may be redistributed consistent with
    this project or the open source license(s) involved.

It can be done by using git commit -s, git commit --sign-off or by manually adding a line like to the commit message.

Signed-off-by: Joe Smith <[email protected]>

Good first issues​

If you're looking where to start, you can check the issues with the good first issue label on Inspektor Gadget. Don't hesitate to talk to us if you need further help.

Proposing new features​

If you want to propose a new feature or do a big change in the architecture it's highly recommended to open an issue first to discuss it with the team.

Writing tests​

We use github.com/stretchr/testify to make tests less verbose.

Planning​

Our planning is published through two different project boards:

BCC​

Porting BCC gadgets​

This project uses some gadgets based on BCC. In the past, we modified the BCC gadgets and executed them from our process, however it was very inflexible and we decided to integrate those gadgets directly into our code base by rewriting their control plane in Golang.

If you want to implement support for a BCC gadget, please read the Rewriting the Control Plane of BCC Tools in Golang blogpost that contains all the details about this process.

Security​

For security, we invite you to take at look at the dedicated document.