Contributing to Cockroach

Getting and building

Assumed

A working C++ compiler (on mac os x something like xcode-select --install will get you started). The compiler must support C++11 (GCC 4.9+ and clang 3.6+ are known to work).
Go environment. Currently a 64-bit version of go 1.5 is required.
Git 1.8+ and Mercurial (for retrieving dependencies).

If you're on Mac OS X, homebrew can be very helpful to fulfill these dependencies.

You can go get -d github.com/cockroachdb/cockroach or, alternatively,

mkdir -p $GOPATH/src/github.com/cockroachdb/
cd $GOPATH/src/github.com/cockroachdb/
git clone git@github.com:cockroachdb/cockroach.git
cd cockroach

Now you should be all set for make build, make test and everything else our Makefile has to offer. Note that the first time you run make various dependent libraries and tools will be downloaded and installed which can be somewhat time consuming. Be patient.

Note that if you edit a .proto or .ts file, you will need to manually regenerate the associated .pb.{go,cc,h} or .js files using go generate ./.... go generate requires a collection of node modules which are installed via npm. If you don't have npm, it typically comes with node. To get it via homebrew: brew install node If you're not using homebrew, make sure you install both node.js and npm. If you plan on working on the UI, check out the ui readme.

To add or update a go dependency:

(cd $GOPATH/src && go get -u ./...) to update the dependencies or go get {package} to add a dependency
glock save github.com/cockroachdb/cockroach to update the GLOCKFILE
go generate ./... to update generated files
create a PR with all the changes

Style guide

We're following the Google Go Code Review fairly closely. In particular, you want to watch out for proper punctuation and capitalization in comments. We use two-space indents in non-Go code (in Go, we follow gofmt which indents with tabs). Format your code assuming it will be read in a window 100 columns wide. Wrap code and comments at 100 characters unless doing so makes the code less legible.

Code review workflow

All contributors need to sign the Contributor License Agreement.
Create a local feature branch to do work on, ideally on one thing at a time. If you are working on your own fork, see this tip on forking in Go, which ensures that Go import paths will be correct.

git checkout -b update-readme

Hack away and commit your changes locally using git add and git commit. Remember to write tests! The following are helpful for running specific subsets of tests:

make test
# Run all tests in ./storage
make test PKG=./storage
# Run all kv tests matching `^TestFoo` with a timeout of 10s
make test PKG=./kv TESTS='^TestFoo' TESTTIMEOUT=10s

When you're ready to commit, do just that with a succinct title and informative message. For example,

$ git commit
> 'update CONTRIBUTING.md
>
> Added details on running specific tests via `make`, and
> the CircleCI-equivalent test suite.
>
> Fixed some formatting.'

Run the whole CI test suite locally: ./build/circle-local.sh. This requires the Docker setup; if you don't have/want that, go generate ./... && make check test testrace is a good first approximation.
When you’re ready for review, groom your work: each commit should pass tests and contain a substantial (but not overwhelming) unit of work. You may also want to git fetch origin and run git rebase -i --exec "make check test" origin/master to make sure you're submitting your changes on top of the newest version of our code. Next, push to your fork:

git push -u <yourfork> update-readme
Then create a pull request using GitHub’s UI.
If you get a test failure in CircleCI, check the Test Failure tab to see why the test failed. When the failure is logged in excerpt.txt, you can find the file from the Artifacts tab and see log messages. (You need to sign in to see the Artifacts tab.)
Address feedback in new commits. Wait (or ask) for new feedback on those commits if they are not straightforward. An LGTM ("looks good to me") by someone qualified is usually posted when you're free to go ahead and merge. Most new contributors aren't allowed to merge themselves; in that case, we'll do it for you. You may also be asked to re-groom your commits.

Debugging

Peeking into a running cluster can be done in several ways:

the net/trace endpoint at /debug/requests. It has a breakdown of the recent traced requests, in particularly slow ones. Two families are traced: node and coord, the former (and likely more interesting one) containing what happens inside of Node/Store/Replica and the other inside of the coordinator (TxnCoordSender).
pprof gives us (among other things) heap and cpu profiles; this golang blog post explains it extremely well and this one by Dmitry Vuykov goes into even more detail. Two caveats: the cockroach binary passed to pprof must be the same as the one creating the profile (not true on OSX in acceptance tests!), and the HTTP client used by pprof doesn't simply swallow self-signed certs (relevant when using SSL). For the latter, a workaround of the form
```
go tool pprof cockroach <(curl -k https://$(hostname):26257/debug/pprof/profile)
```
will do the trick.

An easy way to locally run a workload against a cluster are the acceptance tests. For example,

make acceptance TESTS='TestPut$$' TESTFLAGS='-v -d 1200s -l .' TESTTIMEOUT=1210s

runs the Put acceptance test for 20 minutes with logging (useful to look at the stacktrace in case of a node dying). When it starts, all the relevant commands for pprof, trace and logs are logged to allow for convenient inspection of the cluster.

cockroachdb/cockroach