135 lines
5.6 KiB
Markdown
135 lines
5.6 KiB
Markdown
# GitLab Developers Guide to Working with Gitaly
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[Gitaly](https://gitlab.com/gitlab-org/gitaly) is a high-level Git RPC service used by GitLab CE/EE,
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Workhorse and GitLab-Shell.
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## Developing new Git features
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Starting with GitLab 10.8, all new Git features should be developed in
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Gitaly.
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> This is a new process that is not clearly defined yet. If you want
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to contribute a Git feature and you're getting stuck, reach out to the
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Gitaly team or `@jacobvosmaer-gitlab`.
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By 'new feature' we mean any method or class in `lib/gitlab/git` that is
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called from outside `lib/gitlab/git`. For new methods that are called
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from inside `lib/gitlab/git`, see 'Modifying existing Git features'
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below.
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There should be no new code that touches Git repositories via
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disk access (e.g. Rugged, `git`, `rm -rf`) anywhere outside
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`lib/gitlab/git`.
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The process for adding new Gitaly features is:
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- exploration / prototyping
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- design and create a new Gitaly RPC [in gitaly-proto](https://gitlab.com/gitlab-org/gitaly-proto)
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- release a new version of gitaly-proto
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- write implementation and tests for the RPC [in Gitaly](https://gitlab.com/gitlab-org/gitaly), in Go or Ruby
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- release a new version of Gitaly
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- write client code in gitlab-ce/ee, gitlab-workhorse or gitlab-shell that calls the new Gitaly RPC
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These steps often overlap. It is possible to use an unreleased version
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of Gitaly and gitaly-proto during testing and development.
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- See the [Gitaly repo](https://gitlab.com/gitlab-org/gitaly/blob/master/CONTRIBUTING.md#development-and-testing-with-a-custom-gitaly-proto) for instructions on writing server side code with an unreleased protocol.
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- See [below](#running-tests-with-a-locally-modified-version-of-gitaly) for instructions on running gitlab-ce tests with a modified version of Gitaly.
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- In GDK run `gdk install` and restart `gdk run` (or `gdk run app`) to use a locally modified Gitaly version for development
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### Gitaly-ruby
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It is possible to implement and test RPC's in Gitaly using Ruby code,
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in
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[gitaly-ruby](https://gitlab.com/gitlab-org/gitaly/tree/master/ruby).
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This should make it easier to contribute for developers who are less
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comfortable writing Go code.
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There is documentation for this approach in [the Gitaly
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repo](https://gitlab.com/gitlab-org/gitaly/blob/master/doc/ruby_endpoint.md).
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## Gitaly-Related Test Failures
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If your test-suite is failing with Gitaly issues, as a first step, try running:
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```shell
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rm -rf tmp/tests/gitaly
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```
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## `TooManyInvocationsError` errors
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During development and testing, you may experience `Gitlab::GitalyClient::TooManyInvocationsError` failures.
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The `GitalyClient` will attempt to block against potential n+1 issues by raising this error
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when Gitaly is called more than 30 times in a single Rails request or Sidekiq execution.
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As a temporary measure, export `GITALY_DISABLE_REQUEST_LIMITS=1` to suppress the error. This will disable the n+1 detection
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in your development environment.
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Please raise an issue in the GitLab CE or EE repositories to report the issue. Include the labels ~Gitaly
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~performance ~"technical debt". Please ensure that the issue contains the full stack trace and error message of the
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`TooManyInvocationsError`. Also include any known failing tests if possible.
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Isolate the source of the n+1 problem. This will normally be a loop that results in Gitaly being called for each
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element in an array. If you are unable to isolate the problem, please contact a member
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of the [Gitaly Team](https://gitlab.com/groups/gl-gitaly/group_members) for assistance.
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Once the source has been found, wrap it in an `allow_n_plus_1_calls` block, as follows:
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```ruby
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# n+1: link to n+1 issue
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Gitlab::GitalyClient.allow_n_plus_1_calls do
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# original code
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commits.each { |commit| ... }
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end
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```
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Once the code is wrapped in this block, this code-path will be excluded from n+1 detection.
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## Request counts
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Commits and other git data, is now fetched through Gitaly. These fetches can,
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much like with a database, be batched. This improves performance for the client
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and for Gitaly itself and therefore for the users too. To keep performance stable
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and guard performance regressions, Gitaly calls can be counted and the call count
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can be tested against. This requires the `:request_store` flag to be set.
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```ruby
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describe 'Gitaly Request count tests' do
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context 'when the request store is activated', :request_store do
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it 'correctly counts the gitaly requests made' do
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expect { subject }.to change { Gitlab::GitalyClient.get_request_count }.by(10)
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end
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end
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end
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```
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## Running tests with a locally modified version of Gitaly
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Normally, gitlab-ce/ee tests use a local clone of Gitaly in
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`tmp/tests/gitaly` pinned at the version specified in
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`GITALY_SERVER_VERSION`. The `GITALY_SERVER_VERSION` file supports
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`=my-branch` syntax to use a custom branch in gitlab-org/gitaly. If
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you want to run tests locally against a modified version of Gitaly you
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can replace `tmp/tests/gitaly` with a symlink. This is much faster
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because the `=my-branch` syntax forces a Gitaly re-install each time
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you run `rspec`.
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```shell
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rm -rf tmp/tests/gitaly
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ln -s /path/to/gitaly tmp/tests/gitaly
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```
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Make sure you run `make` in your local Gitaly directory before running
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tests. Otherwise, Gitaly will fail to boot.
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If you make changes to your local Gitaly in between test runs you need
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to manually run `make` again.
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Note that CI tests will not use your locally modified version of
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Gitaly. To use a custom Gitaly version in CI you need to update
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GITALY_SERVER_VERSION. You can use the format `=revision` to use a
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non-tagged commit from https://gitlab.com/gitlab-org/gitaly in CI.
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---
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[Return to Development documentation](README.md)
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