Configure Gitaly (FREE SELF)

The Gitaly service itself is configured by using a TOML configuration file.

To change Gitaly settings:

For Omnibus GitLab

Edit /etc/gitlab/gitlab.rb and add or change the Gitaly settings.
Save the file and reconfigure GitLab.

For installations from source

Edit /home/git/gitaly/config.toml and add or change the Gitaly settings.
Save the file and restart GitLab.

The following configuration options are also available:

Enabling TLS support.
Configuring the number of gitaly-ruby workers.
Limiting RPC concurrency.

About the Gitaly token

The token referred to throughout the Gitaly documentation is just an arbitrary password selected by the administrator. It is unrelated to tokens created for the GitLab API or other similar web API tokens.

Run Gitaly on its own server

By default, Gitaly is run on the same server as Gitaly clients and is configured as above. Single-server installations are best served by this default configuration used by:

Omnibus GitLab.
The GitLab source installation guide.

However, Gitaly can be deployed to its own server, which can benefit GitLab installations that span multiple machines.

NOTE: When configured to run on their own servers, Gitaly servers must be upgraded before Gitaly clients in your cluster.

The process for setting up Gitaly on its own server is:

Install Gitaly.
Configure authentication.
Configure Gitaly servers.
Configure Gitaly clients.
Disable Gitaly where not required (optional).

When running Gitaly on its own server, note the following regarding GitLab versions:

From GitLab 11.4, Gitaly was able to serve all Git requests without requiring a shared NFS mount for Git repository data, except for the Elasticsearch indexer.
From GitLab 11.8, the Elasticsearch indexer also uses Gitaly for data access. NFS can still be leveraged for redundancy on block-level Git data, but should be mounted only on the Gitaly servers.
From GitLab 11.8 to 12.2, it is possible to use Elasticsearch in a Gitaly setup that doesn't use NFS. To use Elasticsearch in these versions, the repository indexer must be enabled in your GitLab configuration.
In GitLab 12.3 and later, the new indexer is the default and no configuration is required.

Network architecture

The following list depicts the network architecture of Gitaly:

GitLab Rails shards repositories into repository storages.
/config/gitlab.yml contains a map from storage names to (Gitaly address, Gitaly token) pairs.
The storage name -> (Gitaly address, Gitaly token) map in /config/gitlab.yml is the single source of truth for the Gitaly network topology.
A (Gitaly address, Gitaly token) corresponds to a Gitaly server.
A Gitaly server hosts one or more storages.
A Gitaly client can use one or more Gitaly servers.
Gitaly addresses must be specified in such a way that they resolve correctly for all Gitaly clients.
Gitaly clients are:
- Puma.
- Sidekiq.
- GitLab Workhorse.
- GitLab Shell.
- Elasticsearch indexer.
- Gitaly itself.
A Gitaly server must be able to make RPC calls to itself by using its own (Gitaly address, Gitaly token) pair as specified in /config/gitlab.yml.
Authentication is done through a static token which is shared among the Gitaly and GitLab Rails nodes.

The following digraph illustrates communication between Gitaly servers and GitLab Rails showing the default ports for HTTP and HTTPs communication.

WARNING: Gitaly servers must not be exposed to the public internet as Gitaly's network traffic is unencrypted by default. The use of firewall is highly recommended to restrict access to the Gitaly server. Another option is to use TLS.

In the following sections, we describe how to configure two Gitaly servers with secret token abc123secret:

gitaly1.internal.
gitaly2.internal.

We assume your GitLab installation has three repository storages:

default.
storage1.
storage2.

You can use as few as one server with one repository storage if desired.

Install Gitaly

Install Gitaly on each Gitaly server using either Omnibus GitLab or install it from source:

For Omnibus GitLab, download and install the Omnibus GitLab package you want but do not provide the EXTERNAL_URL= value.
To install from source, follow the steps at Install Gitaly.

Configure Gitaly servers

To configure Gitaly servers, you must:

Configure authentication.
Configure storage paths.
Enable the network listener.

The git user must be able to read, write, and set permissions on the configured storage path.

To avoid downtime while rotating Gitaly's token, you can temporarily disable authentication using the gitaly['auth_transitioning'] setting. For more information, see the documentation on enabling "auth transitioning mode".

Configure authentication

Gitaly and GitLab use two shared secrets for authentication:

Gitaly token: used to authenticate gRPC requests to Gitaly
GitLab Shell token: used for authentication callbacks from GitLab Shell to the GitLab internal API

For Omnibus GitLab

To configure the Gitaly token, edit /etc/gitlab/gitlab.rb:

gitaly['auth_token'] = 'abc123secret'

There are two ways to configure the GitLab Shell token.

Method 1 (recommended):

Copy /etc/gitlab/gitlab-secrets.json from the Gitaly client to same path on the Gitaly servers (and any other Gitaly clients).

Method 2:

Edit /etc/gitlab/gitlab.rb:

gitlab_shell['secret_token'] = 'shellsecret'

For installations from source

Copy /home/git/gitlab/.gitlab_shell_secret from the Gitaly client to the same path on the Gitaly servers (and any other Gitaly clients).
On the Gitaly clients, edit /home/git/gitlab/config/gitlab.yml:
```
gitlab:
  gitaly:
    token: 'abc123secret'
```
Save the file and restart GitLab.
On the Gitaly servers, edit /home/git/gitaly/config.toml:
```
[auth]
token = 'abc123secret'
```
Save the file and restart GitLab.

Configure Gitaly server

For Omnibus GitLab

Edit /etc/gitlab/gitlab.rb:

# Avoid running unnecessary services on the Gitaly server
postgresql['enable'] = false
redis['enable'] = false
nginx['enable'] = false
puma['enable'] = false
sidekiq['enable'] = false
gitlab_workhorse['enable'] = false
grafana['enable'] = false
gitlab_exporter['enable'] = false
gitlab_kas['enable'] = false

# If you run a separate monitoring node you can disable these services
prometheus['enable'] = false
alertmanager['enable'] = false

# If you don't run a separate monitoring node you can
# enable Prometheus access & disable these extra services.
# This makes Prometheus listen on all interfaces. You must use firewalls to restrict access to this address/port.
# prometheus['listen_address'] = '0.0.0.0:9090'
# prometheus['monitor_kubernetes'] = false

# If you don't want to run monitoring services uncomment the following (not recommended)
# node_exporter['enable'] = false

# Prevent database connections during 'gitlab-ctl reconfigure'
gitlab_rails['auto_migrate'] = false

# Configure the gitlab-shell API callback URL. Without this, `git push` will
# fail. This can be your 'front door' GitLab URL or an internal load
# balancer.
# Don't forget to copy `/etc/gitlab/gitlab-secrets.json` from Gitaly client to Gitaly server.
gitlab_rails['internal_api_url'] = 'https://gitlab.example.com'

# Make Gitaly accept connections on all network interfaces. You must use
# firewalls to restrict access to this address/port.
# Comment out following line if you only want to support TLS connections
gitaly['listen_addr'] = "0.0.0.0:8075"

# Authentication token to ensure only authorized servers can communicate with
# Gitaly server
gitaly['auth_token'] = 'AUTH_TOKEN'

Append the following to /etc/gitlab/gitlab.rb for each respective Gitaly server:

On gitaly1.internal:

git_data_dirs({
  'default' => {
    'path' => '/var/opt/gitlab/git-data'
  },
  'storage1' => {
    'path' => '/mnt/gitlab/git-data'
  },
})

On gitaly2.internal:

git_data_dirs({
  'storage2' => {
    'path' => '/srv/gitlab/git-data'
  },
})

Save the file and reconfigure GitLab.
Run sudo /opt/gitlab/embedded/bin/gitaly-hooks check /var/opt/gitlab/gitaly/config.toml to confirm that Gitaly can perform callbacks to the GitLab internal API.

For installations from source

Edit /home/git/gitaly/config.toml:

listen_addr = '0.0.0.0:8075'

runtime_dir = '/var/opt/gitlab/gitaly'

[logging]
format = 'json'
level = 'info'
dir = '/var/log/gitaly'

For GitLab 14.9 and earlier, set internal_socket_dir = '/var/opt/gitlab/gitaly' instead of runtime_dir.

Append the following to /home/git/gitaly/config.toml for each respective Gitaly server:

On gitaly1.internal:

[[storage]]
name = 'default'
path = '/var/opt/gitlab/git-data/repositories'

[[storage]]
name = 'storage1'
path = '/mnt/gitlab/git-data/repositories'

On gitaly2.internal:

[[storage]]
name = 'storage2'
path = '/srv/gitlab/git-data/repositories'

Edit /home/git/gitlab-shell/config.yml:
```
gitlab_url: https://gitlab.example.com
```
Save the files and restart GitLab.
Run sudo -u git /home/git/gitaly/gitaly-hooks check /home/git/gitaly/config.toml to confirm that Gitaly can perform callbacks to the GitLab internal API.

WARNING: If directly copying repository data from a GitLab server to Gitaly, ensure that the metadata file, default path /var/opt/gitlab/git-data/repositories/.gitaly-metadata, is not included in the transfer. Copying this file causes GitLab to use the Rugged patches for repositories hosted on the Gitaly server, leading to Error creating pipeline and Commit not found errors, or stale data.

Configure Gitaly clients

As the final step, you must update Gitaly clients to switch from using local Gitaly service to use the Gitaly servers you just configured.

NOTE: GitLab requires a default repository storage to be configured. Read more about this limitation.

This can be risky because anything that prevents your Gitaly clients from reaching the Gitaly servers causes all Gitaly requests to fail. For example, any sort of network, firewall, or name resolution problems.

Additionally, you must disable Rugged if previously enabled manually.

Gitaly makes the following assumptions:

Your gitaly1.internal Gitaly server can be reached at gitaly1.internal:8075 from your Gitaly clients, and that Gitaly server can read, write, and set permissions on /var/opt/gitlab/git-data and /mnt/gitlab/git-data.
Your gitaly2.internal Gitaly server can be reached at gitaly2.internal:8075 from your Gitaly clients, and that Gitaly server can read, write, and set permissions on /srv/gitlab/git-data.
Your gitaly1.internal and gitaly2.internal Gitaly servers can reach each other.

You can't define Gitaly servers with some as a local Gitaly server (without gitaly_address) and some as remote server (with gitaly_address) unless you use mixed configuration.

For Omnibus GitLab

Edit /etc/gitlab/gitlab.rb:

# Use the same token value configured on all Gitaly servers
gitlab_rails['gitaly_token'] = '<AUTH_TOKEN>'

git_data_dirs({
  'default'  => { 'gitaly_address' => 'tcp://gitaly1.internal:8075' },
  'storage1' => { 'gitaly_address' => 'tcp://gitaly1.internal:8075' },
  'storage2' => { 'gitaly_address' => 'tcp://gitaly2.internal:8075' },
})

Alternatively, if each Gitaly server is configured to use a different authentication token:

git_data_dirs({
  'default'  => { 'gitaly_address' => 'tcp://gitaly1.internal:8075', 'gitaly_token' => '<AUTH_TOKEN_1>' },
  'storage1' => { 'gitaly_address' => 'tcp://gitaly1.internal:8075', 'gitaly_token' => '<AUTH_TOKEN_1>' },
  'storage2' => { 'gitaly_address' => 'tcp://gitaly2.internal:8075', 'gitaly_token' => '<AUTH_TOKEN_2>' },
})

Save the file and reconfigure GitLab.
Run sudo gitlab-rake gitlab:gitaly:check on the Gitaly client (for example, the Rails application) to confirm it can connect to Gitaly servers.
Tail the logs to see the requests:
```
sudo gitlab-ctl tail gitaly
```

For installations from source

Edit /home/git/gitlab/config/gitlab.yml:

gitlab:
  repositories:
    storages:
      default:
        gitaly_address: tcp://gitaly1.internal:8075
        gitaly_token: AUTH_TOKEN_1
        path: /some/local/path
      storage1:
        gitaly_address: tcp://gitaly1.internal:8075
        gitaly_token: AUTH_TOKEN_1
        path: /some/local/path
      storage2:
        gitaly_address: tcp://gitaly2.internal:8075
        gitaly_token: AUTH_TOKEN_2
        path: /some/local/path

NOTE: /some/local/path should be set to a local folder that exists, however no data is stored in this folder. This requirement is scheduled to be removed when this issue is resolved.

Save the file and restart GitLab.
Run sudo -u git -H bundle exec rake gitlab:gitaly:check RAILS_ENV=production to confirm the Gitaly client can connect to Gitaly servers.
Tail the logs to see the requests:
```
tail -f /home/git/gitlab/log/gitaly.log
```

When you tail the Gitaly logs on your Gitaly server, you should see requests coming in. One sure way to trigger a Gitaly request is to clone a repository from GitLab over HTTP or HTTPS.

WARNING: If you have server hooks configured, either per repository or globally, you must move these to the Gitaly servers. If you have multiple Gitaly servers, copy your server hooks to all Gitaly servers.

Mixed configuration

GitLab can reside on the same server as one of many Gitaly servers, but doesn't support configuration that mixes local and remote configuration. The following setup is incorrect, because:

All addresses must be reachable from the other Gitaly servers.
storage1 is assigned a Unix socket for gitaly_address which is invalid for some of the Gitaly servers.

git_data_dirs({
  'default' => { 'gitaly_address' => 'tcp://gitaly1.internal:8075' },
  'storage1' => { 'path' => '/mnt/gitlab/git-data' },
  'storage2' => { 'gitaly_address' => 'tcp://gitaly2.internal:8075' },
})

To combine local and remote Gitaly servers, use an external address for the local Gitaly server. For example:

git_data_dirs({
  'default' => { 'gitaly_address' => 'tcp://gitaly1.internal:8075' },
  # Address of the GitLab server that also has Gitaly running on it
  'storage1' => { 'gitaly_address' => 'tcp://gitlab.internal:8075', 'path' => '/mnt/gitlab/git-data' },
  'storage2' => { 'gitaly_address' => 'tcp://gitaly2.internal:8075' },
})

# Make Gitaly accept connections on all network interfaces
gitaly['listen_addr'] = "0.0.0.0:8075"

# Or for TLS
gitaly['tls_listen_addr'] = "0.0.0.0:9999"
gitaly['certificate_path'] = "/etc/gitlab/ssl/cert.pem"
gitaly['key_path'] = "/etc/gitlab/ssl/key.pem"

path can be included only for storage shards on the local Gitaly server. If it's excluded, default Git storage directory is used for that storage shard.

GitLab requires a default repository storage

When adding Gitaly servers to an environment, you might want to replace the original default Gitaly service. However, you can't reconfigure the GitLab application servers to remove the default entry from git_data_dirs because GitLab requires a git_data_dirs entry called default. Read more about this limitation.

To work around the limitation:

Define an additional storage location on the new Gitaly service and configure the additional storage to be default.
In the Admin Area, set default to a weight of zero to prevent repositories being stored there.

Disable Gitaly where not required (optional)

If you run Gitaly as a remote service, consider disabling the local Gitaly service that runs on your GitLab server by default, and run it only where required.

Disabling Gitaly on the GitLab instance makes sense only when you run GitLab in a custom cluster configuration, where Gitaly runs on a separate machine from the GitLab instance. Disabling Gitaly on all machines in the cluster is not a valid configuration (some machines much act as Gitaly servers).

To disable Gitaly on a GitLab server:

For Omnibus GitLab

Edit /etc/gitlab/gitlab.rb:
```
gitaly['enable'] = false
```
Save the file and reconfigure GitLab.

For installations from source

Edit /etc/default/gitlab:
```
gitaly_enabled=false
```
Save the file and restart GitLab.

Enable TLS support

Introduced in GitLab 11.8.

Introduced in GitLab 13.6, outgoing TLS connections to GitLab provide client certificates if configured.

Gitaly supports TLS encryption. To communicate with a Gitaly instance that listens for secure connections, use the tls:// URL scheme in the gitaly_address of the corresponding storage entry in the GitLab configuration.

Gitaly provides the same server certificates as client certificates in TLS connections to GitLab. This can be used as part of a mutual TLS authentication strategy when combined with reverse proxies (for example, NGINX) that validate client certificate to grant access to GitLab.

You must supply your own certificates as this isn't provided automatically. The certificate corresponding to each Gitaly server must be installed on that Gitaly server.

Additionally, the certificate (or its certificate authority) must be installed on all:

Gitaly servers.
Gitaly clients that communicate with it.

Note the following:

The certificate must specify the address you use to access the Gitaly server. You must add the hostname or IP address as a Subject Alternative Name to the certificate.
You can configure Gitaly servers with both an unencrypted listening address listen_addr and an encrypted listening address tls_listen_addr at the same time. This allows you to gradually transition from unencrypted to encrypted traffic if necessary.

To configure Gitaly with TLS:

For Omnibus GitLab

Create certificates for Gitaly servers.
On the Gitaly clients, copy the certificates (or their certificate authority) into /etc/gitlab/trusted-certs:
```
sudo cp cert.pem /etc/gitlab/trusted-certs/
```

On the Gitaly clients, edit git_data_dirs in /etc/gitlab/gitlab.rb as follows:

git_data_dirs({
  'default' => { 'gitaly_address' => 'tls://gitaly1.internal:9999' },
  'storage1' => { 'gitaly_address' => 'tls://gitaly1.internal:9999' },
  'storage2' => { 'gitaly_address' => 'tls://gitaly2.internal:9999' },
})

Save the file and reconfigure GitLab.

On the Gitaly servers, create the /etc/gitlab/ssl directory and copy your key and certificate there:

sudo mkdir -p /etc/gitlab/ssl
sudo chmod 755 /etc/gitlab/ssl
sudo cp key.pem cert.pem /etc/gitlab/ssl/
sudo chmod 644 key.pem cert.pem

Copy all Gitaly server certificates (or their certificate authority) to /etc/gitlab/trusted-certs on all Gitaly servers and clients so that Gitaly servers and clients trust the certificate when calling into themselves or other Gitaly servers:
```
sudo cp cert1.pem cert2.pem /etc/gitlab/trusted-certs/
```

Edit /etc/gitlab/gitlab.rb and add:

gitaly['tls_listen_addr'] = "0.0.0.0:9999"
gitaly['certificate_path'] = "/etc/gitlab/ssl/cert.pem"
gitaly['key_path'] = "/etc/gitlab/ssl/key.pem"

Save the file and reconfigure GitLab.
Verify Gitaly traffic is being served over TLS by observing the types of Gitaly connections.
Optional. Improve security by:
1. Disabling non-TLS connections by commenting out or deleting gitaly['listen_addr'] in /etc/gitlab/gitlab.rb.
2. Saving the file.
3. Reconfiguring GitLab.

For installations from source

Create certificates for Gitaly servers.

On the Gitaly clients, copy the certificates into the system trusted certificates:

sudo cp cert.pem /usr/local/share/ca-certificates/gitaly.crt
sudo update-ca-certificates

On the Gitaly clients, edit storages in /home/git/gitlab/config/gitlab.yml as follows:

gitlab:
  repositories:
    storages:
      default:
        gitaly_address: tls://gitaly1.internal:9999
        path: /some/local/path
      storage1:
        gitaly_address: tls://gitaly1.internal:9999
        path: /some/local/path
      storage2:
        gitaly_address: tls://gitaly2.internal:9999
        path: /some/local/path

NOTE: /some/local/path should be set to a local folder that exists, however no data is stored in this folder. This requirement is scheduled to be removed when Gitaly issue #1282 is resolved.

Save the file and restart GitLab.
On the Gitaly servers, create or edit /etc/default/gitlab and add:
```
export SSL_CERT_DIR=/etc/gitlab/ssl
```

On the Gitaly servers, create the /etc/gitlab/ssl directory and copy your key and certificate there:

sudo mkdir -p /etc/gitlab/ssl
sudo chmod 755 /etc/gitlab/ssl
sudo cp key.pem cert.pem /etc/gitlab/ssl/
sudo chmod 644 key.pem cert.pem

Copy all Gitaly server certificates (or their certificate authority) to the system trusted certificates folder so Gitaly server trusts the certificate when calling into itself or other Gitaly servers.
```
sudo cp cert.pem /usr/local/share/ca-certificates/gitaly.crt
sudo update-ca-certificates
```

Edit /home/git/gitaly/config.toml and add:

tls_listen_addr = '0.0.0.0:9999'

[tls]
certificate_path = '/etc/gitlab/ssl/cert.pem'
key_path = '/etc/gitlab/ssl/key.pem'

Save the file and restart GitLab.
Verify Gitaly traffic is being served over TLS by observing the types of Gitaly connections.
Optional. Improve security by:
1. Disabling non-TLS connections by commenting out or deleting listen_addr in /home/git/gitaly/config.toml.
2. Saving the file.
3. Restarting GitLab.

Observe type of Gitaly connections

For information on observing the type of Gitaly connections being served, see the relevant documentation.

`gitaly-ruby`

Gitaly was developed to replace the Ruby application code in GitLab.

To save time and avoid the risk of rewriting existing application logic, we chose to copy some application code from GitLab into Gitaly.

To be able to run that code, gitaly-ruby was created, which is a "sidecar" process for the main Gitaly Go process. Some examples of things that are implemented in gitaly-ruby are:

RPCs that deal with wikis.
RPCs that create commits on behalf of a user, such as merge commits.

We recommend:

At least 300 MB memory per worker.
No more than one worker per core.

NOTE: gitaly-ruby is planned to be eventually removed. To track progress, see the Remove the Gitaly-Ruby sidecar epic.

Configure number of `gitaly-ruby` workers

gitaly-ruby has much less capacity than Gitaly implemented in Go. If your Gitaly server has to handle lots of requests, the default setting of having just one active gitaly-ruby sidecar might not be enough.

If you see ResourceExhausted errors from Gitaly, it's very likely that you have not enough gitaly-ruby capacity.

You can increase the number of gitaly-ruby processes on your Gitaly server with the following settings:

For Omnibus GitLab

Edit /etc/gitlab/gitlab.rb:

# Default is 2 workers. The minimum is 2; 1 worker is always reserved as
# a passive stand-by.
gitaly['ruby_num_workers'] = 4

Save the file, and then reconfigure GitLab.

For installations from source

Edit /home/git/gitaly/config.toml:
```
[gitaly-ruby]
num_workers = 4
```
Save the file and restart GitLab.

Limit RPC concurrency

Clone traffic can put a large strain on your Gitaly service. The bulk of the work gets done in the either of the following RPCs:

SSHUploadPackWithSidechannel (for Git SSH).
PostUploadPackWithSidechannel (for Git HTTP).

To prevent such workloads from overwhelming your Gitaly server, you can set concurrency limits in Gitaly's configuration file. For example:

# in /etc/gitlab/gitlab.rb

gitaly['concurrency'] = [
  {
    'rpc' => "/gitaly.SmartHTTPService/PostUploadPackWithSidechanel",
    'max_per_repo' => 20,
    'max_queue_time' => "1s",
    'max_queue_size' => 10
  },
  {
    'rpc' => "/gitaly.SSHService/SSHUploadPackWithSidechannel",
    'max_per_repo' => 20
    'max_queue_time' => "1s",
    'max_queue_size' => 10
  }
]

rpc is the name of the RPC to set a concurrency limit for per repository.
max_per_repo is the maximum number of in-flight RPC calls for the given RPC per repository.
max_queue_time is the maximum amount of time a request can wait in the concurrency queue to be picked up by Gitaly.
max_queue_size is the maximum size the concurrency queue can grow to before requests are rejected by Gitaly.

This limits the number of in-flight RPC calls for the given RPCs. The limit is applied per repository. In the example above:

Each repository served by the Gitaly server can have at most 20 simultaneous PostUploadPackWithSidechannel and SSHUploadPackWithSidechannel RPC calls in flight.
If another request comes in for a repository that has used up its 20 slots, that request gets queued.
If a request waits in the queue for more than 1 second, it is rejected with an error.
If the queue grows beyond 10, subsequent requests are rejected with an error.

You can observe the behavior of this queue using the Gitaly logs and Prometheus. For more information, see the relevant documentation.

Control groups

FLAG: On self-managed GitLab, by default cgroups are not available. To make it available, ask an administrator to enable the feature flag named gitaly_run_cmds_in_cgroup.

Gitaly shells out to Git for many of its operations. Git can consume a lot of resources for certain operations, especially for large repositories.

Control groups (cgroups) in Linux allow limits to be imposed on how much memory and CPU can be consumed. See the cgroups Linux man page for more information. cgroups can be useful for protecting the system against resource exhaustion because of overcomsumption of memory and CPU.

Gitaly has built-in cgroups control. When configured, Gitaly assigns Git processes to a cgroup based on the repository the Git command is operating in. Each cgroup has a memory and CPU limit. When a cgroup reaches its:

Memory limit, the kernel looks through the processes for a candidate to kill.
CPU limit, processes are not killed, but the processes are prevented from consuming more CPU than allowed.

The main reason to configure cgroups for your GitLab installation is that it protects against system resource starvation due to a few large repositories or bad actors.

Some Git operations are expensive by nature. git clone, for instance, spawns a git-upload-pack process on the server that can consume a lot of memory for large repositories. For example, a client that keeps on cloning a large repository over and over again. This situation could potentially use up all of the memory on a server, causing other operations to fail for other users.

There are many ways someone can create a repository that can consume large amounts of memory when cloned or downloaded. Using cgroups allows the kernel to kill these operations before they hog up all system resources.

Configure cgroups in Gitaly

Two ways of configuring cgroups are available.

Configure cgroups (new method)

This method of configuring cgroups introduced in GitLab 15.1.

Gitaly creates a pool of cgroups that are isolated based on the repository used in the Git command to be placed under one of these cgroups.

To configure cgroups in Gitaly, add gitaly['cgroups'] to /etc/gitlab/gitlab.rb.

For example:

# in /etc/gitlab/gitlab.rb
gitaly['cgroups_mountpoint'] = "/sys/fs/cgroup"
gitaly['cgroups_hierarchy_root'] =>"gitaly"
gitaly['cgroups_memory_bytes'] = 64424509440,  # 60gb
gitaly['cgroups_cpu_shares'] = 1024
gitaly['cgroups_repositories_count'] => 1000,
gitaly['cgroups_repositories_memory_bytes'] => 32212254720 # 20gb
gitaly['cgroups_repositories_cpu_shares'] => 512

cgroups_mountpoint is where the parent cgroup directory is mounted. Defaults to /sys/fs/cgroup.
cgroups_hierarchy_root is the parent cgroup under which Gitaly creates groups, and is expected to be owned by the user and group Gitaly runs as. Omnibus GitLab creates the set of directories mountpoint/<cpu|memory>/hierarchy_root when Gitaly starts.
cgroups_memory_bytes is the total memory limit that is imposed collectively on all Git processes that Gitaly spawns. 0 implies no limit.
cgroups_cpu_shares is the cpu limit that is imposed collectively on all Git processes that Gitaly spawns. 0 implies no limit. The maximum is 1024 shares, which represents 100% of CPU.
cgroups_repositories_count is the number of cgroups in the cgroups pool. Each time a new Git command is spawned, Gitaly assigns it to one of these cgroups based on the repository the command is for. A circular hashing algorithm assigns Git commands to these cgroups, so a Git command for a repository is always assigned to the same cgroup.
cgroups_repositories_memory_bytes is the total memory limit that is imposed collectively on all Git processes that Gitaly spawns. 0 implies no limit. This value cannot exceed that of the top level cgroups_memory_bytes.
cgroups_repositories_cpu_shares is the CPU limit that is imposed collectively on all Git processes Gitaly spawns. 0 implies no limit. The maximum is 1024 shares, which represents 100% of CPU. This value cannot exceed that of the top levelcgroups_cpu_shares.

Configure cgroups (legacy method)

To configure cgroups in Gitaly for GitLab versions using the legacy method, add gitaly['cgroups'] to /etc/gitlab/gitlab.rb. For example:

# in /etc/gitlab/gitlab.rb
gitaly['cgroups_count'] = 1000
gitaly['cgroups_mountpoint'] = "/sys/fs/cgroup"
gitaly['cgroups_hierarchy_root'] = "gitaly"
gitaly['cgroups_memory_limit'] = 32212254720
gitaly['cgroups_memory_enabled'] = true
gitaly['cgroups_cpu_shares'] = 1024
gitaly['cgroups_cpu_enabled'] = true

cgroups_count is the number of cgroups created. Each time a new command is spawned, Gitaly assigns it to one of these cgroups based on the command line arguments of the command. A circular hashing algorithm assigns commands to these cgroups.
cgroups_mountpoint is where the parent cgroup directory is mounted. Defaults to /sys/fs/cgroup.
cgroups_hierarchy_root is the parent cgroup under which Gitaly creates groups, and is expected to be owned by the user and group Gitaly runs as. Omnibus GitLab creates the set of directories mountpoint/<cpu|memory>/hierarchy_root when Gitaly starts.
cgroups_memory_enabled enables or disables the memory limit on cgroups.
cgroups_memory_bytes is the total memory limit each cgroup imposes on the processes added to it.
cgroups_cpu_enabled enables or disables the CPU limit on cgroups.
cgroups_cpu_shares is the CPU limit each cgroup imposes on the processes added to it. The maximum is 1024 shares, which represents 100% of CPU.

Configuring oversubscription

In the previous example using the new configuration method:

The top level memory limit is capped at 60gb.
Each of the 1000 cgroups in the repositories pool is capped at 20gb.

This is called "oversubscription". Each cgroup in the pool has a much larger capacity than 1/1000th of the top-level memory limit.

This strategy has two main benefits:

It gives the host protection from overall memory starvation (OOM), because the top-level cgroup's memory limit can be set to a threshold smaller than the host's capacity. Processes outside of that cgroup are not at risk of OOM.
It allows each individual cgroup in the pool to burst up to a generous upper bound (in this example 20 GB) that is smaller than the parent cgroup's limit, but substantially larger than 1/N of the parent's limit. In this example, up to 3 child cgroups can concurrently burst up to their max. In general, all 1000 cgroups would use much less than the 20 GB.

Background Repository Optimization

Empty directories and unneeded configuration settings may accumulate in a repository and slow down Git operations. Gitaly can schedule a daily background task with a maximum duration to clean up these items and improve performance.

WARNING: This is an experimental feature and may place significant load on the host while running. Make sure to schedule this during off-peak hours and keep the duration short (for example, 30-60 minutes).

For Omnibus GitLab

Edit /etc/gitlab/gitlab.rb and add:

gitaly['daily_maintenance_start_hour'] = 4
gitaly['daily_maintenance_start_minute'] = 30
gitaly['daily_maintenance_duration'] = '30m'
gitaly['daily_maintenance_storages'] = ["default"]

For installations from source

Edit /home/git/gitaly/config.toml and add:

[daily_maintenance]
start_hour = 4
start_minute = 30
duration = '30m'
storages = ["default"]

Rotate Gitaly authentication token

Rotating credentials in a production environment often requires downtime, causes outages, or both.

However, you can rotate Gitaly credentials without a service interruption. Rotating a Gitaly authentication token involves:

Verifying authentication monitoring.
Enabling "auth transitioning" mode.
Updating Gitaly authentication tokens.
Ensuring there are no authentication failures.
Disabling "auth transitioning" mode.
Verifying authentication is enforced.

This procedure also works if you are running GitLab on a single server. In that case, "Gitaly server" and "Gitaly client" refers to the same machine.

Verify authentication monitoring

Before rotating a Gitaly authentication token, verify that you can monitor the authentication behavior of your GitLab installation using Prometheus.

You can then continue the rest of the procedure.

Enable "auth transitioning" mode

Temporarily disable Gitaly authentication on the Gitaly servers by putting them into "auth transitioning" mode as follows:

# in /etc/gitlab/gitlab.rb
gitaly['auth_transitioning'] = true

After you have made this change, your Prometheus query should return something like:

{enforced="false",status="would be ok"}  4424.985419441742

Because enforced="false", it is safe to start rolling out the new token.

Update Gitaly authentication token

To update to a new Gitaly authentication token, on each Gitaly client and Gitaly server:

Update the configuration:

# in /etc/gitlab/gitlab.rb

gitaly['auth_token'] = '<new secret token>'

Restart Gitaly:
```
gitlab-ctl restart gitaly
```

If you run your Prometheus query while this change is being rolled out, you see non-zero values for the enforced="false",status="denied" counter.

Ensure there are no authentication failures

After the new token is set, and all services involved have been restarted, you will temporarily see a mix of:

status="would be ok".
status="denied".

After the new token is picked up by all Gitaly clients and Gitaly servers, the only non-zero rate should be enforced="false",status="would be ok".

Disable "auth transitioning" mode

To re-enable Gitaly authentication, disable "auth transitioning" mode. Update the configuration on your Gitaly servers as follows:

# in /etc/gitlab/gitlab.rb
gitaly['auth_transitioning'] = false

WARNING: Without completing this step, you have no Gitaly authentication.

Verify authentication is enforced

Refresh your Prometheus query. You should now see a similar result as you did at the start. For example:

{enforced="true",status="ok"}  4424.985419441742

enforced="true" means that authentication is being enforced.

Pack-objects cache (FREE SELF)

Introduced in GitLab 13.11.

It's enabled on GitLab.com.

It's recommended for production use.

Gitaly, the service that provides storage for Git repositories, can be configured to cache a short rolling window of Git fetch responses. This can reduce server load when your server receives lots of CI fetch traffic.

Overview

The pack-objects cache wraps git pack-objects, an internal part of Git that gets invoked indirectly via the PostUploadPack and SSHUploadPack Gitaly RPCs. These are the RPCs that Gitaly runs when a user does a Git fetch via HTTP or SSH, respectively. When the cache is enabled, anything that uses PostUploadPack or SSHUploadPack can benefit from it. It is orthogonal to:

The transport (HTTP or SSH).
Git protocol version (v0 or v2).
The type of fetch (full clones, incremental fetches, shallow clones, partial clones, and so on).

The strength of this cache is its ability to deduplicate concurrent identical fetches. It:

Can benefit GitLab instances where your users run CI/CD pipelines with many concurrent jobs. There should be a noticeable reduction in server CPU utilization.
Does not benefit unique fetches at all. For example, if you run a spot check by cloning a repository to your local computer, you are unlikely to see a benefit from this cache because your fetch is probably unique.

The pack-objects cache is a local cache. It:

Stores its metadata in the memory of the Gitaly process it is enabled in.
Stores the actual Git data it is caching in files on local storage.

Using local files has the benefit that the operating system may automatically keep parts of the pack-objects cache files in RAM, making it faster.

Because the pack-objects cache can lead to a significant increase in disk write IO, it is off by default.

Configure the cache

These are the configuration settings for the pack-objects cache. Each setting is discussed in greater detail below.

Setting	Default	Description
`enabled`	`false`	Turns on the cache. When off, Gitaly runs a dedicated `git pack-objects` process for each request.
`dir`	`<PATH TO FIRST STORAGE>/+gitaly/PackObjectsCache`	Local directory where cache files get stored.
`max_age`	`5m` (5 minutes)	Cache entries older than this get evicted and removed from disk.

In /etc/gitlab/gitlab.rb, set:

gitaly['pack_objects_cache_enabled'] = true
## gitaly['pack_objects_cache_dir'] = '/var/opt/gitlab/git-data/repositories/+gitaly/PackObjectsCache'
## gitaly['pack_objects_cache_max_age'] = '5m'

`enabled` defaults to `false`

The cache is disabled by default. This is because in some cases, it can create an extreme increase in the number of bytes written to disk. On GitLab.com, we have verified that our repository storage disks can handle this extra workload, but we felt we cannot assume this is true everywhere.

Cache storage directory `dir`

The cache needs a directory to store its files in. This directory should be:

In a file system with enough space. If the cache file system runs out of space, all fetches start failing.
On a disk with enough IO bandwidth. If the cache disk runs out of IO bandwidth, all fetches, and probably the entire server, slows down.

By default, the cache storage directory is set to a subdirectory of the first Gitaly storage defined in the configuration file.

Multiple Gitaly processes can use the same directory for cache storage. Each Gitaly process uses a unique random string as part of the cache filenames it creates. This means:

They do not collide.
They do not reuse another process's files.

While the default directory puts the cache files in the same file system as your repository data, this is not requirement. You can put the cache files on a different file system if that works better for your infrastructure.

The amount of IO bandwidth required from the disk depends on:

The size and shape of the repositories on your Gitaly server.
The kind of traffic your users generate.

You can use the gitaly_pack_objects_generated_bytes_total metric as a pessimistic estimate, pretending your cache hit ratio is 0%.

The amount of space required depends on:

The bytes per second that your users pull from the cache.
The size of the max_age cache eviction window.

If your users pull 100 MB/s and you use a 5 minute window, then on average you have 5*60*100MB = 30GB of data in your cache directory. This is an expected average, not a guarantee. Peak size may exceed this average.

Cache eviction window `max_age`

The max_age configuration setting lets you control the chance of a cache hit and the average amount of storage used by cache files. Entries older than max_age get evicted from the in-memory metadata store, and deleted from disk.

Eviction does not interfere with ongoing requests, so it is OK for max_age to be less than the time it takes to do a fetch over a slow connection. This is because Unix filesystems do not truly delete a file until all processes that are reading the deleted file have closed it.

Observe the cache

The cache can be observed using metrics and in the following logged information:

Message	Fields	Description
`generated bytes`	`bytes`, `cache_key`	Logged when an entry was added to the cache
`served bytes`	`bytes`, `cache_key`	Logged when an entry was read from the cache

In the case of a:

Cache miss, Gitaly logs both a generated bytes and a served bytes message.
Cache hit, Gitaly logs only a served bytes message.

Example:

{
  "bytes":26186490,
  "cache_key":"1b586a2698ca93c2529962e85cda5eea8f0f2b0036592615718898368b462e19",
  "correlation_id":"01F1MY8JXC3FZN14JBG1H42G9F",
  "grpc.meta.deadline_type":"none",
  "grpc.method":"PackObjectsHook",
  "grpc.request.fullMethod":"/gitaly.HookService/PackObjectsHook",
  "grpc.request.glProjectPath":"root/gitlab-workhorse",
  "grpc.request.glRepository":"project-2",
  "grpc.request.repoPath":"@hashed/d4/73/d4735e3a265e16eee03f59718b9b5d03019c07d8b6c51f90da3a666eec13ab35.git",
  "grpc.request.repoStorage":"default",
  "grpc.request.topLevelGroup":"@hashed",
  "grpc.service":"gitaly.HookService",
  "grpc.start_time":"2021-03-25T14:57:52.747Z",
  "level":"info",
  "msg":"generated bytes",
  "peer.address":"@",
  "pid":20961,
  "span.kind":"server",
  "system":"grpc",
  "time":"2021-03-25T14:57:53.543Z"
}
{
  "bytes":26186490,
  "cache_key":"1b586a2698ca93c2529962e85cda5eea8f0f2b0036592615718898368b462e19",
  "correlation_id":"01F1MY8JXC3FZN14JBG1H42G9F",
  "grpc.meta.deadline_type":"none",
  "grpc.method":"PackObjectsHook",
  "grpc.request.fullMethod":"/gitaly.HookService/PackObjectsHook",
  "grpc.request.glProjectPath":"root/gitlab-workhorse",
  "grpc.request.glRepository":"project-2",
  "grpc.request.repoPath":"@hashed/d4/73/d4735e3a265e16eee03f59718b9b5d03019c07d8b6c51f90da3a666eec13ab35.git",
  "grpc.request.repoStorage":"default",
  "grpc.request.topLevelGroup":"@hashed",
  "grpc.service":"gitaly.HookService",
  "grpc.start_time":"2021-03-25T14:57:52.747Z",
  "level":"info",
  "msg":"served bytes",
  "peer.address":"@",
  "pid":20961,
  "span.kind":"server",
  "system":"grpc",
  "time":"2021-03-25T14:57:53.543Z"
}

Repository consistency checks

Gitaly runs repository consistency checks:

When triggering a repository check.
When changes are fetched from a mirrored repository.
When users push changes into repository.

These consistency checks verify that a repository has all required objects and that these objects are valid objects. They can be categorized as:

Basic checks that assert that a repository doesn't become corrupt. This includes connectivity checks and checks that objects can be parsed.
Security checks that recognize objects that are suitable to exploit past security-related bugs in Git.
Cosmetic checks that verify that all object metadata is valid. Older Git versions and other Git implementations may have produced objects with invalid metadata, but newer versions can interpret these malformed objects.

Removing malformed objects that fail the consistency checks requires a rewrite of the repository's history, which often can't be done. Therefore, Gitaly by default disables consistency checks for a range of cosmetic issues that don't negatively impact repository consistency.

By default, Gitaly doesn't disable basic or security-related checks so to not distribute objects that can trigger known vulnerabilities in Git clients. This also limits the ability to import repositories containing such objects even if the project doesn't have malicious intent.

Override repository consistency checks

Instance administrators can override consistency checks if they must process repositories that do not pass consistency checks.

For Omnibus GitLab installations, edit /etc/gitlab/gitlab.rb and set the following keys (in this example, to disable the hasDotgit consistency check):

ignored_git_errors = ["hasDotgit = ignore"]
omnibus_gitconfig['system'] = {
        "fsck" => ignored_git_errors,
        "fetch.fsck" => ignored_git_errors,
        "receive.fsck" => ignored_git_errors,
}

For source installs, edit the Gitaly configuration (gitaly.toml) to do the equivalent:

[[git.config]]
key = "fsck.hasDotgit"
value = "ignore"

[[git.config]]
key = "fetch.fsck.hasDotgit"
value = "ignore"

[[git.config]]
key = "receive.fsck.hasDotgit"
value = "ignore"

Configure Gitaly (FREE SELF)

About the Gitaly token

Run Gitaly on its own server

Network architecture

Install Gitaly

Configure Gitaly servers

Configure authentication

Configure Gitaly server

Configure Gitaly clients

Mixed configuration

GitLab requires a default repository storage

Disable Gitaly where not required (optional)

Enable TLS support

Observe type of Gitaly connections

gitaly-ruby

Configure number of gitaly-ruby workers

Limit RPC concurrency

Control groups

Configure cgroups in Gitaly

Configure cgroups (new method)

Configure cgroups (legacy method)

Configuring oversubscription

Background Repository Optimization

Rotate Gitaly authentication token

Verify authentication monitoring

Enable "auth transitioning" mode

Update Gitaly authentication token

Ensure there are no authentication failures

Disable "auth transitioning" mode

Verify authentication is enforced

Pack-objects cache (FREE SELF)

Overview

Configure the cache

enabled defaults to false

Cache storage directory dir

Cache eviction window max_age

Observe the cache

Repository consistency checks

Override repository consistency checks

`gitaly-ruby`

Configure number of `gitaly-ruby` workers

`enabled` defaults to `false`

Cache storage directory `dir`

Cache eviction window `max_age`