58 KiB
stage | group | info |
---|---|---|
Systems | Gitaly | To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments |
Configure Gitaly Cluster (FREE SELF)
Configure Gitaly Cluster using either:
- Gitaly Cluster configuration instructions available as part of reference architectures for installations of up to:
- The custom configuration instructions that follow on this page.
Smaller GitLab installations may need only Gitaly itself.
Requirements
The minimum recommended configuration for a Gitaly Cluster requires:
- 1 load balancer
- 1 PostgreSQL server (PostgreSQL 11 or newer)
- 3 Praefect nodes
- 3 Gitaly nodes (1 primary, 2 secondary)
See the design document for implementation details.
NOTE: If not set in GitLab, feature flags are read as false from the console and Praefect uses their default value. The default value depends on the GitLab version.
Network latency and connectivity
Network latency for Gitaly Cluster should ideally be measurable in single-digit milliseconds. Latency is particularly important for:
- Gitaly node health checks. Nodes must be able to respond within 1 second.
- Reference transactions that enforce strong consistency. Lower latencies mean Gitaly nodes can agree on changes faster.
Achieving acceptable latency between Gitaly nodes:
- On physical networks generally means high bandwidth, single location connections.
- On the cloud generally means within the same region, including allowing cross availability zone replication. These links are designed for this type of synchronization. Latency of less than 2ms should be sufficient for Gitaly Cluster.
If you can't provide low network latencies for replication (for example, between distant locations), consider Geo. For more information, see Comparison to Geo.
Gitaly Cluster components communicate with each other over many routes. Your firewall rules must allow the following for Gitaly Cluster to function properly:
From | To | Default port | TLS port |
---|---|---|---|
GitLab | Praefect load balancer | 2305 |
3305 |
Praefect load balancer | Praefect | 2305 |
3305 |
Praefect | Gitaly | 8075 |
9999 |
Praefect | GitLab (internal API) | 80 |
443 |
Gitaly | GitLab (internal API) | 80 |
443 |
Gitaly | Praefect load balancer | 2305 |
3305 |
Gitaly | Praefect | 2305 |
3305 |
Gitaly | Gitaly | 8075 |
9999 |
NOTE: Gitaly does not directly connect to Praefect. However, requests from Gitaly to the Praefect load balancer may still be blocked unless firewalls on the Praefect nodes allow traffic from the Gitaly nodes.
Praefect database storage
The requirements are relatively low because the database contains only metadata of:
- Where repositories are located.
- Some queued work.
It depends on the number of repositories, but a useful minimum is 5-10 GB, similar to the main GitLab application database.
Setup Instructions
If you installed GitLab using the Omnibus GitLab package (highly recommended), follow the steps below:
- Preparation
- Configuring the Praefect database
- Configuring the Praefect proxy/router
- Configuring each Gitaly node (once for each Gitaly node)
- Configure the load balancer
- Updating the GitLab server configuration
- Configure Grafana
Preparation
Before beginning, you should already have a working GitLab instance. Learn how to install GitLab.
Provision a PostgreSQL server. We recommend using the PostgreSQL that is shipped with Omnibus GitLab and use it to configure the PostgreSQL database. You can use an external PostgreSQL server (version 11 or newer) but you must set it up manually.
Prepare all your new nodes by installing GitLab. You need:
- 1 PostgreSQL node
- 1 PgBouncer node (optional)
- At least 1 Praefect node (minimal storage required)
- 3 Gitaly nodes (high CPU, high memory, fast storage)
- 1 GitLab server
You also need the IP/host address for each node:
PRAEFECT_LOADBALANCER_HOST
: the IP/host address of Praefect load balancerPOSTGRESQL_HOST
: the IP/host address of the PostgreSQL serverPGBOUNCER_HOST
: the IP/host address of the PostgreSQL serverPRAEFECT_HOST
: the IP/host address of the Praefect serverGITALY_HOST_*
: the IP or host address of each Gitaly serverGITLAB_HOST
: the IP/host address of the GitLab server
If you are using Google Cloud Platform, SoftLayer, or any other vendor that provides a virtual private cloud (VPC) you can use the private addresses for each cloud instance (corresponds to "internal address" for Google Cloud Platform) for PRAEFECT_HOST
, GITALY_HOST_*
, and GITLAB_HOST
.
Secrets
The communication between components is secured with different secrets, which are described below. Before you begin, generate a unique secret for each, and make note of it. This enables you to replace these placeholder tokens with secure tokens as you complete the setup process.
GITLAB_SHELL_SECRET_TOKEN
: this is used by Git hooks to make callback HTTP API requests to GitLab when accepting a Git push. This secret is shared with GitLab Shell for legacy reasons.PRAEFECT_EXTERNAL_TOKEN
: repositories hosted on your Praefect cluster can only be accessed by Gitaly clients that carry this token.PRAEFECT_INTERNAL_TOKEN
: this token is used for replication traffic inside your Praefect cluster. This is distinct fromPRAEFECT_EXTERNAL_TOKEN
because Gitaly clients must not be able to access internal nodes of the Praefect cluster directly; that could lead to data loss.PRAEFECT_SQL_PASSWORD
: this password is used by Praefect to connect to PostgreSQL.PRAEFECT_SQL_PASSWORD_HASH
: the hash of password of the Praefect user. Usegitlab-ctl pg-password-md5 praefect
to generate the hash. The command asks for the password forpraefect
user. EnterPRAEFECT_SQL_PASSWORD
plaintext password. By default, Praefect usespraefect
user, but you can change it.PGBOUNCER_SQL_PASSWORD_HASH
: the hash of password of the PgBouncer user. PgBouncer uses this password to connect to PostgreSQL. For more details see bundled PgBouncer documentation.
We note in the instructions below where these secrets are required.
NOTE:
Omnibus GitLab installations can use gitlab-secrets.json
for GITLAB_SHELL_SECRET_TOKEN
.
PostgreSQL
NOTE: Do not store the GitLab application database and the Praefect database on the same PostgreSQL server if using Geo. The replication state is internal to each instance of GitLab and should not be replicated.
These instructions help set up a single PostgreSQL database, which creates a single point of failure. To avoid this, you can configure your own clustered PostgreSQL. Support for PostgreSQL replication and failover using Omnibus GitLab is being tracked in a relevant epic.
The following options are available:
- For non-Geo installations, either:
- Use one of the documented PostgreSQL setups.
- Use your own third-party database setup. This requires manual setup.
- For Geo instances, either:
- Set up a separate PostgreSQL instance.
- Use a cloud-managed PostgreSQL service. AWS Relational Database Service is recommended.
Setting up PostgreSQL creates empty Praefect tables. For more information, see the relevant troubleshooting section.
Running GitLab and Praefect databases on the same server
The GitLab application database and the Praefect database can be run on the same server. However, Praefect should have its own database server when using Omnibus GitLab PostgreSQL. If there is a failover, Praefect isn't aware and starts to fail as the database it's trying to use would either:
- Be unavailable.
- In read-only mode.
Manual database setup
To complete this section you need:
- One Praefect node
- One PostgreSQL node (version 11 or newer)
- A PostgreSQL user with permissions to manage the database server
In this section, we configure the PostgreSQL database. This can be used for both external and Omnibus-provided PostgreSQL server.
To run the following instructions, you can use the Praefect node, where psql
is installed
by Omnibus GitLab (/opt/gitlab/embedded/bin/psql
). If you are using the Omnibus-provided
PostgreSQL you can use gitlab-psql
on the PostgreSQL node instead:
-
Create a new user
praefect
to be used by Praefect:CREATE ROLE praefect WITH LOGIN PASSWORD 'PRAEFECT_SQL_PASSWORD';
Replace
PRAEFECT_SQL_PASSWORD
with the strong password you generated in the preparation step. -
Create a new database
praefect_production
that is owned bypraefect
user.CREATE DATABASE praefect_production WITH OWNER praefect ENCODING UTF8;
For using Omnibus-provided PgBouncer you need to take the following additional steps. We strongly recommend using the PostgreSQL that is shipped with Omnibus as the backend. The following instructions only work on Omnibus-provided PostgreSQL:
-
For Omnibus-provided PgBouncer, you need to use the hash of
praefect
user instead the of the actual password:ALTER ROLE praefect WITH PASSWORD 'md5<PRAEFECT_SQL_PASSWORD_HASH>';
Replace
<PRAEFECT_SQL_PASSWORD_HASH>
with the hash of the password you generated in the preparation step. It is prefixed withmd5
literal. -
The PgBouncer that is shipped with Omnibus is configured to use
auth_query
and usespg_shadow_lookup
function. You need to create this function inpraefect_production
database:CREATE OR REPLACE FUNCTION public.pg_shadow_lookup(in i_username text, out username text, out password text) RETURNS record AS $$ BEGIN SELECT usename, passwd FROM pg_catalog.pg_shadow WHERE usename = i_username INTO username, password; RETURN; END; $$ LANGUAGE plpgsql SECURITY DEFINER; REVOKE ALL ON FUNCTION public.pg_shadow_lookup(text) FROM public, pgbouncer; GRANT EXECUTE ON FUNCTION public.pg_shadow_lookup(text) TO pgbouncer;
The database used by Praefect is now configured.
You can now configure Praefect to use the database:
praefect['database_host'] = POSTGRESQL_HOST
praefect['database_port'] = 5432
praefect['database_user'] = 'praefect'
praefect['database_password'] = PRAEFECT_SQL_PASSWORD
praefect['database_dbname'] = 'praefect_production'
If you see Praefect database errors after configuring PostgreSQL, see troubleshooting steps.
Reads distribution caching
Praefect performance can be improved by additionally configuring the database_direct
settings:
praefect['database_direct_host'] = POSTGRESQL_HOST
praefect['database_direct_port'] = 5432
# Use the following to override parameters of direct database connection.
# Comment out where the parameters are the same for both connections.
praefect['database_direct_user'] = 'praefect'
praefect['database_direct_password'] = PRAEFECT_SQL_PASSWORD
praefect['database_direct_dbname'] = 'praefect_production'
#praefect['database_direct_sslmode'] = '...'
#praefect['database_direct_sslcert'] = '...'
#praefect['database_direct_sslkey'] = '...'
#praefect['database_direct_sslrootcert'] = '...'
Once configured, this connection is automatically used for the SQL LISTEN feature and allows Praefect to receive notifications from PostgreSQL for cache invalidation.
Verify this feature is working by looking for the following log entry in the Praefect log:
reads distribution caching is enabled by configuration
Use PgBouncer
To reduce PostgreSQL resource consumption, we recommend setting up and configuring PgBouncer in front of the PostgreSQL instance. However, PgBouncer isn't required because Praefect makes a low number of connections. If you choose to use PgBouncer, you can use the same PgBouncer instance for both the GitLab application database and the Praefect database.
To configure PgBouncer in front of the PostgreSQL instance, you must point Praefect to PgBouncer by setting database parameters on Praefect configuration:
praefect['database_host'] = PGBOUNCER_HOST
praefect['database_port'] = 6432
praefect['database_user'] = 'praefect'
praefect['database_password'] = PRAEFECT_SQL_PASSWORD
praefect['database_dbname'] = 'praefect_production'
#praefect['database_sslmode'] = '...'
#praefect['database_sslcert'] = '...'
#praefect['database_sslkey'] = '...'
#praefect['database_sslrootcert'] = '...'
Praefect requires an additional connection to the PostgreSQL that supports the
LISTEN feature. With PgBouncer
this feature is only available with session
pool mode (pool_mode = session
).
It is not supported in transaction
pool mode (pool_mode = transaction
).
To configure the additional connection, you must either:
- Configure a new PgBouncer database that uses to the same PostgreSQL database endpoint,
but with different pool mode. That is,
pool_mode = session
. - Connect Praefect directly to PostgreSQL and bypass PgBouncer.
Configure a new PgBouncer database with pool_mode = session
We recommend using PgBouncer with session
pool mode. You can use the
bundled PgBouncer or use an external PgBouncer and
configure it manually.
The following example uses the bundled PgBouncer and sets up two separate connection pools on PostgreSQL host,
one in session
pool mode and the other in transaction
pool mode. For this example to work,
you need to prepare PostgreSQL server as documented in in the setup instructions:
pgbouncer['databases'] = {
# Other database configuration including gitlabhq_production
...
praefect_production: {
host: POSTGRESQL_HOST,
# Use `pgbouncer` user to connect to database backend.
user: 'pgbouncer',
password: PGBOUNCER_SQL_PASSWORD_HASH,
pool_mode: 'transaction'
},
praefect_production_direct: {
host: POSTGRESQL_HOST,
# Use `pgbouncer` user to connect to database backend.
user: 'pgbouncer',
password: PGBOUNCER_SQL_PASSWORD_HASH,
dbname: 'praefect_production',
pool_mode: 'session'
},
...
}
# Allow the praefect user to connect to PgBouncer
pgbouncer['users'] = {
'praefect': {
'password': PRAEFECT_SQL_PASSWORD_HASH,
}
}
Both praefect_production
and praefect_production_direct
use the same database endpoint
(praefect_production
), but with different pool modes. This translates to the following
databases
section of PgBouncer:
[databases]
praefect_production = host=POSTGRESQL_HOST auth_user=pgbouncer pool_mode=transaction
praefect_production_direct = host=POSTGRESQL_HOST auth_user=pgbouncer dbname=praefect_production pool_mode=session
Now you can configure Praefect to use PgBouncer for both connections:
praefect['database_host'] = PGBOUNCER_HOST
praefect['database_port'] = 6432
praefect['database_user'] = 'praefect'
# `PRAEFECT_SQL_PASSWORD` is the plain-text password of
# Praefect user. Not to be confused with `PRAEFECT_SQL_PASSWORD_HASH`.
praefect['database_password'] = PRAEFECT_SQL_PASSWORD
praefect['database_dbname'] = 'praefect_production'
praefect['database_direct_dbname'] = 'praefect_production_direct'
# There is no need to repeat the following. Parameters of direct
# database connection will fall back to the values above.
#praefect['database_direct_host'] = PGBOUNCER_HOST
#praefect['database_direct_port'] = 6432
#praefect['database_direct_user'] = 'praefect'
#praefect['database_direct_password'] = PRAEFECT_SQL_PASSWORD
With this configuration, Praefect uses PgBouncer for both connection types.
NOTE:
Omnibus GitLab handles the authentication requirements (using auth_query
), but if you are preparing
your databases manually and configuring an external PgBouncer, you must include praefect
user and
its password in the file used by PgBouncer. For example, userlist.txt
if the auth_file
configuration option is set. For more details, consult the PgBouncer documentation.
Configure Praefect to connect directly to PostgreSQL
As an alternative to configuring PgBouncer with session
pool mode, Praefect can be configured to use different connection parameters for direct access
to PostgreSQL. This is the connection that supports the LISTEN
feature.
An example of Praefect configuration that bypasses PgBouncer and directly connects to PostgreSQL:
praefect['database_direct_host'] = POSTGRESQL_HOST
praefect['database_direct_port'] = 5432
# Use the following to override parameters of direct database connection.
# Comment out where the parameters are the same for both connections.
praefect['database_direct_user'] = 'praefect'
praefect['database_direct_password'] = PRAEFECT_SQL_PASSWORD
praefect['database_direct_dbname'] = 'praefect_production'
#praefect['database_direct_sslmode'] = '...'
#praefect['database_direct_sslcert'] = '...'
#praefect['database_direct_sslkey'] = '...'
#praefect['database_direct_sslrootcert'] = '...'
Praefect
Introduced in GitLab 13.4, Praefect nodes can no longer be designated as
primary
.
If there are multiple Praefect nodes:
- Designate one node as the deploy node, and configure it using the following steps.
- Complete the following steps for each additional node.
To complete this section you need a configured PostgreSQL server, including:
WARNING: Praefect should be run on a dedicated node. Do not run Praefect on the application server, or a Gitaly node.
On the Praefect node:
- Disable all other services by editing
/etc/gitlab/gitlab.rb
:
# Avoid running unnecessary services on the Praefect server
gitaly['enable'] = false
postgresql['enable'] = false
redis['enable'] = false
nginx['enable'] = false
puma['enable'] = false
sidekiq['enable'] = false
gitlab_workhorse['enable'] = false
prometheus['enable'] = false
alertmanager['enable'] = false
grafana['enable'] = false
gitlab_exporter['enable'] = false
gitlab_kas['enable'] = false
# Enable only the Praefect service
praefect['enable'] = true
# Prevent database migrations from running on upgrade automatically
praefect['auto_migrate'] = false
gitlab_rails['auto_migrate'] = false
-
Configure Praefect to listen on network interfaces by editing
/etc/gitlab/gitlab.rb
:praefect['listen_addr'] = '0.0.0.0:2305'
-
Configure Prometheus metrics by editing
/etc/gitlab/gitlab.rb
:# Enable Prometheus metrics access to Praefect. You must use firewalls # to restrict access to this address/port. # The default metrics endpoint is /metrics praefect['prometheus_listen_addr'] = '0.0.0.0:9652' # Some metrics run queries against the database. Enabling separate database metrics allows # these metrics to be collected when the metrics are # scraped on a separate /db_metrics endpoint. praefect['separate_database_metrics'] = true
-
Configure a strong
auth_token
for Praefect by editing/etc/gitlab/gitlab.rb
. This is needed by clients outside the cluster (like GitLab Shell) to communicate with the Praefect cluster:praefect['auth_token'] = 'PRAEFECT_EXTERNAL_TOKEN'
-
Configure Praefect to connect to the PostgreSQL database. We highly recommend using PgBouncer as well.
If you want to use a TLS client certificate, the options below can be used:
# Connect to PostgreSQL using a TLS client certificate # praefect['database_sslcert'] = '/path/to/client-cert' # praefect['database_sslkey'] = '/path/to/client-key' # Trust a custom certificate authority # praefect['database_sslrootcert'] = '/path/to/rootcert'
By default, Praefect refuses to make an unencrypted connection to PostgreSQL. You can override this by uncommenting the following line:
# praefect['database_sslmode'] = 'disable'
-
Configure the Praefect cluster to connect to each Gitaly node in the cluster by editing
/etc/gitlab/gitlab.rb
.The virtual storage's name must match the configured storage name in GitLab configuration. In a later step, we configure the storage name as
default
so we usedefault
here as well. This cluster has three Gitaly nodesgitaly-1
,gitaly-2
, andgitaly-3
, which are intended to be replicas of each other.WARNING: If you have data on an already existing storage called
default
, you should configure the virtual storage with another name and migrate the data to the Gitaly Cluster storage afterwards.Replace
PRAEFECT_INTERNAL_TOKEN
with a strong secret, which is used by Praefect when communicating with Gitaly nodes in the cluster. This token is distinct from thePRAEFECT_EXTERNAL_TOKEN
.Replace
GITALY_HOST_*
with the IP or host address of the each Gitaly node.More Gitaly nodes can be added to the cluster to increase the number of replicas. More clusters can also be added for very large GitLab instances.
NOTE: When adding additional Gitaly nodes to a virtual storage, all storage names within that virtual storage must be unique. Additionally, all Gitaly node addresses referenced in the Praefect configuration must be unique.
# Name of storage hash must match storage name in git_data_dirs on GitLab # server ('default') and in git_data_dirs on Gitaly nodes ('gitaly-1') praefect['virtual_storages'] = { 'default' => { 'nodes' => { 'gitaly-1' => { 'address' => 'tcp://GITALY_HOST_1:8075', 'token' => 'PRAEFECT_INTERNAL_TOKEN', }, 'gitaly-2' => { 'address' => 'tcp://GITALY_HOST_2:8075', 'token' => 'PRAEFECT_INTERNAL_TOKEN' }, 'gitaly-3' => { 'address' => 'tcp://GITALY_HOST_3:8075', 'token' => 'PRAEFECT_INTERNAL_TOKEN' } } } }
NOTE: In GitLab 13.8 and earlier, Gitaly nodes were configured directly under the virtual storage, and not under the
nodes
key. -
Introduced in GitLab 13.1 and later, enable distribution of reads.
-
Save the changes to
/etc/gitlab/gitlab.rb
and reconfigure Praefect:gitlab-ctl reconfigure
-
For:
-
The "deploy node":
-
Enable Praefect database auto-migration again by setting
praefect['auto_migrate'] = true
in/etc/gitlab/gitlab.rb
. -
To ensure database migrations are only run during reconfigure and not automatically on upgrade, run:
sudo touch /etc/gitlab/skip-auto-reconfigure
-
-
The other nodes, you can leave the settings as they are. Though
/etc/gitlab/skip-auto-reconfigure
isn't required, you may want to set it to prevent GitLab running reconfigure automatically when running commands such asapt-get update
. This way any additional configuration changes can be done and then reconfigure can be run manually.
-
-
Save the changes to
/etc/gitlab/gitlab.rb
and reconfigure Praefect:gitlab-ctl reconfigure
-
To ensure that Praefect has updated its Prometheus listen address, restart Praefect:
gitlab-ctl restart praefect
-
Verify that Praefect can reach PostgreSQL:
sudo -u git /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml sql-ping
If the check fails, make sure you have followed the steps correctly. If you edit
/etc/gitlab/gitlab.rb
, remember to runsudo gitlab-ctl reconfigure
again before trying thesql-ping
command.
Enable TLS support
Introduced in GitLab 13.2.
Praefect supports TLS encryption. To communicate with a Praefect instance that listens for secure connections, you must:
- Ensure Gitaly is configured for TLS and use a
tls://
URL scheme in thegitaly_address
of the corresponding storage entry in the GitLab configuration. - Bring your own certificates because this isn't provided automatically. The certificate corresponding to each Praefect server must be installed on that Praefect server.
Additionally the certificate, or its certificate authority, must be installed on all Gitaly servers and on all Praefect clients that communicate with it following the procedure described in GitLab custom certificate configuration (and repeated below).
Note the following:
-
The certificate must specify the address you use to access the Praefect server. You must add the hostname or IP address as a Subject Alternative Name to the certificate.
-
When running Praefect sub-commands such as
dial-nodes
andlist-untracked-repositories
from the command line with Gitaly TLS enabled, you must set theSSL_CERT_DIR
orSSL_CERT_FILE
environment variable so that the Gitaly certificate is trusted. For example:sudo SSL_CERT_DIR=/etc/gitlab/trusted-certs /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml dial-nodes
-
You can configure Praefect servers with both an unencrypted listening address
listen_addr
and an encrypted listening addresstls_listen_addr
at the same time. This allows you to do a gradual transition from unencrypted to encrypted traffic, if necessary.To disable the unencrypted listener, set
praefect['listen_addr'] = nil
.
To configure Praefect with TLS:
For Omnibus GitLab
-
Create certificates for Praefect servers.
-
On the Praefect 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
-
Edit
/etc/gitlab/gitlab.rb
and add:praefect['tls_listen_addr'] = "0.0.0.0:3305" praefect['certificate_path'] = "/etc/gitlab/ssl/cert.pem" praefect['key_path'] = "/etc/gitlab/ssl/key.pem"
-
Save the file and reconfigure.
-
On the Praefect clients (including each Gitaly server), copy the certificates, or their certificate authority, into
/etc/gitlab/trusted-certs
:sudo cp cert.pem /etc/gitlab/trusted-certs/
-
On the Praefect clients (except Gitaly servers), edit
git_data_dirs
in/etc/gitlab/gitlab.rb
as follows:git_data_dirs({ "default" => { "gitaly_address" => 'tls://PRAEFECT_LOADBALANCER_HOST:3305', "gitaly_token" => 'PRAEFECT_EXTERNAL_TOKEN' } })
-
Save the file and reconfigure GitLab.
For installations from source
-
Create certificates for Praefect servers.
-
On the Praefect 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
-
On the Praefect clients (including each Gitaly server), copy the certificates, or their certificate authority, into the system trusted certificates:
sudo cp cert.pem /usr/local/share/ca-certificates/praefect.crt sudo update-ca-certificates
-
On the Praefect clients (except Gitaly servers), edit
storages
in/home/git/gitlab/config/gitlab.yml
as follows:gitlab: repositories: storages: default: gitaly_address: tls://PRAEFECT_LOADBALANCER_HOST:3305 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.
-
Copy all Praefect server certificates, or their certificate authority, to the system trusted certificates on each Gitaly server so the Praefect server trusts the certificate when called by Gitaly servers:
sudo cp cert.pem /usr/local/share/ca-certificates/praefect.crt sudo update-ca-certificates
-
Edit
/home/git/praefect/config.toml
and add:tls_listen_addr = '0.0.0.0:3305' [tls] certificate_path = '/etc/gitlab/ssl/cert.pem' key_path = '/etc/gitlab/ssl/key.pem'
-
Save the file and restart GitLab.
Gitaly
NOTE: Complete these steps for each Gitaly node.
To complete this section you need:
- Configured Praefect node
- 3 (or more) servers, with GitLab installed, to be configured as Gitaly nodes. These should be dedicated nodes, do not run other services on these nodes.
Every Gitaly server assigned to the Praefect cluster needs to be configured. The configuration is the same as a normal standalone Gitaly server, except:
- The storage names are exposed to Praefect, not GitLab
- The secret token is shared with Praefect, not GitLab
The configuration of all Gitaly nodes in the Praefect cluster can be identical, because we rely on Praefect to route operations correctly.
Particular attention should be shown to:
- The
gitaly['auth_token']
configured in this section must match thetoken
value underpraefect['virtual_storages']['nodes']
on the Praefect node. This was set in the previous section. This document uses the placeholderPRAEFECT_INTERNAL_TOKEN
throughout. - The storage names in
git_data_dirs
configured in this section must match the storage names underpraefect['virtual_storages']
on the Praefect node. This was set in the previous section. This document usesgitaly-1
,gitaly-2
, andgitaly-3
as Gitaly storage names.
For more information on Gitaly server configuration, see our Gitaly documentation.
-
SSH into the Gitaly node and login as root:
sudo -i
-
Disable all other services by editing
/etc/gitlab/gitlab.rb
:# Disable all other services on the Praefect node postgresql['enable'] = false redis['enable'] = false nginx['enable'] = false grafana['enable'] = false puma['enable'] = false sidekiq['enable'] = false gitlab_workhorse['enable'] = false prometheus_monitoring['enable'] = false gitlab_kas['enable'] = false # Enable only the Gitaly service gitaly['enable'] = true # Enable Prometheus if needed prometheus['enable'] = true # Disable database migrations to prevent database connections during 'gitlab-ctl reconfigure' gitlab_rails['auto_migrate'] = false
-
Configure Gitaly to listen on network interfaces by editing
/etc/gitlab/gitlab.rb
:# Make Gitaly accept connections on all network interfaces. # Use firewalls to restrict access to this address/port. gitaly['listen_addr'] = '0.0.0.0:8075' # Enable Prometheus metrics access to Gitaly. You must use firewalls # to restrict access to this address/port. gitaly['prometheus_listen_addr'] = '0.0.0.0:9236'
-
Configure a strong
auth_token
for Gitaly by editing/etc/gitlab/gitlab.rb
. This is needed by clients to communicate with this Gitaly nodes. Typically, this token is the same for all Gitaly nodes.gitaly['auth_token'] = 'PRAEFECT_INTERNAL_TOKEN'
-
Configure the GitLab Shell secret token, which is needed for
git push
operations. Either:-
Method 1:
- Copy
/etc/gitlab/gitlab-secrets.json
from the Gitaly client to same path on the Gitaly servers and any other Gitaly clients. - Reconfigure GitLab on Gitaly servers.
- Copy
-
Method 2:
-
Edit
/etc/gitlab/gitlab.rb
. -
Replace
GITLAB_SHELL_SECRET_TOKEN
with the real secret.gitlab_shell['secret_token'] = 'GITLAB_SHELL_SECRET_TOKEN'
-
-
-
Configure and
internal_api_url
, which is also needed forgit push
operations:# 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. # Examples: 'https://gitlab.example.com', 'http://1.2.3.4' gitlab_rails['internal_api_url'] = 'http://GITLAB_HOST'
-
Configure the storage location for Git data by setting
git_data_dirs
in/etc/gitlab/gitlab.rb
. Each Gitaly node should have a unique storage name (such asgitaly-1
).Instead of configuring
git_data_dirs
uniquely for each Gitaly node, it is often easier to have include the configuration for all Gitaly nodes on every Gitaly node. This is supported because the Praefectvirtual_storages
configuration maps each storage name (such asgitaly-1
) to a specific node, and requests are routed accordingly. This means every Gitaly node in your fleet can share the same configuration.# You can include the data dirs for all nodes in the same config, because # Praefect will only route requests according to the addresses provided in the # prior step. git_data_dirs({ "gitaly-1" => { "path" => "/var/opt/gitlab/git-data" }, "gitaly-2" => { "path" => "/var/opt/gitlab/git-data" }, "gitaly-3" => { "path" => "/var/opt/gitlab/git-data" } })
-
Save the changes to
/etc/gitlab/gitlab.rb
and reconfigure Gitaly:gitlab-ctl reconfigure
-
To ensure that Gitaly has updated its Prometheus listen address, restart Gitaly:
gitlab-ctl restart gitaly
The steps above must be completed for each Gitaly node!
After all Gitaly nodes are configured, run the Praefect connection checker to verify Praefect can connect to all Gitaly servers in the Praefect configuration.
-
SSH into each Praefect node and run the Praefect connection checker:
sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml dial-nodes
Load Balancer
In a fault-tolerant Gitaly configuration, a load balancer is needed to route internal traffic from the GitLab application to the Praefect nodes. The specifics on which load balancer to use or the exact configuration is beyond the scope of the GitLab documentation.
NOTE:
The load balancer must be configured to accept traffic from the Gitaly nodes in
addition to the GitLab nodes. Some requests handled by
gitaly-ruby
sidecar processes call into the main Gitaly
process. gitaly-ruby
uses the Gitaly address set in the GitLab server's
git_data_dirs
setting to make this connection.
We hope that if you're managing fault-tolerant systems like GitLab, you have a load balancer of choice already. Some examples include HAProxy (open-source), Google Internal Load Balancer, AWS Elastic Load Balancer, F5 Big-IP LTM, and Citrix Net Scaler. This documentation outlines what ports and protocols you need configure.
NOTE:
We recommend the equivalent of HAProxy leastconn
load-balancing strategy because long-running operations (for example,
clones) keep some connections open for extended periods.
LB Port | Backend Port | Protocol |
---|---|---|
2305 | 2305 | TCP |
GitLab
To complete this section you need:
The Praefect cluster needs to be exposed as a storage location to the GitLab
application. This is done by updating the git_data_dirs
.
Particular attention should be shown to:
- the storage name added to
git_data_dirs
in this section must match the storage name underpraefect['virtual_storages']
on the Praefect nodes. This was set in the Praefect section of this guide. This document usesdefault
as the Praefect storage name.
-
SSH into the GitLab node and login as root:
sudo -i
-
Configure the
external_url
so that files could be served by GitLab by proper endpoint access by editing/etc/gitlab/gitlab.rb
:You need to replace
GITLAB_SERVER_URL
with the real external facing URL on which current GitLab instance is serving:external_url 'GITLAB_SERVER_URL'
-
Disable the default Gitaly service running on the GitLab host. It isn't needed because GitLab connects to the configured cluster.
WARNING: If you have existing data stored on the default Gitaly storage, you should migrate the data your Gitaly Cluster storage first.
gitaly['enable'] = false
-
Add the Praefect cluster as a storage location by editing
/etc/gitlab/gitlab.rb
.You need to replace:
PRAEFECT_LOADBALANCER_HOST
with the IP address or hostname of the load balancer.PRAEFECT_EXTERNAL_TOKEN
with the real secret
If you are using TLS:
- The
gitaly_address
should begin withtls://
instead. - The port should be changed to
3305
.
git_data_dirs({ "default" => { "gitaly_address" => "tcp://PRAEFECT_LOADBALANCER_HOST:2305", "gitaly_token" => 'PRAEFECT_EXTERNAL_TOKEN' } })
-
Configure the GitLab Shell secret token so that callbacks from Gitaly nodes during a
git push
are properly authenticated. Either:-
Method 1:
- Copy
/etc/gitlab/gitlab-secrets.json
from the Gitaly client to same path on the Gitaly servers and any other Gitaly clients. - Reconfigure GitLab on Gitaly servers.
- Copy
-
Method 2:
-
Edit
/etc/gitlab/gitlab.rb
. -
Replace
GITLAB_SHELL_SECRET_TOKEN
with the real secret.gitlab_shell['secret_token'] = 'GITLAB_SHELL_SECRET_TOKEN'
-
-
-
Add Prometheus monitoring settings by editing
/etc/gitlab/gitlab.rb
. If Prometheus is enabled on a different node, make edits on that node instead.You need to replace:
PRAEFECT_HOST
with the IP address or hostname of the Praefect nodeGITALY_HOST_*
with the IP address or hostname of each Gitaly node
prometheus['scrape_configs'] = [ { 'job_name' => 'praefect', 'static_configs' => [ 'targets' => [ 'PRAEFECT_HOST:9652', # praefect-1 'PRAEFECT_HOST:9652', # praefect-2 'PRAEFECT_HOST:9652', # praefect-3 ] ] }, { 'job_name' => 'praefect-gitaly', 'static_configs' => [ 'targets' => [ 'GITALY_HOST_1:9236', # gitaly-1 'GITALY_HOST_2:9236', # gitaly-2 'GITALY_HOST_3:9236', # gitaly-3 ] ] } ]
-
Save the changes to
/etc/gitlab/gitlab.rb
and reconfigure GitLab:gitlab-ctl reconfigure
-
Verify on each Gitaly node the Git Hooks can reach GitLab. On each Gitaly node run:
- For GitLab 15.3 and later, run
sudo /opt/gitlab/embedded/bin/gitaly check /var/opt/gitlab/gitaly/config.toml
. - For GitLab 15.2 and earlier, run
sudo /opt/gitlab/embedded/bin/gitaly-hooks check /var/opt/gitlab/gitaly/config.toml
.
- For GitLab 15.3 and later, run
-
Verify that GitLab can reach Praefect:
gitlab-rake gitlab:gitaly:check
-
Check that the Praefect storage is configured to store new repositories:
- On the top bar, select Menu > Admin.
- On the left sidebar, select Settings > Repository.
- Expand the Repository storage section.
Following this guide, the
default
storage should have weight 100 to store all new repositories. -
Verify everything is working by creating a new project. Check the "Initialize repository with a README" box so that there is content in the repository that viewed. If the project is created, and you can see the README file, it works!
Use TCP for existing GitLab instances
When adding Gitaly Cluster to an existing Gitaly instance, the existing Gitaly storage
must be listening on TCP/TLS. If gitaly_address
is not specified, then a Unix socket is used,
which prevents the communication with the cluster.
For example:
git_data_dirs({
'default' => { 'gitaly_address' => 'tcp://old-gitaly.internal:8075' },
'cluster' => {
'gitaly_address' => 'tls://<PRAEFECT_LOADBALANCER_HOST>:3305',
'gitaly_token' => '<praefect_external_token>'
}
})
See Mixed Configuration for further information on running multiple Gitaly storages.
Grafana
Grafana is included with GitLab, and can be used to monitor your Praefect cluster. See Grafana Dashboard Service for detailed documentation.
To get started quickly:
-
SSH into the GitLab node (or whichever node has Grafana enabled) and login as root:
sudo -i
-
Enable the Grafana login form by editing
/etc/gitlab/gitlab.rb
.grafana['disable_login_form'] = false
-
Save the changes to
/etc/gitlab/gitlab.rb
and reconfigure GitLab:gitlab-ctl reconfigure
-
Set the Grafana administrator password. This command prompts you to enter a new password:
gitlab-ctl set-grafana-password
-
In your web browser, open
/-/grafana
(such ashttps://gitlab.example.com/-/grafana
) on your GitLab server.Login using the password you set, and the username
admin
. -
Go to Explore and query
gitlab_build_info
to verify that you are getting metrics from all your machines.
Congratulations! You've configured an observable fault-tolerant Praefect cluster.
Configure replication factor
WARNING: Configurable replication factors require repository-specific primary nodes to be used.
Praefect supports configuring a replication factor on a per-repository basis, by assigning specific storage nodes to host a repository.
Praefect does not store the actual replication factor, but assigns enough storages to host the repository so the desired replication factor is met. If a storage node is later removed from the virtual storage, the replication factor of repositories assigned to the storage is decreased accordingly.
You can configure:
-
A default replication factor for each virtual storage that is applied to newly-created repositories. The configuration is added to the
/etc/gitlab/gitlab.rb
file:praefect['virtual_storages'] = { 'default' => { 'default_replication_factor' => 1, # ... } }
-
A replication factor for an existing repository using the
set-replication-factor
sub-command.set-replication-factor
automatically assigns or unassigns random storage nodes as necessary to reach the desired replication factor. The repository's primary node is always assigned first and is never unassigned.sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml set-replication-factor -virtual-storage <virtual-storage> -repository <relative-path> -replication-factor <replication-factor>
-virtual-storage
is the virtual storage the repository is located in.-repository
is the repository's relative path in the storage.-replication-factor
is the desired replication factor of the repository. The minimum value is1
, as the primary needs a copy of the repository. The maximum replication factor is the number of storages in the virtual storage.
On success, the assigned host storages are printed. For example:
$ sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml set-replication-factor -virtual-storage default -repository @hashed/3f/db/3fdba35f04dc8c462986c992bcf875546257113072a909c162f7e470e581e278.git -replication-factor 2 current assignments: gitaly-1, gitaly-2
If default_replication_factor
is unset, the repositories are always replicated on every node defined in virtual_storages
. If a new
node is introduced to the virtual storage, both new and existing repositories are replicated to the node automatically.
Repository storage recommendations
The size of the required storage can vary between instances and depends on the set replication factor. You might want to include implementing repository storage redundancy.
For a replication factor:
- Of
1
: NFS, Gitaly, and Gitaly Cluster have roughly the same storage requirements. - More than
1
: The amount of required storage isused space * replication factor
.used space
should include any planned future growth.
Repository verification
Introduced in GitLab 15.0.
Praefect stores metadata about the repositories in a database. If the repositories are modified on disk without going through Praefect, the metadata can become inaccurate. Because the metadata is used for replication and routing decisions, any inaccuracies may cause problems. Praefect contains a background worker that periodically verifies the metadata against the actual state on the disks. The worker:
- Picks up a batch of replicas to verify on healthy storages. The replicas are either unverified or have exceeded the configured verification interval. Replicas that have never been verified are prioritized, followed by the other replicas ordered by longest time since the last successful verification.
- Checks whether the replicas exist on their respective storages. If the:
- Replica exists, update its last successful verification time.
- Replica doesn't exist, remove its metadata record.
- Check failed, the replica is picked up for verification again when the next worker dequeues more work.
The worker acquires an exclusive verification lease on each of the replicas it is about to verify. This avoids multiple workers from verifying the same replica concurrently. The worker releases the leases when it has completed its check. Praefect contains a background goroutine that releases stale leases every 10 seconds when workers are terminated for some reason without releasing the lease.
The worker logs each of the metadata removals prior to executing them. The perform_deletions
key
indicates whether the invalid metadata records are actually deleted or not. For example:
{
"level": "info",
"msg": "removing metadata records of non-existent replicas",
"perform_deletions": false,
"replicas": {
"default": {
"@hashed/6b/86/6b86b273ff34fce19d6b804eff5a3f5747ada4eaa22f1d49c01e52ddb7875b4b.git": [
"praefect-internal-0"
]
}
}
}
Configure the verification worker
The worker is enabled by default and verifies the metadata records every seven days. The verification interval is configurable with any valid Go duration string.
To verify the metadata every three days:
praefect['background_verification_verification_interval'] = '72h'
Values of 0 and below disable the background verifier.
praefect['background_verification_verification_interval'] = '0'
Enable deletions
WARNING:
Deletions are disabled by default due to a race condition with repository renames that can cause incorrect
deletions. This is especially prominent in Geo instances as Geo performs more renames than instances without Geo.
You should enable deletions only if the gitaly_praefect_generated_replica_paths
feature flag is enabled.
By default, the worker does not delete invalid metadata records but simply logs them and outputs Prometheus metrics for them.
You can enable deleting invalid metadata records with:
praefect['background_verification_delete_invalid_records'] = true
Prioritize verification manually
You can prioritize verification of some replicas ahead of their next scheduled verification time. This might be needed after a disk failure, for example, when the administrator knows that the disk contents may have changed. Praefect would eventually verify the replicas again, but users may encounter errors in the meantime.
To manually prioritize reverification of some replicas, use the praefect verify
subcommand. The subcommand marks
replicas as unverified. Unverified replicas are prioritized by the background verification worker. The verification
worker must be enabled for the replicas to be verified.
Prioritize verifying the replicas of a specific repository:
sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml verify -repository-id=<repository-id>
Prioritize verifying all replicas stored on a virtual storage:
sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml verify -virtual-storage=<virtual-storage>
Prioritize verifying all replicas stored on a storage:
sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml verify -virtual-storage=<virtual-storage> -storage=<storage>
The output includes the number of replicas that were marked unverified.
Automatic failover and primary election strategies
Praefect regularly checks the health of each Gitaly node. This is used to automatically fail over to a newly-elected primary Gitaly node if the current primary node is found to be unhealthy.
We recommend using repository-specific primary nodes. This is the only available election strategy from GitLab 14.0.
Repository-specific primary nodes
Introduced in GitLab 13.12.
Gitaly Cluster supports electing repository-specific primary Gitaly nodes. Repository-specific
Gitaly primary nodes are enabled in /etc/gitlab/gitlab.rb
by setting
praefect['failover_election_strategy'] = 'per_repository'
.
Praefect's deprecated election strategies:
- Elected a primary Gitaly node for each virtual storage, which was used as the primary node for each repository in the virtual storage.
- Prevented horizontal scaling of a virtual storage. The primary Gitaly node needed a replica of each repository and thus became the bottleneck.
The per_repository
election strategy solves this problem by electing a primary Gitaly node separately for each
repository. Combined with configurable replication factors, you can
horizontally scale storage capacity and distribute write load across Gitaly nodes.
Primary elections are run:
- In GitLab 14.1 and later, lazily. This means that Praefect doesn't immediately elect a new primary node if the current one is unhealthy. A new primary is elected if it is necessary to serve a request while the current primary is unavailable.
- In GitLab 13.12 to GitLab 14.0 when:
- Praefect starts up.
- The cluster's consensus of a Gitaly node's health changes.
A valid primary node candidate is a Gitaly node that:
- Is healthy. A Gitaly node is considered healthy if
>=50%
Praefect nodes have successfully health checked the Gitaly node in the previous ten seconds. - Has a fully up to date copy of the repository.
If there are multiple primary node candidates, Praefect:
- Picks one of them randomly.
- Prioritizes promoting a Gitaly node that is assigned to host the repository. If there are no assigned Gitaly nodes to elect as the primary, Praefect may temporarily elect an unassigned one. The unassigned primary is demoted in favor of an assigned one when one becomes available.
If there are no valid primary candidates for a repository:
- The unhealthy primary node is demoted and the repository is left without a primary node.
- Operations that require a primary node fail until a primary is successfully elected.
Migrate to repository-specific primary Gitaly nodes
New Gitaly Clusters can start using the per_repository
election strategy immediately.
To migrate existing clusters:
-
Praefect nodes didn't historically keep database records of every repository stored on the cluster. When the
per_repository
election strategy is configured, Praefect expects to have database records of each repository. A background database migration is included in GitLab 13.6 and later to create any missing database records for repositories. Before migrating, check Praefect's logs to verify that the database migration ran.Check Praefect's logs for
repository importer finished
message. Thevirtual_storages
field contains the names of virtual storages and whether they've had any missing database records created.For example, the
default
virtual storage has been successfully migrated:{"level":"info","msg":"repository importer finished","pid":19752,"time":"2021-04-28T11:41:36.743Z","virtual_storages":{"default":true}}
If a virtual storage has not been successfully migrated, it would have
false
next to it:{"level":"info","msg":"repository importer finished","pid":19752,"time":"2021-04-28T11:41:36.743Z","virtual_storages":{"default":false}}
The database migration runs when Praefect starts. If the database migration is unsuccessful, you can restart a Praefect node to reattempt it.
-
Running two different election strategies side by side can cause a split brain, where different Praefect nodes consider repositories to have different primaries. This can be avoided either:
-
If a short downtime is acceptable:
-
Shut down all Praefect nodes before changing the election strategy. Do this by running
gitlab-ctl stop praefect
on the Praefect nodes. -
On the Praefect nodes, configure the election strategy in
/etc/gitlab/gitlab.rb
withpraefect['failover_election_strategy'] = 'per_repository'
. -
Run
gitlab-ctl reconfigure && gitlab-ctl start
to reconfigure and start the Praefects.
-
-
If downtime is unacceptable:
-
Determine which Gitaly node is the current primary.
-
Comment out the secondary Gitaly nodes from the virtual storage's configuration in
/etc/gitlab/gitlab.rb
on all Praefect nodes. This ensures there's only one Gitaly node configured, causing both of the election strategies to elect the same Gitaly node as the primary. -
Run
gitlab-ctl reconfigure
on all Praefect nodes. Wait until all Praefect processes have restarted and the old processes have exited. This can take up to one minute. -
On all Praefect nodes, configure the election strategy in
/etc/gitlab/gitlab.rb
withpraefect['failover_election_strategy'] = 'per_repository'
. -
Run
gitlab-ctl reconfigure
on all Praefect nodes. Wait until all of the Praefect processes have restarted and the old processes have exited. This can take up to one minute. -
Uncomment the secondary Gitaly node configuration commented out in the earlier step on all Praefect nodes.
-
Run
gitlab-ctl reconfigure
on all Praefect nodes to reconfigure and restart the Praefect processes.
-
-
Deprecated election strategies
WARNING: The below election strategies are deprecated and were removed in GitLab 14.0. Migrate to repository-specific primary nodes.
-
PostgreSQL: Enabled by default until GitLab 14.0, and equivalent to:
praefect['failover_election_strategy'] = 'sql'
.This configuration option:
- Allows multiple Praefect nodes to coordinate via the PostgreSQL database to elect a primary Gitaly node.
- Causes Praefect nodes to elect a new primary Gitaly node, monitor its health, and elect a new primary Gitaly node if the current one is not reached within 10 seconds by a majority of the Praefect nodes.
-
Memory: Enabled by setting
praefect['failover_election_strategy'] = 'local'
in/etc/gitlab/gitlab.rb
on the Praefect node.If a sufficient number of health checks fail for the current primary Gitaly node, a new primary is elected. Do not use with multiple Praefect nodes! Using with multiple Praefect nodes is likely to result in a split brain.