1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
|
# Praefect: High Availability
NOTE: **Note:** Praefect is an experimental service, and data loss is likely.
Praefect is an optional reverse-proxy for [Gitaly](../index.md) to manage a
cluster of Gitaly nodes for high availability. Initially, high availability
be implemented through asynchronous replication. If a Gitaly node becomes
unavailable, it will be possible to fail over to a warm Gitaly replica.
The first minimal version will support:
- Eventual consistency of the secondary replicas.
- Automatic fail over from the primary to the secondary.
- Reporting of possible data loss if replication queue is non empty.
Follow the [HA Gitaly epic](https://gitlab.com/groups/gitlab-org/-/epics/1489)
for updates and roadmap.
## Requirements for configuring Gitaly for High Availability
NOTE: **Note:** this reference architecture is not highly available because
Praefect is a single point of failure.
The minimal [alpha](https://about.gitlab.com/handbook/product/#alpha-beta-ga)
reference architecture additionally requires:
- 1 Praefect node
- 1 PostgreSQL server (PostgreSQL 9.6 or newer)
- 3 Gitaly nodes (1 primary, 2 secondary)
![Alpha architecture diagram](img/praefect_architecture_v12_10.png)
See the [design
document](https://gitlab.com/gitlab-org/gitaly/-/blob/master/doc/design_ha.md)
for implementation details.
## Setup Instructions
If you [installed](https://about.gitlab.com/install/) GitLab using the Omnibus
package (highly recommended), follow the steps below:
1. [Preparation](#preparation)
1. [Configuring the Praefect database](#postgresql)
1. [Configuring the Praefect proxy/router](#praefect)
1. [Configuring each Gitaly node](#gitaly) (once for each Gitaly node)
1. [Updating the GitLab server configuration](#gitlab)
### Preparation
Before beginning, you should already have a working GitLab instance. [Learn how
to install GitLab](https://about.gitlab.com/install/).
Provision a PostgreSQL server (PostgreSQL 9.6 or newer). Configuration through
the GitLab Omnibus distribution is not yet supported. Follow this
[issue](https://gitlab.com/gitlab-org/gitaly/issues/2476) for updates.
Prepare all your new nodes by [installing
GitLab](https://about.gitlab.com/install/).
- 1 Praefect node (minimal storage required)
- 3 Gitaly nodes (high CPU, high memory, fast storage)
You will need the IP/host address for each node.
1. `POSTGRESQL_SERVER_ADDRESS`: the IP/host address of the PostgreSQL server
1. `PRAEFECT_SERVER_ADDRESS`: the IP/host address of the Praefect server
1. `GITALY_SERVER_ADDRESS`: the IP/host address of each Gitaly node
#### 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 will make it easy to replace these placeholder tokens
with secure tokens as you complete the setup process.
1. `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.
1. `PRAEFECT_EXTERNAL_TOKEN`: repositories hosted on your Praefect cluster can
only be accessed by Gitaly clients that carry this token.
1. `PRAEFECT_INTERNAL_TOKEN`: this token is used for replication traffic inside
your Praefect cluster. This is distinct from `PRAEFECT_EXTERNAL_TOKEN`
because Gitaly clients must not be able to access internal nodes of the
Praefect cluster directly; that could lead to data loss.
1. `PRAEFECT_SQL_PASSWORD`: this password is used by Praefect to connect to
PostgreSQL.
1. `GRAFANA_PASSWORD`: this password is used to access the `admin`
account in the Grafana dashboards.
We will note in the instructions below where these secrets are required.
### PostgreSQL
NOTE: **Note:** don't reuse the GitLab application database for the Praefect
database.
To complete this section you will need:
- 1 Praefect node
- 1 PostgreSQL server (PostgreSQL 9.6 or newer)
- An SQL user with permissions to create databases
During this section, we will configure the PostgreSQL server, from the Praefect
node, using `psql` which is installed by GitLab Omnibus.
1. SSH into the **Praefect** node and login as root:
```shell
sudo -i
```
1. Connect to the PostgreSQL server with administrative access. This is likely
the `postgres` user. The database `template1` is used because it is created
by default on all PostgreSQL servers.
```shell
/opt/gitlab/embedded/bin/psql -U postgres -d template1 -h POSTGRESQL_SERVER_ADDRESS
```
Create a new user `praefect` which will be used by Praefect. Replace
`PRAEFECT_SQL_PASSWORD` with the strong password you generated in the
preparation step.
```sql
CREATE ROLE praefect WITH LOGIN CREATEDB PASSWORD 'PRAEFECT_SQL_PASSWORD';
```
1. Reconnect to the PostgreSQL server, this time as the `praefect` user:
```shell
/opt/gitlab/embedded/bin/psql -U praefect -d template1 -h POSTGRESQL_SERVER_ADDRESS
```
Create a new database `praefect_production`. By creating the database while
connected as the `praefect` user, we are confident they have access.
```sql
CREATE DATABASE praefect_production WITH ENCODING=UTF8;
```
The database used by Praefect is now configured.
### Praefect
To complete this section you will need:
- [Configured PostgreSQL server](#postgresql), including:
- IP/host address (`POSTGRESQL_SERVER_ADDRESS`)
- password (`PRAEFECT_SQL_PASSWORD`)
Praefect should be run on a dedicated node. Do not run Praefect on the
application server, or a Gitaly node.
1. SSH into the **Praefect** node and login as root:
```shell
sudo -i
```
1. Disable all other services by editing `/etc/gitlab/gitlab.rb`:
```ruby
# Disable all other services on the Praefect node
postgresql['enable'] = false
redis['enable'] = false
nginx['enable'] = false
prometheus['enable'] = false
grafana['enable'] = false
unicorn['enable'] = false
sidekiq['enable'] = false
gitlab_workhorse['enable'] = false
gitaly['enable'] = false
# Enable only the Praefect service
praefect['enable'] = true
# Prevent database connections during 'gitlab-ctl reconfigure'
gitlab_rails['rake_cache_clear'] = false
gitlab_rails['auto_migrate'] = false
```
1. Configure **Praefect** to listen on network interfaces by editing
`/etc/gitlab/gitlab.rb`:
```ruby
# Make Praefect accept connections on all network interfaces.
# Use firewalls to restrict access to this address/port.
praefect['listen_addr'] = '0.0.0.0:2305'
# Enable Prometheus metrics access to Praefect. You must use firewalls
# to restrict access to this address/port.
praefect['prometheus_listen_addr'] = '0.0.0.0:9652'
```
1. Configure a strong `auth_token` for **Praefect** by editing
`/etc/gitlab/gitlab.rb`. This will be needed by clients outside the cluster
(like GitLab Shell) to communicate with the Praefect cluster :
```ruby
praefect['auth_token'] = 'PRAEFECT_EXTERNAL_TOKEN'
```
1. Configure **Praefect** to connect to the PostgreSQL database by editing
`/etc/gitlab/gitlab.rb`.
You will need to replace `POSTGRESQL_SERVER_ADDRESS` with the IP/host address
of the database, and `PRAEFECT_SQL_PASSWORD` with the strong password set
above.
```ruby
praefect['database_host'] = 'POSTGRESQL_SERVER_ADDRESS'
praefect['database_port'] = 5432
praefect['database_user'] = 'praefect'
praefect['database_password'] = 'PRAEFECT_SQL_PASSWORD'
praefect['database_dbname'] = 'praefect_production'
```
If you want to use a TLS client certificate, the options below can be used:
```ruby
# Connect to PostreSQL 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 will refuse to make an unencrypted connection to
PostgreSQL. You can override this by uncommenting the following line:
```ruby
# praefect['database_sslmode'] = 'disable'
```
1. Configure the **Praefect** cluster to connect to each Gitaly node in the
cluster by editing `/etc/gitlab/gitlab.rb`.
In the example below we have configured one cluster named `praefect`. This
cluster has three Gitaly nodes `gitaly-1`, `gitaly-2`, and `gitaly-3`, which
will be replicas of each other.
Replace `PRAEFECT_INTERNAL_TOKEN` with a strong secret, which will be used by
Praefect when communicating with Gitaly nodes in the cluster. This token is
distinct from the `PRAEFECT_EXTERNAL_TOKEN`.
Replace `GITALY_HOST` with the IP/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: **Note:** The `gitaly-1` node is currently denoted the primary. This
can be used to manually fail from one node to another. This will be removed
in the future to allow for automatic failover.
```ruby
# Name of storage hash must match storage name in git_data_dirs on GitLab
# server ('praefect') and in git_data_dirs on Gitaly nodes ('gitaly-1')
praefect['virtual_storages'] = {
'praefect' => {
'gitaly-1' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN',
'primary' => true
},
'gitaly-2' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN'
},
'gitaly-3' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN'
}
}
}
```
1. Save the changes to `/etc/gitlab/gitlab.rb` and [reconfigure Praefect](../restart_gitlab.md#omnibus-gitlab-reconfigure):
```shell
gitlab-ctl reconfigure
```
1. Verify that Praefect can reach PostgreSQL:
```shell
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 run `sudo gitlab-ctl reconfigure`
again before trying the `sql-ping` command.
### Gitaly
NOTE: **Note:** Complete these steps for **each** Gitaly node.
To complete this section you will need:
- [Configured Praefect node](#praefect)
- 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](../index.md),
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 the `token`
value under `praefect['virtual_storages']` on the Praefect node. This was set
in the [previous section](#praefect). This document uses the placeholder
`PRAEFECT_INTERNAL_TOKEN` throughout.
- the storage names in `git_data_dirs` configured in this section must match the
storage names under `praefect['virtual_storages']` on the Praefect node. This
was set in the [previous section](#praefect). This document uses `gitaly-1`,
`gitaly-2`, and `gitaly-3` as Gitaly storage names.
For more information on Gitaly server configuration, see our [Gitaly
documentation](index.md#3-gitaly-server-configuration).
1. SSH into the **Gitaly** node and login as root:
```shell
sudo -i
```
1. Disable all other services by editing `/etc/gitlab/gitlab.rb`:
```ruby
# Disable all other services on the Praefect node
postgresql['enable'] = false
redis['enable'] = false
nginx['enable'] = false
prometheus['enable'] = false
grafana['enable'] = false
unicorn['enable'] = false
sidekiq['enable'] = false
gitlab_workhorse['enable'] = false
prometheus_monitoring['enable'] = false
# Enable only the Praefect service
gitaly['enable'] = true
# Prevent database connections during 'gitlab-ctl reconfigure'
gitlab_rails['rake_cache_clear'] = false
gitlab_rails['auto_migrate'] = false
```
1. Configure **Gitaly** to listen on network interfaces by editing
`/etc/gitlab/gitlab.rb`:
```ruby
# 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'
```
1. Configure a strong `auth_token` for **Gitaly** by editing
`/etc/gitlab/gitlab.rb`. This will be needed by clients to communicate with
this Gitaly nodes. Typically, this token will be the same for all Gitaly
nodes.
```ruby
gitaly['auth_token'] = 'PRAEFECT_INTERNAL_TOKEN'
```
1. Configure the GitLab Shell `secret_token`, and `internal_api_url` which are
needed for `git push` operations.
If you have already configured [Gitaly on its own server](../index.md)
```ruby
gitlab_shell['secret_token'] = 'GITLAB_SHELL_SECRET_TOKEN'
# 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://example.gitlab.com', 'http://1.2.3.4'
gitlab_rails['internal_api_url'] = 'GITLAB_SERVER_URL'
```
1. 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
(eg `gitaly-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 Praefect `virtual_storages`
configuration maps each storage name (eg `gitaly-1`) to a specific node, and
requests are routed accordingly. This means every Gitaly node in your fleet
can share the same configuration.
```ruby
# 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"
}
})
```
1. Save the changes to `/etc/gitlab/gitlab.rb` and [reconfigure Gitaly](../restart_gitlab.md#omnibus-gitlab-reconfigure):
```shell
gitlab-ctl reconfigure
```
1. To ensure that Gitaly [has updated its Prometheus listen address](https://gitlab.com/gitlab-org/gitaly/-/issues/2521), [restart Gitaly](../restart_gitlab.md#omnibus-gitlab-restart):
```shell
gitlab-ctl restart gitaly
```
**Complete these steps for each Gitaly node!**
After all Gitaly nodes are configured, you can run the Praefect connection
checker to verify Praefect can connect to all Gitaly servers in the Praefect
config.
1. SSH into the **Praefect** node and run the Praefect connection checker:
```shell
sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml dial-nodes
```
### GitLab
To complete this section you will need:
- [Configured Praefect node](#praefect)
- [Configured Gitaly nodes](#gitaly)
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 under `praefect['virtual_storages']` on the Praefect node. This
was set in the [Praefect](#praefect) section of this guide. This document uses
`praefect` as the Praefect storage name.
1. SSH into the **GitLab** node and login as root:
```shell
sudo -i
```
1. Add the Praefect cluster as a storage location by editing
`/etc/gitlab/gitlab.rb`.
You will need to replace:
- `PRAEFECT_HOST` with the IP address or hostname of the Praefect node
- `PRAEFECT_EXTERNAL_TOKEN` with the real secret
```ruby
git_data_dirs({
"default" => {
"path" => "/var/opt/gitlab/git-data"
},
"praefect" => {
"gitaly_address" => "tcp://PRAEFECT_HOST:2305",
"gitaly_token" => 'PRAEFECT_EXTERNAL_TOKEN'
}
})
```
1. Configure the `gitlab_shell['secret_token']` so that callbacks from Gitaly
nodes during a `git push` are properly authenticated by editing
`/etc/gitlab/gitlab.rb`:
You will need to replace `GITLAB_SHELL_SECRET_TOKEN` with the real secret.
```ruby
gitlab_shell['secret_token'] = 'GITLAB_SHELL_SECRET_TOKEN'
```
1. Configure the `external_url` so that files could be served by GitLab
by proper endpoint access by editing `/etc/gitlab/gitlab.rb`:
You will need to replace `GITLAB_SERVER_URL` with the real URL on which
current GitLab instance is serving:
```ruby
external_url 'GITLAB_SERVER_URL'
```
1. Add Prometheus monitoring settings by editing `/etc/gitlab/gitlab.rb`.
You will need to replace:
- `PRAEFECT_HOST` with the IP address or hostname of the Praefect node
- `GITALY_HOST` with the IP address or hostname of each Gitaly node
```ruby
prometheus['scrape_configs'] = [
{
'job_name' => 'praefect',
'static_configs' => [
'targets' => [
'PRAEFECT_HOST:9652' # praefect
]
]
},
{
'job_name' => 'praefect-gitaly',
'static_configs' => [
'targets' => [
'GITALY_HOST:9236', # gitaly-1
'GITALY_HOST:9236', # gitaly-2
'GITALY_HOST:9236', # gitaly-3
]
]
}
]
grafana['disable_login_form'] = false
```
1. Save the changes to `/etc/gitlab/gitlab.rb` and [reconfigure GitLab](../restart_gitlab.md#omnibus-gitlab-reconfigure):
```shell
gitlab-ctl reconfigure
```
1. Verify that GitLab can reach Praefect:
```shell
gitlab-rake gitlab:gitaly:check
```
1. Set the Grafana admin password. This command will prompt you to enter a new password:
```shell
gitlab-ctl set-grafana-password
```
1. Update the **Repository storage** settings from **Admin Area > Settings >
Repository > Repository storage** to make the newly configured Praefect
cluster the storage location for new Git repositories.
- Deselect the **default** storage location
- Select the **praefect** storage location
1. Verify everything is still 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!
1. Inspect metrics by browsing to `/-/grafana` on your GitLab server.
Log in with `admin` / `GRAFANA_PASSWORD`. Go to 'Explore' and query
`gitlab_build_info` to verify that you are getting metrics from all your
machines.
Congratulations! You have configured a highly available Praefect cluster.
### Failover
There are two ways to do a failover from one internal Gitaly node to another as the primary. Manually, or automatically.
As an example, in this `config.toml` we have one virtual storage named "default" with two internal Gitaly nodes behind it.
One is deemed the "primary". This means that read and write traffic will go to `internal_storage_0`, and writes
will get replicated to `internal_storage_1`:
```toml
socket_path = "/path/to/Praefect.socket"
# failover_enabled will enable automatic failover
failover_enabled = false
[logging]
format = "json"
level = "info"
[[virtual_storage]]
name = "default"
[[virtual_storage.node]]
name = "internal_storage_0"
address = "tcp://localhost:9999"
primary = true
token = "supersecret"
[[virtual_storage.node]]
name = "internal_storage_1"
address = "tcp://localhost:9998"
token = "supersecret"
```
#### Manual failover
In order to failover from using one internal Gitaly node to using another, a manual failover step can be used. Unless `failover_enabled` is set to `true`
in the `config.toml`, the only way to fail over from one primary to using another node as the primary is to do a manual failover.
1. Move `primary = true` from the current `[[virtual_storage.node]]` to another node in `/etc/gitlab/gitlab.rb`:
```ruby
praefect['virtual_storages'] = {
'praefect' => {
'gitaly-1' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN',
# no longer the primary
},
'gitaly-2' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN',
# this is the new primary
'primary' => true
},
'gitaly-3' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN',
}
}
}
```
1. Save the file and [reconfigure GitLab](../restart_gitlab.md#omnibus-gitlab-reconfigure).
On a restart, Praefect will send write traffic to `internal_storage_1`. `internal_storage_0` is the new secondary now,
and replication jobs will be created to replicate repository data to `internal_storage_0` **from** `internal_storage_1`
#### Automatic failover
When automatic failover is enabled, Praefect will do automatic detection of the health of internal Gitaly nodes. If the
primary has a certain amount of healthchecks fail, it will decide to promote one of the secondaries to be primary, and
demote the primary to be a secondary.
1. To enable automatic failover, edit `/etc/gitlab/gitlab.rb`:
```ruby
# failover_enabled turns on automatic failover
praefect['failover_enabled'] = true
praefect['virtual_storages'] = {
'praefect' => {
'gitaly-1' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN',
'primary' => true
},
'gitaly-2' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN'
},
'gitaly-3' => {
'address' => 'tcp://GITALY_HOST:8075',
'token' => 'PRAEFECT_INTERNAL_TOKEN'
}
}
}
```
1. Save the file and [reconfigure GitLab](../restart_gitlab.md#omnibus-gitlab-reconfigure).
Below is the picture when Praefect starts up with the config.toml above:
```mermaid
graph TD
A[Praefect] -->|Mutator RPC| B(internal_storage_0)
B --> |Replication|C[internal_storage_1]
```
Let's say suddenly `internal_storage_0` goes down. Praefect will detect this and
automatically switch over to `internal_storage_1`, and `internal_storage_0` will serve as a secondary:
```mermaid
graph TD
A[Praefect] -->|Mutator RPC| B(internal_storage_1)
B --> |Replication|C[internal_storage_0]
```
NOTE: **Note:**: Currently this feature is supported for setups that only have 1 Praefect instance. Praefect instances running,
for example behind a load balancer, `failover_enabled` should be disabled. The reason is The reason is because there
is no coordination that currently happens across different Praefect instances, so there could be a situation where
two Praefect instances think two different Gitaly nodes are the primary.
## Migrating existing repositories to Praefect
If your GitLab instance already has repositories, these won't be migrated
automatically.
Repositories may be moved from one storage location using the [Repository
API](../../api/projects.html#edit-project):
```shell
curl --request PUT \
--header "PRIVATE-TOKEN: <your_access_token>" \
--data "repository_storage=praefect" \
https://example.gitlab.com/api/v4/projects/123
```
## Debugging Praefect
If you receive an error, check `/var/log/gitlab/gitlab-rails/production.log`.
Here are common errors and potential causes:
- 500 response code
- **ActionView::Template::Error (7:permission denied)**
- `praefect['auth_token']` and `gitlab_rails['gitaly_token']` do not match on the GitLab server.
- **Unable to save project. Error: 7:permission denied**
- Secret token in `praefect['storage_nodes']` on GitLab server does not match the
value in `gitaly['auth_token']` on one or more Gitaly servers.
- 503 response code
- **GRPC::Unavailable (14:failed to connect to all addresses)**
- GitLab was unable to reach Praefect.
- **GRPC::Unavailable (14:all SubCons are in TransientFailure...)**
- Praefect cannot reach one or more of its child Gitaly nodes. Try running
the Praefect connection checker to diagnose.
|