1--- 2stage: Create 3group: Gitaly 4info: 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 5type: reference 6--- 7 8# Recovery options 9 10Gitaly Cluster can [recover from certain types of failure](recovery.md). 11 12## Primary Node Failure 13 14Gitaly Cluster recovers from a failing primary Gitaly node by promoting a healthy secondary as the 15new primary. 16 17In GitLab 14.1 and later, Gitaly Cluster: 18 19- Elects a healthy secondary with a fully up to date copy of the repository as the new primary. 20- Repository becomes unavailable if there are no fully up to date copies of it on healthy secondaries. 21 22To minimize data loss in GitLab 13.0 to 14.0, Gitaly Cluster: 23 24- Switches repositories that are outdated on the new primary to [read-only mode](#read-only-mode). 25- Elects the secondary with the least unreplicated writes from the primary to be the new 26 primary. Because there can still be some unreplicated writes, 27 [data loss can occur](#check-for-data-loss). 28 29### Read-only mode 30 31> - Introduced in GitLab 13.0 as [generally available](https://about.gitlab.com/handbook/product/gitlab-the-product/#generally-available-ga). 32> - Between GitLab 13.0 and GitLab 13.2, read-only mode applied to the whole virtual storage and occurred whenever failover occurred. 33> - [In GitLab 13.3 and later](https://gitlab.com/gitlab-org/gitaly/-/issues/2862), read-only mode applies on a per-repository basis and only occurs if a new primary is out of date. 34new primary. If the failed primary contained unreplicated writes, [data loss can occur](#check-for-data-loss). 35> - Removed in GitLab 14.1. Instead, repositories [become unavailable](#unavailable-repositories). 36 37When Gitaly Cluster switches to a new primary in GitLab 13.0 to 14.0, repositories enter 38read-only mode if they are out of date. This can happen after failing over to an outdated 39secondary. Read-only mode eases data recovery efforts by preventing writes that may conflict 40with the unreplicated writes on other nodes. 41 42To enable writes again in GitLab 13.0 to 14.0, an administrator can: 43 441. [Check](#check-for-data-loss) for data loss. 451. Attempt to [recover](#data-recovery) missing data. 461. Either [enable writes](#enable-writes-or-accept-data-loss) in the virtual storage or 47 [accept data loss](#enable-writes-or-accept-data-loss) if necessary, depending on the version of 48 GitLab. 49 50## Unavailable repositories 51 52> - From GitLab 13.0 through 14.0, repositories became read-only if they were outdated on the primary but fully up to date on a healthy secondary. `dataloss` sub-command displays read-only repositories by default through these versions. 53> - Since GitLab 14.1, Praefect contains more responsive failover logic which immediately fails over to one of the fully up to date secondaries rather than placing the repository in read-only mode. Since GitLab 14.1, the `dataloss` sub-command displays repositories which are unavailable due to having no fully up to date copies on healthy Gitaly nodes. 54 55A repository is unavailable if all of its up to date replicas are unavailable. Unavailable repositories are 56not accessible through Praefect to prevent serving stale data that may break automated tooling. 57 58### Check for data loss 59 60The Praefect `dataloss` subcommand identifies: 61 62- Copies of repositories in GitLab 13.0 to GitLab 14.0 that at are likely to be outdated. 63 This can help identify potential data loss after a failover. 64- Repositories in GitLab 14.1 and later that are unavailable. This helps identify potential 65 data loss and repositories which are no longer accessible because all of their up-to-date 66 replicas copies are unavailable. 67 68The following parameters are available: 69 70- `-virtual-storage` that specifies which virtual storage to check. Because they might require 71 an administrator to intervene, the default behavior is to display: 72 - In GitLab 13.0 to 14.0, copies of read-only repositories. 73 - In GitLab 14.1 and later, unavailable repositories. 74- In GitLab 14.1 and later, [`-partially-unavailable`](#unavailable-replicas-of-available-repositories) 75 that specifies whether to include in the output repositories that are available but have 76 some assigned copies that are not available. 77 78NOTE: 79`dataloss` is still in beta and the output format is subject to change. 80 81To check for repositories with outdated primaries or for unavailable repositories, run: 82 83```shell 84sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml dataloss [-virtual-storage <virtual-storage>] 85``` 86 87Every configured virtual storage is checked if none is specified: 88 89```shell 90sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml dataloss 91``` 92 93Repositories are listed in the output that have either: 94 95- An outdated copy of the repository on the primary, in GitLab 13.0 to GitLab 14.0. 96- No healthy and fully up-to-date copies available, in GitLab 14.1 and later. 97 98The following information is printed for each repository: 99 100- A repository's relative path to the storage directory identifies each repository and groups the related 101 information. 102- The repository's current status is printed in parentheses next to the disk path: 103 - In GitLab 13.0 to 14.0, either `(read-only)` if the repository's primary node is outdated 104 and can't accept writes. Otherwise, `(writable)`. 105 - In GitLab 14.1 and later, `(unavailable)` is printed next to the disk path if the 106 repository is unavailable. 107- The primary field lists the repository's current primary. If the repository has no primary, the field shows 108 `No Primary`. 109- The In-Sync Storages lists replicas which have replicated the latest successful write and all writes 110 preceding it. 111- The Outdated Storages lists replicas which contain an outdated copy of the repository. Replicas which have no copy 112 of the repository but should contain it are also listed here. The maximum number of changes the replica is missing 113 is listed next to replica. It's important to notice that the outdated replicas may be fully up to date or contain 114 later changes but Praefect can't guarantee it. 115 116Additional information includes: 117 118- Whether a node is assigned to host the repository is listed with each node's status. 119 `assigned host` is printed next to nodes that are assigned to store the repository. The 120 text is omitted if the node contains a copy of the repository but is not assigned to store 121 the repository. Such copies aren't kept in sync by Praefect, but may act as replication 122 sources to bring assigned copies up to date. 123- In GitLab 14.1 and later, `unhealthy` is printed next to the copies that are located 124 on unhealthy Gitaly nodes. 125 126Example output: 127 128```shell 129Virtual storage: default 130 Outdated repositories: 131 @hashed/3f/db/3fdba35f04dc8c462986c992bcf875546257113072a909c162f7e470e581e278.git (unavailable): 132 Primary: gitaly-1 133 In-Sync Storages: 134 gitaly-2, assigned host, unhealthy 135 Outdated Storages: 136 gitaly-1 is behind by 3 changes or less, assigned host 137 gitaly-3 is behind by 3 changes or less 138``` 139 140A confirmation is printed out when every repository is available. For example: 141 142```shell 143Virtual storage: default 144 All repositories are available! 145``` 146 147#### Unavailable replicas of available repositories 148 149NOTE: 150In GitLab 14.0 and earlier, the flag is `-partially-replicated` and the output shows any repositories with assigned nodes with outdated 151copies. 152 153To also list information of repositories which are available but are unavailable from some of the assigned nodes, 154use the `-partially-unavailable` flag. 155 156A repository is available if there is a healthy, up to date replica available. Some of the assigned secondary 157replicas may be temporarily unavailable for access while they are waiting to replicate the latest changes. 158 159```shell 160sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml dataloss [-virtual-storage <virtual-storage>] [-partially-unavailable] 161``` 162 163Example output: 164 165```shell 166Virtual storage: default 167 Outdated repositories: 168 @hashed/3f/db/3fdba35f04dc8c462986c992bcf875546257113072a909c162f7e470e581e278.git: 169 Primary: gitaly-1 170 In-Sync Storages: 171 gitaly-1, assigned host 172 Outdated Storages: 173 gitaly-2 is behind by 3 changes or less, assigned host 174 gitaly-3 is behind by 3 changes or less 175``` 176 177With the `-partially-unavailable` flag set, a confirmation is printed out if every assigned replica is fully up to 178date and healthy. 179 180For example: 181 182```shell 183Virtual storage: default 184 All repositories are fully available on all assigned storages! 185``` 186 187### Check repository checksums 188 189To check a project's repository checksums across on all Gitaly nodes, run the 190[replicas Rake task](../raketasks/praefect.md#replica-checksums) on the main GitLab node. 191 192### Accept data loss 193 194WARNING: 195`accept-dataloss` causes permanent data loss by overwriting other versions of the repository. Data 196[recovery efforts](#data-recovery) must be performed before using it. 197 198If it is not possible to bring one of the up to date replicas back online, you may have to accept data 199loss. When accepting data loss, Praefect marks the chosen replica of the repository as the latest version 200and replicates it to the other assigned Gitaly nodes. This process overwrites any other version of the 201repository so care must be taken. 202 203```shell 204sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml accept-dataloss 205-virtual-storage <virtual-storage> -repository <relative-path> -authoritative-storage <storage-name> 206``` 207 208### Enable writes or accept data loss 209 210WARNING: 211`accept-dataloss` causes permanent data loss by overwriting other versions of the repository. 212Data [recovery efforts](#data-recovery) must be performed before using it. 213 214Praefect provides the following subcommands to re-enable writes or accept data loss: 215 216- In GitLab 13.2 and earlier, `enable-writes` to re-enable virtual storage for writes after 217 data recovery attempts: 218 219 ```shell 220 sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml enable-writes -virtual-storage <virtual-storage> 221 ``` 222 223- In GitLab 13.3 and later, if it is not possible to bring one of the up to date nodes back 224 online, you may have to accept data loss: 225 226 ```shell 227 sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml accept-dataloss -virtual-storage <virtual-storage> -repository <relative-path> -authoritative-storage <storage-name> 228 ``` 229 230 When accepting data loss, Praefect: 231 232 1. Marks the chosen copy of the repository as the latest version. 233 1. Replicates the copy to the other assigned Gitaly nodes. 234 235 This process overwrites any other copy of the repository so care must be taken. 236 237## Data recovery 238 239If a Gitaly node fails replication jobs for any reason, it ends up hosting outdated versions of the 240affected repositories. Praefect provides tools for: 241 242- [Automatic](#automatic-reconciliation) reconciliation, for GitLab 13.4 and later. 243- [Manual](#manual-reconciliation) reconciliation, for: 244 - GitLab 13.3 and earlier. 245 - Repositories upgraded to GitLab 13.4 and later without entries in the `repositories` table. In 246 GitLab 13.6 and later, [a migration is run](https://gitlab.com/gitlab-org/gitaly/-/issues/3033) 247 when Praefect starts for these repositories. 248 249These tools reconcile the outdated repositories to bring them fully up to date again. 250 251### Automatic reconciliation 252 253> [Introduced](https://gitlab.com/gitlab-org/gitaly/-/issues/2717) in GitLab 13.4. 254 255Praefect automatically reconciles repositories that are not up to date. By default, this is done every 256five minutes. For each outdated repository on a healthy Gitaly node, the Praefect picks a 257random, fully up-to-date replica of the repository on another healthy Gitaly node to replicate from. A 258replication job is scheduled only if there are no other replication jobs pending for the target 259repository. 260 261The reconciliation frequency can be changed via the configuration. The value can be any valid 262[Go duration value](https://pkg.go.dev/time#ParseDuration). Values below 0 disable the feature. 263 264Examples: 265 266```ruby 267praefect['reconciliation_scheduling_interval'] = '5m' # the default value 268``` 269 270```ruby 271praefect['reconciliation_scheduling_interval'] = '30s' # reconcile every 30 seconds 272``` 273 274```ruby 275praefect['reconciliation_scheduling_interval'] = '0' # disable the feature 276``` 277 278### Manual reconciliation 279 280WARNING: 281The `reconcile` sub-command was removed in GitLab 14.1. Use [automatic reconciliation](#automatic-reconciliation) instead. 282Manual reconciliation may produce excess replication jobs and is limited in functionality. Manual reconciliation does not 283work when [repository-specific primary nodes](praefect.md#repository-specific-primary-nodes) are enabled. 284 285The Praefect `reconcile` sub-command allows for the manual reconciliation between two Gitaly nodes. The 286command replicates every repository on a later version on the reference storage to the target storage. 287 288```shell 289sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml reconcile -virtual <virtual-storage> -reference <up-to-date-storage> -target <outdated-storage> -f 290``` 291 292- Replace the placeholder `<virtual-storage>` with the virtual storage containing the Gitaly node storage to be checked. 293- Replace the placeholder `<up-to-date-storage>` with the Gitaly storage name containing up to date repositories. 294- Replace the placeholder `<outdated-storage>` with the Gitaly storage name containing outdated repositories. 295 296### Manually remove repositories 297 298> - [Introduced](https://gitlab.com/gitlab-org/gitaly/-/merge_requests/3767) in GitLab 14.3. 299> - [Introduced](https://gitlab.com/gitlab-org/gitaly/-/merge_requests/4054) in GitLab 14.6, support for dry-run mode. 300 301The `remove-repository` Praefect sub-command removes a repository from a Gitaly Cluster, and all state associated with a given repository including: 302 303- On-disk repositories on all relevant Gitaly nodes. 304- Any database state tracked by Praefect. 305 306In GitLab 14.6 and later, by default, the command operates in dry-run mode. In earlier versions, the command didn't support dry-run mode. For example: 307 308```shell 309sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml remove-repository -virtual-storage <virtual-storage> -repository <repository> 310``` 311 312- Replace `<virtual-storage>` with the name of the virtual storage containing the repository. 313- Replace `<repository>` with the relative path of the repository to remove. 314- In GitLab 14.6 and later, add `-apply` to run the command outside of dry-run mode and remove the repository. For example: 315 316 ```shell 317 sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml remove-repository -virtual-storage <virtual-storage> -repository <repository> -apply 318 ``` 319 320- `-virtual-storage` is the virtual storage the repository is located in. Virtual storages are configured in `/etc/gitlab/gitlab.rb` under `praefect['virtual_storages]` and looks like the following: 321 322 ```ruby 323 praefect['virtual_storages'] = { 324 'default' => { 325 ... 326 }, 327 'storage-1' => { 328 ... 329 } 330 } 331 ``` 332 333 In this example, the virtual storage to specify is `default` or `storage-1`. 334 335- `-repository` is the repository's relative path in the storage [beginning with `@hashed`](../repository_storage_types.md#hashed-storage). 336 For example: 337 338 ```plaintext 339 @hashed/f5/ca/f5ca38f748a1d6eaf726b8a42fb575c3c71f1864a8143301782de13da2d9202b.git 340 ``` 341 342Parts of the repository can continue to exist after running `remove-repository`. This can be because of: 343 344- A deletion error. 345- An in-flight RPC call targeting the repository. 346 347If this occurs, run `remove-repository` again. 348 349### Manually list untracked repositories 350 351> [Introduced](https://gitlab.com/gitlab-org/gitaly/-/merge_requests/3926) in GitLab 14.4. 352 353The `list-untracked-repositories` Praefect sub-command lists repositories of the Gitaly Cluster that both: 354 355- Exist for at least one Gitaly storage. 356- Aren't tracked in the Praefect database. 357 358The command outputs: 359 360- Result to `STDOUT` and the command's logs. 361- Errors to `STDERR`. 362 363Each entry is a complete JSON string with a newline at the end (configurable using the 364`-delimiter` flag). For example: 365 366```plaintext 367sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml list-untracked-repositories 368{"virtual_storage":"default","storage":"gitaly-1","relative_path":"@hashed/ab/cd/abcd123456789012345678901234567890123456789012345678901234567890.git"} 369{"virtual_storage":"default","storage":"gitaly-1","relative_path":"@hashed/ab/cd/abcd123456789012345678901234567890123456789012345678901234567891.git"} 370``` 371 372### Manually track repositories 373 374> - [Introduced](https://gitlab.com/gitlab-org/omnibus-gitlab/-/merge_requests/5658) in GitLab 14.4. 375> - [Introduced](https://gitlab.com/gitlab-org/omnibus-gitlab/-/merge_requests/5789) in GitLab 14.6, support for immediate replication. 376 377The `track-repository` Praefect sub-command adds repositories on disk to the Praefect database to be tracked. 378 379```shell 380sudo /opt/gitlab/embedded/bin/praefect -config /var/opt/gitlab/praefect/config.toml track-repository -virtual-storage <virtual-storage> -repository <repository> -replicate-immediately 381``` 382 383- `-virtual-storage` is the virtual storage the repository is located in. Virtual storages are configured in `/etc/gitlab/gitlab.rb` under `praefect['virtual_storages]` and looks like the following: 384 385 ```ruby 386 praefect['virtual_storages'] = { 387 'default' => { 388 ... 389 }, 390 'storage-1' => { 391 ... 392 } 393 } 394 ``` 395 396 In this example, the virtual storage to specify is `default` or `storage-1`. 397 398- `-repository` is the repository's relative path in the storage [beginning with `@hashed`](../repository_storage_types.md#hashed-storage). 399 For example: 400 401 ```plaintext 402 @hashed/f5/ca/f5ca38f748a1d6eaf726b8a42fb575c3c71f1864a8143301782de13da2d9202b.git 403 ``` 404 405- `-authoritative-storage` is the storage we want Praefect to treat as the primary. Required if 406 [per-repository replication](praefect.md#configure-replication-factor) is set as the replication strategy. 407- `-replicate-immediately`, available in GitLab 14.6 and later, causes the command to replicate the repository to its secondaries immediately. 408 Otherwise, replication jobs are scheduled for execution in the database and are picked up by a Praefect background process. 409 410The command outputs: 411 412- Results to `STDOUT` and the command's logs. 413- Errors to `STDERR`. 414 415This command fails if: 416 417- The repository is already being tracked by the Praefect database. 418- The repository does not exist on disk. 419