Job logs

Renamed from job traces to job logs in GitLab 12.5.

Job logs are sent by a runner while it's processing a job. You can see logs in job pages, pipelines, email notifications, etc.

Data flow

In general, there are two states for job logs: log and archived log. In the following table you can see the phases a log goes through:

Phase	State	Condition	Data flow	Stored path
1: patching	log	When a job is running	Runner => Puma => file storage	#{ROOT_PATH}/gitlab-ci/builds/#{YYYY_mm}/#{project_id}/#{job_id}.log
2: overwriting	log	When a job is finished	Runner => Puma => file storage	#{ROOT_PATH}/gitlab-ci/builds/#{YYYY_mm}/#{project_id}/#{job_id}.log
3: archiving	archived log	After a job is finished	Sidekiq moves log to artifacts folder	#{ROOT_PATH}/gitlab-rails/shared/artifacts/#{disk_hash}/#{YYYY_mm_dd}/#{job_id}/#{job_artifact_id}/job.log
4: uploading	archived log	After a log is archived	Sidekiq moves archived log to object storage (if configured)	#{bucket_name}/#{disk_hash}/#{YYYY_mm_dd}/#{job_id}/#{job_artifact_id}/job.log

The ROOT_PATH varies per environment. For Omnibus GitLab it would be /var/opt/gitlab, and for installations from source it would be /home/git/gitlab.

Changing the job logs local location

To change the location where the job logs are stored, follow the steps below.

In Omnibus installations:

1. Edit /etc/gitlab/gitlab.rb and add or amend the following line:

   gitlab_ci['builds_directory'] = '/mnt/to/gitlab-ci/builds'

2. Save the file and reconfigure GitLab for the changes to take effect.

Alternatively, if you have existing job logs you can follow these steps to move the logs to a new location without losing any data.

1. Pause continuous integration data processing by updating this setting in /etc/gitlab/gitlab.rb. Jobs in progress are not affected, based on how data flow works.

   sidekiq['queue_selector'] = true
   sidekiq['queue_groups'] = [
     "feature_category!=continuous_integration"
   ]

2. Save the file and reconfigure GitLab for the changes to take effect.

3. Set the new storage location in /etc/gitlab/gitlab.rb:

   gitlab_ci['builds_directory'] = '/mnt/to/gitlab-ci/builds'

4. Save the file and reconfigure GitLab for the changes to take effect.

5. Use rsync to move job logs from the current location to the new location:

   sudo rsync -avzh --remove-source-files --ignore-existing --progress /var/opt/gitlab/gitlab-ci/builds/ /mnt/to/gitlab-ci/builds`

   Use --ignore-existing so you don't override new job logs with older versions of the same log.

6. Unpause continuous integration data processing by editing /etc/gitlab/gitlab.rb and removing the sidekiq setting you updated earlier.

7. Save the file and reconfigure GitLab for the changes to take effect.

8. Remove the old job logs storage location:

   sudo rm -rf /var/opt/gitlab/gitlab-ci/builds`

In installations from source:

1. Edit /home/git/gitlab/config/gitlab.yml and add or amend the following lines:

   gitlab_ci:
     # The location where build logs are stored (default: builds/).
     # Relative paths are relative to Rails.root.
     builds_path: path/to/builds/

2. Save the file and restart GitLab for the changes to take effect.

Uploading logs to object storage

Archived logs are considered as job artifacts. Therefore, when you set up the object storage integration, job logs are automatically migrated to it along with the other job artifacts.

See "Phase 4: uploading" in Data flow to learn about the process.

Prevent local disk usage

If you want to avoid any local disk usage for job logs, you can do so using one of the following options:

• Enable the beta incremental logging feature.
• Set the job logs location to an NFS drive.

How to remove job logs

There isn't a way to automatically expire old job logs, but it's safe to remove them if they're taking up too much space. If you remove the logs manually, the job output in the UI is empty.

For example, to delete all job logs older than 60 days, run the following from a shell in your GitLab instance:

WARNING: This command permanently deletes the log files and is irreversible.

find /var/opt/gitlab/gitlab-rails/shared/artifacts -name "job.log" -mtime +60 -delete

New incremental logging architecture

• Introduced in GitLab 10.4.

NOTE: This beta feature is off by default. See below for how to enable or disable it.

By combining the process with object storage settings, we can completely bypass the local file storage. This is a useful option if GitLab is installed as cloud-native, for example on Kubernetes.

The data flow is the same as described in the data flow section with one change: the stored path of the first two phases is different. This incremental log architecture stores chunks of logs in Redis and a persistent store (object storage or database) instead of file storage. Redis is used as first-class storage, and it stores up-to 128KB of data. After the full chunk is sent, it is flushed to a persistent store, either object storage (temporary directory) or database. After a while, the data in Redis and a persistent store is archived to object storage.

The data are stored in the following Redis namespace: Gitlab::Redis::SharedState.

Here is the detailed data flow:

1. The runner picks a job from GitLab
2. The runner sends a piece of log to GitLab
3. GitLab appends the data to Redis
4. After the data in Redis reaches 128KB, the data is flushed to a persistent store (object storage or the database).
5. The above steps are repeated until the job is finished.
6. After the job is finished, GitLab schedules a Sidekiq worker to archive the log.
7. The Sidekiq worker archives the log to object storage and cleans up the log in Redis and a persistent store (object storage or the database).

Enabling incremental logging

The following commands are to be issued in a Rails console:

# Omnibus GitLab
gitlab-rails console

# Installation from source
cd /home/git/gitlab
sudo -u git -H bin/rails console -e production

To check if incremental logging (trace) is enabled:

Feature.enabled?(:ci_enable_live_trace)

To enable incremental logging (trace):

Feature.enable(:ci_enable_live_trace)

NOTE: The transition period is handled gracefully. Upcoming logs are generated with the incremental architecture, and on-going logs stay with the legacy architecture, which means that on-going logs aren't forcibly re-generated with the incremental architecture.

To disable incremental logging (trace):

Feature.disable('ci_enable_live_trace')

NOTE: The transition period is handled gracefully. Upcoming logs are generated with the legacy architecture, and on-going incremental logs stay with the incremental architecture, which means that on-going incremental logs aren't forcibly re-generated with the legacy architecture.

Potential implications

In some cases, having data stored on Redis could incur data loss:

1. Case 1: When all data in Redis are accidentally flushed

   • On going incremental logs could be recovered by re-sending logs (this is supported by all versions of GitLab Runner).
   • Finished jobs which have not archived incremental logs lose the last part (~128KB) of log data.

2. Case 2: When Sidekiq workers fail to archive (e.g., there was a bug that prevents archiving process, Sidekiq inconsistency, etc.)

   • All log data in Redis is deleted after one week. If the Sidekiq workers can't finish by the expiry date, the part of log data is lost.

Another issue that might arise is that it could consume all memory on the Redis instance. If the number of jobs is 1000, 128MB (128KB * 1000) is consumed.

Also, it could pressure the database replication lag. INSERTs are generated to indicate that we have log chunk. UPDATEs with 128KB of data is issued once we receive multiple chunks.