162 lines
6.9 KiB
Markdown
162 lines
6.9 KiB
Markdown
# Job logs
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> [Renamed from job traces to job logs](https://gitlab.com/gitlab-org/gitlab/issues/29121) in GitLab 12.5.
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Job logs are sent by GitLab Runner while it's processing a job. You can see
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logs in job pages, pipelines, email notifications, etc.
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## Data flow
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In general, there are two states for job logs: `log` and `archived log`.
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In the following table you can see the phases a log goes through:
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| Phase | State | Condition | Data flow | Stored path |
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| -------------- | ------------ | ----------------------- | -----------------------------------------| ----------- |
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| 1: patching | log | When a job is running | GitLab Runner => Unicorn => file storage | `#{ROOT_PATH}/gitlab-ci/builds/#{YYYY_mm}/#{project_id}/#{job_id}.log` |
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| 2: overwriting | log | When a job is finished | GitLab Runner => Unicorn => file storage | `#{ROOT_PATH}/gitlab-ci/builds/#{YYYY_mm}/#{project_id}/#{job_id}.log` |
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| 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` |
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| 4: uploading | archived log | After a log is archived | Sidekiq moves archived log to [object storage](#uploading-logs-to-object-storage) (if configured) | `#{bucket_name}/#{disk_hash}/#{YYYY_mm_dd}/#{job_id}/#{job_artifact_id}/job.log` |
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The `ROOT_PATH` varies per environment. For Omnibus GitLab it
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would be `/var/opt/gitlab`, and for installations from source
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it would be `/home/git/gitlab`.
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## Changing the job logs local location
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To change the location where the job logs will be stored, follow the steps below.
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**In Omnibus installations:**
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1. Edit `/etc/gitlab/gitlab.rb` and add or amend the following line:
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```ruby
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gitlab_ci['builds_directory'] = '/mnt/to/gitlab-ci/builds'
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```
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1. Save the file and [reconfigure GitLab](restart_gitlab.md#omnibus-gitlab-reconfigure) for the
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changes to take effect.
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**In installations from source:**
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1. Edit `/home/git/gitlab/config/gitlab.yml` and add or amend the following lines:
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```yaml
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gitlab_ci:
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# The location where build logs are stored (default: builds/).
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# Relative paths are relative to Rails.root.
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builds_path: path/to/builds/
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```
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1. Save the file and [restart GitLab](restart_gitlab.md#installations-from-source) for the changes
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to take effect.
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## Uploading logs to object storage
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Archived logs are considered as [job artifacts](job_artifacts.md).
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Therefore, when you [set up the object storage integration](job_artifacts.md#object-storage-settings),
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job logs are automatically migrated to it along with the other job artifacts.
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See "Phase 4: uploading" in [Data flow](#data-flow) to learn about the process.
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## How to remove job logs
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There isn't a way to automatically expire old job logs, but it's safe to remove
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them if they're taking up too much space. If you remove the logs manually, the
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job output in the UI will be empty.
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## New incremental logging architecture
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> - [Introduced](https://gitlab.com/gitlab-org/gitlab-foss/merge_requests/18169) in GitLab 10.4.
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> - [Announced as generally available](https://gitlab.com/gitlab-org/gitlab-foss/issues/46097) in GitLab 11.0.
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NOTE: **Note:**
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This feature is off by default. See below for how to [enable or disable](#enabling-incremental-logging) it.
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By combining the process with object storage settings, we can completely bypass
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the local file storage. This is a useful option if GitLab is installed as
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cloud-native, for example on Kubernetes.
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The data flow is the same as described in the [data flow section](#data-flow)
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with one change: _the stored path of the first two phases is different_. This incremental
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log architecture stores chunks of logs in Redis and a persistent store (object storage or database) instead of
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file storage. Redis is used as first-class storage, and it stores up-to 128KB
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of data. Once the full chunk is sent, it is flushed to a persistent store, either object storage (temporary directory) or database.
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After a while, the data in Redis and a persitent store will be archived to [object storage](#uploading-logs-to-object-storage).
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The data are stored in the following Redis namespace: `Gitlab::Redis::SharedState`.
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Here is the detailed data flow:
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1. GitLab Runner picks a job from GitLab
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1. GitLab Runner sends a piece of log to GitLab
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1. GitLab appends the data to Redis
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1. Once the data in Redis reach 128KB, the data is flushed to a persistent store (object storage or the database).
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1. The above steps are repeated until the job is finished.
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1. Once the job is finished, GitLab schedules a Sidekiq worker to archive the log.
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1. The Sidekiq worker archives the log to object storage and cleans up the log
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in Redis and a persistent store (object storage or the database).
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### Enabling incremental logging
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The following commands are to be issued in a Rails console:
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```sh
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# Omnibus GitLab
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gitlab-rails console
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# Installation from source
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cd /home/git/gitlab
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sudo -u git -H bin/rails console RAILS_ENV=production
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```
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**To check if incremental logging (trace) is enabled:**
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```ruby
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Feature.enabled?('ci_enable_live_trace')
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```
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**To enable incremental logging (trace):**
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```ruby
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Feature.enable('ci_enable_live_trace')
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```
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NOTE: **Note:**
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The transition period will be handled gracefully. Upcoming logs will be
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generated with the incremental architecture, and on-going logs will stay with the
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legacy architecture, which means that on-going logs won't be forcibly
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re-generated with the incremental architecture.
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**To disable incremental logging (trace):**
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```ruby
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Feature.disable('ci_enable_live_trace')
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```
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NOTE: **Note:**
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The transition period will be handled gracefully. Upcoming logs will be generated
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with the legacy architecture, and on-going incremental logs will stay with the incremental
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architecture, which means that on-going incremental logs won't be forcibly re-generated
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with the legacy architecture.
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### Potential implications
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In some cases, having data stored on Redis could incur data loss:
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1. **Case 1: When all data in Redis are accidentally flushed**
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- On going incremental logs could be recovered by re-sending logs (this is
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supported by all versions of the GitLab Runner).
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- Finished jobs which have not archived incremental logs will lose the last part
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(~128KB) of log data.
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1. **Case 2: When Sidekiq workers fail to archive (e.g., there was a bug that
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prevents archiving process, Sidekiq inconsistency, etc.)**
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- Currently all log data in Redis will be deleted after one week. If the
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Sidekiq workers can't finish by the expiry date, the part of log data will be lost.
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Another issue that might arise is that it could consume all memory on the Redis
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instance. If the number of jobs is 1000, 128MB (128KB * 1000) is consumed.
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Also, it could pressure the database replication lag. `INSERT`s are generated to
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indicate that we have log chunk. `UPDATE`s with 128KB of data is issued once we
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receive multiple chunks.
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