Retrieving diff of recently deleted MR returns a 500 (#537705) · Issues · GitLab.org / GitLab

Retrieving diff of recently deleted MR returns a 500

<details> <summary> Everyone can contribute. [Help move this issue forward](https://handbook.gitlab.com/handbook/marketing/developer-relations/contributor-success/community-contributors-workflows/#contributor-links) while earning points, leveling up and collecting rewards. </summary> - [Close this issue](https://contributors.gitlab.com/manage-issue?action=close&projectId=278964&issueIid=537705) </details>  ### Summary An API request to get an MR diff (`GET /api/:version/projects/:id/merge_requests/:merge_request_iid/diffs`) returns a `500` if the MR was very recently deleted (`DELETE /api/:version/projects/:id/merge_requests/:merge_request_iid`). Subsequent calls to the same API returns the expected `404` response after some time has passed. ### Steps to reproduce We encounter this situation periodically with frequently running canaries from two overlapping features that end up doing the following: 1. Feature A Canary: Creates an MR. 1. Feature B Canary: Detects the new MR has been created, begins performing some work related to it. 1. Feature A Canary: Completes its testing. Deletes MR to clean up resources used. 1. Feature B Canary: Tries to retrieve a diff for the MR that was just deleted, gets a `500` response. 1. Feature B Canary: Performs a retry on the same MR diff API call, gets the expected `404` response. ### Example Project Not available. ### What is the current *bug* behavior? Calling a `GET /api/:version/projects/:id/merge_requests/:merge_request_iid/diffs` for an MR that was deleted within a second of a `DELETE /api/:version/projects/:id/merge_requests/:merge_request_iid` call returns an unexpected `500` response. ### What is the expected *correct* behavior? The `GET /api/:version/projects/:id/merge_requests/:merge_request_iid/diffs` request should return a `404`. ### Relevant logs and/or screenshots Note that the `GET` that returns a `500` and the `DELETE` show as starting at the same time in the logs. I suspect the issue is happening when requests are overlapping in this way. #### gitlab-rails/api_json.log --- | \@timestamp | severity | duration_s | status | method | path | | --- | --- | --- | --- | --- | --- | | 2025-04-25 14:53:09.017 | INFO | 0.0698 | 404 | GET | /api/v4/projects/21/merge_requests/454523/diffs | | 2025-04-25 14:52:18.147 | INFO | 0.06286 | 404 | GET | /api/v4/projects/21/merge_requests/454523/diffs | | 2025-04-25 14:52:07.126 | INFO | 0.05128 | 404 | GET | /api/v4/projects/21/merge_requests/454523/diffs | | 2025-04-25 14:52:05.622 | INFO | 0.21384 | 204 | DELETE | /api/v4/projects/21/merge_requests/454523 | | 2025-04-25 14:52:05.622 | INFO | 0.16735 | 500 | GET | /api/v4/projects/21/merge_requests/454523/diffs | | 2025-04-25 14:52:02.113 | INFO | 0.16227 | 200 | GET | /api/v4/projects/21/merge_requests/454523 | --- For every instance of a `500` where we see this, the exception fields logged are: - `exception.class`: `NoMethodError` - `exception.message`: `undefined method ``target_project' for nil` - `exception.backtrace`: ``` [ "app/models/merge_request_diff.rb:536:in `project'", "lib/gitlab/diff/file_collection/merge_request_diff_base.rb:20:in `initialize'", "lib/gitlab/diff/file_collection/paginated_merge_request_diff.rb:19:in `initialize'", "app/models/merge_request_diff.rb:493:in `new'", "app/models/merge_request_diff.rb:493:in `block in paginated_diffs'", "app/models/merge_request_diff.rb:763:in `fetching_repository_diffs'", "app/models/merge_request_diff.rb:490:in `paginated_diffs'", "lib/api/merge_requests.rb:606:in `block (2 levels) in %3Cclass:MergeRequests%3E'", "grape (2.0.0) lib/grape/endpoint.rb:58:in `call'", "grape (2.0.0) lib/grape/endpoint.rb:58:in `block (2 levels) in generate_api_method'", "activesupport (7.0.8.7) lib/active_support/notifications.rb:208:in `instrument'", "grape (2.0.0) lib/grape/endpoint.rb:57:in `block in generate_api_method'", "grape (2.0.0) lib/grape/endpoint.rb:328:in `execute'", "grape (2.0.0) 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"lib/gitlab/middleware/sidekiq_web_static.rb:20:in `call'", "lib/gitlab/metrics/requests_rack_middleware.rb:83:in `call'", "gitlab-labkit (0.37.0) lib/labkit/middleware/rack.rb:22:in `block in call'", "gitlab-labkit (0.37.0) lib/labkit/context.rb:35:in `with_context'", "gitlab-labkit (0.37.0) lib/labkit/middleware/rack.rb:21:in `call'", "actionpack (7.0.8.7) lib/action_dispatch/middleware/request_id.rb:26:in `call'", "actionpack (7.0.8.7) lib/action_dispatch/middleware/host_authorization.rb:131:in `call'", "railties (7.0.8.7) lib/rails/engine.rb:530:in `call'", "railties (7.0.8.7) lib/rails/railtie.rb:226:in `public_send'", "railties (7.0.8.7) lib/rails/railtie.rb:226:in `method_missing'", "lib/gitlab/middleware/release_env.rb:12:in `call'", "rack (2.2.13) lib/rack/urlmap.rb:74:in `block in call'", "rack (2.2.13) lib/rack/urlmap.rb:58:in `each'", "rack (2.2.13) lib/rack/urlmap.rb:58:in `call'", "puma (6.5.0) lib/puma/configuration.rb:279:in `call'", "puma (6.5.0) lib/puma/request.rb:99:in `block in handle_request'", "puma (6.5.0) lib/puma/thread_pool.rb:389:in `with_force_shutdown'", "puma (6.5.0) lib/puma/request.rb:98:in `handle_request'", "puma (6.5.0) lib/puma/server.rb:468:in `process_client'", "puma (6.5.0) lib/puma/server.rb:249:in `block in run'", "puma (6.5.0) lib/puma/thread_pool.rb:166:in `block in spawn_thread'" ] ``` ### Output of checks      #### Results of GitLab environment info  <details> <summary>Expand for output related to GitLab environment info</summary> <pre> /opt/gitlab/embedded/lib/ruby/gems/3.3.0/gems/fast_gettext-2.3.0/lib/fast_gettext/vendor/mofile.rb:24: warning: prime was loaded from the standard library, but is not part of the default gems starting from Ruby 3.1.0. You can add prime to your Gemfile or gemspec to silence this warning. System information System: Proxy: no Current User: git Using RVM: no Ruby Version: 3.3.7 Gem Version: 3.6.7 Bundler Version:2.6.5 Rake Version: 13.0.6 Redis Version: 7.2.7 Sidekiq Version:7.3.9 Go Version: unknown GitLab information Version: 17.11.0-pre Revision: 1bcb23968e5 Directory: /opt/gitlab/embedded/service/gitlab-rails DB Adapter: PostgreSQL DB Version: 16.8 URL: https://{redacted} HTTP Clone URL: https://{redacted}/some-group/some-project.git SSH Clone URL: git@e2e.gamma.dev.us-east-1.gitlab.falco.ai.aws.dev:some-group/some-project.git Elasticsearch: no Geo: no Using LDAP: no Using Omniauth: yes Omniauth Providers: GitLab Shell Version: 14.41.0 Repository storages: - default: unix:/var/opt/gitlab/gitaly/gitaly.socket GitLab Shell path: /opt/gitlab/embedded/service/gitlab-shell Gitaly - default Address: unix:/var/opt/gitlab/gitaly/gitaly.socket - default Version: 17.10.0-rc1-197-g58bf41c6a - default Git Version: 2.49.0.gl1 </pre> </details> #### Results of GitLab application Check  <details> <summary>Expand for output related to the GitLab application check</summary> <pre> /opt/gitlab/embedded/lib/ruby/gems/3.3.0/gems/fast_gettext-2.3.0/lib/fast_gettext/vendor/mofile.rb:24: warning: prime was loaded from the standard library, but is not part of the default gems starting from Ruby 3.1.0. You can add prime to your Gemfile or gemspec to silence this warning. Checking GitLab subtasks ... Checking GitLab Shell ... GitLab Shell: ... GitLab Shell version >= 14.41.0 ? ... OK (14.41.0) Running /opt/gitlab/embedded/service/gitlab-shell/bin/gitlab-shell-check Internal API available: OK Redis available via internal API: OK gitlab-shell self-check successful Checking GitLab Shell ... Finished Checking Gitaly ... Gitaly: ... default ... OK Checking Gitaly ... Finished Checking Sidekiq ... Sidekiq: ... Running? ... yes Number of Sidekiq processes (cluster/worker) ... 1/1 Checking Sidekiq ... Finished Checking Incoming Email ... Incoming Email: ... Reply by email is disabled in config/gitlab.yml Checking Incoming Email ... Finished Checking LDAP ... LDAP: ... LDAP is disabled in config/gitlab.yml Checking LDAP ... Finished Checking GitLab App ... Database config exists? ... yes Tables are truncated? ... skipped All migrations up? ... yes Database contains orphaned GroupMembers? ... no GitLab config exists? ... yes GitLab config up to date? ... yes Cable config exists? ... yes Resque config exists? ... yes Log directory writable? ... yes Tmp directory writable? ... yes Uploads directory exists? ... yes Uploads directory has correct permissions? ... yes Uploads directory tmp has correct permissions? ... yes Systemd unit files or init script exist? ... skipped (omnibus-gitlab has neither init script nor systemd units) Systemd unit files or init script up-to-date? ... skipped (omnibus-gitlab has neither init script nor systemd units) Projects have namespace: ... 3/1 ... yes 13/4 ... yes 19/5 ... yes 11/6 ... yes 19/7 ... yes 19/8 ... yes 19/9 ... yes 31/10 ... yes 31/11 ... yes 37/12 ... yes 40/13 ... yes 39/15 ... yes 19/16 ... yes 50/17 ... yes 29/18 ... yes 57/20 ... yes 57/21 ... yes 57/22 ... yes 13/23 ... yes 57/24 ... yes 44/25 ... yes 78/26 ... yes 19/27 ... yes 13/28 ... yes 57/29 ... yes 13/30 ... yes 13/31 ... yes 13/32 ... yes 13/33 ... yes Redis version >= 6.2.14? ... yes Ruby version >= 3.0.6 ? ... yes (3.3.7) Git user has default SSH configuration? ... yes Active users: ... 42 Is authorized keys file accessible? ... yes GitLab configured to store new projects in hashed storage? ... yes All projects are in hashed storage? ... yes Elasticsearch version 7.x-8.x or OpenSearch version 1.x ... skipped (Advanced Search is disabled) All migrations must be finished before doing a major upgrade ... skipped (Advanced Search is disabled) Checking GitLab App ... Finished Checking GitLab subtasks ... Finished </pre> </details> ### Possible fixes

issue