• Douwe Maan's avatar
    Merge branch '18451-track-new-redis-connections' into 'master' · 8249fdcd
    Douwe Maan authored
    Resolve "Track the number of new Redis connections per transaction"
    
    ## What does this MR do?
    
    Add a new metric counter, `new_redis_connections`, that contains the number of calls to `Redis::Client#connect` in the current transaction.
    
    ## Are there points in the code the reviewer needs to double check?
    
    Not sure. I tested this in kind of a brute-force way:
    
    1. Add a debugger in the monkey-patched `connect` method.
    2. With metrics enabled, start the app and load a page.
    3. The first Redis connection is created by `Rack::Attack` and isn't in a transaction, but still works fine.
    4. The second Redis connection is within a transaction (the page load), and increments the counter.
    5. If I reload the page, neither debugger is hit.
    6. If I use a Redis client and do `CLIENT KILL` on my two existing clients, then reload the page, I get 3 and 4 again.
    7. If I disable metrics collection, the debugger never gets hit.
    
    ## Why was this MR needed?
    
    We may have a Redis connection leak somewhere, so adding metrics will let us track this.
    
    ## What are the relevant issue numbers?
    
    Closes #18451.
    
    ## Screenshots (if relevant)
    
    Hahaha nope, not relevant.
    
    ## Does this MR meet the acceptance criteria?
    
    - [ ] [CHANGELOG](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CHANGELOG) entry added
    - [ ] [Documentation created/updated](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/doc/development/doc_styleguide.md)
    - [ ] API support added
    - [ ] Tests
      - [ ] Added for this feature/bug
      - [ ] All builds are passing
    - [ ] Conform by the [style guides](https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#style-guides)
    - [ ] Branch has no merge conflicts with `master` (if you do - rebase it please)
    - [ ] [Squashed related commits together](https://git-scm.com/book/en/Git-Tools-Rewriting-History#Squashing-Commits)
    
    cc @yorickpeterse 
    
    See merge request !4649
    8249fdcd
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CHANGELOG 151 KB