BigW Consortium Gitlab

  1. 17 Aug, 2016 1 commit
    • Tracking of custom events · d345591f
      Yorick Peterse authored
      GitLab Performance Monitoring is now able to track custom events not
      directly related to application performance. These events include the
      number of tags pushed, repositories created, builds registered, etc.
      
      The use of these events is to get a better overview of how a GitLab
      instance is used and how that may affect performance. For example, a
      large number of Git pushes may have a negative impact on the underlying
      storage engine.
      
      Events are stored in the "events" measurement and are not prefixed with
      "rails_" or "sidekiq_", this makes it easier to query events with the
      same name triggered from different parts of the application. All events
      being stored in the same measurement also makes it easier to downsample
      data.
      
      Currently the following events are tracked:
      
      * Creating repositories
      * Removing repositories
      * Changing the default branch of a repository
      * Pushing a new tag
      * Removing an existing tag
      * Pushing a commit (along with the branch being pushed to)
      * Pushing a new branch
      * Removing an existing branch
      * Importing a repository (along with the URL we're importing)
      * Forking a repository (along with the source/target path)
      * CI builds registered (and when no build could be found)
      * CI builds being updated
      * Rails and Sidekiq exceptions
      
      Fixes gitlab-org/gitlab-ce#13720
  2. 28 Jun, 2016 1 commit
    • Use clock_gettime for all performance timestamps · d7b4f36a
      Yorick Peterse authored
      Process.clock_gettime allows getting the real time in nanoseconds as
      well as allowing one to get a monotonic timestamp. This offers greater
      accuracy without the overhead of having to allocate a Time instance. In
      general using Time.now/Time.new is about 2x slower than using
      Process.clock_gettime(). For example:
      
          require 'benchmark/ips'
      
          Benchmark.ips do |bench|
            bench.report 'Time.now' do
              Time.now.to_f
            end
      
            bench.report 'clock_gettime' do
              Process.clock_gettime(Process::CLOCK_MONOTONIC, :millisecond)
            end
      
            bench.compare!
          end
      
      Running this benchmark gives:
      
          Calculating -------------------------------------
                      Time.now   108.052k i/100ms
                 clock_gettime   125.984k i/100ms
          -------------------------------------------------
                      Time.now      2.343M (± 7.1%) i/s -     11.670M
                 clock_gettime      4.979M (± 0.8%) i/s -     24.945M
      
          Comparison:
                 clock_gettime:  4979393.8 i/s
                      Time.now:  2342986.8 i/s - 2.13x slower
      
      Another benefit of using Process.clock_gettime() is that we can simplify
      the code a bit since it can give timestamps in nanoseconds out of the
      box.
  3. 08 Apr, 2016 1 commit
    • Use more accurate timestamps for InfluxDB. · aa7cddc4
      Yorick Peterse authored
      This changes the timestamp of metrics to be more accurate/unique by
      using Time#to_f combined with a small random jitter value. This
      combination hopefully reduces the amount of collisions, though there's
      no way to fully prevent any from occurring.
      
      Fixes gitlab-com/operations#175
  4. 31 Dec, 2015 3 commits
    • Removed tracking of hostnames for metrics · cafc784e
      Yorick Peterse authored
      This isn't hugely useful and mostly wastes InfluxDB space. We can re-add
      this whenever needed (but only once we really need it).
    • Use separate series for Rails/Sidekiq transactions · bd9f86bb
      Yorick Peterse authored
      This removes the need for tagging all metrics with a "process_type" tag.
    • Removed various default metrics tags · c936e4e3
      Yorick Peterse authored
      While it's useful to keep track of the different versions (Ruby, GitLab,
      etc) doing so for every point wastes disk space and possibly also RAM
      (which InfluxDB is all to eager to gobble up). If we want to see the
      performance differences between different GitLab versions simply looking
      at the performance since the last release date should suffice.
  5. 29 Dec, 2015 1 commit
    • Write to InfluxDB directly via UDP · 620e7bb3
      Yorick Peterse authored
      This removes the need for Sidekiq and any overhead/problems introduced
      by TCP. There are a few things to take into account:
      
      1. When writing data to InfluxDB you may still get an error if the
         server becomes unavailable during the write. Because of this we're
         catching all exceptions and just ignore them (for now).
      2. Writing via UDP apparently requires the timestamp to be in
         nanoseconds. Without this data either isn't written properly.
      3. Due to the restrictions on UDP buffer sizes we're writing metrics one
         by one, instead of writing all of them at once.
  6. 17 Dec, 2015 1 commit
    • Storing of application metrics in InfluxDB · 141e946c
      Yorick Peterse authored
      This adds the ability to write application metrics (e.g. SQL timings) to
      InfluxDB. These metrics can in turn be visualized using Grafana, or
      really anything else that can read from InfluxDB. These metrics can be
      used to track application performance over time, between different Ruby
      versions, different GitLab versions, etc.
      
      == Transaction Metrics
      
      Currently the following is tracked on a per transaction basis (a
      transaction is a Rails request or a single Sidekiq job):
      
      * Timings per query along with the raw (obfuscated) SQL and information
        about what file the query originated from.
      * Timings per view along with the path of the view and information about
        what file triggered the rendering process.
      * The duration of a request itself along with the controller/worker
        class and method name.
      * The duration of any instrumented method calls (more below).
      
      == Sampled Metrics
      
      Certain metrics can't be directly associated with a transaction. For
      example, a process' total memory usage is unrelated to any running
      transactions. While a transaction can result in the memory usage going
      up there's no accurate way to determine what transaction is to blame,
      this becomes especially problematic in multi-threaded environments.
      
      To solve this problem there's a separate thread that takes samples at a
      fixed interval. This thread (using the class Gitlab::Metrics::Sampler)
      currently tracks the following:
      
      * The process' total memory usage.
      * The number of file descriptors opened by the process.
      * The amount of Ruby objects (using ObjectSpace.count_objects).
      * GC statistics such as timings, heap slots, etc.
      
      The default/current interval is 15 seconds, any smaller interval might
      put too much pressure on InfluxDB (especially when running dozens of
      processes).
      
      == Method Instrumentation
      
      While currently not yet used methods can be instrumented to track how
      long they take to run. Unlike the likes of New Relic this doesn't
      require modifying the source code (e.g. including modules), it all
      happens from the outside. For example, to track `User.by_login` we'd add
      the following code somewhere in an initializer:
      
          Gitlab::Metrics::Instrumentation.
            instrument_method(User, :by_login)
      
      to instead instrument an instance method:
      
          Gitlab::Metrics::Instrumentation.
            instrument_instance_method(User, :save)
      
      Instrumentation for either all public model methods or a few crucial
      ones will be added in the near future, I simply haven't gotten to doing
      so just yet.
      
      == Configuration
      
      By default metrics are disabled. This means users don't have to bother
      setting anything up if they don't want to. Metrics can be enabled by
      editing one's gitlab.yml configuration file (see
      config/gitlab.yml.example for example settings).
      
      == Writing Data To InfluxDB
      
      Because InfluxDB is still a fairly young product I expect the worse.
      Data loss, unexpected reboots, the database not responding, you name it.
      Because of this data is _not_ written to InfluxDB directly, instead it's
      queued and processed by Sidekiq. This ensures that users won't notice
      anything when InfluxDB is giving trouble.
      
      The metrics worker can be started in a standalone manner as following:
      
          bundle exec sidekiq -q metrics
      
      The corresponding class is called MetricsWorker.