Add documentation

lib/gitlab_monitor.rb

 module GitLab
+  # GitLab Monitoring
   module Monitor
     autoload :CLI,               "gitlab_monitor/cli"
     autoload :TimeTracker,       "gitlab_monitor/util"

lib/gitlab_monitor/cli.rb

 module GitLab
   module Monitor
+    # Stores runner classes in a single place
+    #
+    # The entry point is the module method "for" which takes the name of a runner.
+    # In case the runner is invalid it will return a NullRunner which fails with an
+    # InvalidCLICommand error, which contains the general application usage instructions.
     module CLI
       EXECUTABLE_NAME = "gitlab-mon".freeze
 
@@ -9,6 +14,8 @@ module GitLab
 
       class InvalidCLICommand < RuntimeError; end
 
+      # Empty runner that will raise an InvalidCLICommand when executed to provide the usage
+      # in the exception message
       class NullRunner
         def initialize(args)
         end
@@ -19,6 +26,12 @@ module GitLab
         end
       end
 
+      # Git runner.
+      #
+      # Takes something that behaves like ARGV with optparse included as an argument.
+      #
+      # It will take 2 positional arguments once parsed, the first one for the repository location,
+      # the optional second one is an IO like object to write to
       class GIT
         COMMAND_NAME = "git".freeze
 

lib/gitlab_monitor/git.rb

@@ -2,6 +2,14 @@ require "open3"
 
 module GitLab
   module Monitor
+    # Git monitoring helping class
+    #
+    # Takes a repository path for construction and provides 2 main methods:
+    #   - pull
+    #   - push
+    #
+    # Both methods return a CommandResult which includes the output of the execution
+    # plus the tracked execution time.
     class Git
       def initialize(repo)
         fail "Repository #{repo} does not exists" unless Dir.exist? repo
@@ -31,6 +39,10 @@ module GitLab
       end
     end
 
+    # Result of a command
+    #
+    # Provides some handy methods for checking if the execution failed and a simple to_s that will
+    # return the command output
     CommandResult = Struct.new(:stdout, :status) do
       def failed?
         status.nonzero?
@@ -45,6 +57,10 @@ module GitLab
       end
     end
 
+    # Handles creating a Git object, probing for both pull and push, and finally writing to metrics
+    #
+    # Optionally takes a metrics object which by default is a PrometheusMetrics, useful to change the
+    # metrics writer to something else.
     class GitProber
       def initialize(options, metrics: PrometheusMetrics.new)
         @metrics = metrics

lib/gitlab_monitor/prometheus.rb

 module GitLab
   module Monitor
+    # Prometheus metrics container
+    #
+    # Provides a simple API to `add` metrics and then turn them `to_s` which will just
+    # dump all the metrics in prometheus format
+    #
+    # The add method also can take any arbitrary amount of labels in a `key: value` format.
     class PrometheusMetrics
       def initialize
         @metrics = {}

lib/gitlab_monitor/util.rb

 module GitLab
   module Monitor
+    # Simple time wrapper that provides a to_i and wraps the execution result
     TrackedResult = Struct.new(:result, :time) do
       def to_i
         time
       end
     end
 
+    # Time tracking object
+    #
+    # Provides a simple time tracking, and returns back the result plus the tracked time
+    # wraped in a TrackedResult struct
     class TimeTracker
       def track
         @start = Time.now.to_f