Adding command line option to specify state file location

README.md

@@ -8,7 +8,7 @@ It can be used to monitor web services and worker services. The web services typ
 This gem is inspired by [HireFire](https://manager.hirefire.io/) and was indeed motivated by the migration
 from [Heroku](https://www.heroku.com/) to Docker Swarm mode.
 
-## Installation (not published yet to rubygems)
+## Installation
 
 Add this line to your application's Gemfile:
 
@@ -36,6 +36,10 @@ Configuration is read from `scaltainer.yml` by default. If you want to read from
 Note that after each run a new file is created (`yourconfig.yml.state`) which stores the state of the previous run.
 This is because there are some configuration parameters (like sensitivity) need to
 remember previous runs.
+If you want to specify a different location for the state file, add the `--state-file` parameter.
+Example:
+
+    scaltainer -f /path/to/configuration/file.yml --state-file /path/to/different/state/file.yml
 
 Typically, the above command should be put inside a cronjob that is triggered every minute or so.
 
@@ -56,6 +60,7 @@ for each worker.
 - `NEW_RELIC_LICENSE_KEY`: New Relic license key. Currently New Relic
 is used to retrieve average response time metric for web services.
 More monitoring services can be added in the future.
+
 - `RESPONSE_TIME_WINDOW`: Time window in minutes to measure
 average response time till the moment. For example 3 means
 measure average response time in the past 3 minutes. Default value is 5.

exe/scaltainer

@@ -3,8 +3,8 @@
 require 'scaltainer'
 
 begin
-  configfile, logger = Scaltainer::Command.parse ARGV
-  Scaltainer::Runner.new configfile, logger
+  configfile, statefile, logger = Scaltainer::Command.parse ARGV
+  Scaltainer::Runner.new configfile, statefile, logger
 rescue => e
   $stderr.puts e.message
   $stderr.puts e.backtrace

lib/scaltainer/command.rb

@@ -4,23 +4,28 @@
 module Scaltainer
   class Command
     def self.parse(args)
-      configfile = 'scaltainer.yml'
+      configfile, statefile = 'scaltainer.yml', nil
       OptionParser.new do |opts|
         opts.banner = "Usage: scaltainer [options]"
-        opts.on("-f", "--file FILE", "Specify configuration file (default: scaltainer.yml)") do |file|
+        opts.on("-f", "--conf-file FILE", "Specify configuration file (default: scaltainer.yml)") do |file|
           configfile = file
         end
+        opts.on("--state-file FILE", "Specify state file (default: <conf-file>.state)") do |file|
+          statefile = file
+        end
         opts.on_tail("-h", "--help", "Show this message") do
           puts opts
           exit
         end     
       end.parse!
 
+      statefile = "#{configfile}.state" unless statefile
+
       raise ConfigurationError.new("File not found: #{configfile}") unless File.exists?(configfile)
       logger = Logger.new(STDOUT)
       logger.level = %w(debug info warn error fatal unknown).find_index((ENV['LOG_LEVEL'] || '').downcase) || 1
 
-      return configfile, logger
+      return configfile, statefile, logger
     end
   end
 end

lib/scaltainer/runner.rb

@@ -2,7 +2,7 @@
 
 module Scaltainer
   class Runner
-    def initialize(configfile, logger)
+    def initialize(configfile, statefile, logger)
       @logger = logger
       @default_service_config = {
         "min" => 0,
@@ -11,11 +11,10 @@ def initialize(configfile, logger)
         "upscale_sensitivity" => 1,
         "downscale_sensitivity" => 1
       }
-      @logger.debug "Scaltainer initialized with configuration file: #{configfile}"
+      @logger.debug "Scaltainer initialized with configuration file: #{configfile}, and state file: #{statefile}"
       config = YAML.load_file configfile
       Docker.logger = @logger
-      statefile = "#{configfile}.state"
-      state = get_state statefile || {}
+      state = get_state(statefile) || {}
       endpoint = config["endpoint"]
       service_prefix = config["stack_name"]
       iterate_services config["web_services"], service_prefix, ServiceTypeWeb.new(endpoint), state