Class: Synapse::ConfigGenerator::Nginx

Inherits:
BaseGenerator
  • Object
show all
Includes:
Logging
Defined in:
lib/synapse/config_generator/nginx.rb

Constant Summary collapse

NAME = 
'nginx'.freeze

Instance Method Summary collapse

Constructor Details

#initialize(opts) ⇒ Nginx

Returns a new instance of Nginx.



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# File 'lib/synapse/config_generator/nginx.rb', line 12

def initialize(opts)
  %w{main events}.each do |req|
    if !opts.fetch('contexts', {}).has_key?(req)
      raise ArgumentError, "nginx requires a contexts.#{req} section"
    end
  end

  @opts = opts
  @contexts = opts['contexts']
  @opts['do_writes'] = true unless @opts.key?('do_writes')
  @opts['do_reloads'] = true unless @opts.key?('do_reloads')

  req_pairs = {
    'do_writes' => ['config_file_path', 'check_command'],
    'do_reloads' => ['reload_command', 'start_command'],
  }

  req_pairs.each do |cond, reqs|
    if opts[cond]
      unless reqs.all? {|req| opts[req]}
        missing = reqs.select {|req| not opts[req]}
        raise ArgumentError, "the `#{missing}` option(s) are required when `#{cond}` is true"
      end
    end
  end

  # how to restart nginx
  @restart_interval = @opts.fetch('restart_interval', 2).to_i
  @restart_jitter = @opts.fetch('restart_jitter', 0).to_f
  @restart_required = false
  @has_started = false

  # virtual clock bookkeeping for controlling how often nginx restarts
  @time = 0
  @next_restart = @time

  # a place to store generated server + upstream stanzas, and watcher
  # revisions so we can save CPU on updates by not re-computing stanzas
  @servers_cache = {}
  @upstreams_cache = {}
  @watcher_revisions = {}
end

Instance Method Details

#construct_name(backend) ⇒ Object

used to build unique, consistent nginx names for backends



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# File 'lib/synapse/config_generator/nginx.rb', line 334

def construct_name(backend)
  name = "#{backend['host']}:#{backend['port']}"
  if backend['name'] && !backend['name'].empty?
    name = "#{backend['name']}_#{name}"
  end

  return name
end

#generate_base_config ⇒ Object

generates the global and defaults sections of the config file



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# File 'lib/synapse/config_generator/nginx.rb', line 151

def generate_base_config
  base_config = ["# auto-generated by synapse at #{Time.now}\n"]

  # The "main" context is special and is the top level
  @contexts['main'].each do |option|
    base_config << "#{option};"
  end
  base_config << "\n"

  # http and streams are generated separately
  @contexts.keys.select{|key| !(["main", "http", "stream"].include?(key))}.each do |context|
    base_config << "#{context} {"
    @contexts[context].each do |option|
      base_config << "\t#{option};"
    end
    base_config << "}\n"
  end
  return base_config
end

#generate_config(watchers) ⇒ Object

generates a new config based on the state of the watchers



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# File 'lib/synapse/config_generator/nginx.rb', line 96

def generate_config(watchers)
  new_config = generate_base_config

  http = (@contexts['http'] || []).collect {|option| "\t#{option};"}
  stream = (@contexts['stream'] || []).collect {|option| "\t#{option};"}

  watchers.each do |watcher|
    watcher_config = watcher.config_for_generator[name]
    next if watcher_config['disabled']
    # There seems to be no way to have empty TCP listeners ... just
    # don't bind the port at all? ... idk
    next if watcher_config['mode'] == 'tcp' && watcher.backends.empty?


    # Only regenerate if something actually changed. This saves a lot
    # of CPU load for high churn systems
    regenerate = watcher.revision != @watcher_revisions[watcher.name] ||
                 @servers_cache[watcher.name].nil? ||
                 @upstreams_cache[watcher.name].nil?

    if regenerate
      @servers_cache[watcher.name] = generate_server(watcher).flatten
      @upstreams_cache[watcher.name] = generate_upstream(watcher).flatten
      @watcher_revisions[watcher.name] = watcher.revision
    end

    section = case watcher_config['mode']
      when 'http'
        http
      when 'tcp'
        stream
      else
        raise ArgumentError, "synapse does not understand #{watcher_config['mode']} as a service mode"
    end
    section << @servers_cache[watcher.name]
    section << @upstreams_cache[watcher.name]
  end

  unless http.empty?
    new_config << 'http {'
    new_config.concat(http.flatten)
    new_config << "}\n"
  end

  unless stream.empty?
    new_config << 'stream {'
    new_config.concat(stream.flatten)
    new_config << "}\n"
  end

  log.debug "synapse: new nginx config: #{new_config}"
  return new_config.flatten.join("\n")
end

#generate_proxy(mode, upstream_name, empty_upstream) ⇒ Object

Nginx has some annoying differences between how upstreams in the http (http) module and the stream (tcp) module address upstreams



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# File 'lib/synapse/config_generator/nginx.rb', line 206

def generate_proxy(mode, upstream_name, empty_upstream)
  upstream_name = "http://#{upstream_name}" if mode == 'http'

  case mode
  when 'http'
    if empty_upstream
      value = "\t\t\treturn 503;"
    else
      value = "\t\t\tproxy_pass #{upstream_name};"
    end
    stanza = [
      "\t\tlocation / {",
      value,
      "\t\t}"
    ]
  when 'tcp'
    stanza = [
      "\t\tproxy_pass #{upstream_name};",
    ]
  else
    []
  end
end

#generate_server(watcher) ⇒ Object 



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# File 'lib/synapse/config_generator/nginx.rb', line 171

def generate_server(watcher)
  watcher_config = watcher.config_for_generator[name]
  unless watcher_config.has_key?('port')
    log.debug "synapse: not generating server stanza for watcher #{watcher.name} because it has no port defined"
    return []
  else
    port = watcher_config['port']
  end

  listen_address = (
    watcher_config['listen_address'] ||
    opts['listen_address'] ||
    'localhost'
  )

  listen_line= [
    "\t\tlisten",
    "#{listen_address}:#{port}",
    watcher_config['listen_options'],
    ';',
  ].compact.join(' ')


  upstream_name = watcher_config.fetch('upstream_name', watcher.name)
  stanza = [
    "\tserver {",
    listen_line,
    watcher_config['server'].map {|c| "\t\t#{c};"},
    generate_proxy(watcher_config['mode'], upstream_name, watcher.backends.empty?),
    "\t}",
  ]
end

#generate_upstream(watcher) ⇒ Object 



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# File 'lib/synapse/config_generator/nginx.rb', line 230

def generate_upstream(watcher)
  backends = {}
  watcher_config = watcher.config_for_generator[name]
  upstream_name = watcher_config.fetch('upstream_name', watcher.name)

  watcher.backends.each {|b| backends[construct_name(b)] = b}

  # nginx doesn't like upstreams with no backends?
  return [] if backends.empty?

  # Note that because we use the config file as the source of truth
  # for whether or not to reload, we want some kind of sorted order
  # by default, in this case we choose asc
  keys = case watcher_config['upstream_order']
  when 'desc'
    backends.keys.sort.reverse
  when 'shuffle'
    backends.keys.shuffle
  when 'no_shuffle'
    backends.keys
  else
    backends.keys.sort
  end

  stanza = [
    "\tupstream #{upstream_name} {",
    watcher_config['upstream'].map {|c| "\t\t#{c};"},
    keys.map {|backend_name|
      backend = backends[backend_name]
      b = "\t\tserver #{backend['host']}:#{backend['port']}"
      b = "#{b} #{watcher_config['server_options']}" if watcher_config['server_options']
      "#{b};"
    },
    "\t}"
  ]
end

#normalize_watcher_provided_config(service_watcher_name, service_watcher_config) ⇒ Object 



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# File 'lib/synapse/config_generator/nginx.rb', line 55

def normalize_watcher_provided_config(service_watcher_name, service_watcher_config)
  service_watcher_config = super(service_watcher_name, service_watcher_config)
  defaults = {
    'mode' => 'http',
    'upstream' => [],
    'server' => [],
    'disabled' => false,
  }

  unless service_watcher_config.include?('port') || service_watcher_config['disabled']
    log.warn "synapse: service #{service_watcher_name}: nginx config does not include a port; only upstream sections for the service will be created; you must move traffic there manually using server sections"
  end

  defaults.merge(service_watcher_config)
end

#restart ⇒ Object

restarts nginx if the time is right



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# File 'lib/synapse/config_generator/nginx.rb', line 311

def restart
  if @time < @next_restart
    log.info "synapse: at time #{@time} waiting until #{@next_restart} to restart"
    return
  end

  @next_restart = @time + @restart_interval
  @next_restart += rand(@restart_jitter * @restart_interval + 1)

  # On the very first restart we may need to start
  start unless @has_started

  res = `#{opts['reload_command']}`.chomp
  unless $?.success?
    log.error "failed to reload nginx via #{opts['reload_command']}: #{res}"
    return
  end
  log.info "synapse: restarted nginx"

  @restart_required = false
end

#start ⇒ Object 



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# File 'lib/synapse/config_generator/nginx.rb', line 297

def start
  log.info "synapse: attempting to run #{opts['start_command']} to get nginx started"
  log.info 'synapse: this can fail if nginx is already running'
  begin
    `#{opts['start_command']}`.chomp
  rescue Exception => e
    log.warn "synapse: error in NGINX start: #{e.inspect}"
    log.warn e.backtrace
  ensure
    @has_started = true
  end
end

#tick(watchers) ⇒ Object 



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# File 'lib/synapse/config_generator/nginx.rb', line 71

def tick(watchers)
  @time += 1

  # Always ensure we try to start at least once
  # Note that this should only trigger during error cases where for
  # some reason Synapse could not start NGINX during the initial restart
  start if opts['do_reloads'] && !@has_started

  # We potentially have to restart if the restart was rate limited
  # in the original call to update_config
  restart if opts['do_reloads'] && @restart_required
end

#update_config(watchers) ⇒ Object 



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# File 'lib/synapse/config_generator/nginx.rb', line 84

def update_config(watchers)
  # generate a new config
  new_config = generate_config(watchers)

  # if we write config files, lets do that and then possibly restart
  if opts['do_writes']
    @restart_required = write_config(new_config)
    restart if opts['do_reloads'] && @restart_required
  end
end

#write_config(new_config) ⇒ Object

writes the config



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# File 'lib/synapse/config_generator/nginx.rb', line 268

def write_config(new_config)
  begin
    old_config = File.read(opts['config_file_path'])
  rescue Errno::ENOENT => e
    log.info "synapse: could not open nginx config file at #{opts['config_file_path']}"
    old_config = ""
  end

  # The first line of the config files contain a timestamp, so to prevent
  # un-needed restarts, only compare after that. We do not split on
  # newlines and compare because this is called a lot, and we need to be
  # as CPU efficient as possible.
  old_version =  old_config[(old_config.index("\n") || 0) + 1..-1]
  new_version =  new_config[(new_config.index("\n") || 0) + 1..-1]
  if old_version == new_version
    return false
  else
    File.open(opts['config_file_path'],'w') {|f| f.write(new_config)}
    check = `#{opts['check_command']}`.chomp
    unless $?.success?
      log.error "synapse: nginx configuration is invalid according to #{opts['check_command']}!"
      log.error 'synapse: not restarting nginx as a result'
      return false
    end

    return true
  end
end