class Sensu::Server::Process

Constants

DEFAULT_HANDLER_NAME
EVENT_FLAPPING_ACTION
METRIC_CHECK_TYPE
STANDARD_CHECK_TYPE

Attributes

in_progress[R]
is_leader[R]

Public Class Methods

new(options={}) click to toggle source

Override Daemon initialize() to support Sensu server leader election and the handling event count.

@param options [Hash]

Calls superclass method Sensu::Daemon.new
# File lib/sensu/server/process.rb, line 41
def initialize(options={})
  super
  @is_leader = false
  @timers[:leader] = Array.new
  @in_progress = Hash.new(0)
end
run(options={}) click to toggle source

Create an instance of the Sensu server process, start the server within the EventMachine event loop, and set up server process signal traps (for stopping).

@param options [Hash]

# File lib/sensu/server/process.rb, line 29
def self.run(options={})
  server = self.new(options)
  EM::run do
    server.start
    server.setup_signal_traps
  end
end

Public Instance Methods

aggregate_check_result(client, check) click to toggle source

Add a check result to one or more aggregates. The aggregate name is determined by the value of check `:aggregates` array, if present, and falling back to `:aggregate` otherwise.

When one or more aggregates are specified as `:aggregates`, the client name and check are updated on each aggregate.

When no aggregates are specified as `:aggregates`, and `:aggregate` is `true` (legacy), the check `:name` is used as the aggregate name.

When no aggregates are specified as `:aggregates` and check `:aggregate` is a string, it used as the aggregate name.

This method will add the client name to configured aggregates, all other processing (e.g. counters) is done by the Sensu API on request.

@param client [Hash] @param check [Hash]

# File lib/sensu/server/process.rb, line 295
def aggregate_check_result(client, check)
  check_aggregate = (check[:aggregate].is_a?(String) ? check[:aggregate] : check[:name])
  aggregate_list = Array(check[:aggregates] || check_aggregate)
  aggregate_list.each do |aggregate|
    @logger.debug("adding check result to aggregate", {
      :aggregate => aggregate,
      :client => client,
      :check => check
    })
    aggregate_member = "#{client[:name]}:#{check[:name]}"
    @redis.sadd("aggregates:#{aggregate}", aggregate_member) do
      @redis.sadd("aggregates", aggregate)
    end
  end
end
become_the_leader() click to toggle source

Become the Sensu server leader, responsible for specific duties (`leader_duties()`). Unless the current process is already the leader, this method sets the leader ID stored in Redis to the unique random leader ID for the process. If the leader ID in Redis is successfully updated, `@is_leader` is set to true and `leader_duties()` is called to begin the tasks/duties of the Sensu server leader.

# File lib/sensu/server/process.rb, line 1029
def become_the_leader
  unless @is_leader
    @redis.set("leader", leader_id) do
      @logger.info("i am now the leader")
      @is_leader = true
      leader_duties
    end
  else
    @logger.debug("i am already the leader")
  end
end
bootstrap() click to toggle source

Bootstrap the Sensu server process, setting up the keepalive and check result consumers, and attemping to become the leader to carry out its duties. This method sets the process/daemon `@state` to `:running`.

# File lib/sensu/server/process.rb, line 1161
def bootstrap
  setup_keepalives
  setup_results
  setup_leader_monitor
  @state = :running
end
calculate_check_execution_splay(check) click to toggle source

Calculate a check execution splay, taking into account the current time and the execution interval to ensure it's consistent between process restarts.

@param check [Hash] definition.

# File lib/sensu/server/process.rb, line 767
def calculate_check_execution_splay(check)
  splay_hash = Digest::MD5.digest(check[:name]).unpack('Q<').first
  current_time = (Time.now.to_f * 1000).to_i
  (splay_hash - current_time) % (check[:interval] * 1000) / 1000.0
end
check_flapping?(stored_event, check) click to toggle source

Determine if a check state is flapping, rapidly changing between an OK and non-OK state. Flap detection is only done for checks that have defined low and hight flap detection thresholds, `:low_flap_threshold` and `:high_flap_threshold`. The `check_history()` method provides the check history and more importantly the total state change precentage value that is compared with the configured thresholds defined in the check data. If a check hasn't been flapping, the `:total_state_change` must be equal to or higher than the `:high_flap_threshold` to be changed to flapping. If a check has been flapping, the `:total_state_change` must be equal to or lower than the `:low_flap_threshold` to no longer be flapping. This method uses the same algorithm as Nagios: nagios.sourceforge.net/docs/3_0/flapping.html

@param stored_event [Hash] @param check [Hash] @return [TrueClass, FalseClass]

# File lib/sensu/server/process.rb, line 423
def check_flapping?(stored_event, check)
  if check.has_key?(:low_flap_threshold) && check.has_key?(:high_flap_threshold)
    was_flapping = stored_event && stored_event[:action] == EVENT_FLAPPING_ACTION
    if was_flapping
      check[:total_state_change] > check[:low_flap_threshold]
    else
      check[:total_state_change] >= check[:high_flap_threshold]
    end
  else
    false
  end
end
check_history(client, check) { |history, total_state_change| ... } click to toggle source

Fetch the execution history for a client/check pair, the 21 most recent check result statuses. This method also calculates the total state change percentage for the history, this value is use for check state flap detection, using a similar algorithm to Nagios: nagios.sourceforge.net/docs/3_0/flapping.html

@param client [Hash] @param check [Hash] @yield [history, total_state_change] callback/block to call

with the check history and calculated total state change
value.

@yieldparam history [Array] containing the last 21 check

result exit status codes.

@yieldparam total_state_change [Float] percentage for the

check history (exit status codes).
# File lib/sensu/server/process.rb, line 384
def check_history(client, check)
  history_key = "history:#{client[:name]}:#{check[:name]}"
  @redis.lrange(history_key, -21, -1) do |history|
    total_state_change = 0
    unless history.length < 21
      state_changes = 0
      change_weight = 0.8
      previous_status = history.first
      history.each do |status|
        unless status == previous_status
          state_changes += change_weight
        end
        change_weight += 0.02
        previous_status = status
      end
      total_state_change = (state_changes.fdiv(20) * 100).to_i
    end
    yield(history, total_state_change)
  end
end
complete_in_progress() { || ... } click to toggle source

Complete in progress work and then call the provided callback. This method will wait until all counters stored in the `@in_progress` hash equal `0`.

@yield [] callback/block to call when in progress work is

completed.
# File lib/sensu/server/process.rb, line 1147
def complete_in_progress
  @logger.info("completing work in progress", :in_progress => @in_progress)
  retry_until_true do
    if @in_progress.values.all? { |count| count == 0 }
      yield
      true
    end
  end
end
create_client(name) click to toggle source

Create a blank client (data). Only the client name is known, the other client attributes must be updated via the API (POST /clients:client). Dynamically created clients and those updated via the API will have client keepalives disabled by default, `:keepalives` is set to `false`.

@param name [String] to use for the client. @return [Hash] client.

# File lib/sensu/server/process.rb, line 581
def create_client(name)
  {
    :name => name,
    :address => "unknown",
    :subscriptions => ["client:#{name}"],
    :keepalives => false,
    :version => VERSION
  }
end
create_client_keepalive_check_results(clients) { || ... } click to toggle source

Create client keepalive check results. This method will retrieve clients from the registry, creating a keepalive check definition for each client, using the `create_keepalive_check()` method, containing client specific keepalive thresholds. If the time since the latest keepalive is equal to or greater than a threshold, the check `:output` is set to a descriptive message, and `:status` is set to the appropriate non-zero value. If a client has been sending keepalives, `:output` and `:status` are set to indicate an OK state. The `publish_check_result()` method is used to publish the client keepalive check results.

@param clients [Array] of client names. @yield [] callback/block called after the client keepalive

check results have been created.
# File lib/sensu/server/process.rb, line 885
def create_client_keepalive_check_results(clients)
  client_keys = clients.map { |client_name| "client:#{client_name}" }
  @redis.mget(*client_keys) do |client_json_objects|
    client_json_objects.each do |client_json|
      unless client_json.nil?
        client = Sensu::JSON.load(client_json)
        next if client[:keepalives] == false
        check = create_keepalive_check(client)
        time_since_last_keepalive = Time.now.to_i - client[:timestamp]
        check[:output] = "No keepalive sent from client for "
        check[:output] << "#{time_since_last_keepalive} seconds"
        case
        when time_since_last_keepalive >= check[:thresholds][:critical]
          check[:output] << " (>=#{check[:thresholds][:critical]})"
          check[:status] = 2
        when time_since_last_keepalive >= check[:thresholds][:warning]
          check[:output] << " (>=#{check[:thresholds][:warning]})"
          check[:status] = 1
        else
          check[:output] = "Keepalive sent from client "
          check[:output] << "#{time_since_last_keepalive} seconds ago"
          check[:status] = 0
        end
        publish_check_result(client[:name], check)
      end
    end
    yield
  end
end
create_client_registration_event(client) click to toggle source

Create and process a client registration event. A registration event is created when a Sensu client is first added to the client registry. The `create_registration_check()` method is called to create a registration check definition for the client.

@param client [Hash] definition.

# File lib/sensu/server/process.rb, line 99
def create_client_registration_event(client)
  check = create_registration_check(client)
  create_event(client, check) do |event|
    event_bridges(event)
    process_event(event)
  end
end
create_event(client, check) { |event| ... } click to toggle source

Create an event, using the provided client and check result data. Existing event data for the client/check pair is fetched from the event registry to be used in the composition of the new event. The silenced registry is used to determine if the event has been silenced.

@param client [Hash] @param check [Hash] @yield callback [event] callback/block called with the

resulting event.

@yieldparam event [Hash]

# File lib/sensu/server/process.rb, line 524
def create_event(client, check)
  check_history(client, check) do |history, total_state_change|
    check[:history] = history
    check[:total_state_change] = total_state_change
    @redis.hget("events:#{client[:name]}", check[:name]) do |event_json|
      stored_event = event_json ? Sensu::JSON.load(event_json) : nil
      flapping = check_flapping?(stored_event, check)
      event = {
        :client => client,
        :check => check,
        :occurrences => 1,
        :occurrences_watermark => 1,
        :action => (flapping ? :flapping : :create),
        :timestamp => Time.now.to_i
      }
      if stored_event
        event[:id] = stored_event[:id]
        event[:last_state_change] = stored_event[:last_state_change]
        event[:last_ok] = stored_event[:last_ok]
        event[:occurrences] = stored_event[:occurrences]
        event[:occurrences_watermark] = stored_event[:occurrences_watermark] || event[:occurrences]
      else
        event[:id] = random_uuid
        event[:last_ok] = event[:timestamp]
      end
      if check[:status] != 0 || flapping
        if history[-1] == history[-2]
          event[:occurrences] += 1
          if event[:occurrences] > event[:occurrences_watermark]
            event[:occurrences_watermark] = event[:occurrences]
          end
        else
          event[:occurrences] = 1
          event[:last_state_change] = event[:timestamp]
        end
      elsif stored_event
        event[:last_state_change] = event[:timestamp]
        event[:action] = :resolve
      end
      if check[:status] == 0
        event[:last_ok] = event[:timestamp]
      end
      event_silenced?(event) do |event|
        yield(event)
      end
    end
  end
end
create_keepalive_check(client) click to toggle source

Create a keepalive check definition for a client. Client definitions may contain `:keepalive` configuration, containing specific thresholds and handler information. The keepalive check definition creation begins with default thresholds, and sets the `:handler` to `keepalive`, if the handler has a local definition. If the client provides its own `:keepalive` configuration, it's deep merged with the defaults. The check `:name`, `:issued`, and `:executed` values are always overridden to guard against an invalid definition.

# File lib/sensu/server/process.rb, line 853
def create_keepalive_check(client)
  check = {
    :thresholds => {
      :warning => 120,
      :critical => 180
    }
  }
  if @settings.handler_exists?(:keepalive)
    check[:handler] = "keepalive"
  end
  if client.has_key?(:keepalive)
    check = deep_merge(check, client[:keepalive])
  end
  timestamp = Time.now.to_i
  check.merge(:name => "keepalive", :issued => timestamp, :executed => timestamp)
end
create_lock_timestamp() click to toggle source

Create a lock timestamp (integer), current time including milliseconds. This method is used by Sensu server leader election.

@return [Integer]

# File lib/sensu/server/process.rb, line 1010
def create_lock_timestamp
  (Time.now.to_f * 1000).to_i
end
create_registration_check(client) click to toggle source

Create a registration check definition for a client. Client definitions may contain `:registration` configuration, containing custom attributes and handler information. By default, the registration check definition sets the `:handler` to `registration`. If the client provides its own `:registration` configuration, it's deep merged with the defaults. The check `:name`, `:output`, `:issued`, and `:executed` values are always overridden to guard against an invalid definition.

# File lib/sensu/server/process.rb, line 77
def create_registration_check(client)
  check = {:handler => "registration", :status => 1}
  if client.has_key?(:registration)
    check = deep_merge(check, client[:registration])
  end
  timestamp = Time.now.to_i
  overrides = {
    :name => "registration",
    :output => "new client registration",
    :issued => timestamp,
    :executed => timestamp
  }
  check.merge(overrides)
end
derive_handlers(handler_list, depth=0) click to toggle source

Derive an array of handler definitions from a list of handler names. This method first checks for the existence of standard handlers, followed by handler extensions. If a handler does not exist for a name, it is logged and ignored. Duplicate handler definitions are removed.

@param handler_list [Array] @param depth [Integer] of handler set expansion. @return [Array]

# File lib/sensu/server/process.rb, line 222
def derive_handlers(handler_list, depth=0)
  handler_list.compact.map { |handler_name|
    case
    when @settings.handler_exists?(handler_name)
      handler = @settings[:handlers][handler_name].merge(:name => handler_name)
      expand_handler_sets(handler, depth)
    when @extensions.handler_exists?(handler_name)
      @extensions[:handlers][handler_name]
    else
      @logger.error("unknown handler", :handler_name => handler_name)
      nil
    end
  }.flatten.compact.uniq
end
determine_stale_check_results(interval = 30) click to toggle source

Determine stale check results, those that have not executed in a specified amount of time (check TTL). This method iterates through stored check results that have a defined TTL value (in seconds). The time since last check execution (in seconds) is calculated for each check result. If the time since last execution is equal to or greater than the check TTL, a warning check result is published with the appropriate check output.

# File lib/sensu/server/process.rb, line 956
def determine_stale_check_results(interval = 30)
  @logger.info("determining stale check results")
  @redis.smembers("ttl") do |result_keys|
    result_keys.each do |result_key|
      @redis.get("result:#{result_key}") do |result_json|
        unless result_json.nil?
          check = Sensu::JSON.load(result_json)
          next unless check[:ttl] && check[:executed] && !check[:force_resolve]
          time_since_last_execution = Time.now.to_i - check[:executed]
          if time_since_last_execution >= check[:ttl]
            client_name = result_key.split(":").first
            keepalive_event_exists?(client_name) do |event_exists|
              unless event_exists
                check[:output] = "Last check execution was "
                check[:output] << "#{time_since_last_execution} seconds ago"
                check[:status] = check[:ttl_status] || 1
                check[:interval] = interval
                publish_check_result(client_name, check)
              end
            end
          end
        else
          @redis.srem("ttl", result_key)
        end
      end
    end
  end
end
determine_stale_clients() click to toggle source

Determine stale clients, those that have not sent a keepalive in a specified amount of time. This method iterates through the client registry, creating a keepalive check result for each client. The `create_client_keepalive_check_results()` method is used to inspect and create keepalive check results for each slice of clients from the registry. A relatively small clients slice size (20) is used to reduce the number of clients inspected within a single tick of the EM reactor.

# File lib/sensu/server/process.rb, line 923
def determine_stale_clients
  @logger.info("determining stale clients")
  @redis.smembers("clients") do |clients|
    client_count = clients.length
    keepalive_check_results = Proc.new do |slice_start, slice_size|
      unless slice_start > client_count - 1
        clients_slice = clients.slice(slice_start..slice_size)
        create_client_keepalive_check_results(clients_slice) do
          keepalive_check_results.call(slice_start + 20, slice_size + 20)
        end
      end
    end
    keepalive_check_results.call(0, 19)
  end
end
event_bridges(event) click to toggle source

Run event bridge extensions, within the Sensu EventMachine reactor (event loop). The extension API `safe_run()` method is used to guard against most errors. Bridges are for relaying Sensu event data to other services.

@param event [Hash]

# File lib/sensu/server/process.rb, line 266
def event_bridges(event)
  @extensions[:bridges].each do |name, bridge|
    bridge.safe_run(event) do |output, status|
      @logger.debug("bridge extension output", {
        :extension => bridge.definition,
        :output => output
      })
    end
  end
end
event_silenced?(event) { |event| ... } click to toggle source

Determine if an event has been silenced. This method compiles an array of possible silenced registry entry keys for the event. An attempt is made to fetch one or more of the silenced registry entries to determine if the event has been silenced. The event data is updated to indicate if the event has been silenced. If the event is silenced and the event action is `:resolve`, silenced registry entries with `:expire_on_resolve` set to true will be deleted. Silencing is disabled for events with a check status of `0` (OK), unless the event action is `:resolve` or `:flapping`.

@param event [Hash] @yield callback [event] callback/block called after the event

data has been updated to indicate if it has been silenced.
# File lib/sensu/server/process.rb, line 450
def event_silenced?(event)
  event[:silenced] = false
  event[:silenced_by] = []
  if event[:check][:status] != 0 || event[:action] != :create
    check_name = event[:check][:name]
    silenced_keys = event[:client][:subscriptions].map { |subscription|
      ["silence:#{subscription}:*", "silence:#{subscription}:#{check_name}"]
    }.flatten
    silenced_keys << "silence:*:#{check_name}"
    @redis.mget(*silenced_keys) do |silenced|
      silenced.compact!
      silenced.each do |silenced_json|
        silenced_info = Sensu::JSON.load(silenced_json)
        if silenced_info[:expire_on_resolve] && event[:action] == :resolve
          silenced_key = "silence:#{silenced_info[:id]}"
          @redis.srem("silenced", silenced_key)
          @redis.del(silenced_key)
        else
          event[:silenced_by] << silenced_info[:id]
        end
      end
      event[:silenced] = !event[:silenced_by].empty?
      yield(event)
    end
  else
    yield(event)
  end
end
expand_handler_sets(handler, depth=0) click to toggle source

Expand event handler sets, creating an array of handler definitions. Handler sets cannot be deeply nested (by choice), this method will return `nil` if an attempt is made to deeply nest. If the provided handler definition is not a set, it is returned.

@param handler [Hash] definition. @param depth [Integer] of the expansion. @return [Array, Hash, Nil]

# File lib/sensu/server/process.rb, line 200
def expand_handler_sets(handler, depth=0)
  if handler[:type] == "set"
    if depth < 2
      derive_handlers(handler[:handlers], depth + 1)
    else
      @logger.error("handler sets cannot be deeply nested", :handler => handler)
      nil
    end
  else
    handler
  end
end
keepalive_event_exists?(client_name) { |event_exists| ... } click to toggle source

Determine if a keepalive event exists for a client.

@param client_name [String] name of client to look up in event registry. @return [TrueClass, FalseClass]

# File lib/sensu/server/process.rb, line 634
def keepalive_event_exists?(client_name)
  @redis.hexists("events:#{client_name}", "keepalive") do |event_exists|
    yield(event_exists)
  end
end
leader_duties() click to toggle source

Set up the leader duties, tasks only performed by a single Sensu server at a time. The duties include publishing check requests, monitoring for stale clients, and pruning check result aggregations.

# File lib/sensu/server/process.rb, line 999
def leader_duties
  setup_check_request_publisher
  setup_client_monitor
  setup_check_result_monitor
end
leader_id() click to toggle source

Create/return the unique Sensu server leader ID for the current process.

@return [String]

# File lib/sensu/server/process.rb, line 1018
def leader_id
  @leader_id ||= random_uuid
end
pause() click to toggle source

Pause the Sensu server process, unless it is being paused or has already been paused. The process/daemon `@state` is first set to `:pausing`, to indicate that it's in progress. All run timers are cancelled, and the references are cleared. The Sensu server will unsubscribe from all transport subscriptions, resign as leader (if currently the leader), then set the process/daemon `@state` to `:paused`.

# File lib/sensu/server/process.rb, line 1183
def pause
  unless @state == :pausing || @state == :paused
    @state = :pausing
    @timers[:run].each do |timer|
      timer.cancel
    end
    @timers[:run].clear
    unsubscribe
    resign_as_leader
    @state = :paused
  end
end
process_check_result(result) click to toggle source

Process a check result, storing its data, inspecting its contents, and taking the appropriate actions (eg. update the event registry). The `@in_progress` counter is incremented by `1` prior to check result processing and then decremented by `1` after updating the event registry. A check result must have a valid client name, associated with a client in the registry or one will be created. If a local check definition exists for the check name, and the check result is not from a standalone check execution, it's merged with the check result for more context.

@param result [Hash] data.

# File lib/sensu/server/process.rb, line 652
def process_check_result(result)
  @in_progress[:check_results] += 1
  @logger.debug("processing result", :result => result)
  retrieve_client(result) do |client|
    unless client.nil?
      check = case
      when @settings.check_exists?(result[:check][:name]) && !result[:check][:standalone]
        @settings[:checks][result[:check][:name]].merge(result[:check])
      else
        result[:check]
      end
      check[:type] ||= STANDARD_CHECK_TYPE
      check[:origin] = result[:client] if check[:source]
      aggregate_check_result(client, check) if check[:aggregates] || check[:aggregate]
      store_check_result(client, check) do
        create_event(client, check) do |event|
          event_bridges(event)
          update_event_registry(event) do |process|
            process_event(event) if process
            @in_progress[:check_results] -= 1
          end
        end
      end
    else
      @logger.warn("halting result processing", :result => result)
      @in_progress[:check_results] -= 1
    end
  end
end
process_client_registration(client) click to toggle source

Process an initial client registration, when it is first added to the client registry. If a registration handler is defined or the client specifies one, a client registration event is created and processed (handled, etc.) for the client (`create_client_registration_event()`).

@param client [Hash] definition.

# File lib/sensu/server/process.rb, line 114
def process_client_registration(client)
  if @settings.handler_exists?("registration") || client[:registration]
    create_client_registration_event(client)
  end
end
process_event(event) click to toggle source

Process an event: filter -> mutate -> handle.

This method determines the appropriate handlers for an event, filtering and mutating the event data for each of them. The `@in_progress` counter is incremented by `1`, for each event handler chain (filter -> mutate -> handle).

@param event [Hash]

# File lib/sensu/server/process.rb, line 245
def process_event(event)
  log_level = event[:check][:type] == METRIC_CHECK_TYPE ? :debug : :info
  @logger.send(log_level, "processing event", :event => event)
  handler_list = Array((event[:check][:handlers] || event[:check][:handler]) || DEFAULT_HANDLER_NAME)
  handlers = derive_handlers(handler_list)
  handlers.each do |handler|
    @in_progress[:events] += 1
    filter_event(handler, event) do |event|
      mutate_event(handler, event) do |event_data|
        handle_event(handler, event_data)
      end
    end
  end
end
publish_check_request(check) click to toggle source

Publish a check request to the Transport. A check request is composed of a check definition (minus `:subscribers` and `:interval`) and an `:issued` timestamp. The check request is published to a Transport pipe, for each of the check `:subscribers` in its definition, eg. “webserver”. JSON serialization is used when publishing the check request payload to the Transport pipes. Transport errors are logged.

@param check [Hash] definition.

# File lib/sensu/server/process.rb, line 739
def publish_check_request(check)
  payload = check.reject do |key, value|
    [:subscribers, :interval].include?(key)
  end
  payload[:issued] = Time.now.to_i
  @logger.info("publishing check request", {
    :payload => payload,
    :subscribers => check[:subscribers]
  })
  check[:subscribers].each do |subscription|
    options = transport_publish_options(subscription, Sensu::JSON.dump(payload))
    @transport.publish(*options) do |info|
      if info[:error]
        @logger.error("failed to publish check request", {
          :subscription => subscription,
          :payload => payload,
          :error => info[:error].to_s
        })
      end
    end
  end
end
publish_check_result(client_name, check) click to toggle source

Publish a check result to the Transport for processing. A check result is composed of a client name and a check definition, containing check `:output` and `:status`. A client signature is added to the check result payload if one is registered for the client. JSON serialization is used when publishing the check result payload to the Transport pipe. Transport errors are logged.

@param client_name [String] @param check [Hash]

# File lib/sensu/server/process.rb, line 825
def publish_check_result(client_name, check)
  payload = {
    :client => client_name,
    :check => check
  }
  @redis.get("client:#{client_name}:signature") do |signature|
    payload[:signature] = signature if signature
    @logger.debug("publishing check result", :payload => payload)
    @transport.publish(:direct, "results", Sensu::JSON.dump(payload)) do |info|
      if info[:error]
        @logger.error("failed to publish check result", {
          :payload => payload,
          :error => info[:error].to_s
        })
      end
    end
  end
end
request_leader_election() click to toggle source

Request a leader election, a process to determine if the current process is the Sensu server leader, with its own/unique duties. A Redis key/value is used as a central lock, using the “SETNX” Redis command to set the key/value if it does not exist, using a timestamp for the value. If the current process was able to create the key/value, it is the leader, and must do the duties of the leader. If the current process was not able to create the key/value, but the current timestamp value is equal to or over 30 seconds ago, the “GETSET” Redis command is used to set a new timestamp and fetch the previous value to compare them, to determine if it was set by the current process. If the current process is able to set the timestamp value, it becomes the leader.

# File lib/sensu/server/process.rb, line 1095
def request_leader_election
  @redis.setnx("lock:leader", create_lock_timestamp) do |created|
    if created
      become_the_leader
    else
      @redis.get("lock:leader") do |current_lock_timestamp|
        new_lock_timestamp = create_lock_timestamp
        if new_lock_timestamp - current_lock_timestamp.to_i >= 30000
          @redis.getset("lock:leader", new_lock_timestamp) do |previous_lock_timestamp|
            if previous_lock_timestamp == current_lock_timestamp
              become_the_leader
            end
          end
        end
      end
    end
  end
end
resign_as_leader() click to toggle source

Resign as leader, if the current process is the Sensu server leader. This method cancels and clears the leader timers, those with references stored in the timers hash under `:leader`, and `@is_leader` is set to `false`. The leader ID and leader lock are not removed from Redis, as they will be updated when another server is elected to be the leader, this method does not need to handle Redis connectivity issues.

# File lib/sensu/server/process.rb, line 1048
def resign_as_leader
  if @is_leader
    @logger.warn("resigning as leader")
    @timers[:leader].each do |timer|
      timer.cancel
    end
    @timers[:leader].clear
    @is_leader = false
  else
    @logger.debug("not currently the leader")
  end
end
resume() click to toggle source

Resume the Sensu server process if it is currently or will soon be paused. The `retry_until_true` helper method is used to determine if the process is paused and if the Redis and transport connections are initiated and connected. If the conditions are met, `bootstrap()` will be called and true is returned to stop `retry_until_true`. If the transport has not yet been initiated, true is is returned, without calling bootstrap, as we expect bootstrap will be called after the transport initializes.

# File lib/sensu/server/process.rb, line 1205
def resume
  retry_until_true(1) do
    if @state == :paused
      if @redis.connected?
        if @transport
          if @transport.connected?
            bootstrap
            true
          end
        else
          true
        end
      end
    end
  end
end
retrieve_client(result) { |client| ... } click to toggle source

Retrieve a client (data) from Redis if it exists. If a client does not already exist, create one (a blank) using the `client_key` as the client name. Dynamically create client data can be updated using the API (POST /clients/:client). If a client does exist and it has a client signature, the check result must have a matching signature or it is discarded.

@param result [Hash] data. @yield [client] callback/block to be called with client data,

either retrieved from Redis, or dynamically created.

@yieldparam client [Hash]

# File lib/sensu/server/process.rb, line 602
def retrieve_client(result)
  client_key = result[:check][:source] || result[:client]
  @redis.get("client:#{client_key}") do |client_json|
    unless client_json.nil?
      client = Sensu::JSON.load(client_json)
      if client[:signature]
        if client[:signature] == result[:signature]
          yield(client)
        else
          @logger.warn("invalid check result signature", {
            :result => result,
            :client => client
          })
          @logger.warn("not retrieving client from the registry", :result => result)
          yield(nil)
        end
      else
        yield(client)
      end
    else
      client = create_client(client_key)
      update_client_registry(client) do
        yield(client)
      end
    end
  end
end
schedule_check_executions(checks) click to toggle source

Schedule check executions, using EventMachine periodic timers, using a calculated execution splay. The timers are stored in the timers hash under `:leader`, as check request publishing is a task for only the Sensu server leader, so they can be cancelled etc. Check requests are not published if subdued.

@param checks [Array] of definitions.

# File lib/sensu/server/process.rb, line 780
def schedule_check_executions(checks)
  checks.each do |check|
    create_check_request = Proc.new do
      unless check_subdued?(check)
        publish_check_request(check)
      else
        @logger.info("check request was subdued", :check => check)
      end
    end
    execution_splay = testing? ? 0 : calculate_check_execution_splay(check)
    interval = testing? ? 0.5 : check[:interval]
    @timers[:leader] << EM::Timer.new(execution_splay) do
      create_check_request.call
      @timers[:leader] << EM::PeriodicTimer.new(interval, &create_check_request)
    end
  end
end
setup_check_request_publisher() click to toggle source

Set up the check request publisher. This method creates an array of check definitions, that are not standalone checks, and do not have `:publish` set to `false`. The array of check definitions includes those from standard checks and extensions (with a defined execution `:interval`). The array is provided to the `schedule_check_executions()` method.

# File lib/sensu/server/process.rb, line 804
def setup_check_request_publisher
  @logger.debug("scheduling check requests")
  standard_checks = @settings.checks.reject do |check|
    check[:standalone] || check[:publish] == false
  end
  extension_checks = @extensions.checks.reject do |check|
    check[:standalone] || check[:publish] == false || !check[:interval].is_a?(Integer)
  end
  schedule_check_executions(standard_checks + extension_checks)
end
setup_check_result_monitor(interval = 30) click to toggle source

Set up the check result monitor, a periodic timer to run `determine_stale_check_results()` every 30 seconds. The timer is stored in the timers hash under `:leader`.

# File lib/sensu/server/process.rb, line 988
def setup_check_result_monitor(interval = 30)
  @logger.debug("monitoring check results")
  @timers[:leader] << EM::PeriodicTimer.new(interval) do
    determine_stale_check_results(interval)
  end
end
setup_client_monitor() click to toggle source

Set up the client monitor, a periodic timer to run `determine_stale_clients()` every 30 seconds. The timer is stored in the timers hash under `:leader`.

# File lib/sensu/server/process.rb, line 942
def setup_client_monitor
  @logger.debug("monitoring client keepalives")
  @timers[:leader] << EM::PeriodicTimer.new(30) do
    determine_stale_clients
  end
end
setup_connections() { || ... } click to toggle source

Set up the Redis and Transport connection objects, `@redis` and `@transport`. This method updates the Redis on error callback to reset the in progress check result counter. This method “drys” up many instances of `setup_redis()` and `setup_transport()`, particularly in the specs.

@yield callback/block called after connecting to Redis and the

Sensu Transport.
# File lib/sensu/server/process.rb, line 56
def setup_connections
  setup_redis do
    @redis.on_error do |error|
      @logger.error("redis connection error", :error => error.to_s)
      @in_progress[:check_results] = 0
    end
    setup_transport do
      yield
    end
  end
end
setup_keepalives() click to toggle source

Set up the client keepalive consumer, keeping the Sensu client registry updated. The consumer receives JSON serialized client keepalives from the transport, parses them, and calls `update_client_registry()` with the client data to update the registry. Transport message acknowledgements are used to ensure the client registry is updated successfully. Keepalive JSON parsing errors are logged.

# File lib/sensu/server/process.rb, line 172
def setup_keepalives
  @logger.debug("subscribing to keepalives")
  @transport.subscribe(:direct, "keepalives", "keepalives", :ack => true) do |message_info, message|
    @logger.debug("received keepalive", :message => message)
    begin
      client = Sensu::JSON.load(message)
      update_client_registry(client) do
        @transport.ack(message_info)
      end
    rescue Sensu::JSON::ParseError => error
      @logger.error("failed to parse keepalive payload", {
        :message => message,
        :error => error.to_s
      })
      @transport.ack(message_info)
    end
  end
end
setup_leader_monitor() click to toggle source

Set up the leader monitor. A one-time timer is used to run `request_leader_exection()` in 2 seconds. A periodic timer is used to update the leader lock timestamp if the current process is the leader, or to run `request_leader_election(), every 10 seconds. The timers are stored in the timers hash under `:run`.

# File lib/sensu/server/process.rb, line 1120
def setup_leader_monitor
  @timers[:run] << EM::Timer.new(2) do
    request_leader_election
  end
  @timers[:run] << EM::PeriodicTimer.new(10) do
    if @is_leader
      update_leader_lock
    else
      request_leader_election
    end
  end
end
setup_results() click to toggle source

Set up the check result consumer. The consumer receives JSON serialized check results from the transport, parses them, and calls `process_check_result()` with the result data to be processed. Transport message acknowledgements are used to ensure that results make it to processing. The transport message acknowledgements are currently done in the next tick of the EventMachine reactor (event loop), as a flow control mechanism. Result JSON parsing errors are logged.

# File lib/sensu/server/process.rb, line 690
def setup_results
  @logger.debug("subscribing to results")
  @transport.subscribe(:direct, "results", "results", :ack => true) do |message_info, message|
    begin
      result = Sensu::JSON.load(message)
      @logger.debug("received result", :result => result)
      process_check_result(result)
    rescue Sensu::JSON::ParseError => error
      @logger.error("failed to parse result payload", {
        :message => message,
        :error => error.to_s
      })
    end
    EM::next_tick do
      @transport.ack(message_info)
    end
  end
end
start() click to toggle source

Start the Sensu server process, connecting to Redis, the Transport, and calling the `bootstrap()` method.

# File lib/sensu/server/process.rb, line 1170
def start
  setup_connections do
    bootstrap
  end
end
stop() click to toggle source

Stop the Sensu server process, pausing it, completing event handling in progress, closing the Redis and transport connections, and exiting the process (exit 0). After pausing the process, the process/daemon `@state` is set to `:stopping`.

Calls superclass method Sensu::Daemon#stop
# File lib/sensu/server/process.rb, line 1227
def stop
  @logger.warn("stopping")
  pause
  @state = :stopping
  complete_in_progress do
    @redis.close if @redis
    @transport.close if @transport
    super
  end
end
store_check_result(client, check) { || ... } click to toggle source

Store check result data. This method stores check result data and the 21 most recent check result statuses for a client/check pair, this history is used for event context and flap detection. The check execution timestamp is also stored, to provide an indication of how recent the data is. Check output is truncated by `truncate_check_output()` before it is stored.

@param client [Hash] @param check [Hash] @yield [] callback/block called after the check data has been

stored (history, etc).
# File lib/sensu/server/process.rb, line 352
def store_check_result(client, check)
  @logger.debug("storing check result", :check => check)
  result_key = "#{client[:name]}:#{check[:name]}"
  history_key = "history:#{result_key}"
  check_truncated = truncate_check_output(check)
  @redis.multi
  @redis.sadd("result:#{client[:name]}", check[:name])
  @redis.set("result:#{result_key}", Sensu::JSON.dump(check_truncated))
  @redis.sadd("ttl", result_key) if check[:ttl]
  @redis.rpush(history_key, check[:status])
  @redis.ltrim(history_key, -21, -1)
  @redis.exec do
    yield
  end
end
transport_publish_options(subscription, message) click to toggle source

Determine the Sensu Transport publish options for a subscription. If a subscription begins with a Transport pipe type, either “direct:” or “roundrobin:”, the subscription uses a direct Transport pipe. If a subscription does not specify a Transport pipe type, a fanout Transport pipe is used.

@param subscription [String] @param message [String] @return [Array] containing the Transport publish options:

the Transport pipe type, pipe, and the message to be
published.
# File lib/sensu/server/process.rb, line 720
def transport_publish_options(subscription, message)
  _, raw_type = subscription.split(":", 2).reverse
  case raw_type
  when "direct", "roundrobin"
    [:direct, subscription, message]
  else
    [:fanout, subscription, message]
  end
end
truncate_check_output(check) click to toggle source

Truncate check output. For metric checks, (`“type”: “metric”`), check output is truncated to a single line and a maximum of 255 characters. Check output is currently left unmodified for standard checks.

@param check [Hash] @return [Hash] check with truncated output.

# File lib/sensu/server/process.rb, line 318
def truncate_check_output(check)
  case check[:type]
  when METRIC_CHECK_TYPE
    begin
      output_lines = check[:output].split("\n")
    rescue ArgumentError
      utf8_output = check[:output].encode("UTF-8", "binary", {
        :invalid => :replace,
        :undef => :replace,
        :replace => ""
      })
      output_lines = utf8_output.split("\n")
    end
    output = output_lines.first || check[:output]
    if output_lines.length > 1 || output.length > 255
      output = output[0..255] + "\n..."
    end
    check.merge(:output => output)
  else
    check
  end
end
unsubscribe() click to toggle source

Unsubscribe from transport subscriptions (all of them). This method is called when there are issues with connectivity, or the process is stopping.

# File lib/sensu/server/process.rb, line 1136
def unsubscribe
  @logger.warn("unsubscribing from keepalive and result queues")
  @transport.unsubscribe if @transport
end
update_client_registry(client) { |true| ... } click to toggle source

Update the Sensu client registry, stored in Redis. Sensu client data is used to provide additional event context and enable agent health monitoring. The client registry supports client signatures, unique string identifiers used for keepalive and result source verification. If a client has a signature, all further registry updates for the client must have the same signature. A client can begin to use a signature if one was not previously configured. JSON serialization is used for the stored client data.

@param client [Hash] @yield [success] passes success status to optional

callback/block.

@yieldparam success [TrueClass,FalseClass] indicating if the

client registry update was a success or the client data was
discarded due to client signature mismatch.
# File lib/sensu/server/process.rb, line 136
def update_client_registry(client)
  @logger.debug("updating client registry", :client => client)
  client_key = "client:#{client[:name]}"
  signature_key = "#{client_key}:signature"
  @redis.setnx(signature_key, client[:signature]) do |created|
    process_client_registration(client) if created
    @redis.get(signature_key) do |signature|
      if (signature.nil? || signature.empty?) && client[:signature]
        @redis.set(signature_key, client[:signature])
      end
      if signature.nil? || signature.empty? || (client[:signature] == signature)
        @redis.multi
        @redis.set(client_key, Sensu::JSON.dump(client))
        @redis.sadd("clients", client[:name])
        @redis.exec do
          yield(true) if block_given?
        end
      else
        @logger.warn("invalid client signature", {
          :client => client,
          :signature => signature
        })
        @logger.warn("not updating client in the registry", :client => client)
        yield(false) if block_given?
      end
    end
  end
end
update_event_registry(event) { |true| ... } click to toggle source

Update the event registry, stored in Redis. This method determines if event data warrants in the creation or update of event data in the registry. If a check `:status` is not `0`, or it has been flapping, an event is created/updated in the registry. If the event `:action` is `:resolve`, the event is removed (resolved) from the registry. If the previous conditions are not met and check `:type` is `metric`, the registry is not updated, but further event processing is required (`yield(true)`). JSON serialization is used when storing data in the registry.

@param event [Hash] @yield callback [event] callback/block called after the event

registry has been updated.

@yieldparam process [TrueClass, FalseClass] indicating if the

event requires further processing.
# File lib/sensu/server/process.rb, line 495
def update_event_registry(event)
  client_name = event[:client][:name]
  if event[:check][:status] != 0 || event[:action] == :flapping
    @redis.hset("events:#{client_name}", event[:check][:name], Sensu::JSON.dump(event)) do
      yield(true)
    end
  elsif event[:action] == :resolve &&
      (event[:check][:auto_resolve] != false || event[:check][:force_resolve])
    @redis.hdel("events:#{client_name}", event[:check][:name]) do
      yield(true)
    end
  elsif event[:check][:type] == METRIC_CHECK_TYPE
    yield(true)
  else
    yield(false)
  end
end
update_leader_lock() click to toggle source

Updates the Sensu server leader lock timestamp. The current leader ID is retrieved from Redis and compared with the leader ID of the current process to determine if it is still the Sensu server leader. If the current process is still the leader, the leader lock timestamp is updated. If the current process is no longer the leader (regicide), `resign_as_leader()` is called for cleanup, so there is not more than one leader.

# File lib/sensu/server/process.rb, line 1069
def update_leader_lock
  @redis.get("leader") do |current_leader_id|
    if current_leader_id == leader_id
      @redis.set("lock:leader", create_lock_timestamp) do
        @logger.debug("updated leader lock timestamp")
      end
    else
      @logger.warn("another sensu server has been elected as leader")
      resign_as_leader
    end
  end
end