Module: Appsignal::Probes

Defined in:
lib/appsignal/probes.rb,
lib/appsignal/probes/gvl.rb,
lib/appsignal/probes/mri.rb,
lib/appsignal/probes/helpers.rb,
lib/appsignal/probes/sidekiq.rb

Class Method Summary collapse

Class Method Details

.register(name, probe) ⇒ void

This method returns an undefined value.

Register a new minutely probe.

Supported probe types are:

  • Lambda - A lambda is an object that listens to a ‘call` method call. This `call` method is called every minute.

  • Class - A class object is an object that listens to a ‘new` and `call` method call. The `new` method is called when the minutely probe thread is started to initialize all probes. This allows probes to load dependencies once beforehand. Their `call` method is called every minute.

  • Class instance - A class instance object is an object that listens to a ‘call` method call. The `call` method is called every minute.

Examples:

Register a new probe

Appsignal::Probes.register :my_probe, lambda {}

Overwrite an existing registered probe

Appsignal::Probes.register :my_probe, lambda {}
Appsignal::Probes.register :my_probe, lambda { puts "hello" }

Add a lambda as a probe

Appsignal::Probes.register :my_probe, lambda { puts "hello" }
# "hello" # printed every minute

Add a probe instance

class MyProbe
  def initialize
    puts "started"
  end

  def call
    puts "called"
  end
end

Appsignal::Probes.register :my_probe, MyProbe.new
# "started" # printed immediately
# "called" # printed every minute

Add a probe class

class MyProbe
  def initialize
    # Add things that only need to be done on start up for this probe
    require "some/library/dependency"
    @cache = {} # initialize a local cache variable
    puts "started"
  end

  def call
    puts "called"
  end
end

Appsignal::Probes.register :my_probe, MyProbe
Appsignal::Probes.start # This is called for you
# "started" # Printed on Appsignal::Probes.start
# "called" # Repeated every minute

Parameters:

  • name (Symbol, String) —

    Name of the probe. Can be used with Appsignal::Probes::ProbeCollection#[]. This name will be used in errors in the log and allows overwriting of probes by registering new ones with the same name.

  • probe (Object) —

    Any object that listens to the ‘call` method will be used as a probe.



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# File 'lib/appsignal/probes.rb', line 137

def register(name, probe)
  probes.internal_register(name, probe)

  initialize_probe(name, probe) if started?
end

.start ⇒ void

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

This method returns an undefined value.



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# File 'lib/appsignal/probes.rb', line 165

def start
  stop
  @started = true
  @thread = Thread.new do
    # Advise multi-threaded app servers to ignore this thread
    # for the purposes of fork safety warnings
    if Thread.current.respond_to?(:thread_variable_set)
      Thread.current.thread_variable_set(:fork_safe, true)
    end

    sleep initial_wait_time
    initialize_probes
    loop do
      start_time = Time.now
      logger = Appsignal.internal_logger
      mutex.synchronize do
        logger.debug("Gathering minutely metrics with #{probe_instances.count} probes")
        probe_instances.each do |name, probe|
          logger.debug("Gathering minutely metrics with '#{name}' probe")
          probe.call
        rescue => ex
          logger.error(
            "Error in minutely probe '#{name}': #{ex.class}: #{ex.message}\n" \
              "#{ex.backtrace.join("\n")}"
          )
        end
      end
      end_time = Time.now
      duration = end_time - start_time
      if duration >= ITERATION_IN_SECONDS
        logger.error(
          "The minutely probes took more than 60 seconds. " \
            "The probes should not take this long as metrics will not " \
            "be accurately reported."
        )
      end
      sleep wait_time
    end
  end
end

.started? ⇒ Boolean?

Returns if the probes thread has been started. If the value is false or nil, it has not been started yet.

Returns:

  • (Boolean, nil) 


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# File 'lib/appsignal/probes.rb', line 210

def started?
  @started
end

.stop ⇒ void

This method returns an undefined value.

Stop the minutely probes mechanism. Stop the thread and clear all probe instances.



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# File 'lib/appsignal/probes.rb', line 218

def stop
  defined?(@thread) && @thread.kill
  @started = false
  probe_instances.clear
end

.unregister(name) ⇒ void

This method returns an undefined value.

Unregister a probe that’s registered with register. Can also be used to unregister automatically registered probes by the gem.

Examples:

Unregister probes

# First register a probe
Appsignal::Probes.register :my_probe, lambda {}

# Then unregister a probe if needed
Appsignal::Probes.unregister :my_probe

Parameters:

  • name (Symbol, String) —

    Name of the probe used to register the probe.



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# File 'lib/appsignal/probes.rb', line 157

def unregister(name)
  probes.unregister(name)

  uninitialize_probe(name)
end