telemetry_poller
Allows to periodically collect measurements and dispatch them as Telemetry events.
telemetry_poller
by default runs a poller to perform VM measurements:
[vm, memory]
- contains the total memory, process memory, and all other keys inerlang:memory/0
[vm, total_run_queue_lengths]
- returns the run queue lengths for CPU and IO schedulers. It contains thetotal
,cpu
andio
measurements[vm, system_counts]
- returns the current process, atom and port count as pererlang:system_info/1
You can directly consume those events after adding telemetry_poller
as a dependency.
Poller also provides a convenient API for running custom pollers.
Defining custom measurements
Poller also includes conveniences for performing process-based measurements as well as custom ones.
Erlang
First define the poller with the custom measurements. The first measurement is the built-in process_info
measurement and the second one is given by a custom module-function-args defined by you:
telemetry_poller:start_link(
[{measurements, [
{process_info, [{name, my_app_worker}, {event, [my_app, worker]}, {keys, [memory, message_queue_len]}]},
{example_app_measurements, dispatch_session_count, []}
]},
{period, timer:seconds(10)}, % configure sampling period - default is timer:seconds(5)
{name, my_app_poller}
]).
Now define the custom measurement and you are good to go:
-module(example_app_measurements).
dispatch_session_count() ->
% emit a telemetry event when called
telemetry:execute([example_app, session_count], #{count => example_app:session_count()}, #{}).
Elixir
You typically start the poller as a child in your supervision tree:
children = [
{:telemetry_poller,
# include custom measurement as an MFA tuple
measurements: [
{:process_info, name: :my_app_worker, event: [:my_app, :worker], keys: [:memory, :message_queue_len]},
{ExampleApp.Measurements, :dispatch_session_count, []},
],
period: :timer.seconds(10), # configure sampling period - default is :timer.seconds(5)
name: :my_app_poller}
]
Supervisor.start_link(children, strategy: :one_for_one)
The poller above has two periodic measurements. The first is the built-in process_info
measurement that will gather the memory and message queue length of a process. The second is given by a custom module-function-args defined by you, such as below:
defmodule ExampleApp.Measurements do
def dispatch_session_count() do
# emit a telemetry event when called
:telemetry.execute([:example_app, :session_count], %{count: ExampleApp.session_count()}, %{})
end
end
Documentation
See documentation for more concrete examples and usage instructions.
Copyright and License
telemetry_poller is copyright (c) 2018 Chris McCord and Erlang Solutions.
telemetry_poller source code is released under Apache License, Version 2.0.