telemetry_metrics_prometheus v0.2.1 TelemetryMetricsPrometheus View Source
Prometheus Reporter for Telemetry.Metrics
definitions.
Provide a list of metric definitions to the init/2
function. It's recommended to
initialize the reporter during application startup.
def start(_type, _args) do
TelemetryMetricsPrometheus.init([
counter("http.request.count"),
sum("http.request.payload_size", unit: :byte),
last_value("vm.memory.total", unit: :byte)
])
# List all child processes to be supervised
children = [
...
]
opts = [strategy: :one_for_one, name: ExampleApp.Supervisor]
Supervisor.start_link(children, opts)
end
By default, metrics are exposed on port 9568
at /metrics
. The port number
can be configured if necessary. You are not required to use the included server,
though it is recommended. https
is not supported yet, in which case exposing
a /metrics
endpoint and calling the scrape/1
function is your best option
until TLS is supported.
Note that aggregations for distributions (histogram) only occur at scrape time. These aggregations only have to process events that have occurred since the last scrape, so it's recommended at this time to keep an eye on scrape durations if you're reporting a large number of disributions or you have a high tag cardinality.
Telemetry.Metrics to Prometheus Equivalents
Metric types:
- Counter - Counter
- Distribution - Histogram
- LastValue - Gauge
- Sum - Counter
- Summary - Summary (Not supported)
Units
Prometheus recommends the usage of base units for compatibility - Base Units.
This is simple to do with :telemetry
and Telemetry.Metrics
as all memory
related measurements in the BEAM are reported in bytes and Metrics provides
automatic time unit conversions.
Note that measurement unit should used as part of the reported name in the case of histograms and gauges to Prometheus. As such, it is important to explicitly define the unit of measure for these types when the unit is time or memory related.
It is suggested to not mix units, e.g. seconds with milliseconds.
It is required to define your buckets according to the end unit translation since this measurements are converted at the time of handling the event, prior to bucketing.
Memory
Report memory as :byte
.
Time
Report durations as :second
. The BEAM and :telemetry
events use :native
time
units. Converting to seconds is as simple as adding the conversion tuple for
the unit - {:native, :second}
Naming
Telemetry.Metrics
definition names do not translate easily to Prometheus naming
conventions. By default, the name provided when creating your definition uses parts
of the provided name to determine what event to listen to and which event measurement
to use.
For example, "http.request.duration"
results in listening for [:http, :request]
events and use :duration
from the event measurements. Prometheus would recommend
a name of http_request_duration_seconds
as a good name.
It is therefore recommended to use the name in your definition to reflect the name
you wish to see reported, e.g. http.request.duration.seconds
or [:http, :request, :duration, :seconds]
and use the :event_name
override and :measurement
options in your definition.
Example:
Metrics.distribution(
"http.request.duration.seconds",
buckets: [0.01, 0.025, 0.05, 0.1, 0.2, 0.5, 1],
event_name: [:http, :request, :complete],
measurement: :duration,
unit: {:native, :second}
)
The exporter sanitizes names to Prometheus' requirements (Metric Naming) and joins the event name parts with an underscore.
Labels
Labels in Prometheus are referred to as :tags
in Telemetry.Metrics
- see the docs
for more information on tag usage.
Important: Each tag + value results in a separate time series. For distributions, this
is further complicated as a time series is created for each bucket plus one for measurements
exceeding the limit of the last bucket - +Inf
.
It is recommended, but not required, to abide by Prometheus' best practices regarding labels - Label Best Practices
Link to this section Summary
Functions
Initializes a reporter instance with the provided Telemetry.Metrics
definitions.
Returns a metrics scrape in Prometheus exposition format for the given reporter
name - defaults to :prometheus_metrics
.
Link to this section Types
metric() View Source
metrics()
View Source
metrics() :: [metric()]
metrics() :: [metric()]
prometheus_option()
View Source
prometheus_option() ::
{:name, atom()}
| {:port, pos_integer()}
| {:monitor_reporter, bool()}
| {:validations,
TelemetryMetricsPrometheus.Registry.validation_opts() | false}
prometheus_option() :: {:name, atom()} | {:port, pos_integer()} | {:monitor_reporter, bool()} | {:validations, TelemetryMetricsPrometheus.Registry.validation_opts() | false}
prometheus_options()
View Source
prometheus_options() :: [prometheus_option()]
prometheus_options() :: [prometheus_option()]
Link to this section Functions
init(metrics, options \\ [])
View Source
init(metrics(), prometheus_options()) :: :ok
init(metrics(), prometheus_options()) :: :ok
Initializes a reporter instance with the provided Telemetry.Metrics
definitions.
Available options:
:name
- name of the reporter instance. Defaults to:prometheus_metrics
:port
- port number for the reporter instance's server. Defaults to9568
:monitor_reporter
- collects metrics on the reporter's ETS table usage. Defaults tofalse
:validations
- Keyword options list to control validations. All validations can be disabled by settingvalidations: false
.:consistent_units
- logs a warning when mixed time units are found in your definitions. Defaults totrue
:require_seconds
- logs a warning if units other than seconds are found in your definitions. Defaults totrue
scrape(name \\ :prometheus_metrics) View Source
Returns a metrics scrape in Prometheus exposition format for the given reporter
name - defaults to :prometheus_metrics
.
Use this function if you wish to expose your metrics through your own server
implementation, though this is not recommended. See the Overview
for further
discussion.