Prometheus.io client for Erlang

Prometheus.io monitoring system and time series database client in Erlang.

• IRC: #erlang on Freenode;
• Slack: #prometheus channel - Browser or App(slack://elixir-lang.slack.com/messages/prometheus).

Integrations

• Cowboy1/2 Exporters and Cowboy2 instrumenter
• Opencensus.io integration
• Ecto Instrumenter
• Elixir client
• Elixir plugs Instrumenters and Exporter
• Extatus - App to report metrics to Prometheus from Elixir GenServers
• Fuse plugin
• Inets HTTPD Exporter
• OS process info Collector (linux, freebsd, macos)
• Phoenix Instrumenter
• RabbitMQ Exporter.

Dashboards

• Beam Dashboards.

Blogs

• Install, Monitor Erlang Releases in Kubernetes with Helm + Prometheus
• Monitoring Elixir apps in 2016: Prometheus and Grafana
• A Simple Erlang Application, with Prometheus.

Erlang VM & OTP Collectors

• Memory Collector
• Mnesia Collector
• Statistics Collector
• System Information Collector.

Compatibility

OTP versions

Version 3.x works on OTP18+. For older version (oldest tested is R16B03) please use 3.x-pre18 branch. 3.x-pre18 will work on all OTP releases starting from R16B03 and its beam will recompile itself to accommodate. For example, this branch is used by RabbitMQ Exporter 3.6.x that should be compatible with all versions starting from R16B03.

Build tools

Rebar3 is supported.

Example Console Session

Run shell with compiled and loaded app:

    $ rebar3 shell

Start prometheus app:

prometheus:start().

Register metrics:

prometheus_gauge:new([{name, pool_size}, {help, "MongoDB Connections pool size"}]),
prometheus_counter:new([{name, http_requests_total}, {help, "Http request count"}]).
prometheus_summary:new([{name, orders}, {help, "Track orders count/total sum"}]).
prometheus_histogram:new([{name, http_request_duration_milliseconds},
                               {labels, [method]},
                               {buckets, [100, 300, 500, 750, 1000]},
                               {help, "Http Request execution time"}]).

Use metrics:

prometheus_gauge:set(pool_size, 365),
prometheus_counter:inc(http_requests_total).
prometheus_summary:observe(orders, 10).
prometheus_summary:observe(orders, 15).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 95).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 100).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 102).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 150).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 250).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 75).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 350).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 550).
prometheus_histogram:observe(http_request_duration_milliseconds, [get], 950).
prometheus_histogram:observe(http_request_duration_milliseconds, [post], 500),
prometheus_histogram:observe(http_request_duration_milliseconds, [post], 150).
prometheus_histogram:observe(http_request_duration_milliseconds, [post], 450).
prometheus_histogram:observe(http_request_duration_milliseconds, [post], 850).
prometheus_histogram:observe(http_request_duration_milliseconds, [post], 750).
prometheus_histogram:observe(http_request_duration_milliseconds, [post], 1650).

Export metrics as text:

io:format(prometheus_text_format:format()).

->

# TYPE http_requests_total counter
# HELP http_requests_total Http request count
http_requests_total 2
# TYPE pool_size gauge
# HELP pool_size MongoDB Connections pool size
pool_size 365
# TYPE orders summary
# HELP orders Track orders count/total sum
orders_count 4
orders_sum 50
# TYPE http_request_duration_milliseconds histogram
# HELP http_request_duration_milliseconds Http Request execution time
http_request_duration_milliseconds_bucket{method="post",le="100"} 0
http_request_duration_milliseconds_bucket{method="post",le="300"} 1
http_request_duration_milliseconds_bucket{method="post",le="500"} 3
http_request_duration_milliseconds_bucket{method="post",le="750"} 4
http_request_duration_milliseconds_bucket{method="post",le="1000"} 5
http_request_duration_milliseconds_bucket{method="post",le="+Inf"} 6
http_request_duration_milliseconds_count{method="post"} 6
http_request_duration_milliseconds_sum{method="post"} 4350
http_request_duration_milliseconds_bucket{method="get",le="100"} 3
http_request_duration_milliseconds_bucket{method="get",le="300"} 6
http_request_duration_milliseconds_bucket{method="get",le="500"} 7
http_request_duration_milliseconds_bucket{method="get",le="750"} 8
http_request_duration_milliseconds_bucket{method="get",le="1000"} 9
http_request_duration_milliseconds_bucket{method="get",le="+Inf"} 9
http_request_duration_milliseconds_count{method="get"} 9
http_request_duration_milliseconds_sum{method="get"} 2622

API

API can be grouped like this:

Standard Metrics & Registry

• prometheus_counter - counter metric, to track counts of events or running totals;
• prometheus_gauge - gauge metric, to report instantaneous values;
• prometheus_histogram - histogram metric, to track distributions of events;
• prometheus_summary - summary metric, to track the size of events;
• prometheus_boolean - boolean metric, to track the state of something;
• prometheus_registry - working with Prometheus registries.

All metrics created via new/1 or declare/1. The difference is that new/1 actually wants metric to be new and raises {mf_already_exists, {Registry, Name}, Message} error if it isn't.

Both new/1 and declare/1 accept options as proplist. Common options are:

• name - metric name, can be an atom or a string (required);
• help - metric help, string (required);
• labels - metric labels, label can be an atom or a string (default is []);
• registry - Prometheus registry for the metric, can be any term. (default is default)

Histogram also accepts buckets option. Please refer to respective modules docs for the more information.

Exposition Formats

• prometheus_text_format - renders metrics for a given registry (default is default) in text format;
• prometheus_protobuf_format - renders metrics for a given registry (default is default) in protobuf v2 format.

General Helpers

• prometheus_buckets - linear or exponential bucket generators;
• prometheus_http - helpers for HTTP instrumenters;
• prometheus_mnesia - Mnesia instrumentation helpers.

Advanced

You will need these modules only if you're writing a custom collector for an app/lib that can't be instrumented directly.

• prometheus_collector - common interface for collectors;
• prometheus_format - common interface for exposition formats;
• prometheus_model_helpers - provides API for working with underlying Prometheus models. You'll use that if you want to create a custom collector.

Build

   $ rebar3 compile

Configuration

Prometheus.erl supports standard Erlang app configuration.

• collectors - List of custom collectors modules to be registered automatically. Can be all_loaded in order to find all modules implementing the prometheus_collector behaviour. Supports an "alias" option default, which will append all default collectors implemented in this library. If undefined, the default collectors implemented in this library will be used.
• instrumenters - List of custom instrumenter modules to be registered automatically. Can be all_loaded in order to find all modules implementing the prometheus_instrumenter behaviour. If undefined, none will be loaded.
• default_metrics - List of metrics to be registered during app startup. Metric format: {Type, Spec} where Type is a metric type (counter, gauge, etc), Spec is a list to be passed to Metric:declare/1. Deprecated format {Registry, Metric, Spec} also supported.

Collectors & Exporters Conventions

Configuration

All 3d-party libraries should be configured via prometheus app env.

Exporters are responsible for maintaining scrape endpoint. Exporters are usually tightly coupled with the web server and are singletons. They should understand these keys:

• path - url for scraping;
• format - scrape format as module name i.e. prometheus_text_format or prometheus_protobuf_format. Exporter-specific options should be under <exporter_name>_exporter for erlang or <Exporter_name>Exporter for Elixir i.e. PlugsExporter or elli_exporter

Collectors collect integration specific metrics i.e. ecto timings, process information and so on. Their configuration should be under <collector_name>_collectorfor erlang or <Collector_name>Collector for Elixir i.e. process_collector, EctoCollector and so on.

Naming

For Erlang: prometheus_<name>_collector/prometheus_<name>_exporter.

For Elixir: Prometheus.<name>Collector/Prometheus.<name>Exporter.