Since quite a while, I have been a big fan of Traefik. Last weekend, I discovered that Traefik itself is capable of exposing metrics data for popular products like e.g. Prometheus, Datadog, etc.. As I typically use Prometheus (amongst others) to feed my Grafana dashboards, I will describe how to make Traefik expose Prometheus-conformant metrics data.

Activating Metrics Exposure

For the activation, you will need to edit your traefik.toml file. Add the following two lines:

[metrics]
  [metrics.prometheus]
activating metrics

This will (a) activate metrics and (b) set the output format to Prometheus. By default, Traefik will attempt to expose metrics data via an entry point named traefik. So, go ahead and create one that listens on a port of your choice:

[entryPoints]
... <your existing entry points>
  [entryPoints.traefik]
    address = ":8083"
creating a metrics entry point

And that's it. Restart Traefik, and you should be able to start scraping.

Scraping

The scraping job to be configured in Prometheus might look like this:

job_name: traefik-metrics
  honor_timestamps: true
  scrape_interval: 15s
  scrape_timeout: 10s
  metrics_path: /metrics
  scheme: http
  static_configs:
  - targets:
    - monitoring.example.com:8083
job configuration in Prometheus

Please take particular note of the metrics_path  attribute: for Traefik, it must be set to /metrics. Otherwise, you'll be getting a 404 "page not found" response.

Available Metrics

The following table lists the metrics items available:

Item
# HELP go_gc_duration_seconds A summary of the GC invocation durations.
# TYPE go_gc_duration_seconds summary
# HELP go_goroutines Number of goroutines that currently exist.
# TYPE go_goroutines gauge
# HELP go_info Information about the Go environment.
# TYPE go_info gauge
# HELP go_memstats_alloc_bytes Number of bytes allocated and still in use.
# TYPE go_memstats_alloc_bytes gauge
# HELP go_memstats_alloc_bytes_total Total number of bytes allocated, even if freed.
# TYPE go_memstats_alloc_bytes_total counter
# HELP go_memstats_buck_hash_sys_bytes Number of bytes used by the profiling bucket hash table.
# TYPE go_memstats_buck_hash_sys_bytes gauge
# HELP go_memstats_frees_total Total number of frees.
# TYPE go_memstats_frees_total counter
# HELP go_memstats_gc_cpu_fraction The fraction of this program's available CPU time used by the GC since the program started.
# TYPE go_memstats_gc_cpu_fraction gauge
# HELP go_memstats_gc_sys_bytes Number of bytes used for garbage collection system metadata.
# TYPE go_memstats_gc_sys_bytes gauge
# HELP go_memstats_heap_alloc_bytes Number of heap bytes allocated and still in use.
# TYPE go_memstats_heap_alloc_bytes gauge
# HELP go_memstats_heap_idle_bytes Number of heap bytes waiting to be used.
# TYPE go_memstats_heap_idle_bytes gauge
# HELP go_memstats_heap_inuse_bytes Number of heap bytes that are in use.
# TYPE go_memstats_heap_inuse_bytes gauge
# HELP go_memstats_heap_objects Number of allocated objects.
# TYPE go_memstats_heap_objects gauge
# HELP go_memstats_heap_released_bytes Number of heap bytes released to OS.
# TYPE go_memstats_heap_released_bytes gauge
# HELP go_memstats_heap_sys_bytes Number of heap bytes obtained from system.
# TYPE go_memstats_heap_sys_bytes gauge
# HELP go_memstats_last_gc_time_seconds Number of seconds since 1970 of last garbage collection.
# TYPE go_memstats_last_gc_time_seconds gauge
# HELP go_memstats_lookups_total Total number of pointer lookups.
# TYPE go_memstats_lookups_total counter
# HELP go_memstats_mallocs_total Total number of mallocs.
# TYPE go_memstats_mallocs_total counter
# HELP go_memstats_mcache_inuse_bytes Number of bytes in use by mcache structures.
# TYPE go_memstats_mcache_inuse_bytes gauge
# HELP go_memstats_mcache_sys_bytes Number of bytes used for mcache structures obtained from system.
# TYPE go_memstats_mcache_sys_bytes gauge
# HELP go_memstats_mspan_inuse_bytes Number of bytes in use by mspan structures.
# TYPE go_memstats_mspan_inuse_bytes gauge
# HELP go_memstats_mspan_sys_bytes Number of bytes used for mspan structures obtained from system.
# TYPE go_memstats_mspan_sys_bytes gauge
# HELP go_memstats_next_gc_bytes Number of heap bytes when next garbage collection will take place.
# TYPE go_memstats_next_gc_bytes gauge
# HELP go_memstats_other_sys_bytes Number of bytes used for other system allocations.
# TYPE go_memstats_other_sys_bytes gauge
# HELP go_memstats_stack_inuse_bytes Number of bytes in use by the stack allocator.
# TYPE go_memstats_stack_inuse_bytes gauge
# HELP go_memstats_stack_sys_bytes Number of bytes obtained from system for stack allocator.
# TYPE go_memstats_stack_sys_bytes gauge
# HELP go_memstats_sys_bytes Number of bytes obtained from system.
# TYPE go_memstats_sys_bytes gauge
# HELP go_threads Number of OS threads created.
# TYPE go_threads gauge
# HELP process_cpu_seconds_total Total user and system CPU time spent in seconds.
# TYPE process_cpu_seconds_total counter
# HELP process_max_fds Maximum number of open file descriptors.
# TYPE process_max_fds gauge
# HELP process_open_fds Number of open file descriptors.
# TYPE process_open_fds gauge
# HELP process_resident_memory_bytes Resident memory size in bytes.
# TYPE process_resident_memory_bytes gauge
# HELP process_start_time_seconds Start time of the process since unix epoch in seconds.
# TYPE process_start_time_seconds gauge
# HELP process_virtual_memory_bytes Virtual memory size in bytes.
# TYPE process_virtual_memory_bytes gauge
# HELP process_virtual_memory_max_bytes Maximum amount of virtual memory available in bytes.
# TYPE process_virtual_memory_max_bytes gauge
# HELP traefik_config_last_reload_failure Last config reload failure
# TYPE traefik_config_last_reload_failure gauge
# HELP traefik_config_last_reload_success Last config reload success
# TYPE traefik_config_last_reload_success gauge
# HELP traefik_config_reloads_failure_total Config failure reloads
# TYPE traefik_config_reloads_failure_total counter
# HELP traefik_config_reloads_total Config reloads
# TYPE traefik_config_reloads_total counter
# HELP traefik_entrypoint_open_connections How many open connections exist on an entrypoint, partitioned by method and protocol.
# TYPE traefik_entrypoint_open_connections gauge
# HELP traefik_entrypoint_request_duration_seconds How long it took to process the request on an entrypoint, partitioned by status code, protocol, and method.
# TYPE traefik_entrypoint_request_duration_seconds histogram
# HELP traefik_entrypoint_requests_total How many HTTP requests processed on an entrypoint, partitioned by status code, protocol, and method.
# TYPE traefik_entrypoint_requests_total counter