Ferricstore.Metrics (ferricstore v0.3.1)

Prometheus-compatible metrics exposition for FerricStore.

Collects server statistics from Ferricstore.Stats, Ferricstore.MemoryGuard, Ferricstore.SlowLog, and BEAM runtime sources, then formats them in the Prometheus text exposition format (version 0.0.4).

No external dependencies are required -- the module produces a plain UTF-8 string that any Prometheus-compatible scraper can consume.

Exposed metrics

Metric name	Type	Source
`ferricstore_connected_clients`	gauge	Ranch listener connection count
`ferricstore_total_connections_received`	counter	`Stats.total_connections/0`
`ferricstore_total_commands_processed`	counter	`Stats.total_commands/0`
`ferricstore_hot_reads_total`	counter	`Stats.total_hot_reads/0`
`ferricstore_cold_reads_total`	counter	`Stats.total_cold_reads/0`
`ferricstore_used_memory_bytes`	gauge	`:erlang.memory(:total)`
`ferricstore_keydir_used_bytes`	gauge	shard ETS table memory
`ferricstore_uptime_seconds`	gauge	`Stats.uptime_seconds/0`
`ferricstore_blocked_clients`	gauge	waiters ETS table size
`ferricstore_tracking_clients`	gauge	tracking connections ETS size
`ferricstore_slowlog_entries`	gauge	`SlowLog.len/0`
`ferricstore_namespace_window_ms`	gauge	`NamespaceConfig.get_all/0`
`ferricstore_namespace_durability`	gauge	`NamespaceConfig.get_all/0`

iex> text = Ferricstore.Metrics.scrape()
iex> String.contains?(text, "ferricstore_uptime_seconds")
true

The FERRICSTORE.METRICS Redis command returns this text as a bulk string.

metric_type()

Handles the FERRICSTORE.METRICS Redis command.

scrape()

Produces a Prometheus text exposition format string containing all FerricStore metrics.

@type metric_type() :: :counter | :gauge

@spec handle(binary(), [binary()]) :: binary() | {:error, binary()}

Handles the FERRICSTORE.METRICS Redis command.

Returns the Prometheus text exposition as a bulk string. Accepts no arguments.

The scrape text on success, or {:error, message} for wrong arguments.

@spec scrape() :: binary()

Produces a Prometheus text exposition format string containing all FerricStore metrics.

Each metric includes a # HELP line describing its purpose, a # TYPE line declaring its Prometheus type, and a sample line with the current value.

A UTF-8 binary string in Prometheus text exposition format.

iex> text = Ferricstore.Metrics.scrape()
iex> text |> String.split("\n") |> Enum.count(&String.starts_with?(&1, "# HELP")) >= 11
true