Memcached¶

The memcached probe monitors a Memcached server via the TCP text protocol (stats command), reporting connection counts, item counts, memory usage, cache hit/miss ratios, command throughput and eviction counters.

Quick start¶

# probes.d/10-memcached.yaml — each file under probes.d/ is a YAML array of probes
- name: memcached
  type: memcached
  params:
    host: localhost
    port: 11211

Parameters¶

Parameter	Must set	Default	Description
`host`	In practice	`localhost`	Server hostname or address
`port`	In practice	`11211`	Server TCP port
`interval`	No	`60`	Seconds between collections
`timeout`	No	`5`	Connection and command timeout in seconds
`instance_name`	No	-	Stable identity of this server instead of host:port

Metrics¶

Metric	Unit	Description
`senhub.memcached.up`	1	1 when the server responds to `stats`, 0 otherwise
`memcached.uptime`	s	Seconds since the Memcached server started
`memcached.current.connections`	{connection}	Active client connections
`memcached.connections.total`	{connection}	Total connections accepted since start
`memcached.current.items`	{item}	Items currently stored
`memcached.items.total`	{item}	Items stored since start
`memcached.bytes`	By	Current memory used for item storage
`memcached.limit_maxbytes`	By	Configured memory limit
`memcached.operations`	{operation}	Get/set/delete/etc. operations, tagged with `command`
`memcached.operations`	#	Cache get operations by result, tagged with `result` (hit, miss)
`memcached.evictions`	{eviction}	Items evicted to free memory

Operational notes¶

Memcached has no authentication mechanism; ensure the port is not exposed to untrusted networks.
Metric names follow the OpenTelemetry Collector contrib memcachedreceiver convention where equivalents exist.

Metric reference¶

Every metric this probe can emit. Metric is the OpenTelemetry name the OTLP, Prometheus and Zabbix outputs derive theirs from. Name is what a Nagios check and the API metrics= filter match. PRTG channel is the label PRTG shows, placeholders filled from the series' tags.

Metric	Name	PRTG channel	Unit	Description
`senhub.memcached.up`	`senhub.memcached.up`	Memcached Reachability	#	1 when the Memcached server is reachable and responding to stats, 0 otherwise
`memcached.uptime`	`memcached.uptime`	Memcached Uptime	s	Time since the Memcached server started
`memcached.current.connections`	`memcached.current.connections`	Memcached Current Connections	#	Number of currently open connections to the Memcached server
`memcached.connections.total`	`memcached.connections.total`	Memcached Total Connections	#	Total connections opened since server start
`memcached.current.items`	`memcached.current.items`	Memcached Current Items	#	Number of items currently stored in the cache
`memcached.items.total`	`memcached.items.total`	Memcached Total Items	#	Total items stored since server start
`memcached.bytes`	`memcached.bytes`	Memcached Memory Used	B	Current number of bytes used to store items
`memcached.limit_maxbytes`	`memcached.limit_maxbytes`	Memcached Memory Limit	B	Maximum number of bytes the server is allowed to use for storage
`memcached.network`	`memcached.network`	Memcached Network	B	Total bytes transferred since server start, by direction (transmit=sent to clients, receive=received from clients)
`memcached.operations`	`memcached.operations`	Memcached Operations	#	Number of cache get operations by result (hit or miss)
`memcached.commands`	`memcached.commands`	Memcached Commands	#	Number of commands executed, by command type (get/set/flush)
`memcached.evictions`	`memcached.evictions`	Memcached Evictions	#	Number of items evicted from the cache due to memory pressure
`memcached.cpu.usage`	`memcached.cpu.usage`	Memcached CPU	s	CPU time consumed by the Memcached process, by state (user or system)