Memcached

Plugin: go.d.plugin Module: memcached

Overview

Monitor Memcached metrics for proficient in-memory key-value store operations. Track cache hits, misses, and memory usage for efficient data caching.

It reads the server's response to the stats command.

This collector is supported on all platforms.

This collector supports collecting metrics from multiple instances of this integration, including remote instances.

Default Behavior

Auto-Detection

If no configuration is given, collector will attempt to connect to memcached instance on 127.0.0.1:11211 address.

Limits

The default configuration for this integration does not impose any limits on data collection.

Performance Impact

The default configuration for this integration is not expected to impose a significant performance impact on the system.

Metrics

Metrics grouped by scope.

The scope defines the instance that the metric belongs to. An instance is uniquely identified by a set of labels.

Per Memcached instance

These metrics refer to the entire monitored application.

This scope has no labels.

Metrics:

Metric	Dimensions	Unit
memcached.cache	available, used	MiB
memcached.net	in, out	kilobits/s
memcached.connections	current, rejected, total	connections/s
memcached.items	current, total	items
memcached.evicted_reclaimed	reclaimed, evicted	items
memcached.get	hints, misses	requests
memcached.get_rate	rate	requests/s
memcached.set_rate	rate	requests/s
memcached.delete	hits, misses	requests
memcached.cas	hits, misses, bad value	requests
memcached.increment	hits, misses	requests
memcached.decrement	hits, misses	requests
memcached.touch	hits, misses	requests
memcached.touch_rate	rate	requests/s

Alerts

The following alerts are available:

Alert name	On metric	Description
memcached_cache_memory_usage	memcached.cache	cache memory utilization
memcached_cache_fill_rate	memcached.cache	average rate the cache fills up (positive), or frees up (negative) space over the last hour
memcached_out_of_cache_space_time	memcached.cache	estimated time the cache will run out of space if the system continues to add data at the same rate as the past hour

Setup

Prerequisites

No action required.

Configuration

File

The configuration file name for this integration is go.d/memcached.conf.

You can edit the configuration file using the edit-config script from the Netdata config directory.

cd /etc/netdata 2>/dev/null || cd /opt/netdata/etc/netdata
sudo ./edit-config go.d/memcached.conf

Options

The following options can be defined globally: update_every, autodetection_retry.

Config options

Name	Description	Default	Required
update_every	Data collection frequency.	1	no
autodetection_retry	Recheck interval in seconds. Zero means no recheck will be scheduled.	0	no
address	The IP address and port where the memcached service listens for connections.	127.0.0.1:11211	yes
timeout	Connection, read, and write timeout duration in seconds. The timeout includes name resolution.	1	no

Examples

Basic

A basic example configuration.

Config

jobs:
  - name: local
    address: 127.0.0.1:11211

Multi-instance

Note: When you define multiple jobs, their names must be unique.

Collecting metrics from local and remote instances.

Config

jobs:
  - name: local
    address: 127.0.0.1:11211

  - name: remote
    address: 203.0.113.0:11211

Troubleshooting

Debug Mode

To troubleshoot issues with the memcached collector, run the go.d.plugin with the debug option enabled. The output should give you clues as to why the collector isn't working.

• Navigate to the plugins.d directory, usually at /usr/libexec/netdata/plugins.d/. If that's not the case on your system, open netdata.conf and look for the plugins setting under [directories].

  cd /usr/libexec/netdata/plugins.d/

• Switch to the netdata user.

  sudo -u netdata -s

• Run the go.d.plugin to debug the collector:

  ./go.d.plugin -d -m memcached

Getting Logs

If you're encountering problems with the memcached collector, follow these steps to retrieve logs and identify potential issues:

• Run the command specific to your system (systemd, non-systemd, or Docker container).
• Examine the output for any warnings or error messages that might indicate issues. These messages should provide clues about the root cause of the problem.

System with systemd

Use the following command to view logs generated since the last Netdata service restart:

journalctl _SYSTEMD_INVOCATION_ID="$(systemctl show --value --property=InvocationID netdata)" --namespace=netdata --grep memcached

System without systemd

Locate the collector log file, typically at /var/log/netdata/collector.log, and use grep to filter for collector's name:

grep memcached /var/log/netdata/collector.log

Note: This method shows logs from all restarts. Focus on the latest entries for troubleshooting current issues.

Docker Container

If your Netdata runs in a Docker container named "netdata" (replace if different), use this command:

docker logs netdata 2>&1 | grep memcached