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Memcached

Plugin: python.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 server response to stats command (stats interface).

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:

MetricDimensionsUnit
memcached.cacheavailable, usedMiB
memcached.netin, outkilobits/s
memcached.connectionscurrent, rejected, totalconnections/s
memcached.itemscurrent, totalitems
memcached.evicted_reclaimedreclaimed, evicteditems
memcached.gethints, missesrequests
memcached.get_rateraterequests/s
memcached.set_rateraterequests/s
memcached.deletehits, missesrequests
memcached.cashits, misses, bad valuerequests
memcached.incrementhits, missesrequests
memcached.decrementhits, missesrequests
memcached.touchhits, missesrequests
memcached.touch_rateraterequests/s

Alerts

The following alerts are available:

Alert nameOn metricDescription
memcached_cache_memory_usage memcached.cachecache memory utilization
memcached_cache_fill_rate memcached.cacheaverage rate the cache fills up (positive), or frees up (negative) space over the last hour
memcached_out_of_cache_space_time memcached.cacheestimated 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 python.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 python.d/memcached.conf

Options

There are 2 sections:

  • Global variables
  • One or more JOBS that can define multiple different instances to monitor.

The following options can be defined globally: priority, penalty, autodetection_retry, update_every, but can also be defined per JOB to override the global values.

Additionally, the following collapsed table contains all the options that can be configured inside a JOB definition.

Every configuration JOB starts with a job_name value which will appear in the dashboard, unless a name parameter is specified.

Config options
NameDescriptionDefaultRequired
hostthe host to connect to.127.0.0.1no
portthe port to connect to.11211no
update_everySets the default data collection frequency.10no
priorityControls the order of charts at the netdata dashboard.60000no
autodetection_retrySets the job re-check interval in seconds.0no
penaltyIndicates whether to apply penalty to update_every in case of failures.yesno
nameJob name. This value will overwrite the job_name value. JOBS with the same name are mutually exclusive. Only one of them will be allowed running at any time. This allows autodetection to try several alternatives and pick the one that works.no

Examples

localhost

An example configuration for localhost.

localhost:
name: 'local'
host: 'localhost'
port: 11211

localipv4

An example configuration for localipv4.

Config
localhost:
name: 'local'
host: '127.0.0.1'
port: 11211

localipv6

An example configuration for localipv6.

Config
localhost:
name: 'local'
host: '::1'
port: 11211

Troubleshooting

Debug Mode

To troubleshoot issues with the memcached collector, run the python.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 python.d.plugin to debug the collector:

    ./python.d.plugin memcached debug trace

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

Do you have any feedback for this page? If so, you can open a new issue on our netdata/learn repository.