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# Memcached


<img src="https://netdata.cloud/img/memcached.svg" width="150"/>


Plugin: go.d.plugin
Module: memcached

<img src="https://img.shields.io/badge/maintained%20by-Netdata-%2300ab44" />

## 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.

## Setup


You can configure the **memcached** collector in two ways:

| Method                | Best for                                                                                 | How to                                                                                                                                 |
|-----------------------|------------------------------------------------------------------------------------------|----------------------------------------------------------------------------------------------------------------------------------------|
| [**UI**](#via-ui)     | Fast setup without editing files                                                         | Go to **Nodes → Configure this node → Collectors → Jobs**, search for **memcached**, then click **+** to add a job. |
| [**File**](#via-file) | If you prefer configuring via file, or need to automate deployments (e.g., with Ansible) | Edit `go.d/memcached.conf` and add a job.                                                                        |

:::important

UI configuration requires paid Netdata Cloud plan.

:::


### Prerequisites

#### UNIX socket access

If you are connecting to Memcached via its UNIX socket, ensure that the `netdata` user
has permission to access it. You can do this by:

1. Adding the `netdata` user to the `memcache` group.
   ```bash
   sudo gpasswd -a netdata memcache
   ```
2. Configuring the socket permissions in `/etc/memcached.conf` so the group has access (e.g. `-a 770`).

**Note**: You may need to restart Memcached after making these changes for them to take effect.



### Configuration

#### Options

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


<details open><summary>Config options</summary>



| Group | Option | Description | Default | Required |
|:------|:-----|:------------|:--------|:---------:|
| **Collection** | update_every | Data collection interval (seconds). | 1 | no |
|  | autodetection_retry | Autodetection retry interval (seconds). Set 0 to disable. | 0 | no |
| **Target** | address | Memcached server address (`IP:PORT`). | 127.0.0.1:11211 | yes |
|  | timeout | Connection, read, write, and name resolution timeout (seconds). | 1 | no |
| **Virtual Node** | vnode | Associates this data collection job with a [Virtual Node](https://learn.netdata.cloud/docs/netdata-agent/configuration/organize-systems-metrics-and-alerts#virtual-nodes). |  | no |


</details>


#### via UI

Configure the **memcached** collector from the Netdata web interface:

1. Go to **Nodes**.
2. Select the node **where you want the memcached data-collection job to run** and click the :gear: (**Configure this node**). That node will run the data collection.
3. The **Collectors → Jobs** view opens by default.
4. In the Search box, type _memcached_ (or scroll the list) to locate the **memcached** collector.
5. Click the **+** next to the **memcached** collector to add a new job.
6. Fill in the job fields, then click **Test** to verify the configuration and **Submit** to save.
    - **Test** runs the job with the provided settings and shows whether data can be collected.
    - If it fails, an error message appears with details (for example, connection refused, timeout, or command execution errors), so you can adjust and retest.


#### via File

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

The file format is YAML. Generally, the structure is:

```yaml
update_every: 1
autodetection_retry: 0
jobs:
  - name: some_name1
  - name: some_name2
```
You can edit the configuration file using the [`edit-config`](https://github.com/netdata/netdata/blob/master/docs/netdata-agent/configuration/README.md#edit-configuration-files) script from the
Netdata [config directory](https://github.com/netdata/netdata/blob/master/docs/netdata-agent/configuration/README.md#locate-your-config-directory).

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

##### Examples

###### Basic

A basic example configuration.

<details open><summary>Config</summary>

```yaml
jobs:
  - name: local
    address: 127.0.0.1:11211

```
</details>

###### Multi-instance

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

Collecting metrics from local and remote instances.


<details open><summary>Config</summary>

```yaml
jobs:
  - name: local
    address: 127.0.0.1:11211

  - name: remote
    address: 203.0.113.0:11211

```
</details>



## Alerts


The following alerts are available:

| Alert name  | On metric | Description |
|:------------|:----------|:------------|
| [ memcached_cache_memory_usage ](https://github.com/netdata/netdata/blob/master/src/health/health.d/memcached.conf) | memcached.cache | cache memory utilization |
| [ memcached_cache_fill_rate ](https://github.com/netdata/netdata/blob/master/src/health/health.d/memcached.conf) | memcached.cache | average rate the cache fills up (positive), or frees up (negative) space over the last hour |
| [ memcached_out_of_cache_space_time ](https://github.com/netdata/netdata/blob/master/src/health/health.d/memcached.conf) | 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 |


## 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 |



## Troubleshooting

### Debug Mode

**Important**: Debug mode is not supported for data collection jobs created via the UI using the Dyncfg feature.

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]`.

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

- Switch to the `netdata` user.

  ```bash
  sudo -u netdata -s
  ```

- Run the `go.d.plugin` to debug the collector:

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

  To debug a specific job:

  ```bash
  ./go.d.plugin -d -m memcached -j jobName
  ```

### 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:

```bash
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:

```bash
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:

```bash
docker logs netdata 2>&1 | grep memcached
```


