--- title: "Memcache monitoring and flush using the nc command" date: "2024-11-01T05:42:45+00:00" summary: image: type: "article" url: "/acquia-cloud-platform/help/92951-memcache-monitoring-and-flush-using-nc-command" id: "51705679-4f27-4b3d-8374-9bb5f73e1a24" --- Table of contents will be added Most Drupal website administrators are interested in quickly monitoring memcache's statistics, and the `**nc**` command is a useful command for interacting with memcache servers. The following details the following functions that can used for memcache servers: * [Retrieve memcache statistics](#retrieve-memcache-statistics) * [Watching statistics in real time](#watching-statistics-real-time) * [Flushing memcache](#flushing-memcache) With the  [**Cloud**](/node/55808) [**Nex**](/node/55808)[**t**](/node/55808) infrastructure being a kubernetes framework, and Acquia’s non-Kubernetes version, referred to as [**Cloud Classic**](/node/55808) infrastructure, there is a difference of for each infrastructure. This article provides commands for both of these, for each memcache server interaction functionality. Retrieve memcache statistics ---------------------------- **Note** In order to run the commands below you need to first connect through SSH into the web server. ### Cloud Next If you are running on the [**Cloud**](/node/55808) [**Nex**](/node/55808)[**t**](/node/55808) infrastructure, use the `**acquia-memcache**` command, instead of the `**nc**` command. #### Step 1. Run acquia-memcache command For the Acquia Cloud Next platform, use the command: acquia-memcache stats * * * ### Cloud Classic #### Step 1.  Find the servers As a preliminary step, you'll need a list of the memcache servers that Drupal is using. As an Acquia Cloud customer, you can find your memcache servers by navigating to the **Application > Environment > Infrastructure (Classic)** page in the Acquia Cloud UI. Find the "web" server(s) that have "Memcache" and note their full DNS name (e.g. "web-123.prod.hosting.acquia.com"). If you have a Drupal 7 application, you can use the following [Drush](http://www.drupal.org/project/drush) command to look up the `memcache_servers` variable: drush vget memcache_servers The output should look something like this: memcache_servers: Array ( [server-1234.prod.hosting.acquia.com:11211] => default [server-5678.prod.hosting.acquia.com:11211] => default ) This array is automatically populated on Acquia Cloud servers using memcache. The format of the servers' array is `hostname:port => bin`. In the sample output, the default memcache bin is split across two memcache hosts — `server-1234.prod.hosting.acquia.com` and `server-5678.prod.hosting.acquia.com`, using port 11211 on each host. #### Step 2. Run the nc command The [Memcached protocol](https://github.com/memcached/memcached/blob/master/doc/protocol.txt) provides a `stats` command that can provide some insight into a few dozen server variables. Many of these server variables count the number of times a particular event occurred since the service was launched. In this example, we echo two commands together: `stats`, followed by `quit` (separated by a newline). The `-q1` option tells the `nc` command to not disconnect immediately. Without this option, `nc` might close the connection before it delivers the output. **Note** You can only use `nc` to connect to a server running memcached from another server in the same cluster. Users cannot connect from their local computers — they must instead SSH into one of their web servers to run these commands. /bin/echo -e 'stats\nquit' | nc -q1 [memcache hostname] [port number] Here's an example using server information from the previous example: /bin/echo -e 'stats\nquit' | nc -q1  $(hostname -s) 11211 * * * * * * Watching statistics in real time -------------------------------- The output of the preceding command should look similar to the following: STAT pid 1216 STAT uptime 2472376 STAT time 1373572082 STAT version 1.4.5 STAT pointer_size 64 STAT rusage_user 66.790000 STAT rusage_system 110.900000 STAT curr_connections 3 STAT total_connections 297279 STAT connection_structures 10 STAT cmd_get 2115470 STAT cmd_set 92126 STAT cmd_flush 0 STAT get_hits 1918776 STAT get_misses 196694 STAT delete_misses 806 STAT delete_hits 1566 STAT incr_misses 0 STAT incr_hits 19 STAT decr_misses 0 STAT decr_hits 0 STAT cas_misses 0 STAT cas_hits 0 STAT cas_badval 0 STAT auth_cmds 0 STAT auth_errors 0 STAT bytes_read 346432348 STAT bytes_written 3932785939 STAT limit_maxbytes 67108864 STAT accepting_conns 1 STAT listen_disabled_num 0 STAT threads 1 STAT conn_yields 0 STAT bytes 46704290 STAT curr_items 21955 STAT total_items 92127 STAT evictions 13531 STAT reclaimed 0 END You can use the `watch` command to monitor all of these statistics in real time. For example: watch -d -n 10 "/bin/echo -e 'stats\nquit' | nc -q1  $(hostname -s) 11211" Adding the `-**d**` option to the watch command highlights the parts of the output that have changed since the last output. The `-**n**` option sets a delay interval; in this example, it's set to 10 seconds. * * * * * * Flushing memcache ----------------- ### Cloud Next To flush memcache on Cloud Next, SSH into your site and then run this command:  acquia-memcache flush_all * * * ### Cloud Classic For clearing memcache, you can SSH into the specific server which is running memcache (you can check it on Cloud UI) and then run the below command - Here's an example: /bin/echo -e 'flush_all\nquit' | nc -q1 $(hostname -s) 11211 If the command completes normally, the output should simply be **OK**. _**Important**_ Because the method described in this section involves flushing memcache for all of your websites on a given server, using this flushing method is not recommended. It cannot be localized to a single environment, and is is an abnormal and potentially dangerous course of action that can result in temporary performance issues (or even downtime), especially if the website has a large volume of traffic to its back-end web servers. Other Drupal websites that share the same memcache servers could also be inadvertently affected. _**This should be a last resort.** If you have concerns, contact_ [_Acquia Support_](/node/57198)_._ In most cases, when a particular part of a Drupal page appears "stuck" in cache, you should use the `drush cache-clear` command. This command can clear a specific cache that appears to be problematic. In _extremely rare circumstances_ you may need to manually trigger a memcache flush. For Drupal 7 websites, you may need to trigger a registry rebuild function. (For more information, see the [Registry Rebuild](https://drupal.org/project/registry_rebuild) module on drupal.org.) If these processes fail, you can attempt a manual memcache flush. The memcache protocol `flush` command allows you to immediately flag all stored values as invalid.