Memcache Commands - HackTricks

# Memcache Commands

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## Commands Cheat-Sheet

From https://lzone.de/cheat-sheet/memcached

The supported commands (the official ones and some unofficial) are documented in the doc/protocol.txt document.

Sadly the syntax description isn’t really clear and a simple help command listing the existing commands would be much better. Here is an overview of the commands you can find in the source (as of 19.08.2016):

| Command | Description | Example | | -------------------- | --------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | ----------------------------- | | get | Reads a value | `get mykey` | | set | Set a key unconditionally |

`set mykey`

Ensure to use \r\n als line breaks when using Unix CLI tools. For example

`printf "set mykey 0 60 4\r\ndata\r\n" | nc localhost 11211` | | add | Add a new key | `add newkey 0 60 5` | | replace | Overwrite existing key | `replace key 0 60 5` | | append | Append data to existing key | `append key 0 60 15` | | prepend | Prepend data to existing key | `prepend key 0 60 15` | | incr | Increments numerical key value by given number | `incr mykey 2` | | decr | Decrements numerical key value by given number | `decr mykey 5` | | delete | Deletes an existing key | `delete mykey` | | flush_all | Invalidate all items immediately | `flush_all` | | flush_all | Invalidate all items in n seconds | `flush_all 900` | | stats | Prints general statistics | `stats` | | | Prints memory statistics | `stats slabs` | | | Print higher level allocation statistics | `stats malloc` | | | Print info on items | `stats items` | | | | `stats detail` | | | | `stats sizes` | | | Resets statistics counters | `stats reset` | | lru_crawler metadump | Dump (most of) the metadata for (all of) the items in the cache | `lru_crawler metadump all` | | version | Prints server version. | `version` | | verbosity | Increases log level | `verbosity` | | quit | Terminate session | `quit` |

#### Traffic Statistics

You can query the current traffic statistics using the command

    stats

You will get a listing which serves the number of connections, bytes in/out and much more.

Example Output:

    STAT pid 14868
    STAT uptime 175931
    STAT time 1220540125
    STAT version 1.2.2
    STAT pointer_size 32
    STAT rusage_user 620.299700
    STAT rusage_system 1545.703017
    STAT curr_items 228
    STAT total_items 779
    STAT bytes 15525
    STAT curr_connections 92
    STAT total_connections 1740
    STAT connection_structures 165
    STAT cmd_get 7411
    STAT cmd_set 28445156
    STAT get_hits 5183
    STAT get_misses 2228
    STAT evictions 0
    STAT bytes_read 2112768087
    STAT bytes_written 1000038245
    STAT limit_maxbytes 52428800
    STAT threads 1
    END

#### Memory Statistics

You can query the current memory statistics using

    stats slabs

Example Output:

    STAT 1:chunk_size 80
    STAT 1:chunks_per_page 13107
    STAT 1:total_pages 1
    STAT 1:total_chunks 13107
    STAT 1:used_chunks 13106
    STAT 1:free_chunks 1
    STAT 1:free_chunks_end 12886
    STAT 2:chunk_size 100
    STAT 2:chunks_per_page 10485
    STAT 2:total_pages 1
    STAT 2:total_chunks 10485
    STAT 2:used_chunks 10484
    STAT 2:free_chunks 1
    STAT 2:free_chunks_end 10477
    [...]
    STAT active_slabs 3
    STAT total_malloced 3145436
    END

If you are unsure if you have enough memory for your memcached instance always look out for the “evictions” counters given by the “stats” command. If you have enough memory for the instance the “evictions” counter should be 0 or at least not increasing.

#### Which Keys Are Used?

There is no builtin function to directly determine the current set of keys. However you can use the

    stats items

command to determine how many keys do exist.

    stats items
    STAT items:1:number 220
    STAT items:1:age 83095
    STAT items:2:number 7
    STAT items:2:age 1405
    [...]
    END

This at least helps to see if any keys are used. To dump the key names from a PHP script that already does the memcache access you can use the PHP code from 100days.de.

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