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Recently I was working on a code release on a site running PHP on Apache httpd, and using memcached. Without getting into specifics, we had a number of issues that were both Apache and memcached problems, and little visibility into them as it was running on an older server without much monitoring in place. I started looking around for simple tools that could provide a bit more insight, without many dependencies (as the machine is a relatively minimalist install). Here are some of the options I found:

  • memcache-top - A top-like script that pulls stats from memcached instances and can show both per-instance, total and average usage %, hit rate, number of connections, time to run the stats query, evictions, gets, sets, and read and write amounts. Best of all, it’s a very small perl script that requires only IO::Socket and Time::HiRes. Here’s a small example of the output:

    memcache-top v0.6       (default port: 11211, color: on, refresh: 3 seconds)
    
    INSTANCE                USAGE   HIT %   CONN    TIME    EVICT   GETS    SETS    READ    WRITE
    127.0.0.1:11211         86.6%   99.4%   115     0.6ms   0.0     4114    1669    1.3M    24.2M
    127.0.0.1:11212         85.5%   59.9%   2       0.4ms   0.0     0       0       90      8055
    
    AVERAGE:                86.0%   79.6%   58      0.5ms   0.0     2057    834     682.4K  12.1M
    
    TOTAL:          0.9GB/  1.0GB           117     1.0ms   0.0     4114    1669    1.3M    24.2M
    
  • damemtop is also a nice top-like memcached tool. On the positive side, you can specify any column from “stats”, “stats items” or “stats slabs” in the configuration file, and can choose between average or one-second snapshots for each column. On the down side, it requires the YAML and AnyEvent Perl modules, so it has some uncommon dependencies.

    damemtop: Tue Jun 26 14:02:24 2012 [sort: hostname asc] [delay: 3s]
    hostname           all_version  all_fill_rate  hit_rate  evictions  curr_items  curr_connections   cmd_get  cmd_set  bytes_written  bytes_read  get_hits  get_misses  
    TOTAL:             
    NA                 NA           NA             NA        NA         NA          NA                 87       32       491,735        30,894      86        1           
    AVERAGE:           
    NA                 NA           86.00%         99.00%    NA         NA          NA                 43       16       122,933        7,723       43        1           
    10.200.1.78:11211  1.2.6        86.63%         98.04%    0          0           -1.00204024880524  51       19       386,492        21,613      50        1           
    10.200.1.78:11212  1.2.6        85.46%         NA        0          0           0                  0        0        11,373         31          0         0           
    10.200.1.79:11211  1.2.6        87.31%         100.00%   0          0           -1.00204024880524  36       13       82,479         9,219       36        0           
    10.200.1.79:11212  1.2.6        85.08%         NA        0          0           0                  0        0        11,389         31          0         0           
    loop took: 0.305617094039917
    

I’m still looking around for something for apache that uses mod_status and isn’t too verbose; ideally I’d like to be able to watch memcached, apache response codes/times, and apache mod_status all in the same terminal window.


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