php and values not returning from memcached

[sjohnsonlist@feedster.com]

That problem I had the other day?  Turns out it was (as I suspected)
(subtle) operator error.  I did upgrade to the newest memcache though but
the problem was mine.

What happened was that for some of the content I was caching it had a null
value which caused memcache to accept it but do nothing with it (as best I
can tell).  So I thought I should be getting a 100% cache hit rate when
really like 1% of my cached content was actually null thus causing the
error.

Scott

> Yeah, I can't remember the differences between 1.1.9 and the current
> release.
>
> But it looks like the two slab stats below are fine... you're not using
> much memory at all.  I'd be interested in seeing your test case to see
> what items aren't being inserted/retrieved.
>
>
> On Wed, 2 Jun 2004 sjohnsonlist@feedster.com wrote:
>
>> Hi Brad,
>>
>> stats slabs
>> STAT 6:chunk_size 64
>> STAT 6:chunks_per_page 16384
>> STAT 6:total_pages 1
>> STAT 6:total_chunks 16384
>> STAT 6:used_chunks 16383
>> STAT 6:free_chunks 1
>> STAT 6:free_chunks_end 15648
>> STAT 7:chunk_size 128
>> STAT 7:chunks_per_page 8192
>> STAT 7:total_pages 1
>> STAT 7:total_chunks 8192
>> STAT 7:used_chunks 8192
>> STAT 7:free_chunks 0
>> STAT 7:free_chunks_end 7211
>> STAT 8:chunk_size 256
>> STAT 8:chunks_per_page 4096
>> STAT 8:total_pages 1
>> STAT 8:total_chunks 4096
>> STAT 8:used_chunks 4096
>> STAT 8:free_chunks 0
>> STAT 8:free_chunks_end 3204
>> STAT 9:chunk_size 512
>> STAT 9:chunks_per_page 2048
>> STAT 9:total_pages 1
>> STAT 9:total_chunks 2048
>> STAT 9:used_chunks 2048
>> STAT 9:free_chunks 0
>> STAT 9:free_chunks_end 1092
>> STAT 10:chunk_size 1024
>> STAT 10:chunks_per_page 1024
>> STAT 10:total_pages 1
>> STAT 10:total_chunks 1024
>> STAT 10:used_chunks 1024
>> STAT 10:free_chunks 0
>> STAT 10:free_chunks_end 60
>> STAT 11:chunk_size 2048
>> STAT 11:chunks_per_page 512
>> STAT 11:total_pages 1
>> STAT 11:total_chunks 512
>> STAT 11:used_chunks 512
>> STAT 11:free_chunks 0
>> STAT 11:free_chunks_end 210
>> STAT 12:chunk_size 4096
>> STAT 12:chunks_per_page 256
>> STAT 12:total_pages 1
>> STAT 12:total_chunks 256
>> STAT 12:used_chunks 256
>> STAT 12:free_chunks 0
>> STAT 12:free_chunks_end 73
>> STAT 13:chunk_size 8192
>> STAT 13:chunks_per_page 128
>> STAT 13:total_pages 1
>> STAT 13:total_chunks 128
>> STAT 13:used_chunks 128
>> STAT 13:free_chunks 0
>> STAT 13:free_chunks_end 57
>> STAT 14:chunk_size 16384
>> STAT 14:chunks_per_page 64
>> STAT 14:total_pages 1
>> STAT 14:total_chunks 64
>> STAT 14:used_chunks 64
>> STAT 14:free_chunks 0
>> STAT 14:free_chunks_end 51
>> STAT 15:chunk_size 32768
>> STAT 15:chunks_per_page 32
>> STAT 15:total_pages 1
>> STAT 15:total_chunks 32
>> STAT 15:used_chunks 32
>> STAT 15:free_chunks 0
>> STAT 15:free_chunks_end 29
>> STAT 16:chunk_size 65536
>> STAT 16:chunks_per_page 16
>> STAT 16:total_pages 1
>> STAT 16:total_chunks 16
>> STAT 16:used_chunks 16
>> STAT 16:free_chunks 0
>> STAT 16:free_chunks_end 15
>> STAT 17:chunk_size 131072
>> STAT 17:chunks_per_page 8
>> STAT 17:total_pages 1
>> STAT 17:total_chunks 8
>> STAT 17:used_chunks 8
>> STAT 17:free_chunks 0
>> STAT 17:free_chunks_end 7
>> STAT active_slabs 12
>> STAT total_malloced 12582912
>>
>> That's from one of my servers and here's from the other one heavily in
>> use:
>>
>> stats slabs
>> STAT 6:chunk_size 64
>> STAT 6:chunks_per_page 16384
>> STAT 6:total_pages 1
>> STAT 6:total_chunks 16384
>> STAT 6:used_chunks 16383
>> STAT 6:free_chunks 1
>> STAT 6:free_chunks_end 15751
>> STAT 7:chunk_size 128
>> STAT 7:chunks_per_page 8192
>> STAT 7:total_pages 1
>> STAT 7:total_chunks 8192
>> STAT 7:used_chunks 8191
>> STAT 7:free_chunks 1
>> STAT 7:free_chunks_end 7167
>> STAT 8:chunk_size 256
>> STAT 8:chunks_per_page 4096
>> STAT 8:total_pages 1
>> STAT 8:total_chunks 4096
>> STAT 8:used_chunks 4096
>> STAT 8:free_chunks 0
>> STAT 8:free_chunks_end 3265
>> STAT 9:chunk_size 512
>> STAT 9:chunks_per_page 2048
>> STAT 9:total_pages 1
>> STAT 9:total_chunks 2048
>> STAT 9:used_chunks 2047
>> STAT 9:free_chunks 1
>> STAT 9:free_chunks_end 1131
>> STAT 10:chunk_size 1024
>> STAT 10:chunks_per_page 1024
>> STAT 10:total_pages 1
>> STAT 10:total_chunks 1024
>> STAT 10:used_chunks 1023
>> STAT 10:free_chunks 1
>> STAT 10:free_chunks_end 641
>> STAT 11:chunk_size 2048
>> STAT 11:chunks_per_page 512
>> STAT 11:total_pages 1
>> STAT 11:total_chunks 512
>> STAT 11:used_chunks 511
>> STAT 11:free_chunks 1
>> STAT 11:free_chunks_end 224
>> STAT 12:chunk_size 4096
>> STAT 12:chunks_per_page 256
>> STAT 12:total_pages 1
>> STAT 12:total_chunks 256
>> STAT 12:used_chunks 256
>> STAT 12:free_chunks 0
>> STAT 12:free_chunks_end 106
>> STAT 13:chunk_size 8192
>> STAT 13:chunks_per_page 128
>> STAT 13:total_pages 1
>> STAT 13:total_chunks 128
>> STAT 13:used_chunks 127
>> STAT 13:free_chunks 1
>> STAT 13:free_chunks_end 72
>> STAT 14:chunk_size 16384
>> STAT 14:chunks_per_page 64
>> STAT 14:total_pages 1
>> STAT 14:total_chunks 64
>> STAT 14:used_chunks 63
>> STAT 14:free_chunks 1
>> STAT 14:free_chunks_end 42
>> STAT 15:chunk_size 32768
>> STAT 15:chunks_per_page 32
>> STAT 15:total_pages 1
>> STAT 15:total_chunks 32
>> STAT 15:used_chunks 31
>> STAT 15:free_chunks 1
>> STAT 15:free_chunks_end 24
>> STAT active_slabs 10
>> STAT total_malloced 10485760
>>
>>
>> Oh and it is memcached 1.1.9.  That's the standard one emerged by gentoo
>> and I'm starting to wonder if this is version hell now that I see I'm
>> dated back to 2003.  Time for an upgrade ...
>>
>> Scott
>>
>> > New items push old items out, unless you use the command line option
>> to
>> > override that.  Try pasting to us the results of "stats slabs" so we
>> can
>> > see how much memory is actually being used, and how.
>> >
>> > flush_all won't make the results of "stats" change.  It just sets an
>> > internal time that items have to be newer than to be returned with
>> "get"
>> > or "get_multi".  So they'll be flushed lazily when they're gotten
>> later.
>> >
>> > - Brad
>> >
>> >
>> > On Wed, 2 Jun 2004 sjohnsonlist@feedster.com wrote:
>> >
>> >> Hi all,
>> >>
>> >> Note: 1st post here so please excuse obvious stupidity but I did read
>> >> through the api docs and server docs w/o seeing anything.
>> >>
>> >> I'm running memcached across 3 servers on gentoo linux, kernel 2.6.5
>> >> environment (400 megs ram, 100 megs ram, 300 megs ram).
>> >>
>> >> What I'm doing is writing a cache loader to pre-populate a cache of
>> data
>> >> pulled from a mysql table.  And what I'm finding is that caching a
>> large
>> >> number of items is leaving a handful without values.
>> >>
>> >> My code is using the php API from this:
>> >> http://www.danga.com/memcached/dist/php-memcached-1.0.10.tar.gz
>> >>
>> >> Basically all I do is loop over my database and call $memc->set($key,
>> >> $value, $expire) and then kill the job if $memc returns false.  It
>> never
>> >> dies so memcache seems to be accepting all my objects fine.  That
>> works
>> >> fine and here's my internal diagnostics at the end of the job:
>> >>
>> >> Total size = 10795847 (this is the sum of the string lengths I
>> loaded)
>> >> 22734 total objects loaded (this is the total # of keys I sent to
>> >> memcache)
>> >>
>> >> Now when I go to retrieve the content, I get this result:
>> >>
>> >> Key=|raw_content_47519384|
>> >> err=No value found for key raw_content_47519384
>> >>
>> >> But I know this was set correctly or my code would have died (and my
>> >> logs
>> >> show it was set correctly).  My guess is that objects are being
>> expired
>> >> from the cache as new objects come in but I am setting a 5 day
>> >> expiration
>> >> time as measured by a time() + (5*86400) value. And this doesn't seem
>> to
>> >> be enough data to overflow a cache of this size.
>> >>
>> >> Here are my stats from the server:
>> >> stats
>> >> STAT pid 25901
>> >> STAT uptime 503
>> >> STAT time 1086201062
>> >> STAT version 1.1.9
>> >> STAT rusage_user 0:118981
>> >> STAT rusage_system 0:190970
>> >> STAT curr_items 4395
>> >> STAT total_items 4395
>> >> STAT bytes 2498844
>> >> STAT curr_connections 1
>> >> STAT total_connections 5094
>> >> STAT connection_structures 4
>> >> STAT cmd_get 697
>> >> STAT cmd_set 4395
>> >> STAT get_hits 498
>> >> STAT get_misses 199
>> >> STAT bytes_read 2454699
>> >> STAT bytes_written 338016
>> >> STAT limit_maxbytes 524288000
>> >> END
>> >> flush_all
>> >> ERROR
>> >>
>> >> Interestingly I'm finding that the flush_all command isn't working.
>> >> That
>> >> feeds very, very wrong.
>> >>
>> >> Comments ?  Thanks in advance.
>> >>
>> >> Scott
>> >>
>> >>
>> >>
>> >>
>> >>
>> >>
>> >
>>
>>
>