https://bugs.koha-community.org/bugzilla3/show_bug.cgi?id=17833
Bug ID: 17833
Summary: Memcached silently fails to _initilize_memcached() on
the second time it is invoked
Change sponsored?: ---
Product: Koha
Version: master
Hardware: All
OS: All
Status: NEW
Severity: enhancement
Priority: P5 - low
Component: Architecture, internals, and plumbing
Assignee: [email protected]
Reporter: [email protected]
QA Contact: [email protected]
When _initilize_memcached() is called the first time, it sets the
'ismemcached'-key and returns 1.
When _initilize_memcached() is called the second time, the 'ismemcached'-key
already exists and '' is returned (this default to False in Perl).
Koha thinks that memcached is not in use and decides to use some other caching
mechanism instead.
Cache::Memcached::Fast returns undef on server error:
https://metacpan.org/pod/Cache::Memcached::Fast#add
Koha MUST listen to undefined, instead of False to define whether or not
memcached is properly working.
Also added simple helpful diagnostics to help identify and log when this
memcached server connection problem arises.
Here is a small test run to verify this behaviour:
root@kohadev:~# echo "fresh memcached start"
fresh memcached start
root@kohadev:~# perl l.pl
127.0.0.1:4545 1.4.14 (Ubuntu)
def : '1'
getkey: 'text'
root@kohadev:~# echo "val already cached"
val already cached
root@kohadev:~# perl l.pl
127.0.0.1:4545 1.4.14 (Ubuntu)
def : ''
getkey: 'text'
root@kohadev:~# echo "memcached killed and not responding"
memcached killed and not responding
root@kohadev:~# perl l.pl
undef
getkey: ''
root@kohadev:~# echo "The return value is undefined"
The return value is undefined
root@kohadev:~#
Here is the code snippet used to test the Memcached-server in the previous
example output:
kivilahtio@koha_ci_1 /h/k/Koha> cat t.pl
use Cache::Memcached::Fast;
use Modern::Perl;
my $memd = new Cache::Memcached::Fast({
servers => [ '/lxcBindMount/tmp/memcached.sock' ],
namespace => 'koha_ci_1:',
connect_timeout => 0.2,
io_timeout => 0.5,
close_on_error => 1,
max_failures => 3,
failure_timeout => 2,
ketama_points => 150,
nowait => 1,
hash_namespace => 1,
});
# Get server versions.
my $versions = $memd->server_versions;
while (my ($server, $version) = each %$versions) {
print "$server $version\n";
}
# Store scalars.
my $rv = $memd->add('skey', 'text');
print "undef\n" if not defined $rv;
print "def : '$rv'\n" if defined $rv;
print "getkey: '".$memd->get('skey')."'\n";
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