XtraDB cluster doesn't check the parameters of wsrep_provider_options

This requires some investigation. Galera is supposed to return an error on an unrecognised parameter. Technically in this case provider should fail to initialize.

If the parameter is set at runtime, Galera returns 'Unknown
parameter' to stderr and also "ERROR 1210 (HY000): Incorrect
arguments to SET" to client.

However, this checking is not done at init.

wsrep_set_params called in galera_init has checking for unknown
parameters. However,

galera::ReplicatorSMM::param_set:

    try
    {
        if (config_.get(key) == value) return;
    }
    catch (gu::NotFound&) {}

applies to all provided options (even base_host). So, rest of the
function is bypassed.

This is because they (the config_ map) are initialised earlier in
gu::Config::parse where there is no checking of keys.

Since gu::Config::parse itself doesn't know about parameters to
distinguish between in/valid parameters, right step here would
be to initialise map with compile-time values (as is done in
galera::ReplicatorSMM::ReplicatorSMM for others), and not to add any
new keys in gu::Config::parse but to throw exception when there is a
new key. , ie. move gu::Config::parse to a latter stage after initialisation of config_ map with compile time values.

Heh, looks like that. Which effectively complicates the configuration code by a factor of two. Needs more thinking.

Question to all concerned:
Currently wsrep_provider_options only shows options that are in use. E.g. if SSL is not configured, available SSL-related options won't be displayed. Should it stay this way or display ALL options (which might be close to 50) ?

On Dec 15, 2013, at 8:45 PM, Alex Yurchenko <email address hidden> wrote:

> Currently wsrep_provider_options only shows options that are in use. E.g. if SSL is not configured, available SSL-related options won't be displayed. Should it stay this way or display ALL options (which might be close to 50) ?

I often use SHOW GLOBAL VARIABLES as a way to see *what* to tune (or at least to remind me what I *could* tune). Hiding variables means that the authoritative list of variables must be in the documentation.

wsrep_provider_options is already unwieldy, I’m not sure turning off hiding will make it any worse really. I guess I vote they all be shown.

Jay Janssen, MySQL Consulting Lead, Percona
http://about.me/jay.janssen

Since all wsrep-provider-options are logged to error log as:

131230 21:10:54 [Note] WSREP: Passing config to GCS: base_host = 127.0.0.1; base_port = 4567; cert.log_conflicts = no; gcache.dir = /pxc/datadir/; gcache.keep_pages_size = 0; gcache.mem_size = 0; gcache.name = /pxc/datadir//galera.cache; gcache.page_size = 128M; gcache.size = 128M; gcs.fc_debug = 0; gcs.fc_factor = 1; gcs.fc_limit = 16; gcs.fc_master_slave = NO; gcs.max_packet_size = 64500; gcs.max_throttle = 0.25; gcs.recv_q_hard_limit = 9223372036854775807; gcs.recv_q_soft_limit = 0.25; gcs.sync_donor = NO; gmcast.listen_addr = tcp://127.0.0.1:4010; replicator.causal_read_timeout = PT30S; replicator.commit_order = 3

I think it should be fine to show only the options explicitly set
(either at startup or runtime).

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PXC-1551