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Type:
Improvement
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Resolution: Done
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Priority:
Minor - P4
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None
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Affects Version/s: None
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Component/s: Sharding
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None
The _id field in config.mongos pings collection comes from the balancer id and is based on the gethostname() call result:
bool Balancer::_init() {
try {
log() << "about to contact config servers and shards" << endl;
// contact the config server and refresh shard information
// checks that each shard is indeed a different process (no hostname mixup)
// these checks are redundant in that they're redone at every new round but we want to do them initially here
// so to catch any problem soon
Shard::reloadShardInfo();
_checkOIDs();
log() << "config servers and shards contacted successfully" << endl;
StringBuilder buf;
buf << getHostNameCached() << ":" << serverGlobalParams.port;
_myid = buf.str();
_started = time(0);
log() << "balancer id: " << _myid << " started at " << time_t_to_String_short(_started) << endl;
return true;
}
The ping _id fields are used by MMS (and probably some other monitoring software) for mongoS auto-discovery. However, in some use cases hostnames might not actually be resolvable, or they might not make any sense at all (e.g. if Dockers containers are used for automation).
I think it will be useful if mongoS would have a parameter to override the ping _id value through the config file.