如何判断MongoDB PHP驱动程序正在读取哪个辅助节点？

Question

I am using the legacy MongoDB driver (1.6.x) to connect to a MongoDB (2.4.x) replicaset. I've got "?readPreference=secondary" in my connection string and two MongoDB secondaries on a replicaSet. My connection string includes all the servers:

mongodb://dev-mongo01:27017,dev-mongo02:27017,dev-mongo03:27017/?replicaSet=dev-mongo-replica&readPreference=secondary

I'd like to find out which secondary the read comes from both to verify the readPreference is working as expected and to calculate the secondary's replication delay. I've tried looking at MongoClient->getConnections(), MongoClient->getHosts(), "serversatus" and "replSetGetStatus" from the admin database but can't find anything that tells me which secondary is providing the data.

Answer 1

If it's just to verify whether your code is reading the right server, mongodb.log is the right place to look for. You'll see who's connecting to the node and its IP address.

Also, you can turn on profiling by set:

db.setProfilingLevel(2);

to record all operations from clients. Be careful because this way it reduce performance a lot. turn it off by:

db.setProfilingLevel(0);

If you are looking for a way to control which secondary should serve specific requests, replica set tag is what you are looking for.

Answer 2

You can call $cursor->info() after you've iterated/read from the cursor to get a data structure which contains a host , port and connection_type_desc keys. The host and port keys specify which MongoDB server satisfied that particular query.

$cursor = $this->mongoclient->selectDB("test")->selectCollection("test")->find();
$cursor->rewind();
print_r($cursor->info()); //MongoDB Cursor Info

See http://php.net/manual/en/mongocursor.info.php