W E N Z I

Mongo Clusters are Like Driving a Big Boat.

CLUSTERS CAN BE BIG

The things about clusters, any clusters, is that a lot of things go any to do anything. That is the nature of clusters. They are like turning a big boat in the ocean as compared to a jet ski.

A change is communicated among the nodes in a cluster, passing through different servers. Now the smaller the cluster, the less things have to talk to each other.

A cluster of one ( as in a single machine ) is instantaneous. A cluster of a thousand may take a lot more time for what ever you are doing to propagate through the cluster.

This brings us to mongo. When you are dealing with a cluster , it is a conversation. You tell / ask a mongo cluster to do something, and it goes off and does it. It will let you know when it is done.

SHARDING AGAIN

Think about a sharding mongo DB cluster. You make a change it will take time for whatever you are doing.

Your change may cause the balancer to start moving data from shard to shard, or refreshing a stale node or whatever.

There are tons of things that a mongo cluster could be doing when you issue commands. So here is the takeaway

Let mongo take it’s time and do what it is going to do

if you issue a command to a mongo cluster, realize that it will take time to complete. Let mongo DB do what it is going to do. It may take time, but something is probably happening and jumping to conclusions will not help.