Another tool for monitoring the performance and health of a MongoDB node is mongostat. You’ll recall that mongotop shows the time in milliseconds that a mongo node spent accessing (read and write) a particular collection. mongostat on the other hand provides more detailed information about the state of a mongo node, including disk usage, data throughput, index misses, locks, etc. However, the data is general to the mongo node and doesn’t indicate which database or collection the status refers to. As you would expect, both utilities, mongotop and mongostat, are required to get......
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In the process of tuning the performance of a MongoDB replica set, it’s useful to be able to observe mongod directly, as opposed to inferring what it’s doing by watching the output of top, for example. For that reason MongoDB comes with a utility, mongotop. The output of mongotop indicates the amount of time the mongod process spend reading and writing to a specific collection during the update interval. I used the following command to run mongotop on an authentication enabled replica set with a two second interval. [watrous@d1t0156g ~]# mongotop -p -u......
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MongoDB connections accommodate a ReadPreference, which in a clustered environment, like a replicaset, indicates how to select the best host for a query. One major consideration when setting the read preference is whether or not you can live with eventually consistent reads, since SECONDARY hosts may lag behind the PRIMARY. Some of the options you can choose include: PRIMARY: This will ensure the most consistency, but also concentrates all your queries on a single host. SECONDARY: This will distribute your queries among secondary nodes and may lag in consistency with the primary primaryPreferred:......
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MongoDB implements a form of replication they call replica sets. Referring to a repica set instead of just calling it replication is a helpful distinction that becomes more obviously useful when you are introduced to sharding in MongoDB since each shard should be comprised of a set of replicas unique to that shard, but we’ll get to that later. For now, I want to show you how easy it is to setup and use replica sets. The setup and initial ‘recovery’ of data to all replicas in the set is quite simple. In......
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