In Oracle developers can run sqls in nologging mode. Is it possible on Mongo DB or Mongo DB writes all operations into the oplog(operations log)?
A standalone server (not part of replica set or sharded cluster) does not employ the oplog.
Related
I want to backup data in mongo shard. How i can backup no downtime because they're in production. I can't do from mongodb official manual.
Back Up a Sharded Cluster with Database Dumps
I have a mongo cluster of 1 Main mongo, with 3 shards en 3 config servers.
Each shard have a primary mongo database, a secundairy mongo database and an arbiter mongo database.
So in total I have 13 servers with mongo on it.
Al the mongo database are running on version 2.6
What I want is to upgrade all the databases to mongo 3.2.
Because this is a production database I want to do this in steps.
Question 1:
Is this possible, without downtime?
Question 2: So can I, for example, upgrade the config servers with from 2.6 to 3.2, without stopping the database cluster.
Question 3: Can a mongo 3.2 secundairy server running along a mongo 2.6 primairy server?
Question 4: Can a shard running on mongo 2.6 runing along with a shard running on mongo 3.2 shard?
Regards,
Q1: Yes. It's called Rolling Maintenance. I recommend to read this guide Your Ultimate Guide to rolling upgrades and to practice the steps in a safe environment before doing it on production.
Basic procedure for all nodes:
shutdown down node
replace binaries
(optional) restart node without --replSet and on different port
(optional) do maintenance work in server
restart node with --replSet and on original port
Q2-5: are preconditions for 1, so, all: yes.
Recently I purchased cluster account from MongoDB atlas. I had checked UI and MongoDB documentation but don't know create oplog db. And how to create a connection string for oplog?
Oplog collection is automatically created and maintained by mongoDB and is created under the local database. It is used internally by mongoDB to maintain the various nodes in sync in a replica set. Assume you have a three node replica set, one primary and two secondary. When a write operation happens in the primary, the event is logged in oplog collection and is used internally to replicate the same change in the secondary nodes.
So to use oplog you will need a MongoDB server configured as a replica set. Standalone instances of mongoDB do not have oplog as there is no need for replication in this case.
However, you may start a standalone instance as a replica set by using the command,
Start Mongo server in replica mode.
mongod --dbPath <path_to_data_file> --replSet rs0
Initiate the replica set.(Execute from mongo shell)
rs.initiate();
oplog is a mongodb replication feature. If you have choose replication cluster, you have it in the database named "local". See the collections in "local" database.
We have Sharded Mongo Cluster.
However some documents are sharded and others are unsharded.
We are planning to migrate these databases to new cluster.
Please update if there is any process or steps to migrate the data from one sharded cluster to the other.
We have two secondaries and 1 primary for each shard,MongoS,3 Config Servers,2 Arbitors.
I understood that copydb can not be used on the sharded collection.
Please suggest if there is any other way.
we are going to use mongo db for an alert monitoring application.
We thought first to write the data to files and then to write it onto mongodb using mongoimport utility. Each file will have 1Mill records on an average.
Here my question is "shall we sharding here...?"
I guess mongoimport is not aware of sharding.
How does sharding works when writes are happening by mongoimport...?
If your collection exists and is sharded and you run mongoimport against a mongos router, then it will respect sharding rules (writes will be distributed according to chunk location).
Footnote
If you have a mongodb cluster, you have to have mongos daemon(s) in there. mongos reads your cluster configuration from config servers and knows where to route requests from your app. In a cluster configuration you should never talk to mongod servers directly, only via mongos. Read more about cluster configuration here.