How to create index on Secondary Replica set in MongoDB. well, creating the index on primary MongoDB is easy and replicate index on secondary too. But creating an index on secondary MongoDB is a little bit tricky and you will learn this in this article.
Overview of creating index on secondary mongoDB
Please understand the use case, Why you required the creation of an index on secodary only. when you required to create an index on secondary only. The main question is why we required to create index on Secondary only, it’s basically for reading optimized use cases, as all read goes to secondary nodes only.
Step 1. Start mongod Processes
Open your linux terminal and type following command to create 3 different directories for primary, secondary and arbital mongodb.
mkdir pri sec arb
Start mongod processes for primary, secondary and arbital on 3 different port by using following command.
mongod --replSet rs1 --logpath "1.log" --dbpath pri --port 27017 --smallfiles --oplogSize 64 --fork mongod --replSet rs1 --logpath "2.log" --dbpath sec --port 27018 --smallfiles --oplogSize 64 --fork mongod --replSet rs1 --logpath "3.log" --dbpath arb --port 27019 --smallfiles --oplogSize 64 --fork
Step 2. Config replicaSet
mongo --port 27017 < config.js
## On the mongo shell add an arbiter:
rs.addArb("localhost:27019")
file config.js
config = { _id: "rs1", members:[
{ _id : 0, host : "localhost:27017"},
{ _id : 1, host : "localhost:27018"}]
};
rs.initiate(config);
rs.status();
Step 2. Access the db, insert some document, and check that the replicaSet is working
Open linux terminal connect to primary node, and add the document as follows
use emp;
db.person.insert({"name":"ranjeet"})
db.person.remove({"name":"Tanisha"})
Step 3. Index on the secondary only
In this step you create index on secondary mongodb only to optimized secondary in mongodb.
- Step 3.1 Stop secondary mongod on port 27018
- ps -ef | grep mongod
- sudo kill pid (for port 27018)
- Step 3.2 Start secondary without –replSet rs1 and add the index to the collection
mongod --logpath "2.log" --dbpath sec --port 27018 --smallfiles --oplogSize 64 --fork
mongo --port 27018
use testDB;
db.person.ensureIndex({"name" : 1});
db.system.indexes.find();
db.system.indexes.find(); is used to check the newly added index.
ps -ef | grep mongod or ps -A | grep mongod sudo kill -9 pid (for port 27018)
mongod --replSet rs1 --logpath "2.log" --dbpath sec --port 27018 --smallfiles --oplogSize 64 --fork mongo --port 27018; use emp; -- check indexes
References
Happy learning to learn How to create index on secondary repolica set in MongoDB for optimized secondary in MongoDB.
