Unable to configure MongoDB replication without initial sync
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06-10-2020 - |
سؤال
I have a big MongoDB database on my production server, which I want to set up as a replica set. I understand that if I enable the replica set option on both servers, it will automatically start to sync the data from scratch. But I don't want to sync from the beginning; instead I want to configure it like MySQL replication.
I would like to follow the following process:
- Take dump from primary
- Restore it on secondary
- Enable replica set in config file, on both servers
- Restart MongoDB.
- Go to primary server and add the secondary node.
Is this possible; or is there any other alternate solution for this?
المحلول
Why do two sets of heavy lifting ??? Let MongoDB do it.
For this example, suppose IP of SECONDARY
is 10.30.50.70
with hostname myslave
STEP 01 : Enable Replica Set on the PRIMARY only
Make the following changes in /etc/mongodb.conf
on the PRIMARY
- enable authorization in
/etc/mongodb.conf
authorization: enabled
under the security YAML tag (MongoDB 2.6+)auth=true
(if you are using MongoDB 2.4)
- Enable replication (suppose your name the replica set
myreplica
)- Put
replSetName: myreplica
under replication YAML tag (MongoDB 2.6+) - Put
replSet = myreplica
(MongoDB 2.4)
- Put
STEP 02 : Restart MongoDB on the PRIMARY
service mongod restart
STEP 03 : Initiate Replica Set on the PRIMARY
rs.initiate();
NOTE: At this point your have a one-node Replica Set
STEP 04 : Perform Steps 01 and 02 on your SECONDARY
NOTE: At this point, the SECONDARY
is replica set enabled but not replicating
STEP 05 : NOW, add the SECONDARY
to the PRIMARY
Goto the PRIMARY and run
rs.add("10.30.50.70:27017")
or
rs.add("myslave:27017")
STEP 06 : Check status of Replica Set
Run this repeatedly
rs.status()
If this command ever freezes, don't worry. It rebuilding all the indexes.
You can open another ssh session on the SECONDARY
, run tail -f
on the mongodb.log
file and see the index rebuild progression.
WHY DO IT THIS WAY ???
MongoDB will do essentially start replication, copy the data, and rebuild indexes in a single operation. As shown, this process is in no way automatic when building an initial replica set. Doing it this way, is less error-prone.
نصائح أخرى
Thanks Rolando.
Luckily I post the same on Google groups, someone from MongoDB helped me to fix my scenario. We can't directly dump, restore and configure replication. Please follow the steps to enable replication for large databases.
1.Copy the MongoDB directory to the secondary server.
2.Enable replication in the Primary config file and restart primary monogDB.
3.Run rs.initiate() in primary.
4.Stop MongoDB in secondary, replace the data directory with the primary data directory.
5.Enable replication in config file and start mongod service.
6.Go to primary and rs.add(secondary:port).
- You can see the secondary server is rebuilding indices and updated data.