How the lock file is shared among the various mongods - mongodb

I am trying to setup a shard and replica set.
My assumption procedure be like this :
Start a replica set (let it be only one, just for testing)
mongo then initiate replica
Start a config server (again let it be one, just for testing)
Start a shard server (again let that be just one)
Add the shard and enable sharding via mongo
What i did :
mongod --replSet rs0 --dbpath data/rs0-0 --unixSocketPrefix data/rs0-0
mongo then rs.initiate()
mongod --configsvr --dbpath data/rs0-0 --unixSocketPrefix data/rs0-0
-- now stucked at step 3.
Error i find is
2017-05-22T20:00:13.857+0530 [initandlisten] exception in initAndListen: 10310 Unable to lock file: data/rs0-0/mongod.lock. Is a mongod instance already running?, terminating
What i have tried :
i have tried with different directories for --unixSocketPrefix options, but each time it hits data/rs0-0/mongod.lock the same file. So it did not worked
It seems simple issue but unable to figure out how the lock file is shared among the various mongods (whether it be config server, or replica set, or shard server)
I am on mongodb 2.6.12

You need to start mongod and config server with different dbpath options.
You can follow the following steps:
mongod --replSet rs0 --dbpath data/rs0-0 --unixSocketPrefix data/rs0-0
or
mongod --replSet rs0 --dbpath data/rs0-0
mongo then rs.initiate()
mkdir -p /data/configdb (grant required permission recursively)
mongod --configsvr --dbpath /data/configdb --port 27019

Related

Problems with WiredTiger in order to deploy a config server in MongoDB

I'm trying to deploy a shared and replicated cluster of MongoDB.
I did the installation like it is indicated in the official page for Ubuntu 20.04: https://www.mongodb.com/docs/manual/tutorial/install-mongodb-on-ubuntu/.
But, when I executed:
mongod --configsvr --port 27001 --replSet config_server --dbpath mongo/data_patients/config/ --bind_ip localhost
I have the following trouble:
and I can't access to the configuration server.

How to get user list from replicaset instance?

I have setup a replica set which includes three members. Below is the three instances launch command:
501 36057 1 0 4:22pm ?? 0:05.02 mongod --replSet replset --dbpath /Users/joey/tmp/replica/replset/rs1/db --logpath /Users/joey/tmp/replica/replset/rs1/mongod.log --port 28017 --logappend --fork
501 36060 1 0 4:22pm ?? 0:04.82 mongod --replSet replset --dbpath /Users/joey/tmp/replica/replset/rs2/db --logpath /Users/joey/tmp/replica/replset/rs2/mongod.log --port 28018 --logappend --fork
501 36063 1 0 4:22pm ?? 0:04.86 mongod --replSet replset --dbpath /Users/joey/tmp/replica/replset/rs3/db --logpath /Users/joey/tmp/replica/replset/rs3/mongod.log --port 28019 --logappend --fork
When I connect to one of this member and run db.getUsers(), I will get an empty array as below:
$ mongo --port 28017
MongoDB shell version v3.4.0
connecting to: mongodb://127.0.0.1:28017/
MongoDB server version: 3.4.0
replset:PRIMARY> db.getUsers()
[ ]
I wander how to get user list in replicaset.
When I connect to one of this member and run db.getUsers(), I will get an empty array
This indicates you haven't set up any users yet. See Enable Authentication in the MongoDB manual.
Below is the three instances launch command
Your launch commands don't include the --keyfile parameter required to enable access control with a replica set. See Enforce Keyfile Access Control in a Replica Set.
For a full reference of recommended security measures (and links to relevant tutorials), see: MongoDB Security Checklist.

Error adding new shard from mongos shell

I'm learning setting up sharding in mongoDB, I plan to have 1 configsvr, 1 shardsvr and 1 mongos
I started the mongods using
mongod --configsvr --replSet foo --dbpath e:\mongodb\configsvr --port 27019
mongod --shardsvr --replSet foo --dbpath e:\mongodb\shardsvr --port 27018
I also connected to each mongods using mongo --port 27019 and mongo --port 27018 and performed rs.initiate() on each
I so started the mongos using
mongos --configdb foo/MY-PC:27019
I finally connected to the mongos using mongo I got an error after using sh.addShard('foo/MY-PC:27018')
Error
{
"ok" : 0,
"errmsg" : "Cannot add foo/MY-PC:27018 as a shard since it is part of a config server replica set",
"code" : 96
}
Please help to solve this error
Thanks all
You set foo/MY-PC as a replica to another mongo server! it's data gonna be copy of that server!
Replication is copying a server's data in an other server so if something happen to it, you wouldn't loose your data! while Sharding is breaking your data into portions so you can speed up your data access speed by accessing different servers at the same time.
So if you shard your data in two portion Data-A and Data-B and your Primary replica server keeps Data-A, then foo/MY-PC would hold the same portion(Data-A) only!

Sharding Mongo Surprised to discover

I am trying to run a sharding in mongo. I ran this commands:
mongod --rest --shardsvr --port 10000 --dbpath data/localhost10000 --logpath data/localhost10000/log
mongod --rest --port 10002 --dbpath data/localhost10002 --logpath data/localhost10002/log
mongos --port 10003 --configdb localhost:10002 > run_routing_service_log
mongo localhost:10003
use admin
db.runCommand({addshard:"localhost:10000", name:"shard10000"});
db.runCommand({addshard:"localhost:10001", name:"shard10001"});
use test_sharding
sh.enableSharding("test_sharding")
db.people.ensureIndex({"zip": 1})
db.people.insert({"name": "a1", "password": "a1", .... )
sh.status()
I am obtain this error:
Surprised to discover that localhost:10002 does not believe it is a config server
Add --configsvr argument in the second mongod command as below.
mongod --rest --port 10002 --dbpath data/localhost10002 --logpath data/localhost10002/log
This should start the configserver on port #10002. However, you might face another issue related to quorum as 3 config-servers are recommended by mongodb official documentation that can be started as the above command on different ports.
Also, I don't see that you have initialized the mongodb shard. That might also create an issue in recognizing correct shard configurations. Following link might be helpful.
http://www.mongodbspain.com/en/2015/01/26/how-to-set-up-a-mongodb-sharded-cluster/

How start Mongo Instance in sharded cluster

I want to deploy a sharded cluster for this i using MongoDB manual.
first i created 3 config servers.
mongod --configsvr --dbpath /data/configdb1 --port 27019 ,
mongod --configsvr --dbpath /data/configdb2 --port 27019 ,
mongod --configsvr --dbpath /data/configdb3 --port 27019
But in second step to Start the mongos Instances i find a command like
mongos --configdb cfg0.example.net:27019,cfg1.example.net:27019,cfg2.example.net:27019
but i can't understand the meaning of
cfg0.example.net
cfg1.example.net
cfg2.example.net
So Please explain meaning of above command and how can i use this according my hostname?
Please check "Deploy a Sharded Cluster", cfg[0-3].example.net means hostnames of 3 config servers, each of mongos server should be started with all config servers configured.
This should solve your issue
[ne#server1~]$mongos configdb"repl/localhost:57040,localhost:57041,localhost:57042" --fork --logpath log.mongos0 --port 27200
about to fork child process, waiting until server is ready for connections.
forked process: 2467
Hope it helps!!!
These are are the config servers connected to the the mongos server