How to configure a MongoDB cluster which supports sessions? - spring

Question

I want to explore the new transaction feature of MongoDB and use Spring Data MongoDB. However, I get the exception message "Sessions are not supported by the MongoDB cluster to which this client is connected". Any hint regarding the config of MongoDB 3.7.9 is appreciated.
The stacktrace starts with:
com.mongodb.MongoClientException: Sessions are not supported by the
MongoDB cluster to which this client is connected
at com.mongodb.MongoClient.startSession(MongoClient.java:555) ~[mongodb-driver-3.8.0-beta2.jar:na]
at org.springframework.data.mongodb.core.SimpleMongoDbFactory.getSession(SimpleMongoDbFactory.java:163)
~[spring-data-mongodb-2.1.0.DATAMONGO-1920-SNAPSHOT.jar:2.1.0.DATAMONGO-1920-SNAPSHOT]

Answer 1

I was having the same issue when I was trying to connect it to a single standalone mongo instance, however as written in the official documentation, that Mongo supports transaction feature for a replica set. So, I then tried to create a replica set with all instances on MongoDB 4.0.0, I was able to successfully execute the code.
So,
Start a replica set (3 members), then try to execute the code, the issue will be resolved.
NB : you can configure a replica set on the same machine for tests https://docs.mongodb.com/manual/tutorial/deploy-replica-set-for-testing/

Answer 2

We were able to config in local as below
On Linux, a default /etc/mongod.conf configuration file is included
when using a package manager to install MongoDB.
On Windows, a
default <install directory>/bin/mongod.cfg configuration file is
included during the installation
On macOS, a default /usr/local/etc/mongod.conf configuration file is included
when installing from MongoDB’s official Homebrew tap.
Add the following config
replication:
oplogSizeMB: 128
replSetName: "rs0"
enableMajorityReadConcern: true
sudo service mongod restart;
mongo;
rs.initiate({
_id: "rs0",
version: 1,
members: [
{ _id: 0, host : "localhost:27017" }
]
}
)
check for the config to be enabled
rs.conf()
we can use the connection URL as
mongodb://localhost/default?ssl=false&replicaSet=rs0&readPreference=primary
docs: config-options single-instance-replication

Answer 3

Replica set is the resolution for the issue for sure
But doing replica of 3 nodes is not mandatory.
Solution 1 (for standalone setup)
For standalone mongo installation you can skip configuring 2nd or 3rd node as described on the official mongo documentations here
And you'll need to set a replSetName in the configuration
replication:
oplogSizeMB: <int>
replSetName: <string>
enableMajorityReadConcern: <boolean>
and then run details of which are here
rs.initiate()
after this the connection string would be like below:-
mongodb://localhost:27017/<database_name>?replicaSet=<replSet_Name>
keys above that you need to replace:-
database_name = name of the database
replSet_Name = name of the replica set you setup in the above configuration
Solution 2 (only for docker based requirement)
Example Docker image with single node replica set acting as primary node for development environment is as below:-
I had hosted the docker image on the docker hub
docker pull krnbr/mongo:latest
Contents of the same Dockerfile are below:-
FROM mongo
RUN echo "rs.initiate({'_id':'rs0','members':[{'_id':0,'host':'127.0.0.1:27017'}]});" > /docker-entrypoint-initdb.d/replica-init.js
RUN cat /docker-entrypoint-initdb.d/replica-init.js
CMD [ "--bind_ip_all", "--replSet", "rs0" ]
Docker run command (replace with the image name that you build yoursef or use the on shared above i.e krnbr/mongo):-
without volume
docker run -d --name mongo -p 27017:27017 <Image Name> mongod --replSet rs0 --port 27017
with volume
docker run -d --name mongo -p 27017:27017 -v ~/.mongodb:/data/db <Image Name> mongod --replSet rs0 --port 27017
for supporting binding of any ip
docker run -d --name mongo -p 27017:27017 -v ~/.mongodb:/data/db <Image Name> mongod --bind_ip_all --replSet rs0 --port 27017

Answer 4

I disabled TLS (inside Spring Data MongoDB), and now the transaction feature with the developement release 3.7.9 works fine.

Answer 5

With the reference to the answer give by #kakabali, I have few a bit different scenario and configure it.
I am configure mongo with spring boot and try to use transactions management and getting the error:
com.mongodb.MongoClientException: Sessions are not supported by the
MongoDB cluster to which this client is connected at
I follow few of the steps given by above answer and added few:
Change the mongo.cfg and added this
replication:
oplogSizeMB: 128
replSetName: "rs0"
enableMajorityReadConcern: true
Restart the service as I am using Windows10.
Open mongo console and run rs.initilize()

Answer 6

Make sure you're using the updated API - for example:
MongoClient mongoClient = MongoClients.create();
MongoDatabase dataBase = mongoClient.getDatabase("mainDatabase");
MongoCollection<Document> collection = dataBase.getCollection("entities");
Also make sure you have mongo.exe open.