golang mongo-db transaction cannot create namespace - mongodb

Question

I am trying to do db transaction with mongo-db in golang but getting cannot create namespace error
// For a replica set, include the replica set name and a seedlist of the members in the URI string; e.g.
// uri := "mongodb://mongodb0.example.com:27017,mongodb1.example.com:27017/?replicaSet=myRepl"
// For a sharded cluster, connect to the mongos instances; e.g.
// uri := "mongodb://mongos0.example.com:27017,mongos1.example.com:27017/"
uri := "mongodb://mongo-0/block-recorder?replicaSet=rs0"
// var uri string
clientOpts := options.Client().ApplyURI(uri)
client, err := mongo.Connect(ctx, clientOpts)
if err != nil {
panic(err)
}
defer func() { _ = client.Disconnect(ctx) }()
// Prereq: Create collections.
wcMajority := writeconcern.New(writeconcern.WMajority(), writeconcern.WTimeout(1*time.Second))
wcMajorityCollectionOpts := options.Collection().SetWriteConcern(wcMajority)
blockCollection := client.Database("block-recorder").Collection("Block", wcMajorityCollectionOpts)
// Step 1: Define the callback that specifies the sequence of operations to perform inside the transaction.
callback := func(sessCtx mongo.SessionContext) (interface{}, error) {
// Important: You must pass sessCtx as the Context parameter to the operations for them to be executed in the
// transaction.
dbBlock := model.TransferBlockData(block)
if _, err := blockCollection.InsertOne(sessCtx, dbBlock); err != nil {
return nil, err
}
return nil, nil
}
// Step 2: Start a session and run the callback using WithTransaction.
session, err := client.StartSession()
if err != nil {
panic(err)
}
defer session.EndSession(ctx)
result, err := session.WithTransaction(ctx, callback)
if err != nil {
panic(err)
}
fmt.Printf("result: %v\n", result)
This is the sample code I am using, Getting below error
panic: multiple write errors: [{write errors: [{Cannot create namespace block-recorder.Block in multi-document transaction.}]}, {<nil>}]
I uses gorm most of the times, This is my first time using mongo with golang, It says create collection first which I am already doing ? Is there any other method to create collection for mongo in golang ?
How to do a proper transaction with struct data example ?

Answer 1

MongoDB server cannot currently create collections in a transaction.
If your application is, say, inserting data into a collection that doesn't exist, the server transparently creates the collection in most cases. But this does not work currently if a transaction is active.
Create the collection ahead of time so that it exists by the time the transaction is executing.
Instantiating a collection object in your application does not actually create a collection. To create a collection, try the equivalent of createCollection in the go driver.