PBM-1308: Improve read/write concern validation (#946)

* Improve validation for read concern

* Add conn level read/write concerns in logs

Author: boris-ilijic

cmd/pbm-agent/agent.go

@@ -103,6 +103,9 @@ func (a *Agent) Start(ctx context.Context) error {
 	logger := log.FromContext(ctx)
 	logger.Printf("pbm-agent:\n%s", version.Current().All(""))
 	logger.Printf("node: %s/%s", a.brief.SetName, a.brief.Me)
+	logger.Printf("conn level ReadConcern: %v; WriteConcern: %v",
+		a.leadConn.MongoOptions().ReadConcern.Level,
+		a.leadConn.MongoOptions().WriteConcern.W)
 
 	c, cerr := ctrl.ListenCmd(ctx, a.leadConn, a.closeCMD)
 

pbm/connect/connect.go

@@ -41,14 +41,25 @@ func Direct(direct bool) MongoOption {
 // If the option is not specified the default is: [readconcern.Majority].
 func ReadConcern(readConcern *readconcern.ReadConcern) MongoOption {
 	return func(opts *options.ClientOptions) error {
-		if readConcern == nil {
-			return errors.New("ReadConcern not specified")
+		if err := validateReadConcern(readConcern); err != nil {
+			return err
 		}
 		opts.SetReadConcern(readConcern)
 		return nil
 	}
 }
 
+func validateReadConcern(readConcern *readconcern.ReadConcern) error {
+	if readConcern == nil {
+		return errors.New("ReadConcern not specified")
+	}
+	if readConcern.Level != readconcern.Local().Level &&
+		readConcern.Level != readconcern.Majority().Level {
+		return errors.New("ReadConcern level is not allowed")
+	}
+	return nil
+}
+
 // WriteConcern option sets level of acknowledgment for write operation.
 // For PBM typically use: [writeconcern.W1] or [writeconcern.Majority].
 // If the option is not specified the default is: [writeconcern.Majority].
@@ -147,6 +158,13 @@ func validateConnStringOpts(opts *options.ClientOptions) error {
 	if err = validateWriteConcern(opts.WriteConcern); err != nil {
 		return err
 	}
+	if err = validateReadConcern(opts.ReadConcern); err != nil {
+		return err
+	}
+	if opts.ReadConcern.Level == readconcern.Majority().Level &&
+		opts.WriteConcern.W == writeconcern.W1().W {
+		return errors.New("ReadConcern majority and WriteConcern 1 is not allowed")
+	}
 
 	return nil
 }