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The MongoDB target only support the projector mode for now.

You need to run a gRPC server accessible by the Connector to make the MongoDB target work.

Projector sidecar

You can create a projector gRPC server using any language or stack. The server must support bidirectional streaming. Below, you can find MongoDB-specific response types:

syntax = "proto3";

package projection;

import "google/protobuf/struct.proto";

message InsertOne {
google.protobuf.Struct document = 1;

message UpdateOne {
google.protobuf.Struct filter = 1;
google.protobuf.Struct update = 2;

message DeleteOne {
google.protobuf.Struct filter = 1;


There are two sections to configure in the Connector configuration: target and grpc. The target section specified the MongoDB configuration, and the grpc section contains the sidecar URL.

For the MongoDB target, you need to configure the following parameters:

  • connectionString: The connection string to the MongoDB instance.
  • database: The name of the database to use.
  • collection: The name of the collection to use.

You can only project to one collection in one database using a single Connector instance.

Here's the sample configuration for this connector:

connectorId: "esdb-mongo-connector"
connectorAssembly: "Eventuous.Connector.EsdbMongo"
enabled: true
exporters: [zipkin]
enabled: true
exporters: [prometheus]
traceSamplerProbability: 0
connectionString: "esdb://localhost:2113?tls=false"
concurrencyLimit: 1
connectionString: "mongodb://mongoadmin:[email protected]:27017"
database: test
collection: bookings
uri: "http://localhost:9091"
credentials: "insecure"


We have a few samples for this target: