Skip to main content
Version: 0.14


MongoDB sink only support the projector mode for now.

You need to run a gRPC server (sidecar or a standalone workload) accessible to the Connector to make the sink work.

Quick start

You can check the samples of MongoDB sidecars:

Both samples contain the following:

  • Code generated from proto-files by language-specific Protobuf transpiler
  • MongoDB-oriented projections DSL for some of the supported operations
  • Bootstrap code for the gRPC server
  • Actual projections for events produced by the sample app

Those examples can help you to understand the concept and implement your own projectors.

Projector sidecar

You can create the projector gRPC server using any language or stack. The server must support bidirectional streaming, and implement the gRPC sidecar interface as described on the gRPC projector page. The Project operation of the Projection server returns the ProjectionResponse message, where the operation field should be set to one of the following MongoDB-specific responses:

syntax = "proto3";

package projection;

import "google/protobuf/struct.proto";

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

message InsertMany {
repeated google.protobuf.Struct documents = 1;

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

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

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

message DeleteMany {
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:secret@localhost:27017"
database: test
collection: bookings
uri: "http://localhost:9091"
credentials: "insecure"