centrifugo-change-stream

Publish MongoDB changes and proxy subscriptions to Centrifugo.

Specifications

MongoDB

This service will establish a connection to MongoDB and watch a change stream on the configured database and collection.

It will also query MongoDB for data to send it to the client (as initial data) when a corresponding channel is subscribed.

Centrifugo

Data from MongoDB change stream will be published to Centrifugo, on the channel with following characteristics:

• namespace: dot-separated MongoDB database and collection (complies with MongoDB namespace);
• channel name: primary key of the document (_id field).

This service will expose a Centrifugo subscribe proxy endpoint on /centrifugo/subscribe. For each subscription, it will send initial data in response data field.

To check the health of the connection with Centrifugo, this service will publish null data to _ channel.

Data flow

sequenceDiagram
    participant MongoDB
    participant Me as This service
    participant Centrifugo as Centrifugo server
    participant Client
    critical
        Me->>+MongoDB: Watch for change stream
        MongoDB-->>-Me: Watch established
    end
    par For each client
        Client->>+Centrifugo: Subscribes
        Centrifugo->>+Me: Proxies subscription
        Me->>+MongoDB: queries current data
        MongoDB-->>-Me: Replies with current data
        Me-->>-Centrifugo: Allows subscription, with initial data
        Centrifugo-->>-Client: Allows subscription
        loop Each update from change stream
            MongoDB-)Me: Sends updated document
            activate Me
            Me-)Centrifugo: Publishes the update
            deactivate Me
            activate Centrifugo
            Centrifugo-)Client: Notifies of the update
            deactivate Centrifugo
        end
    end

Usage

$ centrifugo-change-stream --help
Usage: centrifugo-change-stream [OPTIONS] --centrifugo-api-key <CENTRIFUGO_API_KEY> --mongodb-database <MONGODB_DATABASE> --mongodb-collection <MONGODB_COLLECTION>

Options:
      --listen-address <LISTEN_ADDRESS>
          Address to listen on [env: LISTEN_ADDRESS=] [default: 0.0.0.0:8080]
      --centrifugo-url <CENTRIFUGO_URL>
          Centrifugo server base URL [env: CENTRIFUGO_URL=] [default: http://centrifugo:8000]
      --centrifugo-api-key <CENTRIFUGO_API_KEY>
          Centrifugo API key [env: CENTRIFUGO_API_KEY=]
      --mongodb-uri <MONGODB_URI>
          URI of MongoDB server [env: MONGODB_URI=] [default: mongodb://mongo]
      --mongodb-database <MONGODB_DATABASE>
          MongoDB database [env: MONGODB_DATABASE=]
      --mongodb-collection <MONGODB_COLLECTION>
          MongoDB collection [env: MONGODB_COLLECTION=]
      --tags-update-buffer <TAGS_UPDATE_BUFFER>
          Size of the tags update channel buffer [env: TAGS_UPDATE_BUFFER=] [default: 10]
  -v, --verbose...
          Increase logging verbosity
  -q, --quiet...
          Decrease logging verbosity
  -h, --help
          Print help