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Conduit Architecture

Here is an overview of the Conduit Architecture.

Conduit Architecture

Conduit is split into the following layers:

  • API layer - exposes the public APIs used to communicate with Conduit. It exposes 2 types of APIs:
    • gRPC - this is the main API provided by Conduit. The gRPC API definition can be found in api.proto, it can be used to generate code for the client.
    • HTTP - the HTTP API is generated using grpc-gateway and forwards the requests to the gRPC API. Conduit exposes an openapi definition that describes the HTTP API, which is also exposed through Swagger UI on http://localhost:8080/openapi/.
  • Orchestration layer - the orchestration layer is responsible for coordinating the flow of operations between the core services. It also takes care of transactions, making sure that changes made to specific entities are not visible to the outside until the whole operation succeeded. There are 3 orchestrators, each responsible for actions related to one of the 3 main entities - pipelines, connectors and processors.
  • Core - we regard the core to be the combination of the entity management layer and the pipeline engine. It provides functionality to the orchestrator layer and does not concern itself with where requests come from and how single operations are combined into more complex flows.
    • Entity management - this layer is concerned with the creation, editing, deletion and storage of the main entities. You can think about this as a simple CRUD layer. It can be split up further using the main entities:
      • Pipeline - this is the central entity managed by the Pipeline Service that ties together all other components. A pipeline contains the configuration that defines how pipeline nodes should be connected together in a running pipeline. It has references to at least one source and one destination connector and zero or multiple processors, a pipeline that does not meet the criteria is regarded as incomplete and can't be started. A pipeline can be either running, stopped or degraded (stopped because of an error). The pipeline can only be edited if it's not in a running state.
      • Connector - a connector takes care of receiving or forwarding records to connector plugins, depending on its type (source or destination). It is also responsible for tracking the connector state as records flow through it. The Connector Service manages the creation of connectors and permanently stores them in the Connector Store. A connector can be configured to reference a number of processors, which will be executed only on records that are received from or forwarded to that specific connector.
      • Processor - processors are stateless components that operate on a single record and can execute arbitrary actions before forwarding the record to the next node in the pipeline. A processor can also choose to drop a record without forwarding it. They can be attached either to a connector or to a pipeline, based on that they are either processing only records that flow from/to a connector or all records that flow through a pipeline.
    • Pipeline Engine - the pipeline engine consists of nodes that can be connected together with Go channels to form a data pipeline.
      • Node - a node is a lightweight component that runs in its own goroutine and runs as long as the incoming channel is open. As soon as the previous node stops forwarding records and closes its out channel, the current node also stops running and closes its out channel. This continues down the pipeline until all records are drained and the pipeline gracefully stops. In case a node experiences an error all other nodes will be notified and stop running as soon as possible without draining the pipeline.
  • Persistence - this layer is used directly by the orchestration layer and indirectly by the core layer (through stores) to persist data. It provides the functionality of creating transactions and storing, retrieving and deleting arbitrary data like configurations or state.
  • Plugins - while this is not a layer in the same sense as the other layers, it is a component separate from everything else. It interfaces with the connector on one side and with Conduit plugins on the other and facilitates the communication between them. A Conduit plugin is a separate process that implements the interface defined in conduit-connector-protocol and provides the read/write functionality for a specific resource (e.g. a database).

For more see GitHub.