Crate hedwig

A Hedwig library for Rust. Hedwig is a message bus that works with arbitrary pubsub services such as AWS SNS/SQS or Google Cloud Pubsub. Messages are validated using a JSON schema. The publisher and consumer are de-coupled and fan-out is supported out of the box.

Example: publish a new message

use hedwig::{Hedwig, MajorVersion, MinorVersion, Version, Message};

fn main() -> Result<(), failure::Error> {
let schema = r#"
    {
      "$id": "https://hedwig.standard.ai/schema",
      "$schema": "https://json-schema.org/draft-04/schema#",
      "description": "Example Schema",
      "schemas": {
          "user-created": {
              "1.*": {
                  "description": "A new user was created",
                  "type": "object",
                  "x-versions": [
                      "1.0"
                  ],
                  "required": [
                      "user_id"
                  ],
                  "properties": {
                      "user_id": {
                          "$ref": "https://hedwig.standard.ai/schema#/definitions/UserId/1.0"
                      }
                  }
              }
          }
      },
      "definitions": {
          "UserId": {
              "1.0": {
                  "type": "string"
              }
          }
      }
    }"#;

    fn router(t: MessageType, v: MajorVersion) -> Option<&'static str> {
        match (t, v) {
            (MessageType::UserCreated, MajorVersion(1)) => Some("dev-user-created-v1"),
            _ => None,
        }
    }

    // create a publisher instance

    let hedwig = Hedwig::new(
        schema,
        "myapp",
        publisher,
        router,
    )?;

    let message = hedwig.build_publish().message(
        Message::new(MessageType::UserCreated,
        Version(MajorVersion(1), MinorVersion(0)),
        UserCreatedData { user_id: "U_123".into() })
    )?.publish()?;

Structs

GooglePublisher	A publisher that uses Google PubSub. To use this class, add feature google.
Hedwig	Central instance to access all Hedwig related resources
HedwigPublishBuilder	A builder for batch publish.
MajorVersion	Major part component in semver
Message	A message builder.
Metadata	Additional metadata associated with a message
MinorVersion	Minor part component in semver
MockPublisher	A mock publisher that doesn't publish messages, but just stores them in-memory for later verification This is useful primarily in tests. To use this class, add feature mock.
ValidatedMessage	A validated message.
Version	A semver version without patch part

Enums

HedwigError	All errors that may be returned when instantiating a new Hedwig instance.
PublishError	All errors that may be returned while publishing a message.

Traits

Publisher

Message publishers.

Type Definitions

MessageRouter

MessageRouter is a function that maps messages to Hedwig topics.