Crate hedwig

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

Examples

Publish a new message

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

fn main() -> Result<(), failure::Error> {
let schema = r#"
    {
      "$id": "https://hedwig.standard.ai/schema",
      "$schema": "http://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.message(
        MessageType::UserCreated,
        Version(MajorVersion(1), MinorVersion(0)),
        UserCreatedData { user_id: "U_123".into() },
    )?;

    hedwig.publish(message)?;

Structs

GooglePublisher	A publisher that uses Google PubSub. To use this class, add feature google.
Hedwig	Central instance to access all Hedwig related resources
MajorVersion	Major part component in semver
Message	Message represents an instance of a message on the message bus.
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.
Version	A semver version without patch part

Enums

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

Traits

Publisher

A trait for message publishers. This may be used to implement custom behavior such as publish to <insert your favorite cloud platform>.

Type Definitions

MessageRouter

MessageRouter is a function that can route messages of a given type and version to a Hedwig topic.