camel-master 0.7.1

Master crate for Rust Camel, re-exporting all public APIs of the workspace
Documentation

camel-master

Leader-only route execution component for rust-camel

Overview

The Master component ensures that only the current leader consumes from a route while delegating endpoint behavior to any wrapped component URI.

It wraps a delegate URI using master:<lockname>:<delegate-uri> and uses the configured leader elector to start or stop the delegate consumer based on leadership.

Features

  • Consumer-only leadership gating
  • Leader election driven startup and shutdown
  • Producer passthrough to delegate endpoints
  • Graceful lifecycle management with drain timeout

Installation

Add to your Cargo.toml:

[dependencies]
camel-master = "0.6"

URI Format

master:<lockname>:<delegate-uri>

URI Options

The master component has no URI query parameters of its own. Any query parameters belong to the delegate URI.

Option Default Description
delegate URI options delegate-defined All options after <delegate-uri> are parsed by the delegate component

Bundle Config

camel-master supports bundle configuration in Camel.toml under [components.master].

Section Key Default Description
[components.master] drain_timeout_ms 5000 Max time to wait for delegate consumer shutdown on leadership loss
[components.master] delegate_retry_max_attempts 30 Max attempts to start the delegate consumer while leading. 0 = unlimited

Usage

Basic Leader-Only Timer

from("master:orders:timer:tick?period=5000")

Only the active leader processes timer ticks for the orders lock.

With Kafka

from("master:invoices:kafka:my-topic")

Only the route instance that holds leadership consumes from the delegated Kafka endpoint.

Producer Passthrough

to("master:mylock:http://api.example.com")

Producer calls are passed through to the delegate producer and are not gated by leadership.

How It Works

When a master consumer starts, it joins leader election with the configured lock name. The delegate consumer is not started until leadership is acquired. On leadership loss, the delegate consumer is stopped and drained up to drain_timeout_ms.

If leadership is gained again, the delegate consumer is started again with the same delegate URI.

Backends

  • NoopPlatformService (default): single-node behavior, always leader
  • KubernetesPlatformService: distributed leader election backed by Kubernetes Leases, configured via [platform] in Camel.toml

Example Camel.toml

[components.master]
drain_timeout_ms = 5000

[platform]
type = "kubernetes"
namespace = "default"

License

Apache-2.0

Contributing

Contributions are welcome! Please see the main repository for details.