Notifier

An HTTP notification client library and CLI tool written in Go.

The Library

A library that implements an HTTP notification client. A client is configured with a URL to which notifications are sent. It exposes a function that takes messages and notifies about them by sending HTTP POST requests to the configured URL with the message content in the request body.

Design

• Non-blocking Notify() — messages are enqueued onto a buffered channel and processed by a fixed worker pool.
• Bounded concurrency — a configurable number of workers limits parallel HTTP requests, preventing file descriptor exhaustion.
• Connection pooling — the underlying http.Transport is tuned to match the worker count (MaxConnsPerHost, MaxIdleConnsPerHost).
• Async error reporting — failures are sent to an error channel the caller can drain at their own pace.

API

// Create a notifier targeting a URL.
n := notifier.New("http://localhost:8080/notify",
    notifier.WithWorkers(10),   // default: 10
    notifier.WithQueueSize(1000), // default: 1000
)

// Enqueue a message (non-blocking while queue has capacity).
err := n.Notify(ctx, "hello world")

// Read errors asynchronously.
go func() {
    for err := range n.Errors() {
        log.Println(err)
    }
}()

// Drain in-flight requests and release resources.
n.Close()

The Executable

A CLI program that uses the library above. It reads from stdin and sends new messages every configurable interval. Each line is interpreted as a new message.

The program implements graceful shutdown on SIGINT/SIGTERM.

Build

go build -o notify ./cmd/notify

Usage

notify --url=URL [<flags>]

Flags:
    --help                 Show help.
    --url URL              Target URL to send notifications to (required).
-i, --interval=5s          Notification interval.

Example

# Send each line of messages.txt as an HTTP POST every 5 seconds.
$ ./notify --url http://localhost:8080/notify < messages.txt

# Custom interval.
$ ./notify --url http://localhost:8080/notify --interval 2s < messages.txt

Testing

go test ./...