Real-Time Messaging with Pub/Sub

Intermediate12 min

Implement real-time event broadcasting using Redis publish/subscribe channels for decoupled microservice communication.

Prerequisites

-Redis installed and running
-Two terminal windows for publisher and subscriber

Steps

Start a subscriber on a channel

Open a terminal and subscribe to a named channel to listen for messages.

$ redis-cli SUBSCRIBE notifications

The subscriber blocks and waits for messages. You will need a second terminal for the publisher.

Publish a message to the channel

In a second terminal, send a message to all subscribers on the channel.

$ redis-cli PUBLISH notifications '{"event":"user.signup","userId":1001}'

Subscribe with pattern matching

Use PSUBSCRIBE to listen to multiple channels matching a glob pattern.

$ redis-cli PSUBSCRIBE 'events.*'

This matches events.user, events.order, events.payment, etc.

Publish to a patterned channel

Send a message to a specific channel that pattern subscribers will receive.

$ redis-cli PUBLISH events.order '{"orderId":5001,"status":"created"}'

Check active channels and subscribers

Inspect which pub/sub channels are currently active.

$ redis-cli PUBSUB CHANNELS '*'

Full Script

full-script.sh

#!/bin/bash
# Redis Pub/Sub Demo
set -euo pipefail

echo "=== Active channels before ==="
redis-cli PUBSUB CHANNELS '*'

echo ""
echo "=== Starting subscriber in background ==="
redis-cli SUBSCRIBE notifications &
SUB_PID=$!
sleep 1

echo ""
echo "=== Publishing messages ==="
redis-cli PUBLISH notifications '{"event":"user.signup","userId":1001}'
redis-cli PUBLISH notifications '{"event":"user.login","userId":1002}'
redis-cli PUBLISH notifications '{"event":"order.created","orderId":5001}'

sleep 1
kill $SUB_PID 2>/dev/null || true

echo ""
echo "=== Active channels after ==="
redis-cli PUBSUB CHANNELS '*'
echo "=== Number of subscribers ==="
redis-cli PUBSUB NUMSUB notifications

FAQ

Discussion

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#!/bin/bash # Redis Pub/Sub Demo set -euo pipefail echo "=== Active channels before ===" redis-cli PUBSUB CHANNELS '*' echo "" echo "=== Starting subscriber in background ===" redis-cli SUBSCRIBE notifications & SUB_PID=$! sleep 1 echo "" echo "=== Publishing messages ===" redis-cli PUBLISH notifications '{"event":"user.signup","userId":1001}' redis-cli PUBLISH notifications '{"event":"user.login","userId":1002}' redis-cli PUBLISH notifications '{"event":"order.created","orderId":5001}' sleep 1 kill $SUB_PID 2>/dev/null || true echo "" echo "=== Active channels after ===" redis-cli PUBSUB CHANNELS '*' echo "=== Number of subscribers ===" redis-cli PUBSUB NUMSUB notifications