mediumSystem Design

What is a message queue and why use one?

Q: What is a message queue and why use one?

## What a message queue gives you A **message queue** is a buffer between **producers** and **consumers**. Producers drop messages in and move on; consumers pull and process them at their own pace. This **decouples** the two sides in time and scale. Producer queue (FIFO buffer) <text

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Understand the problem

Explain message queues.

message-queue

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Producer / consumer workers

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import queue, threading, time

q = queue.Queue()

def worker(name):
    while True:
        job = q.get()
        if job is None:           # shutdown signal
            break
        print(name, "processing", job)
        time.sleep(0.05)          # simulate work
        q.task_done()

workers = [threading.Thread(target=worker, args=("w" + str(i),)) for i in range(2)]
for t in workers:
    t.start()

for i in range(6):                # producer enqueues, decoupled from consumers
    q.put("job-" + str(i))

q.join()                          # wait until all jobs processed
for _ in workers:
    q.put(None)
for t in workers:
    t.join()
print("done")

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