Go Channels: Buffered vs Unbuffered — Usage in Worker Pool & Fan-In/Fan-Out Patterns

1. Channel Basics

Go channels enable safe communication between goroutines.
They can be:

• Unbuffered: No internal capacity. Send blocks until another goroutine receives.
• Buffered: Has internal queue of fixed size. Send blocks only when the buffer is full.

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2. Unbuffered Channels

Behavior:

• Acts as a synchronization point — sender and receiver must meet.
• Guarantees that message is received immediately when sent.

Use Cases:

• When strict ordering or synchronization is required.
• When workload is small or predictable.
• Ensures deterministic control flow (safer for correctness).

Pros:

• Simpler logic — less risk of hidden race conditions.
• Implicit synchronization between goroutines.
• Low memory usage.

Cons:

• Can easily lead to deadlocks if sends/receives are not perfectly balanced.
• Reduced throughput due to blocking behavior.
• Workers often idle waiting for messages.

Example (Worker Pool - Unbuffered):

jobs := make(chan Job)
results := make(chan Result)

for w := 0; w < 3; w++ {
    go worker(jobs, results)
}

for _, job := range jobList {
    jobs <- job // blocks until a worker picks it
}
close(jobs)

➡️ Ensures that no jobs are queued unless a worker is ready.

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3. Buffered Channels

Behavior:

• Adds a message queue between sender and receiver.
• Sends only block when the buffer is full; receives block when empty.

Use Cases:

• When producers are faster than consumers.
• For parallel pipelines or batched workloads.
• When slight decoupling improves throughput.

Pros:

• Higher concurrency and throughput.
• Smooths out producer-consumer speed differences.
• Avoids deadlocks in many fan-out patterns.

Cons:

• Harder to reason about timing and ordering.
• Risk of memory buildup if buffer size is large or unbounded producers.
• Doesn’t provide natural backpressure if buffer is too big.

Example (Worker Pool - Buffered):

jobs := make(chan Job, 10)
results := make(chan Result, 10)

for w := 0; w < 3; w++ {
    go worker(jobs, results)
}

for _, job := range jobList {
    jobs <- job // won’t block until buffer fills
}
close(jobs)

➡️ Decouples producer and workers — improves throughput.

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4. Fan-In / Fan-Out with Channels

Pattern	Description	Channel Type Choice
Fan-Out	Multiple workers read from one channel.	Either works — buffered improves throughput; unbuffered ensures tight sync.
Fan-In	Multiple producers send to one channel, one consumer reads.	Buffered preferred to prevent producer blocking if consumer is slow.

Example (Fan-In using Buffered Channel):

merged := make(chan string, 100)
for _, src := range sources {
    go func(ch <-chan string) {
        for msg := range ch {
            merged <- msg
        }
    }(src)
}

Buffered channel prevents producer goroutines from blocking if consumer lags.

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5. Design Guidelines

Scenario	Recommended Channel Type	Reason
Tight synchronization between goroutines	Unbuffered	Ensures handoff safety and timing accuracy
High-throughput worker pools	Buffered	Avoids blocking, improves concurrency
Fan-in from multiple producers	Buffered	Prevents blocking producers
Fan-out to multiple workers with stable load	Unbuffered	Keeps coordination strict and predictable
Burst or uneven workloads	Buffered	Provides a queue to absorb spikes

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6. Summary

Aspect	Unbuffered	Buffered
Synchronization	Strong	Loose
Performance	Lower	Higher (with proper sizing)
Risk of Deadlocks	Higher	Lower (but logic complexity increases)
Recommended for	Controlled flow, testing	Production pipelines, real workloads