5 network mistakes

Quick reference

1. ❌ No timeout on a request — A hung peer holds workers until the pool is empty. ✅ Connect and read timeouts — Fail fast and keep capacity for healthy peers.

2. ❌ A new connection per call — Every call pays TCP and TLS before the first byte. ✅ Pool with keep-alive — One handshake serves hundreds of requests.

3. ❌ MTU set too small — More packets, more headers, and UDP gets fragmented. ✅ Match the smallest link MTU — Usually 1500 on the internet; jumbo stays inside.

4. ❌ Retry immediately, ten times — A struggling service gets ten times the load. ✅ Backoff with jitter — Spread retries and give the service room to recover.

5. ❌ Health check that only pings — The host is up while its database connection is dead. ✅ Check the real dependency — A shallow check sends traffic to a broken app.

Explained

The five

1. No timeouts. A request with no timeout waits for ever. One hung peer holds a worker, then the next, until the pool is empty. Set connect and read timeouts below your caller's timeout. \2. No keep-alive. A new connection per call pays TCP and TLS handshakes before every request, plus slow start. A pool with keep-alive pays once, saving one or two round trips. \3. Tiny MTU. An MTU smaller than the path is not a safety net, it is overhead: more packets, more headers, and fragmented UDP. Path MTU discovery depends on ICMP, and a black hole still swallows the message that reports the limit. Match the smallest link, usually 1500 on the internet. \4. Retry storms. Retrying immediately, ten times, multiplies load on a service already struggling. Add backoff and jitter, cap the attempts and the total time, and retry only idempotent calls. \5. Health checks that lie. A health check that only pings says the machine is up, not that the app can serve. The process may be running with a dead database connection. Check the dependency the request needs, and keep the check cheap enough to run often.

What they share

Each is cheap to leave alone and expensive to discover.

In one line

Set one timeout

$curl --max-time 5 -sI URL