Cascading failure.

also: cascading failures · cascade failure · cascade failures · death spiral · thread pool exhaustion

One slow or failing service exhausts its callers' threads or connections, so failure spreads up the call chain.

the two-minute refresher

C slows down; B's threads all wait on C; B stops accepting A's calls; A backs up too.
Slow is worse than down: a dead service fails fast, a slow one holds resources.
Defences: tight timeouts, circuit breakers, bulkheads and load shedding.
Retries without backoff make it worse.

also: cascading failures · cascade failure · cascade failures · death spiral · thread pool exhaustion

One slow or failing service exhausts its callers' threads or connections, so failure spreads up the call chain.

C slows down; B's threads all wait on C; B stops accepting A's calls; A backs up too.
Slow is worse than down: a dead service fails fast, a slow one holds resources.
Defences: tight timeouts, circuit breakers, bulkheads and load shedding.
Retries without backoff make it worse.