async – Page 5 – Türker Yıldırım

A queue table is not a queue

Deep diveMay 7, 201810 min read

SELECT … WHERE processed = 0 LIMIT 1, and two workers taking the same row. SKIP LOCKED makes the table viable; it does not make it a broker.

A stream is not a list, and XADD is not RPUSH

NoteMarch 29, 20181 min read

A list used as a queue loses the message when a consumer crashes mid-work, because BRPOP removes it and there is no record that anything was in flight.…

Claim a queue row without two workers taking it

SnippetMarch 7, 20181 min read

XAUTOCLAIM does not exist yet, so XCLAIM and a timer

NoteFebruary 27, 20181 min read

When a consumer dies its pending entries belong to a name that will never acknowledge them, so something has to reassign them — and in Redis 5 that…

Promise.finally is the one everyone wrote by hand

NoteJanuary 9, 20182 min read

Turning off a loading spinner has to happen on both the success and the failure path, so it got duplicated into then and catch, and one of the…

A circuit breaker before the third-party outage

Deep diveDecember 21, 201710 min read

A payment provider was slow and the whole site went down with it. A timeout bounds one request; it does nothing about how many are waiting at once.

Alerting that people do not learn to ignore

Deep diveDecember 13, 201710 min read

340 alerts in a month, four of which mattered. An alert channel nobody reads is the same as no alerting, and the cause is alerting on causes.

Retry only what is safe to retry

NoteNovember 8, 20171 min read

A retry policy applied at the HTTP client level retries everything, including the POST that succeeded and whose response was lost. The safety of a retry is a…

Prefetch decides whether one slow consumer blocks the rest

NoteNovember 2, 20171 min read

RabbitMQ pushes messages to a consumer up to the prefetch limit without waiting for acknowledgements. With the default of unlimited, one consumer takes the whole queue into its…

Designing an API two mobile clients can live with

Deep diveNovember 2, 201714 min read

Two apps, two release cycles, and neither can be forced to update. What is additive, what is not, and the decisions that have to be made before the…