async – Page 8 – Türker Yıldırım

Exponential backoff needs jitter or everything retries together

NoteOctober 13, 20151 min read

Backing off exponentially stops a failing dependency being hammered. What it does not stop is synchronisation: every client that failed at the same moment retries at the same…

A Redis cache layer that does not go stale

Deep diveJune 10, 20159 min read

The cache made it fast and made it wrong. Key design, invalidation on write rather than on a timer, and why KEYS is the command that takes the…

A database table is a queue until SELECT FOR UPDATE says otherwise

NoteJanuary 29, 20152 min read

A jobs table is a perfectly good queue for one worker. Add a second and both claim the same row, because SELECT then UPDATE is two statements with…

A long-running worker holds a database connection that already died

NoteOctober 30, 20143 min read

A queue worker that runs for days is a PHP process living outside every assumption the language makes about lifetime, and the first one to break is the…

Sending a value back into a generator with send()

NoteMay 22, 20143 min read

Generators are usually introduced as a way to produce a sequence lazily, and the arrow is described as pointing one way. It does not: yield is an expression,…

A command object is a controller action you can queue later

NoteFebruary 27, 20143 min read

“Send the confirmation in the background” arrives as a requirement long after the code that sends it has settled into a controller method, wired to a request and…