Reference

Reference: controller.yaml

autoscaling

When the controller adds or removes instances (ADR-0034).

autoscaling.applications

Application processes to watch (application-tier classification).

autoscaling.applications[].comm

Process name prefix (/proc/<pid>/comm), e.g. php-fpm8.3, node, uvicorn.

autoscaling.applications[].cpus

CPUs allotted to it (saturated at 90 %).

autoscaling.applications[].kind

php, node or python.

autoscaling.applications[].name

Name of the application tier, for logs and status.

autoscaling.cooldown

Minimum time between two scaling actions.

autoscaling.inflight_per_loop

Requests in flight per event loop that count as fully loaded.

autoscaling.lag_saturated

Loop lag that counts as fully saturated.

autoscaling.mode

off: never scale; observe: classify and log only; web-tier: add and remove instances when the web tier is saturated or idle.

autoscaling.p99_target_ms

p99 latency (ms) that counts as fully loaded; absent: latency does not raise the pressure.

autoscaling.scale_in_below

PressureScore below which the pool counts as idle.

autoscaling.scale_in_window

How long the pressure must stay below scale_in_below before an instance is removed.

autoscaling.scale_out_above

PressureScore above which the web tier is saturated (ADR-0034).

autoscaling.scale_out_window

How long the pressure must stay above scale_out_above before an instance is added.

controller

Where the controller keeps its state, its control socket, the scalwsd binary and the configuration it runs.

controller.config

Source of new configuration generations.

controller.listen

How instances share the listeners (ADR-0033): inherited (default), the controller opens them and hands every instance the same sockets (one accept queue: balanced, nothing to migrate on scale-in); reuseport: each instance binds its own SO_REUSEPORT socket (needs net.ipv4.tcp_migrate_req=1 for scale-in).

controller.socket

Local control API (created 0600).

controller.state_dir

Generations and instance records (created 0700).

controller.webd_binary

The scalwsd binary the controller starts as instances.

instances

How many scalwsd instances run, on which CPUs, and how they start, drain and restart.

instances.allow_drain_without_migration

Allow scale-in without net.ipv4.tcp_migrate_req=1 (queued connections of a leaving instance are then reset). Default false.

instances.cpus

CPUs instances may use, e.g. "0-5" or "0,2,4".

instances.cpus_per_instance

CPUs each instance is pinned to (one event loop each).

instances.drain_timeout

Time a leaving instance gets to finish its connections.

instances.kill_grace

Time after the drain timeout before a leaving instance is killed.

instances.max

Instances started at most.

instances.max_restarts

Crashes within restart_window after which an instance is not restarted again.

instances.metrics_base_port

Metrics/readiness port of instance i: metrics_base_port + i on 127.0.0.1.

instances.min

Instances kept running at least.

instances.min_free_ram_mib

Free host memory (MiB) required before a new instance starts.

instances.restart_window

Window in which crashes are counted for max_restarts.

instances.roll_on_upgrade

Roll instances onto a replaced scalwsd binary when the controller starts (a package upgrade): a copy of the current generation, without reading config. Default true; false only logs which instances run the old binary.

instances.start_timeout

Time a new instance gets to become ready; it is stopped otherwise.