Documentation
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Overview ¶
Package drainbudget is the one reading of a process's two drain knobs, PRE_STOP_DELAY and SHUTDOWN_TIMEOUT: how a value is written, what zero and a negative value mean, and the defaults.
Two parties read those variables and must agree to the second: the server, which flips readiness, pauses PRE_STOP_DELAY and then shuts down bounded by SHUTDOWN_TIMEOUT; and forge's renderer, which derives the pod's terminationGracePeriodSeconds from the same two values (pkg/deploy). When they disagree the kubelet SIGKILLs a replica mid-drain, or holds a dead one for a budget nobody asked for. Each party used to carry its own parser, and they drifted: one read "-1s" (no pause) as malformed and fell back to the default. Both now call this package.
The rule:
- A value is a Go duration ("30s", "1m30s", "500ms", "-1s", and "0"). Empty is unset. Anything else is an error — a bare count of seconds ("30") included.
- Zero, set or unset, is the default: 5s for PRE_STOP_DELAY, 30s for SHUTDOWN_TIMEOUT.
- Negative is none: a phase that takes no time. Never unbounded.
WHY NO BARE SECONDS. A forge server reads both knobs as google.protobuf.Duration config fields, and the config language takes a Go duration only: a bare number has no unit, and for any other Duration field ("500" as an RPC timeout) guessing seconds is the wrong guess as often as not. This reader used to accept "30" as well, so the renderer derived a grace period from a value the server itself refused to boot on. Both readers now take the same language, the config loader's.
It has no dependencies beyond the standard library, so the renderer can import it without linking serverkit.
Index ¶
Constants ¶
const ( // EnvPreStopDelay is how long the process keeps serving after its // readiness flips to draining, so load balancers observe the failing // probe before anything stops. EnvPreStopDelay = "PRE_STOP_DELAY" // EnvShutdownTimeout bounds everything after the pre-stop pause. EnvShutdownTimeout = "SHUTDOWN_TIMEOUT" // DefaultPreStopDelay is what a zero or unset PRE_STOP_DELAY means. DefaultPreStopDelay = 5 * time.Second // DefaultShutdownTimeout is what a zero or unset SHUTDOWN_TIMEOUT means. DefaultShutdownTimeout = 30 * time.Second )
Variables ¶
This section is empty.
Functions ¶
func Effective ¶
Effective is the length of a drain phase configured as d: def when d is zero, none (0) when d is negative, d otherwise.
Types ¶
type Budget ¶
Budget is a process's two drain knobs as configured — before Effective applies the rule, so a zero still means "the default" and a negative still means "none". Its fields map one to one onto serverkit.Config's PreStopDelay and ShutdownTimeout.
func FromEnv ¶
FromEnv reads both knobs through getenv — os.Getenv in a main; a library never reads the environment itself. An unset variable is zero (the default). A malformed one is an error naming the variable: a server should refuse to boot rather than run a budget its pod's grace period was not derived from.
Source Files