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1d9e864f78
## What changed? Improve OTEL for Chasm. ## Why? Better observability. ## How did you test it? - [ ] built - [x] run locally and tested manually - [ ] covered by existing tests - [ ] added new unit test(s) - [ ] added new functional test(s) ## Potential risks Low; both changes are behind the "is OTEL enabled check".
80 lines
2.9 KiB
Go
80 lines
2.9 KiB
Go
package chasm
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import (
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"fmt"
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"slices"
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"go.opentelemetry.io/otel/attribute"
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"go.opentelemetry.io/otel/trace"
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"go.temporal.io/api/serviceerror"
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"go.temporal.io/server/common/telemetry"
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)
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// ErrInvalidTransition is returned from [Transition.Apply] on an invalid state transition.
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var ErrInvalidTransition = serviceerror.NewFailedPrecondition("invalid transition")
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// A StateMachine is anything that can get and set a comparable state S and re-generate tasks based on current state.
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// It is meant to be used with [Transition] objects to safely transition their state on a given event.
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type StateMachine[S comparable] interface {
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StateMachineState() S
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SetStateMachineState(S)
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}
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// Transition represents a state machine transition for a machine of type SM with state S and event E.
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type Transition[S comparable, SM StateMachine[S], E any] struct {
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// Source states that are valid for this transition.
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Sources []S
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// Destination state to transition to.
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Destination S
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// Function to apply the transition. Mutate the state machine object here and schedule tasks.
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apply func(SM, MutableContext, E) error
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}
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// NewTransition creates a new [Transition] from the given source states to a destination state for a given event.
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// The apply function is called after verifying the transition is possible but before setting the destination state,
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// so it can inspect the current (source) state.
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func NewTransition[S comparable, SM StateMachine[S], E any](src []S, dst S, apply func(SM, MutableContext, E) error) Transition[S, SM, E] {
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return Transition[S, SM, E]{
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Sources: src,
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Destination: dst,
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apply: apply,
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}
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}
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// Possible returns a boolean indicating whether the transition is possible for the current state.
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func (t Transition[S, SM, E]) Possible(sm SM) bool {
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return slices.Contains(t.Sources, sm.StateMachineState())
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}
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// Apply applies a transition event to the given state machine changing the state machine's state to the transition's
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// Destination on success. The apply function is called before the state is changed, so it can inspect the current
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// (source) state.
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func (t Transition[S, SM, E]) Apply(sm SM, ctx MutableContext, event E) (retErr error) {
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prevState := sm.StateMachineState()
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// Defer to always emit the transition telemetry event.
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if telemetry.DebugMode() {
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defer func() {
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attrs := []attribute.KeyValue{
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attribute.String("chasm.transition.source", fmt.Sprintf("%v", prevState)),
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attribute.String("chasm.transition.destination", fmt.Sprintf("%v", t.Destination)),
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}
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if retErr != nil {
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attrs = append(attrs, attribute.String("chasm.transition.error", retErr.Error()))
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}
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span := trace.SpanFromContext(ctx.goContext())
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span.AddEvent("chasm.transition", trace.WithAttributes(attrs...))
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}()
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}
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if !t.Possible(sm) {
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return fmt.Errorf("%w from %v", ErrInvalidTransition, prevState)
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}
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if err := t.apply(sm, ctx, event); err != nil {
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return err
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}
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sm.SetStateMachineState(t.Destination)
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return nil
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}
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