/
resolver_static.go
77 lines (58 loc) · 1.88 KB
/
resolver_static.go
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// Copyright The OpenTelemetry Authors
// SPDX-License-Identifier: Apache-2.0
package loadbalancingexporter // import "github.com/open-telemetry/opentelemetry-collector-contrib/exporter/loadbalancingexporter"
import (
"context"
"errors"
"sort"
"sync"
"go.opencensus.io/stats"
"go.opencensus.io/tag"
)
var _ resolver = (*staticResolver)(nil)
var (
errNoEndpoints = errors.New("no endpoints specified for the static resolver")
staticResolverMutators = []tag.Mutator{tag.Upsert(tag.MustNewKey("resolver"), "static"), successTrueMutator}
)
type staticResolver struct {
endpoints []string
onChangeCallbacks []func([]string)
once sync.Once // we trigger the onChange only once
}
func newStaticResolver(endpoints []string) (*staticResolver, error) {
if len(endpoints) == 0 {
return nil, errNoEndpoints
}
// make sure we won't change the provided slice
endpointsCopy := make([]string, len(endpoints))
copy(endpointsCopy, endpoints)
// sort is a guarantee that the order of endpoints doesn't matter
sort.Strings(endpointsCopy)
return &staticResolver{
endpoints: endpointsCopy,
}, nil
}
func (r *staticResolver) start(ctx context.Context) error {
_, err := r.resolve(ctx) // right now, this can't fail
return err
}
func (r *staticResolver) shutdown(context.Context) error {
r.endpoints = nil
for _, callback := range r.onChangeCallbacks {
callback(r.endpoints)
}
return nil
}
func (r *staticResolver) resolve(ctx context.Context) ([]string, error) {
_ = stats.RecordWithTags(ctx, staticResolverMutators, mNumResolutions.M(1))
r.once.Do(func() {
_ = stats.RecordWithTags(ctx, staticResolverMutators, mNumBackends.M(int64(len(r.endpoints))))
for _, callback := range r.onChangeCallbacks {
callback(r.endpoints)
}
})
return r.endpoints, nil
}
func (r *staticResolver) onChange(f func([]string)) {
r.onChangeCallbacks = append(r.onChangeCallbacks, f)
}