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decorator.go
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decorator.go
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// Copyright (c) 2019 Uber Technologies, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package impl
import (
"context"
"fmt"
"sync/atomic"
log "github.com/sirupsen/logrus"
"github.com/opentracing/opentracing-go"
"github.com/uber/peloton/pkg/storage/cassandra/api"
)
// Decorate invokes all the decorators on the function, usage:
// Decorate(aFunc, Instrument(s), Trace(c, "execute"))()
func Decorate(ef api.FuncType, decorators ...api.Decorator) api.FuncType {
for _, decorator := range decorators {
ef = decorator(ef)
}
return ef
}
/* TODO: slu figure out if it is possible to keep the instrumentation not using uber go-common
// Instrument decorator sends timing and counter metrics
func Instrument(ctx context.Context, s *Store, funcName string) api.Decorator {
scope := s.scope
return func(ef api.FuncType) api.FuncType {
return func() error {
if scope == nil {
return ef()
}
if tags, ok := tagsFromContext(ctx); ok {
scope = scope.Tagged(tags)
}
concurrentRoutines := atomic.LoadInt32(&s.concurrency)
scope.Gauge("usage").Update(int64(concurrentRoutines))
return scope.InstrumentedCall(funcName).Exec(ef)
}
}
}
*/
// Count decorator sends success and failure count metrics
func Count(ctx context.Context, s *Store, funcName string) api.Decorator {
scope := s.scope
return func(ef api.FuncType) api.FuncType {
return func() error {
if scope == nil {
return ef()
}
if tags, ok := tagsFromContext(ctx); ok {
scope = scope.Tagged(tags)
}
errors := scope.Counter(fmt.Sprintf("%s.errors", funcName))
success := scope.Counter(fmt.Sprintf("%s.success", funcName))
if err := ef(); err != nil {
errors.Inc(1)
return err
}
success.Inc(1)
return nil
}
}
}
// Trace decorator starts a new span for the underlying function call
func Trace(ctx context.Context, funcName string) api.Decorator {
return func(ef api.FuncType) api.FuncType {
return func() error {
span := opentracing.SpanFromContext(ctx)
if span != nil {
child := opentracing.StartSpan(funcName, opentracing.ChildOf(span.Context()))
defer child.Finish()
}
return ef()
}
}
}
// Safeguard ensures that the connection is neither closed nor overflooded
func Safeguard(s *Store) api.Decorator {
return func(ef api.FuncType) api.FuncType {
return func() error {
if s.isClosed() {
log.Debug("store already closed")
return api.ErrClosed
}
atomic.AddInt32(&s.concurrency, 1)
defer atomic.AddInt32(&s.concurrency, -1)
if atomic.LoadInt32(&s.concurrency) > int32(s.maxConcurrency) {
log.Debugf("over capacity %d", s.maxConcurrency)
return api.ErrOverCapacity
}
return ef()
}
}
}
func tagsFromContext(ctx context.Context) (map[string]string, bool) {
s, ok := ctx.Value(api.TagKey).(map[string]string)
return s, ok
}