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worker_group.go
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worker_group.go
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// Copyright 2024 Northern.tech AS
//
// 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 worker
import (
"context"
"encoding/json"
"sync"
"sync/atomic"
"time"
natsio "github.com/nats-io/nats.go"
"github.com/pkg/errors"
"github.com/mendersoftware/go-lib-micro/log"
"github.com/mendersoftware/workflows/client/nats"
"github.com/mendersoftware/workflows/model"
"github.com/mendersoftware/workflows/store"
)
type workerGroup struct {
mu sync.Mutex // Mutex to protect the shared firstDone channel
firstDone chan struct{} // First worker finished
done chan struct{} // All workers finished
termID int32 // ID of the first worker to finish
sidecarDone chan struct{}
workerCount int32
input <-chan *natsio.Msg
notifyPeriod time.Duration
client nats.Client
store store.DataStore
}
func NewWorkGroup(
input <-chan *natsio.Msg,
notifyPeriod time.Duration,
nc nats.Client,
ds store.DataStore,
) *workerGroup {
return &workerGroup{
sidecarDone: make(chan struct{}),
done: make(chan struct{}),
firstDone: make(chan struct{}),
input: input,
notifyPeriod: notifyPeriod,
client: nc,
store: ds,
}
}
// Done returns a channel (barrier) that is closed when the last worker
// has exited.
func (w *workerGroup) Done() <-chan struct{} {
return w.done
}
// FirstDone returns a channel (barrier) that is closed when the first
// worker has exited.
func (w *workerGroup) FirstDone() <-chan struct{} {
return w.firstDone
}
// TermID is the ID of the first worker that quit.
func (w *workerGroup) TermID() int32 {
return w.termID
}
func (w *workerGroup) RunWorker(ctx context.Context) {
id := atomic.AddInt32(&w.workerCount, 1)
l := log.FromContext(ctx)
l = l.F(log.Ctx{"worker_id": id})
ctx = log.WithContext(ctx, l)
sidecarChan := make(chan *natsio.Msg, 1)
sidecarDone := make(chan struct{})
defer func() {
l.Info("worker shutting down")
close(sidecarChan)
w.mu.Lock()
remaining := atomic.AddInt32(&w.workerCount, -1)
// Is this the last worker to quit?
if remaining <= 0 {
select {
case <-w.done:
default:
close(w.done)
}
} else {
// Is this the first worker to quit?
select {
case <-w.firstDone:
default:
w.termID = id
close(w.firstDone)
}
}
w.mu.Unlock()
}()
l.Info("worker starting up")
// workerSidecar is responsible for notifying the broker about slow workflows
go w.workerSidecar(ctx, sidecarChan, sidecarDone)
w.workerMain(ctx, sidecarChan, sidecarDone)
}
func (w *workerGroup) workerMain(
ctx context.Context,
sidecarChan chan *natsio.Msg,
sidecarDone chan struct{},
) {
l := log.FromContext(ctx)
ctxDone := ctx.Done()
timeoutTimer := newStoppedTimer()
for {
var (
msg *natsio.Msg
isOpen bool
)
select {
case msg, isOpen = <-w.input:
if !isOpen {
return
}
case <-sidecarDone:
return
case <-ctxDone:
return
}
// Notify the sidecar routine about the new message
select {
case sidecarChan <- msg:
case <-timeoutTimer.After(w.notifyPeriod / 8):
l.Warn("timeout notifying sidecar routine about message")
case <-sidecarDone:
return
case <-ctxDone:
return
}
job := &model.Job{}
err := json.Unmarshal(msg.Data, job)
if err != nil {
l.Error(errors.Wrap(err, "failed to unmarshall message"))
if err := msg.Term(); err != nil {
l.Error(errors.Wrap(err, "failed to term the message"))
}
continue
}
// process the job
l.Infof("processing job %s workflow %s", job.ID, job.WorkflowName)
err = processJob(ctx, job, w.store, w.client)
if err != nil {
l.Errorf("error processing job: %s", err.Error())
} else {
l.Infof("finished job %s workflow %s", job.ID, job.WorkflowName)
}
// stop the in progress ticker and ack the message
select {
case sidecarChan <- nil:
case <-timeoutTimer.After(w.notifyPeriod):
l.Errorf("timeout notifying sidecar about job completion")
case <-ctxDone:
return
case <-sidecarDone:
return
}
// Release message
if err := msg.AckSync(); err != nil {
l.Error(errors.Wrap(err, "failed to ack the message"))
}
}
}
// workerSidecar helps notifying the NATS server about slow workflows.
// When workerMain picks up a new task, this routine is woken up and starts
// a timer that sends an "IN PROGRESS" package back to the broker if the worker
// takes too long.
func (w *workerGroup) workerSidecar(
ctx context.Context,
msgIn <-chan *natsio.Msg,
done chan<- struct{},
) {
var (
isOpen bool
msgInProgress *natsio.Msg
ctxDone = ctx.Done()
l = log.FromContext(ctx)
)
defer close(done)
t := newStoppedTimer()
for {
select {
case <-t.C:
ctx, cancel := context.WithTimeout(ctx, w.notifyPeriod)
err := msgInProgress.InProgress(natsio.Context(ctx))
cancel()
if err != nil {
l.Errorf("error notifying broker about message in progress: %s", err)
// If the +WPI message fails, let's not try again, but
// wait for the next message.
} else {
t.Reset(w.notifyPeriod)
}
case msgInProgress, isOpen = <-msgIn:
if !isOpen {
return
} else if msgInProgress == nil {
t.Stop()
} else {
t.Reset(w.notifyPeriod)
}
case <-ctxDone:
return
}
}
}