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wrapper.go
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wrapper.go
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package module
import (
"fmt"
"math/rand"
"sync"
"time"
"github.com/elastic/beats/libbeat/beat"
"github.com/elastic/beats/libbeat/common"
"github.com/elastic/beats/libbeat/logp"
"github.com/elastic/beats/libbeat/monitoring"
"github.com/elastic/beats/libbeat/testing"
"github.com/elastic/beats/metricbeat/mb"
)
// Expvar metric names.
const (
successesKey = "success"
failuresKey = "failures"
eventsKey = "events"
)
var (
debugf = logp.MakeDebug("module")
fetchesLock = sync.Mutex{}
fetches = map[string]*stats{}
)
// Wrapper contains the Module and the private data associated with
// running the Module and its MetricSets.
//
// Use NewWrapper or NewWrappers to construct new Wrappers.
type Wrapper struct {
mb.Module
metricSets []*metricSetWrapper // List of pointers to its associated MetricSets.
// Options
maxStartDelay time.Duration
eventModifiers []mb.EventModifier
}
// metricSetWrapper contains the MetricSet and the private data associated with
// running the MetricSet. It contains a pointer to the parent Module.
type metricSetWrapper struct {
mb.MetricSet
module *Wrapper // Parent Module.
stats *stats // stats for this MetricSet.
}
// stats bundles common metricset stats.
type stats struct {
key string // full stats key
ref uint32 // number of modules/metricsets reusing stats instance
success *monitoring.Int // Total success events.
failures *monitoring.Int // Total error events.
events *monitoring.Int // Total events published.
}
// NewWrapper create a new Module and its associated MetricSets based
// on the given configuration.
func NewWrapper(config *common.Config, r *mb.Register, options ...Option) (*Wrapper, error) {
module, metricsets, err := mb.NewModule(config, r)
if err != nil {
return nil, err
}
wrapper := &Wrapper{
Module: module,
metricSets: make([]*metricSetWrapper, len(metricsets)),
}
for _, applyOption := range options {
applyOption(wrapper)
}
for i, ms := range metricsets {
wrapper.metricSets[i] = &metricSetWrapper{
MetricSet: ms,
module: wrapper,
stats: getMetricSetStats(wrapper.Name(), ms.Name()),
}
}
return wrapper, nil
}
// Wrapper methods
// Start starts the Module's MetricSet workers which are responsible for
// fetching metrics. The workers will continue to periodically fetch until the
// done channel is closed. When the done channel is closed all MetricSet workers
// will stop and the returned output channel will be closed.
//
// The returned channel is buffered with a length one one. It must drained to
// prevent blocking the operation of the MetricSets.
//
// Start should be called only once in the life of a Wrapper.
func (mw *Wrapper) Start(done <-chan struct{}) <-chan beat.Event {
debugf("Starting %s", mw)
out := make(chan beat.Event, 1)
// Start one worker per MetricSet + host combination.
var wg sync.WaitGroup
wg.Add(len(mw.metricSets))
for _, msw := range mw.metricSets {
go func(msw *metricSetWrapper) {
defer releaseStats(msw.stats)
defer wg.Done()
defer msw.close()
msw.run(done, out)
}(msw)
}
// Close the output channel when all writers to the channel have stopped.
go func() {
wg.Wait()
close(out)
debugf("Stopped %s", mw)
}()
return out
}
// String returns a string representation of Wrapper.
func (mw *Wrapper) String() string {
return fmt.Sprintf("Wrapper[name=%s, len(metricSetWrappers)=%d]",
mw.Name(), len(mw.metricSets))
}
// MetricSets return the list of metricsets of the module
func (mw *Wrapper) MetricSets() []*metricSetWrapper {
return mw.metricSets
}
// metricSetWrapper methods
func (msw *metricSetWrapper) run(done <-chan struct{}, out chan<- beat.Event) {
defer logp.Recover(fmt.Sprintf("recovered from panic while fetching "+
"'%s/%s' for host '%s'", msw.module.Name(), msw.Name(), msw.Host()))
// Start each metricset randomly over a period of MaxDelayPeriod.
if msw.module.maxStartDelay > 0 {
delay := time.Duration(rand.Int63n(int64(msw.module.maxStartDelay)))
debugf("%v/%v will start after %v", msw.module.Name(), msw.Name(), delay)
select {
case <-done:
return
case <-time.After(delay):
}
}
debugf("Starting %s", msw)
defer debugf("Stopped %s", msw)
// Events and errors are reported through this.
reporter := &eventReporter{
msw: msw,
out: out,
done: done,
}
switch ms := msw.MetricSet.(type) {
case mb.PushMetricSet:
ms.Run(reporter.V1())
case mb.PushMetricSetV2:
ms.Run(reporter.V2())
case mb.EventFetcher, mb.EventsFetcher,
mb.ReportingMetricSet, mb.ReportingMetricSetV2:
msw.startPeriodicFetching(reporter)
default:
// Earlier startup stages prevent this from happening.
logp.Err("MetricSet '%s/%s' does not implement an event producing interface",
msw.Module().Name(), msw.Name())
}
}
// startPeriodicFetching performs an immediate fetch for the MetricSet then it
// begins a continuous timer scheduled loop to fetch data. To stop the loop the
// done channel should be closed.
func (msw *metricSetWrapper) startPeriodicFetching(reporter reporter) {
// Fetch immediately.
msw.fetch(reporter)
// Start timer for future fetches.
t := time.NewTicker(msw.Module().Config().Period)
defer t.Stop()
for {
select {
case <-reporter.V2().Done():
return
case <-t.C:
msw.fetch(reporter)
}
}
}
// fetch invokes the appropriate Fetch method for the MetricSet and publishes
// the result using the publisher client. This method will recover from panics
// and log a stack track if one occurs.
func (msw *metricSetWrapper) fetch(reporter reporter) {
switch fetcher := msw.MetricSet.(type) {
case mb.EventFetcher:
msw.singleEventFetch(fetcher, reporter)
case mb.EventsFetcher:
msw.multiEventFetch(fetcher, reporter)
case mb.ReportingMetricSet:
reporter.StartFetchTimer()
fetcher.Fetch(reporter.V1())
case mb.ReportingMetricSetV2:
reporter.StartFetchTimer()
fetcher.Fetch(reporter.V2())
default:
panic(fmt.Sprintf("unexpected fetcher type for %v", msw))
}
}
func (msw *metricSetWrapper) singleEventFetch(fetcher mb.EventFetcher, reporter reporter) {
reporter.StartFetchTimer()
event, err := fetcher.Fetch()
reporter.V1().ErrorWith(err, event)
}
func (msw *metricSetWrapper) multiEventFetch(fetcher mb.EventsFetcher, reporter reporter) {
reporter.StartFetchTimer()
events, err := fetcher.Fetch()
if len(events) == 0 {
reporter.V1().ErrorWith(err, nil)
} else {
for _, event := range events {
reporter.V1().ErrorWith(err, event)
}
}
}
// close closes the underlying MetricSet if it implements the mb.Closer
// interface.
func (msw *metricSetWrapper) close() error {
if closer, ok := msw.MetricSet.(mb.Closer); ok {
return closer.Close()
}
return nil
}
// String returns a string representation of metricSetWrapper.
func (msw *metricSetWrapper) String() string {
return fmt.Sprintf("metricSetWrapper[module=%s, name=%s, host=%s]",
msw.module.Name(), msw.Name(), msw.Host())
}
func (msw *metricSetWrapper) Test(d testing.Driver) {
d.Run(msw.Name(), func(d testing.Driver) {
events := make(chan beat.Event, 1)
done := receiveOneEvent(d, events, msw.module.maxStartDelay+5*time.Second)
msw.run(done, events)
})
}
type reporter interface {
StartFetchTimer()
V1() mb.PushReporter
V2() mb.PushReporterV2
}
// eventReporter implements the Reporter interface which is a callback interface
// used by MetricSet implementations to report an event(s), an error, or an error
// with some additional metadata.
type eventReporter struct {
msw *metricSetWrapper
done <-chan struct{}
out chan<- beat.Event
start time.Time // Start time of the current fetch (or zero for push sources).
}
// startFetchTimer demarcates the start of a new fetch. The elapsed time of a
// fetch is computed based on the time of this call.
func (r *eventReporter) StartFetchTimer() { r.start = time.Now() }
func (r *eventReporter) V1() mb.PushReporter {
return reporterV1{v2: r.V2(), module: r.msw.module.Name()}
}
func (r *eventReporter) V2() mb.PushReporterV2 { return reporterV2{r} }
// reporterV1 wraps V2 to provide a v1 interface.
type reporterV1 struct {
v2 mb.PushReporterV2
module string
}
func (r reporterV1) Done() <-chan struct{} { return r.v2.Done() }
func (r reporterV1) Event(event common.MapStr) bool { return r.ErrorWith(nil, event) }
func (r reporterV1) Error(err error) bool { return r.ErrorWith(err, nil) }
func (r reporterV1) ErrorWith(err error, meta common.MapStr) bool {
// Skip nil events without error
if err == nil && meta == nil {
return true
}
return r.v2.Event(mb.TransformMapStrToEvent(r.module, meta, err))
}
type reporterV2 struct {
*eventReporter
}
func (r reporterV2) Done() <-chan struct{} { return r.done }
func (r reporterV2) Error(err error) bool { return r.Event(mb.Event{Error: err}) }
func (r reporterV2) Event(event mb.Event) bool {
if event.Took == 0 && !r.start.IsZero() {
event.Took = time.Since(r.start)
}
if event.Timestamp.IsZero() {
if !r.start.IsZero() {
event.Timestamp = r.start
} else {
event.Timestamp = time.Now().UTC()
}
}
if event.Host == "" {
event.Host = r.msw.Host()
}
if event.Error == nil {
r.msw.stats.success.Add(1)
} else {
r.msw.stats.failures.Add(1)
}
if event.Namespace == "" {
event.Namespace = r.msw.Registration().Namespace
}
beatEvent := event.BeatEvent(r.msw.module.Name(), r.msw.MetricSet.Name(), r.msw.module.eventModifiers...)
if !writeEvent(r.done, r.out, beatEvent) {
return false
}
r.msw.stats.events.Add(1)
return true
}
// other utility functions
func writeEvent(done <-chan struct{}, out chan<- beat.Event, event beat.Event) bool {
select {
case <-done:
return false
case out <- event:
return true
}
}
func getMetricSetStats(module, name string) *stats {
key := fmt.Sprintf("metricbeat.%s.%s", module, name)
fetchesLock.Lock()
defer fetchesLock.Unlock()
if s := fetches[key]; s != nil {
s.ref++
return s
}
reg := monitoring.Default.NewRegistry(key)
s := &stats{
key: key,
ref: 1,
success: monitoring.NewInt(reg, successesKey),
failures: monitoring.NewInt(reg, failuresKey),
events: monitoring.NewInt(reg, eventsKey),
}
fetches[key] = s
return s
}
func releaseStats(s *stats) {
fetchesLock.Lock()
defer fetchesLock.Unlock()
s.ref--
if s.ref > 0 {
return
}
delete(fetches, s.key)
monitoring.Default.Remove(s.key)
}