Stop re-using processors defined in the config (#34761)

* Stop re-using processors defined in the config

After introducing the `SafeProcessor` wrapper in
#34647 we started returning
errors when a processor is being used after its `Close` function has
been called.

This led to dropped events and error spam in logs but also confirmed
that the root cause of the problem was not just a race condition on
`Close` but re-used processors somewhere.

After a long investigation such code that's re-using processors was
finally found.

This is the change that removes re-using the processors and
instantiates them on each input restart.

* Fix linter issues

* Add changelog entry

CHANGELOG.next.asciidoc

@@ -96,6 +96,7 @@ https://github.com/elastic/beats/compare/v8.2.0\...main[Check the HEAD diff]
 - Prevent Elasticsearch from spewing log warnings about redundant wildcard when setting up ingest pipelines. {issue}34249[34249] {pull}34550[34550]
 - Gracefully handle Windows event channel not found errors in winlog input. {issue}30201[30201] {pull}34605[34605]
 - Fix the issue of `cometd` input worker getting closed in case of a network connection issue and an EOF error. {issue}34326[34326] {pull}34327[34327]
+- Fix errors and panics due to re-used processors {pull}34761[34761]
 
 *Heartbeat*
 

filebeat/channel/runner.go

@@ -24,6 +24,7 @@ import (
 	"github.com/elastic/beats/v7/libbeat/processors"
 	"github.com/elastic/beats/v7/libbeat/processors/add_formatted_index"
 	"github.com/elastic/beats/v7/libbeat/publisher/pipetool"
+
 	conf "github.com/elastic/elastic-agent-libs/config"
 	"github.com/elastic/elastic-agent-libs/mapstr"
 )
@@ -127,27 +128,27 @@ func newCommonConfigEditor(
 		return nil, err
 	}
 
-	var indexProcessor processors.Processor
-	if !config.Index.IsEmpty() {
-		staticFields := fmtstr.FieldsForBeat(beatInfo.Beat, beatInfo.Version)
-		timestampFormat, err := fmtstr.NewTimestampFormatString(&config.Index, staticFields)
-		if err != nil {
-			return nil, err
-		}
-		indexProcessor = add_formatted_index.New(timestampFormat)
-	}
-
-	userProcessors, err := processors.New(config.Processors)
-	if err != nil {
-		return nil, err
-	}
-
 	serviceType := config.ServiceType
 	if serviceType == "" {
 		serviceType = config.Module
 	}
 
 	return func(clientCfg beat.ClientConfig) (beat.ClientConfig, error) {
+		var indexProcessor processors.Processor
+		if !config.Index.IsEmpty() {
+			staticFields := fmtstr.FieldsForBeat(beatInfo.Beat, beatInfo.Version)
+			timestampFormat, err := fmtstr.NewTimestampFormatString(&config.Index, staticFields)
+			if err != nil {
+				return clientCfg, err
+			}
+			indexProcessor = add_formatted_index.New(timestampFormat)
+		}
+
+		userProcessors, err := processors.New(config.Processors)
+		if err != nil {
+			return clientCfg, err
+		}
+
 		meta := clientCfg.Processing.Meta.Clone()
 		fields := clientCfg.Processing.Fields.Clone()
 
@@ -191,6 +192,6 @@ func newCommonConfigEditor(
 
 func setOptional(to mapstr.M, key string, value string) {
 	if value != "" {
-		to.Put(key, value)
+		_, _ = to.Put(key, value)
 	}
 }

libbeat/processors/safe_processor.go

@@ -23,6 +23,7 @@ import (
 
 	"github.com/elastic/beats/v7/libbeat/beat"
 	"github.com/elastic/elastic-agent-libs/config"
+	"github.com/elastic/elastic-agent-libs/logp"
 )
 
 var ErrClosed = errors.New("attempt to use a closed processor")
@@ -45,6 +46,7 @@ func (p *SafeProcessor) Close() (err error) {
 	if atomic.CompareAndSwapUint32(&p.closed, 0, 1) {
 		return Close(p.Processor)
 	}
+	logp.L().Warnf("tried to close already closed %q processor", p.Processor.String())
 	return nil
 }