Add shipper.max_procs option

CHANGELOG.asciidoc

@@ -62,6 +62,7 @@ https://github.com/elastic/beats/compare/v1.1.0...master[Check the HEAD diff]
 - Add option to elasticsearch output to pass http parameters in index operations {issue}805[805]
 - Improve logstash and elasticsearch backoff behavior. {pull}927[927]
 - Add experimental Kafka output. {pull}942[942]
+- Add config file option to configure GOMAXPROCS. {pull}969[969]
 
 *Packetbeat*
 - Change the DNS library used throughout the dns package to github.com/miekg/dns. {pull}803[803]

libbeat/beat/beat.go

@@ -220,6 +220,13 @@ func (b *Beat) LoadConfig() error {
 
 	logp.Debug("beat", "Initializing output plugins")
 
+	if b.Config.Shipper.MaxProcs != nil {
+		maxProcs := *b.Config.Shipper.MaxProcs
+		if maxProcs > 0 {
+			runtime.GOMAXPROCS(maxProcs)
+		}
+	}
+
 	pub, err := publisher.New(b.Name, b.Config.Output, b.Config.Shipper)
 	if err != nil {
 		return fmt.Errorf("error Initialising publisher: %v\n", err)

libbeat/docs/shipperconfig.asciidoc

@@ -153,6 +153,11 @@ value is 1000.
 
 (DO NOT TOUCH) The internal queue size for bulk events in the processing pipeline. The default value is 0.
 
+===== max_procs
+
+Sets the maximum number of CPUs that can be executing simultaneously. The
+default is the number of logical CPUs available in the system.
+
 ===== geoip.paths
 
 This configuration option is currently used by Packetbeat only.

libbeat/publisher/publish.go

@@ -86,6 +86,8 @@ type ShipperConfig struct {
 	// internal publisher queue sizes
 	QueueSize     *int `yaml:"queue_size"`
 	BulkQueueSize *int `yaml:"bulk_queue_size"`
+
+	MaxProcs *int `yaml:"max_procs"`
 }
 
 type Topology struct {