have flightGroups take some time to allow reuse

Author: moshegood

internal/streams/stream_provider_server_side.go

@@ -3,6 +3,7 @@ package streams
 import (
 	"net/http"
 	"sync"
+	"time"
 
 	"github.com/launchdarkly/ld-relay/v8/internal/sdkauth"
 
@@ -109,6 +110,7 @@ func (r *serverSideEnvStreamRepository) Replay(channel, id string) chan eventsou
 // getReplayEvent will return a ServerSidePutEvent with all the data needed for a Replay.
 func (r *serverSideEnvStreamRepository) getReplayEvent() (eventsource.Event, error) {
 	data, err, _ := r.flightGroup.Do("getReplayEvent", func() (interface{}, error) {
+		start := time.Now()
 		flags, err := r.store.GetAll(ldstoreimpl.Features())
 
 		if err != nil {
@@ -126,7 +128,12 @@ func (r *serverSideEnvStreamRepository) getReplayEvent() (eventsource.Event, err
 			{Kind: ldstoreimpl.Segments(), Items: removeDeleted(segments)},
 		}
 
+		// This call uses a lot of system resources (RAM in particular).
 		event := MakeServerSidePutEvent(allData)
+		// So we sleep for a bit to allow a bunch of concurrent calls to
+		// all make use of this same flightGroup.
+		time.Sleep(2*time.Second - time.Since(start))
+
 		return event, nil
 	})