From 523e9e4652fba3ea2379b60ece7f65259b60a14d Mon Sep 17 00:00:00 2001
From: Nathan VanBenschoten <nvanbenschoten@gmail.com>
Date: Thu, 17 Jun 2021 23:52:01 -0400
Subject: [PATCH] Export TeeEventListener

I plan to use this is CockroachDB to tee events to a new `pebbleMetricListener`
object that will listen to and expose metrics on write stalls. This will give us
better visibility into these events.
---
 cmd/pebble/compact.go | 70 +++----------------------------------------
 event.go              | 64 +++++++++++++++++++++++++++++++++++++++
 2 files changed, 68 insertions(+), 66 deletions(-)

diff --git a/cmd/pebble/compact.go b/cmd/pebble/compact.go
index 1dcb87d4d9..d1f78fe392 100644
--- a/cmd/pebble/compact.go
+++ b/cmd/pebble/compact.go
@@ -114,8 +114,10 @@ func open(dir string, listener pebble.EventListener) (*replay.DB, error) {
 
 	opts.EventListener = listener
 	if verbose {
-		opts.EventListener = teeEventListener(opts.EventListener,
-			pebble.MakeLoggingEventListener(nil))
+		opts.EventListener = pebble.TeeEventListener(
+			opts.EventListener,
+			pebble.MakeLoggingEventListener(nil),
+		)
 	}
 	rd, err := replay.Open(dir, opts)
 	return rd, err
@@ -422,67 +424,3 @@ func removeAll(dir string) {
 		log.Fatal(err)
 	}
 }
-
-// teeEventListener wraps two event listeners, forwarding all events to both.
-func teeEventListener(a, b pebble.EventListener) pebble.EventListener {
-	a.EnsureDefaults(nil)
-	b.EnsureDefaults(nil)
-	return pebble.EventListener{
-		BackgroundError: func(err error) {
-			a.BackgroundError(err)
-			b.BackgroundError(err)
-		},
-		CompactionBegin: func(info pebble.CompactionInfo) {
-			a.CompactionBegin(info)
-			b.CompactionBegin(info)
-		},
-		CompactionEnd: func(info pebble.CompactionInfo) {
-			a.CompactionEnd(info)
-			b.CompactionEnd(info)
-		},
-		FlushBegin: func(info pebble.FlushInfo) {
-			a.FlushBegin(info)
-			b.FlushBegin(info)
-		},
-		FlushEnd: func(info pebble.FlushInfo) {
-			a.FlushEnd(info)
-			b.FlushEnd(info)
-		},
-		ManifestCreated: func(info pebble.ManifestCreateInfo) {
-			a.ManifestCreated(info)
-			b.ManifestCreated(info)
-		},
-		ManifestDeleted: func(info pebble.ManifestDeleteInfo) {
-			a.ManifestDeleted(info)
-			b.ManifestDeleted(info)
-		},
-		TableCreated: func(info pebble.TableCreateInfo) {
-			a.TableCreated(info)
-			b.TableCreated(info)
-		},
-		TableDeleted: func(info pebble.TableDeleteInfo) {
-			a.TableDeleted(info)
-			b.TableDeleted(info)
-		},
-		TableIngested: func(info pebble.TableIngestInfo) {
-			a.TableIngested(info)
-			b.TableIngested(info)
-		},
-		WALCreated: func(info pebble.WALCreateInfo) {
-			a.WALCreated(info)
-			b.WALCreated(info)
-		},
-		WALDeleted: func(info pebble.WALDeleteInfo) {
-			a.WALDeleted(info)
-			b.WALDeleted(info)
-		},
-		WriteStallBegin: func(info pebble.WriteStallBeginInfo) {
-			a.WriteStallBegin(info)
-			b.WriteStallBegin(info)
-		},
-		WriteStallEnd: func() {
-			a.WriteStallEnd()
-			b.WriteStallEnd()
-		},
-	}
-}
diff --git a/event.go b/event.go
index 00a6ff3032..b57801a2d6 100644
--- a/event.go
+++ b/event.go
@@ -559,3 +559,67 @@ func MakeLoggingEventListener(logger Logger) EventListener {
 		},
 	}
 }
+
+// TeeEventListener wraps two EventListeners, forwarding all events to both.
+func TeeEventListener(a, b EventListener) EventListener {
+	a.EnsureDefaults(nil)
+	b.EnsureDefaults(nil)
+	return EventListener{
+		BackgroundError: func(err error) {
+			a.BackgroundError(err)
+			b.BackgroundError(err)
+		},
+		CompactionBegin: func(info CompactionInfo) {
+			a.CompactionBegin(info)
+			b.CompactionBegin(info)
+		},
+		CompactionEnd: func(info CompactionInfo) {
+			a.CompactionEnd(info)
+			b.CompactionEnd(info)
+		},
+		FlushBegin: func(info FlushInfo) {
+			a.FlushBegin(info)
+			b.FlushBegin(info)
+		},
+		FlushEnd: func(info FlushInfo) {
+			a.FlushEnd(info)
+			b.FlushEnd(info)
+		},
+		ManifestCreated: func(info ManifestCreateInfo) {
+			a.ManifestCreated(info)
+			b.ManifestCreated(info)
+		},
+		ManifestDeleted: func(info ManifestDeleteInfo) {
+			a.ManifestDeleted(info)
+			b.ManifestDeleted(info)
+		},
+		TableCreated: func(info TableCreateInfo) {
+			a.TableCreated(info)
+			b.TableCreated(info)
+		},
+		TableDeleted: func(info TableDeleteInfo) {
+			a.TableDeleted(info)
+			b.TableDeleted(info)
+		},
+		TableIngested: func(info TableIngestInfo) {
+			a.TableIngested(info)
+			b.TableIngested(info)
+		},
+		WALCreated: func(info WALCreateInfo) {
+			a.WALCreated(info)
+			b.WALCreated(info)
+		},
+		WALDeleted: func(info WALDeleteInfo) {
+			a.WALDeleted(info)
+			b.WALDeleted(info)
+		},
+		WriteStallBegin: func(info WriteStallBeginInfo) {
+			a.WriteStallBegin(info)
+			b.WriteStallBegin(info)
+		},
+		WriteStallEnd: func() {
+			a.WriteStallEnd()
+			b.WriteStallEnd()
+		},
+	}
+}