From a56e0226e61bbcfca88b1e0012e27463d10c0fe4 Mon Sep 17 00:00:00 2001
From: Jacob Marble <jacobmarble@influxdata.com>
Date: Thu, 23 Jan 2020 15:27:25 -0800
Subject: [PATCH] fix(storage): check engine closed before collecting index
 metrics (#16656)

---
 CHANGELOG.md      |  3 +++
 storage/engine.go | 19 +++++++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 6791d0cfbb6..81035821554 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -8,6 +8,9 @@
 1. [16504](https://github.com/influxdata/influxdb/pull/16504): Add backup and restore
 1. [16522](https://github.com/influxdata/influxdb/pull/16522): Introduce resource logger to tasks, buckets and organizations
 
+### Bug Fixes
+1. [16656](https://github.com/influxdata/influxdb/pull/16656): Check engine closed before collecting index metrics
+
 ### UI Improvements
 
 1. [16575](https://github.com/influxdata/influxdb/pull/16575): Swap billingURL with checkoutURL
diff --git a/storage/engine.go b/storage/engine.go
index 32150c9570f..4ec0660944c 100644
--- a/storage/engine.go
+++ b/storage/engine.go
@@ -52,7 +52,7 @@ type Engine struct {
 	nodeID   *int // Not used by default.
 
 	mu      sync.RWMutex
-	closing chan struct{} //closing returns the zero value when the engine is shutting down.
+	closing chan struct{} // closing returns the zero value when the engine is shutting down.
 	index   *tsi1.Index
 	sfile   *tsdb.SeriesFile
 	engine  *tsm1.Engine
@@ -703,7 +703,7 @@ func (e *Engine) CreateBackup(ctx context.Context) (int, []string, error) {
 // FetchBackupFile writes a given backup file to the provided writer.
 // After a successful write, the internal copy is removed.
 func (e *Engine) FetchBackupFile(ctx context.Context, backupID int, backupFile string, w io.Writer) error {
-	span, _ := tracing.StartSpanFromContext(ctx)
+	span, ctx := tracing.StartSpanFromContext(ctx)
 	defer span.Finish()
 
 	e.mu.RLock()
@@ -762,6 +762,11 @@ func (e *Engine) fetchBackup(ctx context.Context, backupID int, backupFile strin
 // InternalBackupPath provides the internal, full path directory name of the backup.
 // This should not be exposed via API.
 func (e *Engine) InternalBackupPath(backupID int) string {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+	if e.closing == nil {
+		return ""
+	}
 	return e.engine.FileStore.InternalBackupPath(backupID)
 }
 
@@ -793,10 +798,20 @@ func (e *Engine) ApplyFnToSeriesIDSet(fn func(*tsdb.SeriesIDSet)) {
 
 // MeasurementCardinalityStats returns cardinality stats for all measurements.
 func (e *Engine) MeasurementCardinalityStats() (tsi1.MeasurementCardinalityStats, error) {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+	if e.closing == nil {
+		return nil, ErrEngineClosed
+	}
 	return e.index.MeasurementCardinalityStats()
 }
 
 // MeasurementStats returns the current measurement stats for the engine.
 func (e *Engine) MeasurementStats() (tsm1.MeasurementStats, error) {
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+	if e.closing == nil {
+		return nil, ErrEngineClosed
+	}
 	return e.engine.MeasurementStats()
 }