From 32e195860b06585c42a516734c16f33c048c5416 Mon Sep 17 00:00:00 2001
From: Edd Robinson <me@edd.io>
Date: Wed, 25 Apr 2018 13:02:09 +0100
Subject: [PATCH 1/2] Log index type when opening shard

---
 tsdb/shard.go | 9 ++++++---
 tsdb/store.go | 2 +-
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/tsdb/shard.go b/tsdb/shard.go
index 99369506d1..689a6e7dc6 100644
--- a/tsdb/shard.go
+++ b/tsdb/shard.go
@@ -366,18 +366,21 @@ func (s *Shard) close() error {
 	return err
 }
 
+// IndexType returns the index version being used for this shard.
+//
+// IndexType returns the empty string if it is called before the shard is opened,
+// since it is only that point that the underlying index type is known.
 func (s *Shard) IndexType() string {
 	s.mu.RLock()
 	defer s.mu.RUnlock()
-	if err := s.ready(); err != nil {
+	if s._engine == nil || s.index == nil { // Shard not open yet.
 		return ""
 	}
-
 	return s.index.Type()
 }
 
 // ready determines if the Shard is ready for queries or writes.
-// It returns nil if ready, otherwise ErrShardClosed or ErrShardDiabled
+// It returns nil if ready, otherwise ErrShardClosed or ErrShardDisabled
 func (s *Shard) ready() error {
 	var err error
 	if s._engine == nil {
diff --git a/tsdb/store.go b/tsdb/store.go
index aecfa18e9e..948e940e22 100644
--- a/tsdb/store.go
+++ b/tsdb/store.go
@@ -322,7 +322,7 @@ func (s *Store) loadShards() error {
 					}
 
 					resC <- &res{s: shard}
-					log.Info("Opened shard", zap.String("path", path), zap.Duration("duration", time.Since(start)))
+					log.Info("Opened shard", zap.String("index_version", shard.IndexType()), zap.String("path", path), zap.Duration("duration", time.Since(start)))
 				}(db.Name(), rp.Name(), sh.Name())
 			}
 		}

From 0b4a403679ddeaf79855614d7f74580fbbbd3644 Mon Sep 17 00:00:00 2001
From: Edd Robinson <me@edd.io>
Date: Wed, 25 Apr 2018 13:47:41 +0100
Subject: [PATCH 2/2] Provide warning when mixed index used on db

---
 tsdb/store.go | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/tsdb/store.go b/tsdb/store.go
index 948e940e22..57de371608 100644
--- a/tsdb/store.go
+++ b/tsdb/store.go
@@ -23,6 +23,7 @@ import (
 	"github.com/influxdata/influxdb/query"
 	"github.com/influxdata/influxql"
 	"go.uber.org/zap"
+	"go.uber.org/zap/zapcore"
 )
 
 var (
@@ -328,6 +329,10 @@ func (s *Store) loadShards() error {
 		}
 	}
 
+	// indexVersions tracks counts of the number of different types of index
+	// being used within each database.
+	indexVersions := make(map[string]map[string]int)
+
 	// Gather results of opening shards concurrently, keeping track of how
 	// many databases we are managing.
 	for i := 0; i < n; i++ {
@@ -337,9 +342,25 @@ func (s *Store) loadShards() error {
 		}
 		s.shards[res.s.id] = res.s
 		s.databases[res.s.database] = struct{}{}
+
+		if _, ok := indexVersions[res.s.database]; !ok {
+			indexVersions[res.s.database] = make(map[string]int, 2)
+		}
+		indexVersions[res.s.database][res.s.IndexType()]++
 	}
 	close(resC)
 
+	// Check if any databases are running multiple index types.
+	for db, idxVersions := range indexVersions {
+		if len(idxVersions) > 1 {
+			var fields []zapcore.Field
+			for idx, cnt := range idxVersions {
+				fields = append(fields, zap.Int(fmt.Sprintf("%s_count", idx), cnt))
+			}
+			s.Logger.Warn("Mixed shard index types", append(fields, logger.Database(db))...)
+		}
+	}
+
 	// Enable all shards
 	for _, sh := range s.shards {
 		sh.SetEnabled(true)