Make query history length configurable

api.go

@@ -100,7 +100,7 @@ func NewAPI(opts ...apiOption) (*API, error) {
 		}()
 	}
 
-	api.tracker = newQueryTracker()
+	api.tracker = newQueryTracker(api.server.queryHistoryLength)
 
 	return api, nil
 }

ctl/server.go

@@ -36,6 +36,7 @@ func BuildServerFlags(cmd *cobra.Command, srv *server.Command) {
 	flags.BoolVar(&srv.Config.Verbose, "verbose", srv.Config.Verbose, "Enable verbose logging")
 	flags.Uint64Var(&srv.Config.MaxMapCount, "max-map-count", srv.Config.MaxMapCount, "Limits the maximum number of active mmaps. Pilosa will fall back to reading files once this is exhausted. Set below your system's vm.max_map_count.")
 	flags.Uint64Var(&srv.Config.MaxFileCount, "max-file-count", srv.Config.MaxFileCount, "Soft limit on the maximum number of fragment files Pilosa keeps open simultaneously.")
+	flags.IntVar(&srv.Config.QueryHistoryLength, "query-history-length", srv.Config.QueryHistoryLength, "Number of queries to remember in history.")
 
 	// TLS
 	SetTLSConfig(flags, "", &srv.Config.TLS.CertificatePath, &srv.Config.TLS.CertificateKeyPath, &srv.Config.TLS.CACertPath, &srv.Config.TLS.SkipVerify, &srv.Config.TLS.EnableClientVerification)

http/client.go

@@ -1302,7 +1302,7 @@ func (c *InternalClient) GetPastQueries(ctx context.Context, uri *pilosa.URI) ([
 		return nil, errors.Wrap(err, "reading")
 	}
 
-	queries := make([]pilosa.PastQueryStatus, 128)
+	queries := make([]pilosa.PastQueryStatus, 100)
 	if err := json.Unmarshal(body, &queries); err != nil {
 		return nil, fmt.Errorf("unmarshal response: %s", err)
 	}

server.go

@@ -86,6 +86,8 @@ type Server struct { // nolint: maligned
 
 	defaultClient InternalClient
 	dataDir       string
+
+	queryHistoryLength int
 }
 
 // Holder returns the holder for server.
@@ -361,6 +363,16 @@ func OptServerRBFConfig(cfg *rbfcfg.Config) ServerOption {
 	}
 }
 
+// OptServerQueryHistoryLength is a functional option on Server
+// used to specify the length of the query history buffer that maintains
+// the information returned at /query-history.
+func OptServerQueryHistoryLength(length int) ServerOption {
+	return func(s *Server) error {
+		s.queryHistoryLength = length
+		return nil
+	}
+}
+
 // NewServer returns a new instance of Server.
 func NewServer(opts ...ServerOption) (*Server, error) {
 	cluster := newCluster()

server/config.go

@@ -206,6 +206,11 @@ type Config struct {
 
 	// RBFConfig defines all externally configurable RBF flags.
 	RBFConfig *rbfcfg.Config
+
+	// QueryHistoryLength sets the maximum number of queries that are maintained
+	// for the /query-history endpoint. This parameter is per-node, and the
+	// result combines the history from all nodes.
+	QueryHistoryLength int
 }
 
 // NewConfig returns an instance of Config with default options.
@@ -230,6 +235,8 @@ func NewConfig() *Config {
 		ImportWorkerPoolSize: runtime.NumCPU(),
 
 		RBFConfig: rbfcfg.NewDefaultConfig(),
+
+		QueryHistoryLength: 100,
 	}
 
 	// Cluster config.

server/server.go

@@ -412,6 +412,7 @@ func (m *Command) SetupServer() error {
 		pilosa.OptServerTxsrc(m.Config.Txsrc),
 		pilosa.OptServerRowcacheOff(m.Config.RowcacheOff),
 		pilosa.OptServerRBFConfig(m.Config.RBFConfig),
+		pilosa.OptServerQueryHistoryLength(m.Config.QueryHistoryLength),
 		coordinatorOpt,
 	}
 

tracker.go

@@ -101,11 +101,11 @@ func (b *ringBuffer) slice() []pastQuery {
 	return append(b.queries[b.start:b.count], b.queries[0:b.start]...)
 }
 
-func newQueryTracker() *queryTracker {
+func newQueryTracker(historyLength int) *queryTracker {
 	done := make(chan struct{})
 	updates := make(chan queryStatusUpdate, 128)
 	checks := make(chan chan<- []*activeQuery)
-	history := newRingBuffer(128)
+	history := newRingBuffer(historyLength)
 	tracker := &queryTracker{
 		updates: updates,
 		checks:  checks,