add mt-write-delay-schema-explain tool

.gitignore

@@ -25,6 +25,7 @@
 /cmd/mt-view-boundaries/mt-view-boundaries
 /cmd/mt-whisper-importer-reader/mt-whisper-importer-reader
 /cmd/mt-whisper-importer-writer/mt-whisper-importer-writer
+/cmd/mt-write-delay-schema-explain/mt-write-delay-schema-explain
 /scripts/build
 build_docker
 build_pkg

cmd/mt-write-delay-schema-explain/main.go

@@ -0,0 +1,104 @@
+package main
+
+import (
+	"flag"
+	"fmt"
+	"os"
+	"runtime"
+	"strconv"
+	"time"
+
+	"github.com/grafana/metrictank/conf"
+	"github.com/grafana/metrictank/logger"
+	"github.com/grafana/metrictank/util/align"
+	log "github.com/sirupsen/logrus"
+)
+
+var (
+	version     = "(none)"
+	showVersion = flag.Bool("version", false, "print version string")
+)
+
+func init() {
+	formatter := &logger.TextFormatter{}
+	formatter.TimestampFormat = "2006-01-02 15:04:05.000"
+	log.SetFormatter(formatter)
+	log.SetLevel(log.InfoLevel)
+}
+
+func main() {
+	flag.Usage = func() {
+		fmt.Println("mt-write-delay-schema-explain")
+		fmt.Println("use this tool to diagnose which retentions may be subject to chunks not showing, if your write queue (temporarily) doesn't drain well")
+		fmt.Println("if the following applies to you:")
+		fmt.Println("* metrictank is struggling to clear the write queue (e.g. cassandra/bigtable has become slow)")
+		fmt.Println("* metrictank only keeps a limited amount of chunks in its ringbuffers (tank)")
+		fmt.Println("* you are concerned that chunks needed to satisfy read queries, are not available in the chunk store")
+		fmt.Println("then this tool will help you understand, which is especially useful if you have multiple retentions with different chunkspans and/or numchunks")
+		fmt.Println("Usage:")
+		fmt.Println()
+		fmt.Printf("	mt-write-delay-schema-explain [flags] last-drain-time [schemas-file]\n")
+		fmt.Println("           (config file defaults to /etc/metrictank/storage-schemas.conf)")
+		fmt.Println("           last-drain-time is the last time the queue was empty")
+		fmt.Println()
+		fmt.Println("Flags:")
+		flag.PrintDefaults()
+	}
+	flag.Parse()
+
+	if *showVersion {
+		fmt.Printf("mt-write-delay-schema-explain (version: %s - runtime: %s)\n", version, runtime.Version())
+		return
+	}
+	if flag.NArg() < 1 || flag.NArg() > 2 {
+		flag.Usage()
+		os.Exit(-1)
+	}
+	lastDrain, err := strconv.Atoi(flag.Arg(0))
+	if err != nil {
+		log.Fatalf("cannot parse last-drain time %q: %s", flag.Arg(0), err.Error())
+	}
+	schemasFile := "/etc/metrictank/storage-schemas.conf"
+	if flag.NArg() == 2 {
+		schemasFile = flag.Arg(1)
+	}
+	schemas, err := conf.ReadSchemas(schemasFile)
+	if err != nil {
+		log.Fatalf("can't read schemas file %q: %s", schemasFile, err.Error())
+	}
+
+	s, def := schemas.ListRaw()
+	now := time.Now()
+
+	for _, schema := range s {
+		display(schema, uint32(lastDrain), uint32(now.Unix()))
+	}
+	fmt.Println("built-in default:")
+	display(def, uint32(lastDrain), uint32(now.Unix()))
+}
+
+func showTime(t uint32) string {
+	return time.Unix(int64(t), 0).UTC().Format("2006-01-02 15:04:05")
+}
+
+func display(schema conf.Schema, lastDrain, now uint32) {
+	fmt.Println("#", schema.Name)
+	fmt.Printf("pattern:   %10s\n", schema.Pattern)
+	fmt.Printf("priority:  %10d\n", schema.Priority)
+	for _, ret := range schema.Retentions.Rets {
+
+		savedUntil := align.Backward(lastDrain, ret.ChunkSpan) // note: exclusive
+
+		inMemorySince := align.Backward(now, ret.ChunkSpan)
+		if ret.NumChunks > 1 {
+			inMemorySince -= (ret.NumChunks - 1) * ret.ChunkSpan
+		}
+
+		if inMemorySince > savedUntil {
+			fmt.Printf("%20s missing data %s - %s (last drain %s)\n", ret.String(), showTime(savedUntil), showTime(inMemorySince), showTime(lastDrain))
+		} else {
+			fmt.Printf("%20s OK\n", ret.String())
+		}
+	}
+	fmt.Println()
+}

docs/tools.md

@@ -942,3 +942,25 @@ Usage of ./mt-whisper-importer-writer:
     	the URI on which we expect chunks to get posted (default "/metrics/import")
 ```
 
+
+## mt-write-delay-schema-explain
+
+```
+mt-write-delay-schema-explain
+use this tool to diagnose which retentions may be subject to chunks not showing, if your write queue (temporarily) doesn't drain well
+if the following applies to you:
+* metrictank is struggling to clear the write queue (e.g. cassandra/bigtable has become slow)
+* metrictank only keeps a limited amount of chunks in its ringbuffers (tank)
+* you are concerned that chunks needed to satisfy read queries, are not available in the chunk store
+then this tool will help you understand, which is especially useful if you have multiple retentions with different chunkspans and/or numchunks
+Usage:
+
+	mt-write-delay-schema-explain [flags] last-drain-time [schemas-file]
+           (config file defaults to /etc/metrictank/storage-schemas.conf)
+           last-drain-time is the last time the queue was empty
+
+Flags:
+  -version
+    	print version string
+```
+