Add small tool to print distribution metric bucket sizes conveniently.

Useful to search for decent bucket sizes interactively.

PiperOrigin-RevId: 480214658

pkg/metric/buckettool/BUILD

@@ -0,0 +1,13 @@
+load("//tools:defs.bzl", "go_binary")
+
+package(licenses = ["notice"])
+
+go_binary(
+    name = "buckettool",
+    srcs = ["buckettool.go"],
+    deps = [
+        "//pkg/log",
+        "//pkg/metric",
+        "//runsc/flag",
+    ],
+)

pkg/metric/buckettool/buckettool.go

@@ -0,0 +1,68 @@
+// Copyright 2019 The gVisor Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// buckettool prints buckets for distribution metrics.
+package main
+
+import (
+	"fmt"
+	"os"
+	"time"
+
+	"gvisor.dev/gvisor/pkg/log"
+	"gvisor.dev/gvisor/pkg/metric"
+	"gvisor.dev/gvisor/runsc/flag"
+)
+
+var (
+	typeFlag             = flag.String("type", "duration", "Type of the bucketer: 'duration' or 'exponential'")
+	numFiniteBucketsFlag = flag.Int("num_finite_buckets", 8, "Number of finite buckets")
+	minDurationFlag      = flag.Duration("min_duration", 5*time.Millisecond, "For -type=duration: Minimum duration")
+	maxDurationFlag      = flag.Duration("max_duration", 10*time.Minute, "For -type=duration: Maximum duration")
+	widthFlag            = flag.Uint64("exponential_width", 5, "For -type=exponential: Initial bucket width")
+	scaleFlag            = flag.Float64("exponential_scale", 10, "For -type=exponential: Scaling factor")
+	growthFlag           = flag.Float64("exponential_growth", 4, "For -type=exponential: Exponential growth factor")
+)
+
+func exitf(format string, values ...any) {
+	log.Warningf(format, values...)
+	os.Exit(1)
+}
+
+func main() {
+	flag.Parse()
+	var bucketer metric.Bucketer
+	var formatVal func(int64) string
+	switch *typeFlag {
+	case "duration":
+		bucketer = metric.NewDurationBucketer(*numFiniteBucketsFlag, *minDurationFlag, *maxDurationFlag)
+		formatVal = func(val int64) string {
+			return time.Duration(val).String()
+		}
+	case "exponential":
+		bucketer = metric.NewExponentialBucketer(*numFiniteBucketsFlag, *widthFlag, *scaleFlag, *growthFlag)
+		formatVal = func(val int64) string {
+			return fmt.Sprintf("%v", val)
+		}
+	default:
+		exitf("Invalid -type: %s", *typeFlag)
+	}
+	fmt.Printf("Number of finite buckets: %d\n", bucketer.NumFiniteBuckets())
+	fmt.Printf("Number of total buckets:  %d\n", bucketer.NumFiniteBuckets()+2)
+	fmt.Printf("> Underflow bucket: (-inf; %s)\n", formatVal(bucketer.LowerBound(0)))
+	for b := 0; b < bucketer.NumFiniteBuckets(); b++ {
+		fmt.Printf("> Bucket index %d: [%s, %s). (Middle: %s)\n", b, formatVal(bucketer.LowerBound(b)), formatVal(bucketer.LowerBound(b+1)), formatVal((bucketer.LowerBound(b)+bucketer.LowerBound(b+1))/2))
+	}
+	fmt.Printf("> Overflow bucket: [%s; +inf)\n", formatVal(bucketer.LowerBound(bucketer.NumFiniteBuckets())))
+}

runsc/flag/flag.go

@@ -29,6 +29,8 @@ type FlagSet = flag.FlagSet
 var (
 	Bool        = flag.Bool
 	CommandLine = flag.CommandLine
+	Duration    = flag.Duration
+	Float64     = flag.Float64
 	Int         = flag.Int
 	Int64       = flag.Int64
 	NewFlagSet  = flag.NewFlagSet
@@ -36,6 +38,7 @@ var (
 	String      = flag.String
 	StringVar   = flag.StringVar
 	Uint        = flag.Uint
+	Uint64      = flag.Uint64
 	Var         = flag.Var
 )