get: Add --range-size to have a random but a defined range pattern

cli/get.go

@@ -53,6 +53,10 @@ var getFlags = []cli.Flag{
 		Name:  "range",
 		Usage: "Do ranged get operations. Will request with random offset and length.",
 	},
+	cli.StringFlag{
+		Name:  "range-size",
+		Usage: "Use a fixed range size while doing random range offsets, --range is implied",
+	},
 	cli.IntFlag{
 		Name:  "versions",
 		Value: 1,
@@ -81,11 +85,22 @@ FLAGS:
 // mainGet is the entry point for get command.
 func mainGet(ctx *cli.Context) error {
 	checkGetSyntax(ctx)
+
+	var rangeSize int64
+	if rs := ctx.String("range-size"); rs != "" {
+		s, err := toSize(rs)
+		if err != nil {
+			return err
+		}
+		rangeSize = int64(s)
+	}
+
 	sse := newSSE(ctx)
 	b := bench.Get{
 		Common:        getCommon(ctx, newGenSource(ctx, "obj.size")),
 		Versions:      ctx.Int("versions"),
-		RandomRanges:  ctx.Bool("range"),
+		RandomRanges:  ctx.Bool("range") || ctx.IsSet("range-size"),
+		RangeSize:     rangeSize,
 		CreateObjects: ctx.Int("objects"),
 		GetOpts:       minio.GetObjectOptions{ServerSideEncryption: sse},
 		ListExisting:  ctx.Bool("list-existing"),

pkg/bench/get.go

@@ -43,6 +43,7 @@ type Get struct {
 	CreateObjects int
 	Versions      int
 	RandomRanges  bool
+	RangeSize     int64
 	ListExisting  bool
 	ListFlat      bool
 }
@@ -288,10 +289,16 @@ func (g *Get) Start(ctx context.Context, wait chan struct{}) (Operations, error)
 				}
 
 				if g.RandomRanges && op.Size > 2 {
-					// Randomize length similar to --obj.randsize
-					size := generator.GetExpRandSize(rng, 0, op.Size-2)
-					start := rng.Int63n(op.Size - size)
-					end := start + size
+					var start, end int64
+					if g.RangeSize <= 0 {
+						// Randomize length similar to --obj.randsize
+						size := generator.GetExpRandSize(rng, 0, op.Size-2)
+						start = rng.Int63n(op.Size - size)
+						end = start + size
+					} else {
+						start = rng.Int63n(op.Size - g.RangeSize)
+						end = start + g.RangeSize - 1
+					}
 					op.Size = end - start + 1
 					opts.SetRange(start, end)
 				}