new driver: kubernetes

Tested with `kind` and GKE.

Note: "nodes" shown in `docker buildx ls` are unrelated to Kubernetes "nodes".
Probably buildx should come up with an alternative term.

Usage:

  $ kind create cluster
  $ export KUBECONFIG="$(kind get kubeconfig-path --name="kind")"

  $ docker buildx create --driver kubernetes --driver-opt replicas=3 --use
  $ docker buildx build -t foo --load .

`--load` loads the image into the local Docker.

Driver opts:

  - `image=IMAGE` - Sets the container image to be used for running buildkit.
  - `namespace=NS` - Sets the Kubernetes namespace. Defaults to the current namespace.
  - `replicas=N` - Sets the number of `Pod` replicas. Defaults to 1.
  - `rootless=(true|false)` - Run the container as a non-root user without `securityContext.privileged`. Defaults to false.
  - `loadbalance=(sticky|random)` - Load-balancing strategy. If set to "sticky", the pod is chosen using the hash of the context path. Defaults to "sticky"

Signed-off-by: Akihiro Suda <akihiro.suda.cz@hco.ntt.co.jp>

vendor/github.com/google/btree/btree_mem.go

@@ -0,0 +1,76 @@
+// Copyright 2014 Google Inc.
+//
+// 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.
+
+// +build ignore
+
+// This binary compares memory usage between btree and gollrb.
+package main
+
+import (
+	"flag"
+	"fmt"
+	"math/rand"
+	"runtime"
+	"time"
+
+	"github.com/google/btree"
+	"github.com/petar/GoLLRB/llrb"
+)
+
+var (
+	size   = flag.Int("size", 1000000, "size of the tree to build")
+	degree = flag.Int("degree", 8, "degree of btree")
+	gollrb = flag.Bool("llrb", false, "use llrb instead of btree")
+)
+
+func main() {
+	flag.Parse()
+	vals := rand.Perm(*size)
+	var t, v interface{}
+	v = vals
+	var stats runtime.MemStats
+	for i := 0; i < 10; i++ {
+		runtime.GC()
+	}
+	fmt.Println("-------- BEFORE ----------")
+	runtime.ReadMemStats(&stats)
+	fmt.Printf("%+v\n", stats)
+	start := time.Now()
+	if *gollrb {
+		tr := llrb.New()
+		for _, v := range vals {
+			tr.ReplaceOrInsert(llrb.Int(v))
+		}
+		t = tr // keep it around
+	} else {
+		tr := btree.New(*degree)
+		for _, v := range vals {
+			tr.ReplaceOrInsert(btree.Int(v))
+		}
+		t = tr // keep it around
+	}
+	fmt.Printf("%v inserts in %v\n", *size, time.Since(start))
+	fmt.Println("-------- AFTER ----------")
+	runtime.ReadMemStats(&stats)
+	fmt.Printf("%+v\n", stats)
+	for i := 0; i < 10; i++ {
+		runtime.GC()
+	}
+	fmt.Println("-------- AFTER GC ----------")
+	runtime.ReadMemStats(&stats)
+	fmt.Printf("%+v\n", stats)
+	if t == v {
+		fmt.Println("to make sure vals and tree aren't GC'd")
+	}
+}