Creating ZK higher level directories.

It seems it's just simpler all around if the zk topology plugin creates
the higher level directories when needed. The deletion still stops at
the root though, seems safer.

doc/TopologyService.md

@@ -264,8 +264,9 @@ and by the root directory to put the Vitess data in. For instance, assuming we
 want to use servers `global_server1,global_server2` in path `/vitess/global`:
 
 ``` sh
-# First create the directory in the global server:
-zk -server global_server1,global_server2 touch -p /vitess/global
+# The root directory in the global server will be created
+# automatically, same as when running this command:
+# zk -server global_server1,global_server2 touch -p /vitess/global
 
 # Set the following flags to let Vitess use this global server:
 # -topo_implementation zk2

examples/local/zk-up.sh

@@ -50,11 +50,7 @@ done
 
 echo "Started zk servers."
 
-# Now create the toplevel directories we'll need, if not there.
-$VTROOT/bin/zk -server $ZK_SERVER touch -p /vitess/global
-$VTROOT/bin/zk -server $ZK_SERVER touch -p /vitess/test
-
-# And also add the CellInfo description for the 'test' cell.
+# Add the CellInfo description for the 'test' cell.
 # If the node already exists, it's fine, means we used existing data.
 $VTROOT/bin/vtctl $TOPOLOGY_FLAGS AddCellInfo \
   -root /vitess/test \

go/vt/topo/zk2topo/file.go

@@ -20,7 +20,6 @@ import (
 	"bytes"
 	"fmt"
 	"path"
-	"strings"
 
 	"github.com/samuel/go-zookeeper/zk"
 	"golang.org/x/net/context"
@@ -30,11 +29,9 @@ import (
 
 // Create is part of the topo.Conn interface.
 func (zs *Server) Create(ctx context.Context, filePath string, contents []byte) (topo.Version, error) {
-	filePath = path.Clean(filePath)
-	depth := strings.Count(filePath, "/")
 	zkPath := path.Join(zs.root, filePath)
 
-	pathCreated, err := CreateRecursive(ctx, zs.conn, zkPath, contents, 0, zk.WorldACL(PermFile), depth)
+	pathCreated, err := CreateRecursive(ctx, zs.conn, zkPath, contents, 0, zk.WorldACL(PermFile), -1)
 	if err != nil {
 		return nil, convertError(err)
 	}

go/vt/topo/zk2topo/server_test.go

@@ -21,7 +21,6 @@ import (
 	"path"
 	"testing"
 
-	"github.com/samuel/go-zookeeper/zk"
 	"golang.org/x/net/context"
 
 	"github.com/youtube/vitess/go/testfiles"
@@ -41,22 +40,12 @@ func TestZk2Topo(t *testing.T) {
 	testIndex := 0
 	test.TopoServerTestSuite(t, func() *topo.Server {
 		// Each test will use its own sub-directories.
+		// The directories will be created when used the first time.
 		testRoot := fmt.Sprintf("/test-%v", testIndex)
 		testIndex++
 
-		ctx := context.Background()
-		c := Connect(serverAddr)
-		if _, err := c.Create(ctx, testRoot, nil, 0, zk.WorldACL(PermDirectory)); err != nil {
-			t.Fatalf("Create(%v) failed: %v", testRoot, err)
-		}
 		globalRoot := path.Join(testRoot, topo.GlobalCell)
-		if _, err := c.Create(ctx, globalRoot, nil, 0, zk.WorldACL(PermDirectory)); err != nil {
-			t.Fatalf("Create(%v) failed: %v", globalRoot, err)
-		}
 		cellRoot := path.Join(testRoot, test.LocalCellName)
-		if _, err := c.Create(ctx, cellRoot, nil, 0, zk.WorldACL(PermDirectory)); err != nil {
-			t.Fatalf("Create(%v) failed: %v", cellRoot, err)
-		}
 
 		// Note we exercise the observer feature here by passing in
 		// the same server twice, with a "|" separator.

go/vt/topo/zk2topo/utils.go

@@ -33,8 +33,9 @@ import (
 // CreateRecursive is a helper function on top of Create. It will
 // create a path and any pieces required, think mkdir -p.
 // Intermediate znodes are always created empty.
-func CreateRecursive(ctx context.Context, conn Conn, zkPath string, value []byte, flags int32, aclv []zk.ACL, maxCreationDepth int) (pathCreated string, err error) {
-	pathCreated, err = conn.Create(ctx, zkPath, value, flags, aclv)
+// Pass maxCreationDepth=-1 to create all nodes to the top.
+func CreateRecursive(ctx context.Context, conn Conn, zkPath string, value []byte, flags int32, aclv []zk.ACL, maxCreationDepth int) (string, error) {
+	pathCreated, err := conn.Create(ctx, zkPath, value, flags, aclv)
 	if err == zk.ErrNoNode {
 		if maxCreationDepth == 0 {
 			return "", zk.ErrNoNode
@@ -54,7 +55,7 @@ func CreateRecursive(ctx context.Context, conn Conn, zkPath string, value []byte
 		}
 		pathCreated, err = conn.Create(ctx, zkPath, value, flags, aclv)
 	}
-	return
+	return pathCreated, err
 }
 
 // ChildrenRecursive returns the relative path of all the children of

test/topo_flavor/zk2.py

@@ -1,13 +1,13 @@
 #!/usr/bin/env python
 
 # Copyright 2017 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.
@@ -50,12 +50,6 @@ class Zk2TopoServer(server.TopoServer):
         '-zk.cfg', '1@%s:%s' % (self.hostname, self.zk_ports),
         'init'])
 
-    # Create toplevel directories for global ZK, and one per cell.
-    run(binary_args('zk') + ['-server', self.addr, 'touch', '-p', '/global'])
-    run(binary_args('zk') + ['-server', self.addr, 'touch', '-p', '/test_nj'])
-    run(binary_args('zk') + ['-server', self.addr, 'touch', '-p', '/test_ny'])
-    run(binary_args('zk') + ['-server', self.addr, 'touch', '-p', '/test_ca'])
-
     # Create the cell configurations using 'vtctl AddCellInfo'
     utils.run_vtctl_vtctl(['AddCellInfo',
                            '-root', '/test_nj',