minio/tree-walk-fs.go

/*
 * Minio Cloud Storage, (C) 2016 Minio, 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.
 */

package main

import (
	"path"
	"sort"
	"strings"
	"time"
)

// Tree walk notify carries a channel which notifies tree walk
// results, additionally it also carries information if treeWalk
// should be timedOut.
type treeWalkerFS struct {
	ch       <-chan treeWalkResultFS
	timedOut bool
}

// Tree walk result carries results of tree walking.
type treeWalkResultFS struct {
	entry string
	err   error
	end   bool
}

// treeWalk walks FS directory tree recursively pushing fileInfo into the channel as and when it encounters files.
func (fs fsObjects) treeWalk(bucket, prefixDir, entryPrefixMatch, marker string, recursive bool, send func(treeWalkResultFS) bool, count *int, isLeaf func(string, string) bool) bool {
	// Example:
	// if prefixDir="one/two/three/" and marker="four/five.txt" treeWalk is recursively
	// called with prefixDir="one/two/three/four/" and marker="five.txt"

	var markerBase, markerDir string
	if marker != "" {
		// Ex: if marker="four/five.txt", markerDir="four/" markerBase="five.txt"
		markerSplit := strings.SplitN(marker, slashSeparator, 2)
		markerDir = markerSplit[0]
		if len(markerSplit) == 2 {
			markerDir += slashSeparator
			markerBase = markerSplit[1]
		}
	}
	entries, err := fs.storage.ListDir(bucket, prefixDir)
	if err != nil {
		send(treeWalkResultFS{err: err})
		return false
	}

	for i, entry := range entries {
		if entryPrefixMatch != "" {
			if !strings.HasPrefix(entry, entryPrefixMatch) {
				entries[i] = ""
				continue
			}
		}
		if isLeaf(bucket, pathJoin(prefixDir, entry)) {
			entries[i] = strings.TrimSuffix(entry, slashSeparator)
		}
	}
	sort.Strings(entries)
	// Skip the empty strings
	for len(entries) > 0 && entries[0] == "" {
		entries = entries[1:]
	}
	if len(entries) == 0 {
		return true
	}
	// example:
	// If markerDir="four/" Search() returns the index of "four/" in the sorted
	// entries list so we skip all the entries till "four/"
	idx := sort.Search(len(entries), func(i int) bool {
		return entries[i] >= markerDir
	})
	entries = entries[idx:]
	*count += len(entries)
	for i, entry := range entries {
		if i == 0 && markerDir == entry {
			if !recursive {
				// Skip as the marker would already be listed in the previous listing.
				*count--
				continue
			}
			if recursive && !strings.HasSuffix(entry, slashSeparator) {
				// We should not skip for recursive listing and if markerDir is a directory
				// for ex. if marker is "four/five.txt" markerDir will be "four/" which
				// should not be skipped, instead it will need to be treeWalk()'ed into.

				// Skip if it is a file though as it would be listed in previous listing.
				*count--
				continue
			}
		}

		if recursive && strings.HasSuffix(entry, slashSeparator) {
			// If the entry is a directory, we will need recurse into it.
			markerArg := ""
			if entry == markerDir {
				// We need to pass "five.txt" as marker only if we are
				// recursing into "four/"
				markerArg = markerBase
			}
			*count--
			prefixMatch := "" // Valid only for first level treeWalk and empty for subdirectories.
			if !fs.treeWalk(bucket, path.Join(prefixDir, entry), prefixMatch, markerArg, recursive, send, count, isLeaf) {
				return false
			}
			continue
		}
		*count--
		if !send(treeWalkResultFS{entry: pathJoin(prefixDir, entry)}) {
			return false
		}
	}
	return true
}

// Initiate a new treeWalk in a goroutine.
func (fs fsObjects) startTreeWalk(bucket, prefix, marker string, recursive bool, isLeaf func(string, string) bool) *treeWalkerFS {
	// Example 1
	// If prefix is "one/two/three/" and marker is "one/two/three/four/five.txt"
	// treeWalk is called with prefixDir="one/two/three/" and marker="four/five.txt"
	// and entryPrefixMatch=""

	// Example 2
	// if prefix is "one/two/th" and marker is "one/two/three/four/five.txt"
	// treeWalk is called with prefixDir="one/two/" and marker="three/four/five.txt"
	// and entryPrefixMatch="th"

	ch := make(chan treeWalkResultFS, maxObjectList)
	walkNotify := treeWalkerFS{ch: ch}
	entryPrefixMatch := prefix
	prefixDir := ""
	lastIndex := strings.LastIndex(prefix, slashSeparator)
	if lastIndex != -1 {
		entryPrefixMatch = prefix[lastIndex+1:]
		prefixDir = prefix[:lastIndex+1]
	}
	count := 0
	marker = strings.TrimPrefix(marker, prefixDir)
	go func() {
		defer close(ch)
		send := func(walkResult treeWalkResultFS) bool {
			if count == 0 {
				walkResult.end = true
			}
			timer := time.After(time.Second * 60)
			select {
			case ch <- walkResult:
				return true
			case <-timer:
				walkNotify.timedOut = true
				return false
			}
		}
		fs.treeWalk(bucket, prefixDir, entryPrefixMatch, marker, recursive, send, &count, isLeaf)
	}()
	return &walkNotify
}

// Save the goroutine reference in the map
func (fs fsObjects) saveTreeWalk(params listParams, walker *treeWalkerFS) {
	fs.listObjectMapMutex.Lock()
	defer fs.listObjectMapMutex.Unlock()

	walkers, _ := fs.listObjectMap[params]
	walkers = append(walkers, walker)

	fs.listObjectMap[params] = walkers
}

// Lookup the goroutine reference from map
func (fs fsObjects) lookupTreeWalk(params listParams) *treeWalkerFS {
	fs.listObjectMapMutex.Lock()
	defer fs.listObjectMapMutex.Unlock()

	if walkChs, ok := fs.listObjectMap[params]; ok {
		for i, walkCh := range walkChs {
			if !walkCh.timedOut {
				newWalkChs := walkChs[i+1:]
				if len(newWalkChs) > 0 {
					fs.listObjectMap[params] = newWalkChs
				} else {
					delete(fs.listObjectMap, params)
				}
				return walkCh
			}
		}
		// As all channels are timed out, delete the map entry
		delete(fs.listObjectMap, params)
	}
	return nil
}