Revert "Revert "Cacheable, multithreaded finder.""
Bug: 62455338
Test: m -j
This reverts commit d1abeb9d982b11fdf4047176d213acc8197c375f.
Change-Id: I9f73031636157511b5f1c6ce8a205e9bc91669ff
diff --git a/finder/finder.go b/finder/finder.go
new file mode 100644
index 0000000..ad85ee9
--- /dev/null
+++ b/finder/finder.go
@@ -0,0 +1,1399 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// 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 finder
+
+import (
+ "bufio"
+ "bytes"
+ "encoding/json"
+ "fmt"
+ "io"
+ "os"
+ "path/filepath"
+ "runtime"
+ "sort"
+ "strings"
+ "sync"
+ "sync/atomic"
+ "time"
+
+ "android/soong/fs"
+ "errors"
+)
+
+// This file provides a Finder struct that can quickly search for files satisfying
+// certain criteria.
+// This Finder gets its speed partially from parallelism and partially from caching.
+// If a Stat call returns the same result as last time, then it means Finder
+// can skip the ReadDir call for that dir.
+
+// The primary data structure used by the finder is the field Finder.nodes ,
+// which is a tree of nodes of type *pathMap .
+// Each node represents a directory on disk, along with its stats, subdirectories,
+// and contained files.
+
+// The common use case for the Finder is that the caller creates a Finder and gives
+// it the same query that was given to it in the previous execution.
+// In this situation, the major events that take place are:
+// 1. The Finder begins to load its db
+// 2. The Finder begins to stat the directories mentioned in its db (using multiple threads)
+// Calling Stat on each of these directories is generally a large fraction of the total time
+// 3. The Finder begins to construct a separate tree of nodes in each of its threads
+// 4. The Finder merges the individual node trees into the main node tree
+// 5. The Finder may call ReadDir a few times if there are a few directories that are out-of-date
+// These ReadDir calls might prompt additional Stat calls, etc
+// 6. The Finder waits for all loading to complete
+// 7. The Finder searches the cache for files matching the user's query (using multiple threads)
+
+// These are the invariants regarding concurrency:
+// 1. The public methods of Finder are threadsafe.
+// The public methods are only performance-optimized for one caller at a time, however.
+// For the moment, multiple concurrent callers shouldn't expect any better performance than
+// multiple serial callers.
+// 2. While building the node tree, only one thread may ever access the <children> collection of a
+// *pathMap at once.
+// a) The thread that accesses the <children> collection is the thread that discovers the
+// children (by reading them from the cache or by having received a response to ReadDir).
+// 1) Consequently, the thread that discovers the children also spawns requests to stat
+// subdirs.
+// b) Consequently, while building the node tree, no thread may do a lookup of its
+// *pathMap via filepath because another thread may be adding children to the
+// <children> collection of an ancestor node. Additionally, in rare cases, another thread
+// may be removing children from an ancestor node if the children were only discovered to
+// be irrelevant after calling ReadDir (which happens if a prune-file was just added).
+// 3. No query will begin to be serviced until all loading (both reading the db
+// and scanning the filesystem) is complete.
+// Tests indicate that it only takes about 10% as long to search the in-memory cache as to
+// generate it, making this not a huge loss in performance.
+// 4. The parsing of the db and the initial setup of the pathMap tree must complete before
+// beginning to call listDirSync (because listDirSync can create new entries in the pathMap)
+
+// see cmd/finder.go or finder_test.go for usage examples
+
+// Update versionString whenever making a backwards-incompatible change to the cache file format
+const versionString = "Android finder version 1"
+
+// a CacheParams specifies which files and directories the user wishes be scanned and
+// potentially added to the cache
+type CacheParams struct {
+ // WorkingDirectory is used as a base for any relative file paths given to the Finder
+ WorkingDirectory string
+
+ // RootDirs are the root directories used to initiate the search
+ RootDirs []string
+
+ // ExcludeDirs are directory names that if encountered are removed from the search
+ ExcludeDirs []string
+
+ // PruneFiles are file names that if encountered prune their entire directory
+ // (including siblings)
+ PruneFiles []string
+
+ // IncludeFiles are file names to include as matches
+ IncludeFiles []string
+}
+
+// a cacheConfig stores the inputs that determine what should be included in the cache
+type cacheConfig struct {
+ CacheParams
+
+ // FilesystemView is a unique identifier telling which parts of which file systems
+ // are readable by the Finder. In practice its value is essentially username@hostname.
+ // FilesystemView is set to ensure that a cache file copied to another host or
+ // found by another user doesn't inadvertently get reused.
+ FilesystemView string
+}
+
+func (p *cacheConfig) Dump() ([]byte, error) {
+ bytes, err := json.Marshal(p)
+ return bytes, err
+}
+
+// a cacheMetadata stores version information about the cache
+type cacheMetadata struct {
+ // The Version enables the Finder to determine whether it can even parse the file
+ // If the version changes, the entire cache file must be regenerated
+ Version string
+
+ // The CacheParams enables the Finder to determine whether the parameters match
+ // If the CacheParams change, the Finder can choose how much of the cache file to reuse
+ // (although in practice, the Finder will probably choose to ignore the entire file anyway)
+ Config cacheConfig
+}
+
+type Logger interface {
+ Output(calldepth int, s string) error
+}
+
+// the Finder is the main struct that callers will want to use
+type Finder struct {
+ // configuration
+ DbPath string
+ numDbLoadingThreads int
+ numSearchingThreads int
+ cacheMetadata cacheMetadata
+ logger Logger
+ filesystem fs.FileSystem
+
+ // temporary state
+ threadPool *threadPool
+ mutex sync.Mutex
+
+ // non-temporary state
+ modifiedFlag int32
+ nodes pathMap
+}
+
+// New creates a new Finder for use
+func New(cacheParams CacheParams, filesystem fs.FileSystem,
+ logger Logger, dbPath string) *Finder {
+
+ numThreads := runtime.NumCPU() * 2
+ numDbLoadingThreads := numThreads
+ numSearchingThreads := numThreads
+
+ metadata := cacheMetadata{
+ Version: versionString,
+ Config: cacheConfig{
+ CacheParams: cacheParams,
+ FilesystemView: filesystem.ViewId(),
+ },
+ }
+
+ finder := &Finder{
+ numDbLoadingThreads: numDbLoadingThreads,
+ numSearchingThreads: numSearchingThreads,
+ cacheMetadata: metadata,
+ logger: logger,
+ filesystem: filesystem,
+
+ nodes: *newPathMap("/"),
+ DbPath: dbPath,
+ }
+
+ finder.loadFromFilesystem()
+
+ finder.verbosef("Done parsing db\n")
+ return finder
+}
+
+// FindNamed searches for every cached file
+func (f *Finder) FindAll() []string {
+ return f.FindAt("/")
+}
+
+// FindNamed searches for every cached file under <rootDir>
+func (f *Finder) FindAt(rootDir string) []string {
+ filter := func(entries DirEntries) (dirNames []string, fileNames []string) {
+ return entries.DirNames, entries.FileNames
+ }
+ return f.FindMatching(rootDir, filter)
+}
+
+// FindNamed searches for every cached file named <fileName>
+func (f *Finder) FindNamed(fileName string) []string {
+ return f.FindNamedAt("/", fileName)
+}
+
+// FindNamedAt searches under <rootPath> for every file named <fileName>
+// The reason a caller might use FindNamedAt instead of FindNamed is if they want
+// to limit their search to a subset of the cache
+func (f *Finder) FindNamedAt(rootPath string, fileName string) []string {
+ filter := func(entries DirEntries) (dirNames []string, fileNames []string) {
+ matches := []string{}
+ for _, foundName := range entries.FileNames {
+ if foundName == fileName {
+ matches = append(matches, foundName)
+ }
+ }
+ return entries.DirNames, matches
+
+ }
+ return f.FindMatching(rootPath, filter)
+}
+
+// FindFirstNamed searches for every file named <fileName>
+// Whenever it finds a match, it stops search subdirectories
+func (f *Finder) FindFirstNamed(fileName string) []string {
+ return f.FindFirstNamedAt("/", fileName)
+}
+
+// FindFirstNamedAt searches for every file named <fileName>
+// Whenever it finds a match, it stops search subdirectories
+func (f *Finder) FindFirstNamedAt(rootPath string, fileName string) []string {
+ filter := func(entries DirEntries) (dirNames []string, fileNames []string) {
+ matches := []string{}
+ for _, foundName := range entries.FileNames {
+ if foundName == fileName {
+ matches = append(matches, foundName)
+ }
+ }
+
+ if len(matches) > 0 {
+ return []string{}, matches
+ }
+ return entries.DirNames, matches
+ }
+ return f.FindMatching(rootPath, filter)
+}
+
+// FindMatching is the most general exported function for searching for files in the cache
+// The WalkFunc will be invoked repeatedly and is expected to modify the provided DirEntries
+// in place, removing file paths and directories as desired.
+// WalkFunc will be invoked potentially many times in parallel, and must be threadsafe.
+func (f *Finder) FindMatching(rootPath string, filter WalkFunc) []string {
+ // set up some parameters
+ scanStart := time.Now()
+ var isRel bool
+ workingDir := f.cacheMetadata.Config.WorkingDirectory
+
+ isRel = !filepath.IsAbs(rootPath)
+ if isRel {
+ rootPath = filepath.Join(workingDir, rootPath)
+ }
+
+ rootPath = filepath.Clean(rootPath)
+
+ // ensure nothing else is using the Finder
+ f.verbosef("FindMatching waiting for finder to be idle\n")
+ f.lock()
+ defer f.unlock()
+
+ node := f.nodes.GetNode(rootPath, false)
+ if node == nil {
+ f.verbosef("No data for path %v ; apparently not included in cache params: %v\n",
+ rootPath, f.cacheMetadata.Config.CacheParams)
+ // path is not found; don't do a search
+ return []string{}
+ }
+
+ // search for matching files
+ f.verbosef("Finder finding %v using cache\n", rootPath)
+ results := f.findInCacheMultithreaded(node, filter, f.numSearchingThreads)
+
+ // format and return results
+ if isRel {
+ for i := 0; i < len(results); i++ {
+ results[i] = strings.Replace(results[i], workingDir+"/", "", 1)
+ }
+ }
+ sort.Strings(results)
+ f.verbosef("Found %v files under %v in %v using cache\n",
+ len(results), rootPath, time.Since(scanStart))
+ return results
+}
+
+// Shutdown saves the contents of the Finder to its database file
+func (f *Finder) Shutdown() {
+ f.verbosef("Shutting down\n")
+ if f.wasModified() {
+ err := f.dumpDb()
+ if err != nil {
+ f.verbosef("%v\n", err)
+ }
+ } else {
+ f.verbosef("Skipping dumping unmodified db\n")
+ }
+}
+
+// End of public api
+
+// joinCleanPaths is like filepath.Join but is faster because
+// joinCleanPaths doesn't have to support paths ending in "/" or containing ".."
+func joinCleanPaths(base string, leaf string) string {
+ if base == "" {
+ return leaf
+ }
+ if base == "/" {
+ return base + leaf
+ }
+ if leaf == "" {
+ return base
+ }
+ return base + "/" + leaf
+}
+
+func (f *Finder) verbosef(format string, args ...interface{}) {
+ f.logger.Output(2, fmt.Sprintf(format, args...))
+}
+
+// loadFromFilesystem populates the in-memory cache based on the contents of the filesystem
+func (f *Finder) loadFromFilesystem() {
+ f.threadPool = newThreadPool(f.numDbLoadingThreads)
+
+ err := f.startFromExternalCache()
+ if err != nil {
+ f.startWithoutExternalCache()
+ }
+
+ startTime := time.Now()
+ f.verbosef("Waiting for pending requests to complete\n")
+ f.threadPool.Wait()
+ f.verbosef("Is idle after %v\n", time.Now().Sub(startTime))
+ f.threadPool = nil
+}
+
+func (f *Finder) startFind(path string) {
+ if !filepath.IsAbs(path) {
+ path = filepath.Join(f.cacheMetadata.Config.WorkingDirectory, path)
+ }
+ node := f.nodes.GetNode(path, true)
+ f.statDirAsync(node)
+}
+
+func (f *Finder) lock() {
+ f.mutex.Lock()
+}
+
+func (f *Finder) unlock() {
+ f.mutex.Unlock()
+}
+
+// a statResponse is the relevant portion of the response from the filesystem to a Stat call
+type statResponse struct {
+ ModTime int64
+ Inode uint64
+ Device uint64
+}
+
+// a pathAndStats stores a path and its stats
+type pathAndStats struct {
+ statResponse
+
+ Path string
+}
+
+// a dirFullInfo stores all of the relevant information we know about a directory
+type dirFullInfo struct {
+ pathAndStats
+
+ FileNames []string
+}
+
+// a PersistedDirInfo is the information about a dir that we save to our cache on disk
+type PersistedDirInfo struct {
+ // These field names are short because they are repeated many times in the output json file
+ P string // path
+ T int64 // modification time
+ I uint64 // inode number
+ F []string // relevant filenames contained
+}
+
+// a PersistedDirs is the information that we persist for a group of dirs
+type PersistedDirs struct {
+ // the device on which each directory is stored
+ Device uint64
+ // the common root path to which all contained dirs are relative
+ Root string
+ // the directories themselves
+ Dirs []PersistedDirInfo
+}
+
+// a CacheEntry is the smallest unit that can be read and parsed from the cache (on disk) at a time
+type CacheEntry []PersistedDirs
+
+// a DirEntries lists the files and directories contained directly within a specific directory
+type DirEntries struct {
+ Path string
+
+ // elements of DirNames are just the dir names; they don't include any '/' character
+ DirNames []string
+ // elements of FileNames are just the file names; they don't include '/' character
+ FileNames []string
+}
+
+// a WalkFunc is the type that is passed into various Find functions for determining which
+// directories the caller wishes be walked. The WalkFunc is expected to decide which
+// directories to walk and which files to consider as matches to the original query.
+type WalkFunc func(DirEntries) (dirs []string, files []string)
+
+// a mapNode stores the relevant stats about a directory to be stored in a pathMap
+type mapNode struct {
+ statResponse
+ FileNames []string
+}
+
+// a pathMap implements the directory tree structure of nodes
+type pathMap struct {
+ mapNode
+
+ path string
+
+ children map[string]*pathMap
+
+ // number of descendent nodes, including self
+ approximateNumDescendents int
+}
+
+func newPathMap(path string) *pathMap {
+ result := &pathMap{path: path, children: make(map[string]*pathMap, 4),
+ approximateNumDescendents: 1}
+ return result
+}
+
+// GetNode returns the node at <path>
+func (m *pathMap) GetNode(path string, createIfNotFound bool) *pathMap {
+ if len(path) > 0 && path[0] == '/' {
+ path = path[1:]
+ }
+
+ node := m
+ for {
+ if path == "" {
+ return node
+ }
+
+ index := strings.Index(path, "/")
+ var firstComponent string
+ if index >= 0 {
+ firstComponent = path[:index]
+ path = path[index+1:]
+ } else {
+ firstComponent = path
+ path = ""
+ }
+
+ child, found := node.children[firstComponent]
+
+ if !found {
+ if createIfNotFound {
+ child = node.newChild(firstComponent)
+ } else {
+ return nil
+ }
+ }
+
+ node = child
+ }
+}
+
+func (m *pathMap) newChild(name string) (child *pathMap) {
+ path := joinCleanPaths(m.path, name)
+ newChild := newPathMap(path)
+ m.children[name] = newChild
+
+ return m.children[name]
+}
+
+func (m *pathMap) UpdateNumDescendents() int {
+ count := 1
+ for _, child := range m.children {
+ count += child.approximateNumDescendents
+ }
+ m.approximateNumDescendents = count
+ return count
+}
+
+func (m *pathMap) UpdateNumDescendentsRecursive() {
+ for _, child := range m.children {
+ child.UpdateNumDescendentsRecursive()
+ }
+ m.UpdateNumDescendents()
+}
+
+func (m *pathMap) MergeIn(other *pathMap) {
+ for key, theirs := range other.children {
+ ours, found := m.children[key]
+ if found {
+ ours.MergeIn(theirs)
+ } else {
+ m.children[key] = theirs
+ }
+ }
+ if other.ModTime != 0 {
+ m.mapNode = other.mapNode
+ }
+ m.UpdateNumDescendents()
+}
+
+func (m *pathMap) DumpAll() []dirFullInfo {
+ results := []dirFullInfo{}
+ m.dumpInto("", &results)
+ return results
+}
+
+func (m *pathMap) dumpInto(path string, results *[]dirFullInfo) {
+ *results = append(*results,
+ dirFullInfo{
+ pathAndStats{statResponse: m.statResponse, Path: path},
+ m.FileNames},
+ )
+ for key, child := range m.children {
+ childPath := joinCleanPaths(path, key)
+ if len(childPath) == 0 || childPath[0] != '/' {
+ childPath = "/" + childPath
+ }
+ child.dumpInto(childPath, results)
+ }
+}
+
+// a semaphore can be locked by up to <capacity> callers at once
+type semaphore struct {
+ pool chan bool
+}
+
+func newSemaphore(capacity int) *semaphore {
+ return &semaphore{pool: make(chan bool, capacity)}
+}
+
+func (l *semaphore) Lock() {
+ l.pool <- true
+}
+
+func (l *semaphore) Unlock() {
+ <-l.pool
+}
+
+// A threadPool runs goroutines and supports throttling and waiting.
+// Without throttling, Go may exhaust the maximum number of various resources, such as
+// threads or file descriptors, and crash the program.
+type threadPool struct {
+ receivedRequests sync.WaitGroup
+ activeRequests semaphore
+}
+
+func newThreadPool(maxNumConcurrentThreads int) *threadPool {
+ return &threadPool{
+ receivedRequests: sync.WaitGroup{},
+ activeRequests: *newSemaphore(maxNumConcurrentThreads),
+ }
+}
+
+// Run requests to run the given function in its own goroutine
+func (p *threadPool) Run(function func()) {
+ p.receivedRequests.Add(1)
+ // If Run() was called from within a goroutine spawned by this threadPool,
+ // then we may need to return from Run() before having capacity to actually
+ // run <function>.
+ //
+ // It's possible that the body of <function> contains a statement (such as a syscall)
+ // that will cause Go to pin it to a thread, or will contain a statement that uses
+ // another resource that is in short supply (such as a file descriptor), so we can't
+ // actually run <function> until we have capacity.
+ //
+ // However, the semaphore used for synchronization is implemented via a channel and
+ // shouldn't require a new thread for each access.
+ go func() {
+ p.activeRequests.Lock()
+ function()
+ p.activeRequests.Unlock()
+ p.receivedRequests.Done()
+ }()
+}
+
+// Wait waits until all goroutines are done, just like sync.WaitGroup's Wait
+func (p *threadPool) Wait() {
+ p.receivedRequests.Wait()
+}
+
+func (f *Finder) serializeCacheEntry(dirInfos []dirFullInfo) ([]byte, error) {
+ // group each dirFullInfo by its Device, to avoid having to repeat it in the output
+ dirsByDevice := map[uint64][]PersistedDirInfo{}
+ for _, entry := range dirInfos {
+ _, found := dirsByDevice[entry.Device]
+ if !found {
+ dirsByDevice[entry.Device] = []PersistedDirInfo{}
+ }
+ dirsByDevice[entry.Device] = append(dirsByDevice[entry.Device],
+ PersistedDirInfo{P: entry.Path, T: entry.ModTime, I: entry.Inode, F: entry.FileNames})
+ }
+
+ cacheEntry := CacheEntry{}
+
+ for device, infos := range dirsByDevice {
+ // find common prefix
+ prefix := ""
+ if len(infos) > 0 {
+ prefix = infos[0].P
+ }
+ for _, info := range infos {
+ for !strings.HasPrefix(info.P+"/", prefix+"/") {
+ prefix = filepath.Dir(prefix)
+ }
+ }
+ // remove common prefix
+ for i := range infos {
+ suffix := strings.Replace(infos[i].P, prefix, "", 1)
+ if len(suffix) > 0 && suffix[0] == '/' {
+ suffix = suffix[1:]
+ }
+ infos[i].P = suffix
+ }
+
+ // turn the map (keyed by device) into a list of structs with labeled fields
+ // this is to improve readability of the output
+ cacheEntry = append(cacheEntry, PersistedDirs{Device: device, Root: prefix, Dirs: infos})
+ }
+
+ // convert to json.
+ // it would save some space to use a different format than json for the db file,
+ // but the space and time savings are small, and json is easy for humans to read
+ bytes, err := json.Marshal(cacheEntry)
+ return bytes, err
+}
+
+func (f *Finder) parseCacheEntry(bytes []byte) ([]dirFullInfo, error) {
+ var cacheEntry CacheEntry
+ err := json.Unmarshal(bytes, &cacheEntry)
+ if err != nil {
+ return nil, err
+ }
+
+ // convert from a CacheEntry to a []dirFullInfo (by copying a few fields)
+ capacity := 0
+ for _, element := range cacheEntry {
+ capacity += len(element.Dirs)
+ }
+ nodes := make([]dirFullInfo, capacity)
+ count := 0
+ for _, element := range cacheEntry {
+ for _, dir := range element.Dirs {
+ path := joinCleanPaths(element.Root, dir.P)
+
+ nodes[count] = dirFullInfo{
+ pathAndStats: pathAndStats{
+ statResponse: statResponse{
+ ModTime: dir.T, Inode: dir.I, Device: element.Device,
+ },
+ Path: path},
+ FileNames: dir.F}
+ count++
+ }
+ }
+ return nodes, nil
+}
+
+// We use the following separator byte to distinguish individually parseable blocks of json
+// because we know this separator won't appear in the json that we're parsing.
+//
+// The newline byte can only appear in a UTF-8 stream if the newline character appears, because:
+// - The newline character is encoded as "0000 1010" in binary ("0a" in hex)
+// - UTF-8 dictates that bytes beginning with a "0" bit are never emitted as part of a multibyte
+// character.
+//
+// We know that the newline character will never appear in our json string, because:
+// - If a newline character appears as part of a data string, then json encoding will
+// emit two characters instead: '\' and 'n'.
+// - The json encoder that we use doesn't emit the optional newlines between any of its
+// other outputs.
+const lineSeparator = byte('\n')
+
+func (f *Finder) readLine(reader *bufio.Reader) ([]byte, error) {
+ return reader.ReadBytes(lineSeparator)
+}
+
+// validateCacheHeader reads the cache header from cacheReader and tells whether the cache is compatible with this Finder
+func (f *Finder) validateCacheHeader(cacheReader *bufio.Reader) bool {
+ cacheVersionBytes, err := f.readLine(cacheReader)
+ if err != nil {
+ f.verbosef("Failed to read database header; database is invalid\n")
+ return false
+ }
+ if len(cacheVersionBytes) > 0 && cacheVersionBytes[len(cacheVersionBytes)-1] == lineSeparator {
+ cacheVersionBytes = cacheVersionBytes[:len(cacheVersionBytes)-1]
+ }
+ cacheVersionString := string(cacheVersionBytes)
+ currentVersion := f.cacheMetadata.Version
+ if cacheVersionString != currentVersion {
+ f.verbosef("Version changed from %q to %q, database is not applicable\n", cacheVersionString, currentVersion)
+ return false
+ }
+
+ cacheParamBytes, err := f.readLine(cacheReader)
+ if err != nil {
+ f.verbosef("Failed to read database search params; database is invalid\n")
+ return false
+ }
+
+ if len(cacheParamBytes) > 0 && cacheParamBytes[len(cacheParamBytes)-1] == lineSeparator {
+ cacheParamBytes = cacheParamBytes[:len(cacheParamBytes)-1]
+ }
+
+ currentParamBytes, err := f.cacheMetadata.Config.Dump()
+ if err != nil {
+ panic("Finder failed to serialize its parameters")
+ }
+ cacheParamString := string(cacheParamBytes)
+ currentParamString := string(currentParamBytes)
+ if cacheParamString != currentParamString {
+ f.verbosef("Params changed from %q to %q, database is not applicable\n", cacheParamString, currentParamString)
+ return false
+ }
+ return true
+}
+
+// loadBytes compares the cache info in <data> to the state of the filesystem
+// loadBytes returns a map representing <data> and also a slice of dirs that need to be re-walked
+func (f *Finder) loadBytes(id int, data []byte) (m *pathMap, dirsToWalk []string, err error) {
+
+ helperStartTime := time.Now()
+
+ cachedNodes, err := f.parseCacheEntry(data)
+ if err != nil {
+ return nil, nil, fmt.Errorf("Failed to parse block %v: %v\n", id, err.Error())
+ }
+
+ unmarshalDate := time.Now()
+ f.verbosef("Unmarshaled %v objects for %v in %v\n",
+ len(cachedNodes), id, unmarshalDate.Sub(helperStartTime))
+
+ tempMap := newPathMap("/")
+ stats := make([]statResponse, len(cachedNodes))
+
+ for i, node := range cachedNodes {
+ // check the file system for an updated timestamp
+ stats[i] = f.statDirSync(node.Path)
+ }
+
+ dirsToWalk = []string{}
+ for i, cachedNode := range cachedNodes {
+ updated := stats[i]
+ // save the cached value
+ container := tempMap.GetNode(cachedNode.Path, true)
+ container.mapNode = mapNode{statResponse: updated}
+
+ // if the metadata changed and the directory still exists, then
+ // make a note to walk it later
+ if !f.isInfoUpToDate(cachedNode.statResponse, updated) && updated.ModTime != 0 {
+ f.setModified()
+ // make a note that the directory needs to be walked
+ dirsToWalk = append(dirsToWalk, cachedNode.Path)
+ } else {
+ container.mapNode.FileNames = cachedNode.FileNames
+ }
+ }
+ // count the number of nodes to improve our understanding of the shape of the tree,
+ // thereby improving parallelism of subsequent searches
+ tempMap.UpdateNumDescendentsRecursive()
+
+ f.verbosef("Statted inodes of block %v in %v\n", id, time.Now().Sub(unmarshalDate))
+ return tempMap, dirsToWalk, nil
+}
+
+// startFromExternalCache loads the cache database from disk
+// startFromExternalCache waits to return until the load of the cache db is complete, but
+// startFromExternalCache does not wait for all every listDir() or statDir() request to complete
+func (f *Finder) startFromExternalCache() (err error) {
+ startTime := time.Now()
+ dbPath := f.DbPath
+
+ // open cache file and validate its header
+ reader, err := f.filesystem.Open(dbPath)
+ if err != nil {
+ return errors.New("No data to load from database\n")
+ }
+ bufferedReader := bufio.NewReader(reader)
+ if !f.validateCacheHeader(bufferedReader) {
+ return errors.New("Cache header does not match")
+ }
+ f.verbosef("Database header matches, will attempt to use database %v\n", f.DbPath)
+
+ // read the file and spawn threads to process it
+ nodesToWalk := [][]*pathMap{}
+ mainTree := newPathMap("/")
+
+ // read the blocks and stream them into <blockChannel>
+ type dataBlock struct {
+ id int
+ err error
+ data []byte
+ }
+ blockChannel := make(chan dataBlock, f.numDbLoadingThreads)
+ readBlocks := func() {
+ index := 0
+ for {
+ // It takes some time to unmarshal the input from json, so we want
+ // to unmarshal it in parallel. In order to find valid places to
+ // break the input, we scan for the line separators that we inserted
+ // (for this purpose) when we dumped the database.
+ data, err := f.readLine(bufferedReader)
+ var response dataBlock
+ done := false
+ if err != nil && err != io.EOF {
+ response = dataBlock{id: index, err: err, data: nil}
+ done = true
+ } else {
+ done = (err == io.EOF)
+ response = dataBlock{id: index, err: nil, data: data}
+ }
+ blockChannel <- response
+ index++
+ duration := time.Since(startTime)
+ f.verbosef("Read block %v after %v\n", index, duration)
+ if done {
+ f.verbosef("Read %v blocks in %v\n", index, duration)
+ close(blockChannel)
+ return
+ }
+ }
+ }
+ go readBlocks()
+
+ // Read from <blockChannel> and stream the responses into <resultChannel>.
+ type workResponse struct {
+ id int
+ err error
+ tree *pathMap
+ updatedDirs []string
+ }
+ resultChannel := make(chan workResponse)
+ processBlocks := func() {
+ numProcessed := 0
+ threadPool := newThreadPool(f.numDbLoadingThreads)
+ for {
+ // get a block to process
+ block, received := <-blockChannel
+ if !received {
+ break
+ }
+
+ if block.err != nil {
+ resultChannel <- workResponse{err: block.err}
+ break
+ }
+ numProcessed++
+ // wait until there is CPU available to process it
+ threadPool.Run(
+ func() {
+ processStartTime := time.Now()
+ f.verbosef("Starting to process block %v after %v\n",
+ block.id, processStartTime.Sub(startTime))
+ tempMap, updatedDirs, err := f.loadBytes(block.id, block.data)
+ var response workResponse
+ if err != nil {
+ f.verbosef(
+ "Block %v failed to parse with error %v\n",
+ block.id, err)
+ response = workResponse{err: err}
+ } else {
+ response = workResponse{
+ id: block.id,
+ err: nil,
+ tree: tempMap,
+ updatedDirs: updatedDirs,
+ }
+ }
+ f.verbosef("Processed block %v in %v\n",
+ block.id, time.Since(processStartTime),
+ )
+ resultChannel <- response
+ },
+ )
+ }
+ threadPool.Wait()
+ f.verbosef("Finished processing %v blocks in %v\n",
+ numProcessed, time.Since(startTime))
+ close(resultChannel)
+ }
+ go processBlocks()
+
+ // Read from <resultChannel> and use the results
+ combineResults := func() (err error) {
+ for {
+ result, received := <-resultChannel
+ if !received {
+ break
+ }
+ if err != nil {
+ // In case of an error, wait for work to complete before
+ // returning the error. This ensures that any subsequent
+ // work doesn't need to compete for resources (and possibly
+ // fail due to, for example, a filesystem limit on the number of
+ // concurrently open files) with past work.
+ continue
+ }
+ if result.err != nil {
+ err = result.err
+ continue
+ }
+ // update main tree
+ mainTree.MergeIn(result.tree)
+ // record any new directories that we will need to Stat()
+ updatedNodes := make([]*pathMap, len(result.updatedDirs))
+ for j, dir := range result.updatedDirs {
+ node := mainTree.GetNode(dir, false)
+ updatedNodes[j] = node
+ }
+ nodesToWalk = append(nodesToWalk, updatedNodes)
+ }
+ return err
+ }
+ err = combineResults()
+ if err != nil {
+ return err
+ }
+
+ f.nodes = *mainTree
+
+ // after having loaded the entire db and therefore created entries for
+ // the directories we know of, now it's safe to start calling ReadDir on
+ // any updated directories
+ for i := range nodesToWalk {
+ f.listDirsAsync(nodesToWalk[i])
+ }
+ f.verbosef("Loaded db and statted its contents in %v\n", time.Since(startTime))
+ return err
+}
+
+// startWithoutExternalCache starts scanning the filesystem according to the cache config
+// startWithoutExternalCache should be called if startFromExternalCache is not applicable
+func (f *Finder) startWithoutExternalCache() {
+ configDirs := f.cacheMetadata.Config.RootDirs
+
+ // clean paths
+ candidates := make([]string, len(configDirs))
+ for i, dir := range configDirs {
+ candidates[i] = filepath.Clean(dir)
+ }
+ // remove duplicates
+ dirsToScan := make([]string, 0, len(configDirs))
+ for _, candidate := range candidates {
+ include := true
+ for _, included := range dirsToScan {
+ if included == "/" || strings.HasPrefix(candidate+"/", included+"/") {
+ include = false
+ break
+ }
+ }
+ if include {
+ dirsToScan = append(dirsToScan, candidate)
+ }
+ }
+
+ // start searching finally
+ for _, path := range dirsToScan {
+ f.verbosef("Starting find of %v\n", path)
+ f.startFind(path)
+ }
+}
+
+// isInfoUpToDate tells whether <new> can confirm that results computed at <old> are still valid
+func (f *Finder) isInfoUpToDate(old statResponse, new statResponse) (equal bool) {
+ if old.Inode != new.Inode {
+ return false
+ }
+ if old.ModTime != new.ModTime {
+ return false
+ }
+ if old.Device != new.Device {
+ return false
+ }
+ return true
+}
+
+func (f *Finder) wasModified() bool {
+ return atomic.LoadInt32(&f.modifiedFlag) > 0
+}
+
+func (f *Finder) setModified() {
+ var newVal int32
+ newVal = 1
+ atomic.StoreInt32(&f.modifiedFlag, newVal)
+}
+
+// sortedDirEntries exports directory entries to facilitate dumping them to the external cache
+func (f *Finder) sortedDirEntries() []dirFullInfo {
+ startTime := time.Now()
+ nodes := make([]dirFullInfo, 0)
+ for _, node := range f.nodes.DumpAll() {
+ if node.ModTime != 0 {
+ nodes = append(nodes, node)
+ }
+ }
+ discoveryDate := time.Now()
+ f.verbosef("Generated %v cache entries in %v\n", len(nodes), discoveryDate.Sub(startTime))
+ less := func(i int, j int) bool {
+ return nodes[i].Path < nodes[j].Path
+ }
+ sort.Slice(nodes, less)
+ sortDate := time.Now()
+ f.verbosef("Sorted %v cache entries in %v\n", len(nodes), sortDate.Sub(discoveryDate))
+
+ return nodes
+}
+
+// serializeDb converts the cache database into a form to save to disk
+func (f *Finder) serializeDb() ([]byte, error) {
+ // sort dir entries
+ var entryList = f.sortedDirEntries()
+
+ // Generate an output file that can be conveniently loaded using the same number of threads
+ // as were used in this execution (because presumably that will be the number of threads
+ // used in the next execution too)
+
+ // generate header
+ header := []byte{}
+ header = append(header, []byte(f.cacheMetadata.Version)...)
+ header = append(header, lineSeparator)
+ configDump, err := f.cacheMetadata.Config.Dump()
+ if err != nil {
+ return nil, err
+ }
+ header = append(header, configDump...)
+
+ // serialize individual blocks in parallel
+ numBlocks := f.numDbLoadingThreads
+ if numBlocks > len(entryList) {
+ numBlocks = len(entryList)
+ }
+ blocks := make([][]byte, 1+numBlocks)
+ blocks[0] = header
+ blockMin := 0
+ wg := sync.WaitGroup{}
+ var errLock sync.Mutex
+
+ for i := 1; i <= numBlocks; i++ {
+ // identify next block
+ blockMax := len(entryList) * i / numBlocks
+ block := entryList[blockMin:blockMax]
+
+ // process block
+ wg.Add(1)
+ go func(index int, block []dirFullInfo) {
+ byteBlock, subErr := f.serializeCacheEntry(block)
+ f.verbosef("Serialized block %v into %v bytes\n", index, len(byteBlock))
+ if subErr != nil {
+ f.verbosef("%v\n", subErr.Error())
+ errLock.Lock()
+ err = subErr
+ errLock.Unlock()
+ } else {
+ blocks[index] = byteBlock
+ }
+ wg.Done()
+ }(i, block)
+
+ blockMin = blockMax
+ }
+
+ wg.Wait()
+
+ if err != nil {
+ return nil, err
+ }
+
+ content := bytes.Join(blocks, []byte{lineSeparator})
+
+ return content, nil
+}
+
+// dumpDb saves the cache database to disk
+func (f *Finder) dumpDb() error {
+ startTime := time.Now()
+ f.verbosef("Dumping db\n")
+
+ tempPath := f.DbPath + ".tmp"
+
+ bytes, err := f.serializeDb()
+ if err != nil {
+ return err
+ }
+ serializeDate := time.Now()
+ f.verbosef("Serialized db in %v\n", serializeDate.Sub(startTime))
+ // dump file and atomically move
+ err = f.filesystem.WriteFile(tempPath, bytes, 0777)
+ if err != nil {
+ return err
+ }
+ err = f.filesystem.Rename(tempPath, f.DbPath)
+ if err != nil {
+ return err
+ }
+
+ f.verbosef("Wrote db in %v\n", time.Now().Sub(serializeDate))
+ return nil
+}
+
+func (f *Finder) statDirAsync(dir *pathMap) {
+ node := dir
+ path := dir.path
+ f.threadPool.Run(
+ func() {
+ updatedStats := f.statDirSync(path)
+
+ if !f.isInfoUpToDate(node.statResponse, updatedStats) {
+ node.mapNode = mapNode{
+ statResponse: updatedStats,
+ FileNames: []string{},
+ }
+ f.setModified()
+ if node.statResponse.ModTime != 0 {
+ // modification time was updated, so re-scan for
+ // child directories
+ f.listDirAsync(dir)
+ }
+ }
+ },
+ )
+}
+
+func (f *Finder) statDirSync(path string) statResponse {
+
+ fileInfo, err := f.filesystem.Lstat(path)
+
+ var stats statResponse
+ if err != nil {
+ // in case of a failure to stat the directory, treat the directory as missing (modTime = 0)
+ return stats
+ }
+ modTime := fileInfo.ModTime()
+ stats = statResponse{}
+ inode, err := f.filesystem.InodeNumber(fileInfo)
+ if err != nil {
+ panic(fmt.Sprintf("Could not get inode number of %v: %v\n", path, err.Error()))
+ }
+ stats.Inode = inode
+ device, err := f.filesystem.DeviceNumber(fileInfo)
+ if err != nil {
+ panic(fmt.Sprintf("Could not get device number of %v: %v\n", path, err.Error()))
+ }
+ stats.Device = device
+ permissionsChangeTime, err := f.filesystem.PermTime(fileInfo)
+
+ if err != nil {
+ panic(fmt.Sprintf("Could not get permissions modification time (CTime) of %v: %v\n", path, err.Error()))
+ }
+ // We're only interested in knowing whether anything about the directory
+ // has changed since last check, so we use the latest of the two
+ // modification times (content modification (mtime) and
+ // permission modification (ctime))
+ if permissionsChangeTime.After(modTime) {
+ modTime = permissionsChangeTime
+ }
+ stats.ModTime = modTime.UnixNano()
+
+ return stats
+}
+
+// pruneCacheCandidates removes the items that we don't want to include in our persistent cache
+func (f *Finder) pruneCacheCandidates(items *DirEntries) {
+
+ for _, fileName := range items.FileNames {
+ for _, abortedName := range f.cacheMetadata.Config.PruneFiles {
+ if fileName == abortedName {
+ items.FileNames = []string{}
+ items.DirNames = []string{}
+ return
+ }
+ }
+ }
+
+ // remove any files that aren't the ones we want to include
+ writeIndex := 0
+ for _, fileName := range items.FileNames {
+ // include only these files
+ for _, includedName := range f.cacheMetadata.Config.IncludeFiles {
+ if fileName == includedName {
+ items.FileNames[writeIndex] = fileName
+ writeIndex++
+ break
+ }
+ }
+ }
+ // resize
+ items.FileNames = items.FileNames[:writeIndex]
+
+ writeIndex = 0
+ for _, dirName := range items.DirNames {
+ items.DirNames[writeIndex] = dirName
+ // ignore other dirs that are known to not be inputs to the build process
+ include := true
+ for _, excludedName := range f.cacheMetadata.Config.ExcludeDirs {
+ if dirName == excludedName {
+ // don't include
+ include = false
+ break
+ }
+ }
+ if include {
+ writeIndex++
+ }
+ }
+ // resize
+ items.DirNames = items.DirNames[:writeIndex]
+}
+
+func (f *Finder) listDirsAsync(nodes []*pathMap) {
+ f.threadPool.Run(
+ func() {
+ for i := range nodes {
+ f.listDirSync(nodes[i])
+ }
+ },
+ )
+}
+
+func (f *Finder) listDirAsync(node *pathMap) {
+ f.threadPool.Run(
+ func() {
+ f.listDirSync(node)
+ },
+ )
+}
+
+func (f *Finder) listDirSync(dir *pathMap) {
+ path := dir.path
+ children, err := f.filesystem.ReadDir(path)
+
+ if err != nil {
+ // if listing the contents of the directory fails (presumably due to
+ // permission denied), then treat the directory as empty
+ children = []os.FileInfo{}
+ }
+
+ var subdirs []string
+ var subfiles []string
+
+ for _, child := range children {
+ linkBits := child.Mode() & os.ModeSymlink
+ isLink := linkBits != 0
+ if child.IsDir() {
+ if !isLink {
+ // Skip symlink dirs.
+ // We don't have to support symlink dirs because
+ // that would cause duplicates.
+ subdirs = append(subdirs, child.Name())
+ }
+ } else {
+ // We do have to support symlink files because the link name might be
+ // different than the target name
+ // (for example, Android.bp -> build/soong/root.bp)
+ subfiles = append(subfiles, child.Name())
+ }
+
+ }
+ parentNode := dir
+
+ entry := &DirEntries{Path: path, DirNames: subdirs, FileNames: subfiles}
+ f.pruneCacheCandidates(entry)
+
+ // create a pathMap node for each relevant subdirectory
+ relevantChildren := map[string]*pathMap{}
+ for _, subdirName := range entry.DirNames {
+ childNode, found := parentNode.children[subdirName]
+ // if we already knew of this directory, then we already have a request pending to Stat it
+ // if we didn't already know of this directory, then we must Stat it now
+ if !found {
+ childNode = parentNode.newChild(subdirName)
+ f.statDirAsync(childNode)
+ }
+ relevantChildren[subdirName] = childNode
+ }
+ // Note that in rare cases, it's possible that we're reducing the set of
+ // children via this statement, if these are all true:
+ // 1. we previously had a cache that knew about subdirectories of parentNode
+ // 2. the user created a prune-file (described in pruneCacheCandidates)
+ // inside <parentNode>, which specifies that the contents of parentNode
+ // are to be ignored.
+ // The fact that it's possible to remove children here means that *pathMap structs
+ // must not be looked up from f.nodes by filepath (and instead must be accessed by
+ // direct pointer) until after every listDirSync completes
+ parentNode.FileNames = entry.FileNames
+ parentNode.children = relevantChildren
+
+}
+
+// listMatches takes a node and a function that specifies which subdirectories and
+// files to include, and listMatches returns the matches
+func (f *Finder) listMatches(node *pathMap,
+ filter WalkFunc) (subDirs []*pathMap, filePaths []string) {
+ entries := DirEntries{
+ FileNames: node.FileNames,
+ }
+ entries.DirNames = make([]string, 0, len(node.children))
+ for childName := range node.children {
+ entries.DirNames = append(entries.DirNames, childName)
+ }
+
+ dirNames, fileNames := filter(entries)
+
+ subDirs = []*pathMap{}
+ filePaths = make([]string, 0, len(fileNames))
+ for _, fileName := range fileNames {
+ filePaths = append(filePaths, joinCleanPaths(node.path, fileName))
+ }
+ subDirs = make([]*pathMap, 0, len(dirNames))
+ for _, childName := range dirNames {
+ child, ok := node.children[childName]
+ if ok {
+ subDirs = append(subDirs, child)
+ }
+ }
+
+ return subDirs, filePaths
+}
+
+// findInCacheMultithreaded spawns potentially multiple goroutines with which to search the cache.
+func (f *Finder) findInCacheMultithreaded(node *pathMap, filter WalkFunc,
+ approxNumThreads int) []string {
+
+ if approxNumThreads < 2 {
+ // Done spawning threads; process remaining directories
+ return f.findInCacheSinglethreaded(node, filter)
+ }
+
+ totalWork := 0
+ for _, child := range node.children {
+ totalWork += child.approximateNumDescendents
+ }
+ childrenResults := make(chan []string, len(node.children))
+
+ subDirs, filePaths := f.listMatches(node, filter)
+
+ // process child directories
+ for _, child := range subDirs {
+ numChildThreads := approxNumThreads * child.approximateNumDescendents / totalWork
+ childProcessor := func(child *pathMap) {
+ childResults := f.findInCacheMultithreaded(child, filter, numChildThreads)
+ childrenResults <- childResults
+ }
+ // If we're allowed to use more than 1 thread to process this directory,
+ // then instead we use 1 thread for each subdirectory.
+ // It would be strange to spawn threads for only some subdirectories.
+ go childProcessor(child)
+ }
+
+ // collect results
+ for i := 0; i < len(subDirs); i++ {
+ childResults := <-childrenResults
+ filePaths = append(filePaths, childResults...)
+ }
+ close(childrenResults)
+
+ return filePaths
+}
+
+// findInCacheSinglethreaded synchronously searches the cache for all matching file paths
+// note findInCacheSinglethreaded runs 2X to 4X as fast by being iterative rather than recursive
+func (f *Finder) findInCacheSinglethreaded(node *pathMap, filter WalkFunc) []string {
+ if node == nil {
+ return []string{}
+ }
+
+ nodes := []*pathMap{node}
+ matches := []string{}
+
+ for len(nodes) > 0 {
+ currentNode := nodes[0]
+ nodes = nodes[1:]
+
+ subDirs, filePaths := f.listMatches(currentNode, filter)
+
+ nodes = append(nodes, subDirs...)
+
+ matches = append(matches, filePaths...)
+ }
+ return matches
+}