package cache import ( "fmt" "io" "io/ioutil" "os" "path" "path/filepath" "strconv" "sync" "github.com/MichaelMure/git-bug/bug" "github.com/MichaelMure/git-bug/entity" "github.com/MichaelMure/git-bug/identity" "github.com/MichaelMure/git-bug/repository" "github.com/MichaelMure/git-bug/util/process" ) // 1: original format // 2: added cache for identities with a reference in the bug cache // 3: CreateUnixTime --> createUnixTime, EditUnixTime --> editUnixTime const formatVersion = 3 var _ repository.RepoCommon = &RepoCache{} // RepoCache is a cache for a Repository. This cache has multiple functions: // // 1. After being loaded, a Bug is kept in memory in the cache, allowing for fast // access later. // 2. The cache maintain in memory and on disk a pre-digested excerpt for each bug, // allowing for fast querying the whole set of bugs without having to load // them individually. // 3. The cache guarantee that a single instance of a Bug is loaded at once, avoiding // loss of data that we could have with multiple copies in the same process. // 4. The same way, the cache maintain in memory a single copy of the loaded identities. // // The cache also protect the on-disk data by locking the git repository for its // own usage, by writing a lock file. Of course, normal git operations are not // affected, only git-bug related one. type RepoCache struct { // the underlying repo repo repository.ClockedRepo // the name of the repository, as defined in the MultiRepoCache name string muBug sync.RWMutex // excerpt of bugs data for all bugs bugExcerpts map[entity.Id]*BugExcerpt // bug loaded in memory bugs map[entity.Id]*BugCache muIdentity sync.RWMutex // excerpt of identities data for all identities identitiesExcerpts map[entity.Id]*IdentityExcerpt // identities loaded in memory identities map[entity.Id]*IdentityCache // the user identity's id, if known userIdentityId entity.Id } func NewRepoCache(r repository.ClockedRepo) (*RepoCache, error) { return NewNamedRepoCache(r, "") } func NewNamedRepoCache(r repository.ClockedRepo, name string) (*RepoCache, error) { c := &RepoCache{ repo: r, name: name, bugs: make(map[entity.Id]*BugCache), identities: make(map[entity.Id]*IdentityCache), } err := c.lock() if err != nil { return &RepoCache{}, err } err = c.load() if err == nil { return c, nil } // Cache is either missing, broken or outdated. Rebuilding. err = c.buildCache() if err != nil { return nil, err } return c, c.write() } // load will try to read from the disk all the cache files func (c *RepoCache) load() error { err := c.loadBugCache() if err != nil { return err } return c.loadIdentityCache() } // write will serialize on disk all the cache files func (c *RepoCache) write() error { err := c.writeBugCache() if err != nil { return err } return c.writeIdentityCache() } func (c *RepoCache) lock() error { lockPath := repoLockFilePath(c.repo) err := repoIsAvailable(c.repo) if err != nil { return err } err = os.MkdirAll(filepath.Dir(lockPath), 0777) if err != nil { return err } f, err := os.Create(lockPath) if err != nil { return err } pid := fmt.Sprintf("%d", os.Getpid()) _, err = f.WriteString(pid) if err != nil { return err } return f.Close() } func (c *RepoCache) Close() error { c.muBug.Lock() defer c.muBug.Unlock() c.muIdentity.Lock() defer c.muIdentity.Unlock() c.identities = make(map[entity.Id]*IdentityCache) c.identitiesExcerpts = nil c.bugs = make(map[entity.Id]*BugCache) c.bugExcerpts = nil lockPath := repoLockFilePath(c.repo) return os.Remove(lockPath) } func (c *RepoCache) buildCache() error { c.muBug.Lock() defer c.muBug.Unlock() c.muIdentity.Lock() defer c.muIdentity.Unlock() _, _ = fmt.Fprintf(os.Stderr, "Building identity cache... ") c.identitiesExcerpts = make(map[entity.Id]*IdentityExcerpt) allIdentities := identity.ReadAllLocalIdentities(c.repo) for i := range allIdentities { if i.Err != nil { return i.Err } c.identitiesExcerpts[i.Identity.Id()] = NewIdentityExcerpt(i.Identity) } _, _ = fmt.Fprintln(os.Stderr, "Done.") _, _ = fmt.Fprintf(os.Stderr, "Building bug cache... ") c.bugExcerpts = make(map[entity.Id]*BugExcerpt) allBugs := bug.ReadAllLocalBugs(c.repo) for b := range allBugs { if b.Err != nil { return b.Err } snap := b.Bug.Compile() c.bugExcerpts[b.Bug.Id()] = NewBugExcerpt(b.Bug, &snap) } _, _ = fmt.Fprintln(os.Stderr, "Done.") return nil } func repoLockFilePath(repo repository.Repo) string { return path.Join(repo.GetPath(), "git-bug", lockfile) } // repoIsAvailable check is the given repository is locked by a Cache. // Note: this is a smart function that will cleanup the lock file if the // corresponding process is not there anymore. // If no error is returned, the repo is free to edit. func repoIsAvailable(repo repository.Repo) error { lockPath := repoLockFilePath(repo) // Todo: this leave way for a racey access to the repo between the test // if the file exist and the actual write. It's probably not a problem in // practice because using a repository will be done from user interaction // or in a context where a single instance of git-bug is already guaranteed // (say, a server with the web UI running). But still, that might be nice to // have a mutex or something to guard that. // Todo: this will fail if somehow the filesystem is shared with another // computer. Should add a configuration that prevent the cleaning of the // lock file f, err := os.Open(lockPath) if err != nil && !os.IsNotExist(err) { return err } if err == nil { // lock file already exist buf, err := ioutil.ReadAll(io.LimitReader(f, 10)) if err != nil { return err } if len(buf) == 10 { return fmt.Errorf("the lock file should be < 10 bytes") } pid, err := strconv.Atoi(string(buf)) if err != nil { return err } if process.IsRunning(pid) { return fmt.Errorf("the repository you want to access is already locked by the process pid %d", pid) } // The lock file is just laying there after a crash, clean it fmt.Println("A lock file is present but the corresponding process is not, removing it.") err = f.Close() if err != nil { return err } err = os.Remove(lockPath) if err != nil { return err } } return nil }