mirror of
https://github.com/MichaelMure/git-bug.git
synced 2024-12-15 18:23:08 +03:00
280 lines
6.8 KiB
Go
280 lines
6.8 KiB
Go
package cache
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import (
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"fmt"
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"io"
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"io/ioutil"
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"os"
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"strconv"
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"sync"
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"github.com/MichaelMure/git-bug/bug"
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"github.com/MichaelMure/git-bug/entity"
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"github.com/MichaelMure/git-bug/identity"
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"github.com/MichaelMure/git-bug/repository"
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"github.com/MichaelMure/git-bug/util/process"
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)
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// 1: original format
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// 2: added cache for identities with a reference in the bug cache
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// 3: no more legacy identity
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// 4: entities make their IDs from data, not git commit
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const formatVersion = 4
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// The maximum number of bugs loaded in memory. After that, eviction will be done.
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const defaultMaxLoadedBugs = 1000
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var _ repository.RepoCommon = &RepoCache{}
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var _ repository.RepoConfig = &RepoCache{}
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var _ repository.RepoKeyring = &RepoCache{}
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// RepoCache is a cache for a Repository. This cache has multiple functions:
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//
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// 1. After being loaded, a Bug is kept in memory in the cache, allowing for fast
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// access later.
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// 2. The cache maintain in memory and on disk a pre-digested excerpt for each bug,
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// allowing for fast querying the whole set of bugs without having to load
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// them individually.
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// 3. The cache guarantee that a single instance of a Bug is loaded at once, avoiding
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// loss of data that we could have with multiple copies in the same process.
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// 4. The same way, the cache maintain in memory a single copy of the loaded identities.
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//
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// The cache also protect the on-disk data by locking the git repository for its
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// own usage, by writing a lock file. Of course, normal git operations are not
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// affected, only git-bug related one.
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type RepoCache struct {
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// the underlying repo
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repo repository.ClockedRepo
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// the name of the repository, as defined in the MultiRepoCache
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name string
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// maximum number of loaded bugs
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maxLoadedBugs int
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muBug sync.RWMutex
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// excerpt of bugs data for all bugs
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bugExcerpts map[entity.Id]*BugExcerpt
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// bug loaded in memory
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bugs map[entity.Id]*BugCache
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// loadedBugs is an LRU cache that records which bugs the cache has loaded in
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loadedBugs *LRUIdCache
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muIdentity sync.RWMutex
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// excerpt of identities data for all identities
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identitiesExcerpts map[entity.Id]*IdentityExcerpt
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// identities loaded in memory
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identities map[entity.Id]*IdentityCache
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// the user identity's id, if known
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userIdentityId entity.Id
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}
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func NewRepoCache(r repository.ClockedRepo) (*RepoCache, error) {
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return NewNamedRepoCache(r, "")
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}
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func NewNamedRepoCache(r repository.ClockedRepo, name string) (*RepoCache, error) {
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c := &RepoCache{
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repo: r,
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name: name,
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maxLoadedBugs: defaultMaxLoadedBugs,
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bugs: make(map[entity.Id]*BugCache),
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loadedBugs: NewLRUIdCache(),
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identities: make(map[entity.Id]*IdentityCache),
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}
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err := c.lock()
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if err != nil {
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return &RepoCache{}, err
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}
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err = c.load()
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if err == nil {
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return c, nil
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}
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// Cache is either missing, broken or outdated. Rebuilding.
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err = c.buildCache()
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if err != nil {
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return nil, err
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}
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return c, c.write()
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}
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// setCacheSize change the maximum number of loaded bugs
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func (c *RepoCache) setCacheSize(size int) {
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c.maxLoadedBugs = size
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c.evictIfNeeded()
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}
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// load will try to read from the disk all the cache files
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func (c *RepoCache) load() error {
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err := c.loadBugCache()
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if err != nil {
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return err
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}
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return c.loadIdentityCache()
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}
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// write will serialize on disk all the cache files
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func (c *RepoCache) write() error {
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err := c.writeBugCache()
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if err != nil {
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return err
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}
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return c.writeIdentityCache()
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}
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func (c *RepoCache) lock() error {
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err := repoIsAvailable(c.repo)
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if err != nil {
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return err
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}
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f, err := c.repo.LocalStorage().Create(lockfile)
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if err != nil {
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return err
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}
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pid := fmt.Sprintf("%d", os.Getpid())
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_, err = f.Write([]byte(pid))
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if err != nil {
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return err
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}
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return f.Close()
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}
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func (c *RepoCache) Close() error {
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c.muBug.Lock()
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defer c.muBug.Unlock()
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c.muIdentity.Lock()
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defer c.muIdentity.Unlock()
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c.identities = make(map[entity.Id]*IdentityCache)
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c.identitiesExcerpts = nil
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c.bugs = make(map[entity.Id]*BugCache)
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c.bugExcerpts = nil
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err := c.repo.Close()
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if err != nil {
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return err
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}
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return c.repo.LocalStorage().Remove(lockfile)
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}
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func (c *RepoCache) buildCache() error {
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// TODO: make that parallel
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c.muBug.Lock()
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defer c.muBug.Unlock()
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c.muIdentity.Lock()
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defer c.muIdentity.Unlock()
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_, _ = fmt.Fprintf(os.Stderr, "Building identity cache... ")
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c.identitiesExcerpts = make(map[entity.Id]*IdentityExcerpt)
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allIdentities := identity.ReadAllLocal(c.repo)
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for i := range allIdentities {
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if i.Err != nil {
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return i.Err
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}
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c.identitiesExcerpts[i.Identity.Id()] = NewIdentityExcerpt(i.Identity)
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}
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_, _ = fmt.Fprintln(os.Stderr, "Done.")
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_, _ = fmt.Fprintf(os.Stderr, "Building bug cache... ")
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c.bugExcerpts = make(map[entity.Id]*BugExcerpt)
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allBugs := bug.ReadAll(c.repo)
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// wipe the index just to be sure
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err := c.repo.ClearBleveIndex("bug")
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if err != nil {
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return err
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}
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for b := range allBugs {
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if b.Err != nil {
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return b.Err
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}
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snap := b.Bug.Compile()
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c.bugExcerpts[b.Bug.Id()] = NewBugExcerpt(b.Bug, &snap)
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if err := c.addBugToSearchIndex(&snap); err != nil {
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return err
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}
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}
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_, _ = fmt.Fprintln(os.Stderr, "Done.")
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return nil
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}
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// repoIsAvailable check is the given repository is locked by a Cache.
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// Note: this is a smart function that will cleanup the lock file if the
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// corresponding process is not there anymore.
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// If no error is returned, the repo is free to edit.
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func repoIsAvailable(repo repository.RepoStorage) error {
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// Todo: this leave way for a racey access to the repo between the test
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// if the file exist and the actual write. It's probably not a problem in
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// practice because using a repository will be done from user interaction
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// or in a context where a single instance of git-bug is already guaranteed
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// (say, a server with the web UI running). But still, that might be nice to
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// have a mutex or something to guard that.
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// Todo: this will fail if somehow the filesystem is shared with another
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// computer. Should add a configuration that prevent the cleaning of the
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// lock file
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f, err := repo.LocalStorage().Open(lockfile)
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if err != nil && !os.IsNotExist(err) {
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return err
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}
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if err == nil {
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// lock file already exist
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buf, err := ioutil.ReadAll(io.LimitReader(f, 10))
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if err != nil {
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return err
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}
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if len(buf) == 10 {
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return fmt.Errorf("the lock file should be < 10 bytes")
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}
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pid, err := strconv.Atoi(string(buf))
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if err != nil {
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return err
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}
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if process.IsRunning(pid) {
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return fmt.Errorf("the repository you want to access is already locked by the process pid %d", pid)
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}
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// The lock file is just laying there after a crash, clean it
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fmt.Println("A lock file is present but the corresponding process is not, removing it.")
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err = f.Close()
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if err != nil {
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return err
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}
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err = repo.LocalStorage().Remove(lockfile)
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if err != nil {
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return err
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}
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}
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return nil
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}
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