1package cache
2
3import (
4 "fmt"
5 "io"
6 "io/ioutil"
7 "os"
8 "path"
9 "path/filepath"
10 "strconv"
11 "sync"
12
13 "github.com/MichaelMure/git-bug/bug"
14 "github.com/MichaelMure/git-bug/entity"
15 "github.com/MichaelMure/git-bug/identity"
16 "github.com/MichaelMure/git-bug/repository"
17 "github.com/MichaelMure/git-bug/util/process"
18)
19
20// 1: original format
21// 2: added cache for identities with a reference in the bug cache
22const formatVersion = 2
23
24const lruCacheSize = 100
25
26var _ repository.RepoCommon = &RepoCache{}
27
28// RepoCache is a cache for a Repository. This cache has multiple functions:
29//
30// 1. After being loaded, a Bug is kept in memory in the cache, allowing for fast
31// access later.
32// 2. The cache maintain in memory and on disk a pre-digested excerpt for each bug,
33// allowing for fast querying the whole set of bugs without having to load
34// them individually.
35// 3. The cache guarantee that a single instance of a Bug is loaded at once, avoiding
36// loss of data that we could have with multiple copies in the same process.
37// 4. The same way, the cache maintain in memory a single copy of the loaded identities.
38//
39// The cache also protect the on-disk data by locking the git repository for its
40// own usage, by writing a lock file. Of course, normal git operations are not
41// affected, only git-bug related one.
42type RepoCache struct {
43 // the underlying repo
44 repo repository.ClockedRepo
45
46 // the name of the repository, as defined in the MultiRepoCache
47 name string
48
49 muBug sync.RWMutex
50 // excerpt of bugs data for all bugs
51 bugExcerpts map[entity.Id]*BugExcerpt
52 // bug loaded in memory
53 bugs map[entity.Id]*BugCache
54
55 // presentBugs is an LRU cache that records which bugs the cache has loaded in
56 presentBugs *LRUIdCache
57
58 muIdentity sync.RWMutex
59 // excerpt of identities data for all identities
60 identitiesExcerpts map[entity.Id]*IdentityExcerpt
61 // identities loaded in memory
62 identities map[entity.Id]*IdentityCache
63
64 // the user identity's id, if known
65 userIdentityId entity.Id
66}
67
68func NewRepoCache(r repository.ClockedRepo) (*RepoCache, error) {
69 return NewNamedRepoCache(r, "")
70}
71
72func NewNamedRepoCache(r repository.ClockedRepo, name string) (*RepoCache, error) {
73 c := &RepoCache{
74 repo: r,
75 name: name,
76 bugs: make(map[entity.Id]*BugCache),
77 identities: make(map[entity.Id]*IdentityCache),
78 }
79
80 err := c.lock()
81 if err != nil {
82 return &RepoCache{}, err
83 }
84
85 err = c.load()
86 if err == nil {
87 return c, nil
88 }
89
90 // Cache is either missing, broken or outdated. Rebuilding.
91 err = c.buildCache()
92 if err != nil {
93 return nil, err
94 }
95
96 return c, c.write()
97}
98
99// load will try to read from the disk all the cache files
100func (c *RepoCache) load() error {
101 err := c.loadBugCache()
102 if err != nil {
103 return err
104 }
105 return c.loadIdentityCache()
106}
107
108// write will serialize on disk all the cache files
109func (c *RepoCache) write() error {
110 err := c.writeBugCache()
111 if err != nil {
112 return err
113 }
114 return c.writeIdentityCache()
115}
116
117func (c *RepoCache) lock() error {
118 lockPath := repoLockFilePath(c.repo)
119
120 err := repoIsAvailable(c.repo)
121 if err != nil {
122 return err
123 }
124
125 err = os.MkdirAll(filepath.Dir(lockPath), 0777)
126 if err != nil {
127 return err
128 }
129
130 f, err := os.Create(lockPath)
131 if err != nil {
132 return err
133 }
134
135 pid := fmt.Sprintf("%d", os.Getpid())
136 _, err = f.WriteString(pid)
137 if err != nil {
138 return err
139 }
140
141 return f.Close()
142}
143
144func (c *RepoCache) Close() error {
145 c.muBug.Lock()
146 defer c.muBug.Unlock()
147 c.muIdentity.Lock()
148 defer c.muIdentity.Unlock()
149
150 c.identities = make(map[entity.Id]*IdentityCache)
151 c.identitiesExcerpts = nil
152 c.bugs = nil
153 c.bugExcerpts = nil
154
155 lockPath := repoLockFilePath(c.repo)
156 return os.Remove(lockPath)
157}
158
159func (c *RepoCache) buildCache() error {
160 c.muBug.Lock()
161 defer c.muBug.Unlock()
162 c.muIdentity.Lock()
163 defer c.muIdentity.Unlock()
164
165 _, _ = fmt.Fprintf(os.Stderr, "Building identity cache... ")
166
167 c.identitiesExcerpts = make(map[entity.Id]*IdentityExcerpt)
168
169 allIdentities := identity.ReadAllLocalIdentities(c.repo)
170
171 for i := range allIdentities {
172 if i.Err != nil {
173 return i.Err
174 }
175
176 c.identitiesExcerpts[i.Identity.Id()] = NewIdentityExcerpt(i.Identity)
177 }
178
179 _, _ = fmt.Fprintln(os.Stderr, "Done.")
180
181 _, _ = fmt.Fprintf(os.Stderr, "Building bug cache... ")
182
183 presentBugs, err := NewLRUIdCache(lruCacheSize, c.onEvict)
184 if err != nil {
185 return err
186 }
187 c.presentBugs = presentBugs
188
189 c.bugExcerpts = make(map[entity.Id]*BugExcerpt)
190
191 allBugs := bug.ReadAllLocalBugs(c.repo)
192
193 for i := 0; i < lruCacheSize; i++ {
194 if len(allBugs) == 0 {
195 break
196 }
197
198 b := <-allBugs
199 if b.Err != nil {
200 return b.Err
201 }
202
203 snap := b.Bug.Compile()
204 c.bugExcerpts[b.Bug.Id()] = NewBugExcerpt(b.Bug, &snap)
205 }
206
207 _, _ = fmt.Fprintln(os.Stderr, "Done.")
208 return nil
209}
210
211func repoLockFilePath(repo repository.Repo) string {
212 return path.Join(repo.GetPath(), "git-bug", lockfile)
213}
214
215// repoIsAvailable check is the given repository is locked by a Cache.
216// Note: this is a smart function that will cleanup the lock file if the
217// corresponding process is not there anymore.
218// If no error is returned, the repo is free to edit.
219func repoIsAvailable(repo repository.Repo) error {
220 lockPath := repoLockFilePath(repo)
221
222 // Todo: this leave way for a racey access to the repo between the test
223 // if the file exist and the actual write. It's probably not a problem in
224 // practice because using a repository will be done from user interaction
225 // or in a context where a single instance of git-bug is already guaranteed
226 // (say, a server with the web UI running). But still, that might be nice to
227 // have a mutex or something to guard that.
228
229 // Todo: this will fail if somehow the filesystem is shared with another
230 // computer. Should add a configuration that prevent the cleaning of the
231 // lock file
232
233 f, err := os.Open(lockPath)
234
235 if err != nil && !os.IsNotExist(err) {
236 return err
237 }
238
239 if err == nil {
240 // lock file already exist
241 buf, err := ioutil.ReadAll(io.LimitReader(f, 10))
242 if err != nil {
243 return err
244 }
245 if len(buf) == 10 {
246 return fmt.Errorf("the lock file should be < 10 bytes")
247 }
248
249 pid, err := strconv.Atoi(string(buf))
250 if err != nil {
251 return err
252 }
253
254 if process.IsRunning(pid) {
255 return fmt.Errorf("the repository you want to access is already locked by the process pid %d", pid)
256 }
257
258 // The lock file is just laying there after a crash, clean it
259
260 fmt.Println("A lock file is present but the corresponding process is not, removing it.")
261 err = f.Close()
262 if err != nil {
263 return err
264 }
265
266 err = os.Remove(lockPath)
267 if err != nil {
268 return err
269 }
270 }
271
272 return nil
273}