Transpiled version (10117L) is out of date.
1 | // the lockFile must be a file separate from any data files. |
2 | // It is created & deleted by this class, and will always have |
3 | // size 0. |
4 | sclass FileBasedLock implements AutoCloseable {
|
5 | File lockFile; |
6 | double timeout = 60.0; // in seconds. refresh happens twice as often |
7 | bool verbose; |
8 | bool haveLock; |
9 | java.util.Timer touchTimer; |
10 | |
11 | // what to put in the lock file when we create it |
12 | settable S contentsForLockFile; |
13 | |
14 | *() {}
|
15 | *(File *lockFile) {}
|
16 | *(File *lockFile, double *timeout) {}
|
17 | |
18 | // returns true iff lock was acquired (or kept) |
19 | synchronized bool tryToLock() {
|
20 | if (haveLock) true; |
21 | |
22 | if (fileExists(lockFile)) {
|
23 | double age = fileAgeInSeconds(lockFile); |
24 | double remaining = timeout-age; |
25 | print("Lock file age: " + lockFile + ": " + iround(age) + " s"
|
26 | + (remaining <= 0 |
27 | ? " - old, deleting" |
28 | : " - please start again in " + nSeconds(iceil(remaining)))); |
29 | |
30 | if (remaining <= 0) {
|
31 | print("Deleting old lock file (program crashed?): " + lockFile + " (age: " + iround(age) + " seconds)");
|
32 | deleteFile(lockFile); |
33 | } |
34 | } |
35 | |
36 | try {
|
37 | mkdirsForFile(lockFile); |
38 | |
39 | // This does the actual atomic file creation |
40 | java.nio.file.Files.createFile(toPath(lockFile)); |
41 | print("Created lock file: " + lockFile);
|
42 | |
43 | // Optionally set the lock file's contents |
44 | if (nempty(contentsForLockFile)) |
45 | writeContents(); |
46 | |
47 | acquired(); |
48 | true; |
49 | } catch e {
|
50 | printExceptionShort("Can't lock", e);
|
51 | false; |
52 | } |
53 | } |
54 | |
55 | void writeContents {
|
56 | saveTextFileWithoutTemp(lockFile, unnull(contentsForLockFile)); |
57 | } |
58 | |
59 | private void acquired {
|
60 | set haveLock; |
61 | startTouchTimer(); |
62 | } |
63 | |
64 | void forceLock ctex {
|
65 | print("Force-locking " + lockFile);
|
66 | writeContents(); |
67 | acquired(); |
68 | } |
69 | |
70 | S lockError() {
|
71 | ret "Couldn't aquire lock file: " + lockFile; |
72 | } |
73 | |
74 | void lockOrFail {
|
75 | if (!tryToLock()) |
76 | fail(lockError()); |
77 | } |
78 | |
79 | synchronized void startTouchTimer {
|
80 | if (touchTimer != null) ret; |
81 | double interval = timeout/2; |
82 | touchTimer = doEvery(interval, r doTouch); |
83 | if (verbose) print("Touch timer started for " + lockFile + " (" + interval + "s)");
|
84 | } |
85 | |
86 | synchronized void doTouch() pcall {
|
87 | if (haveLock) {
|
88 | if (verbose) print("Touching lock file: " + lockFile);
|
89 | //touchExistingFile(lockFile); |
90 | touchFile(lockFile); |
91 | } |
92 | } |
93 | |
94 | public synchronized void close() pcall {
|
95 | dispose touchTimer; |
96 | if (haveLock) {
|
97 | haveLock = false; |
98 | if (verbose) print("Deleting lock file: " + lockFile);
|
99 | deleteFile(lockFile); |
100 | } |
101 | } |
102 | |
103 | synchronized void _simulateCrash {
|
104 | dispose touchTimer; |
105 | } |
106 | |
107 | void deleteOnExit {
|
108 | if (haveLock) |
109 | lockFile.deleteOnExit(); |
110 | } |
111 | |
112 | S actualContents() {
|
113 | ret loadTextFile(lockFile); |
114 | } |
115 | |
116 | bool hasExpectedContents() {
|
117 | ret eq(unnull(contentsForLockFile), actualContents()); |
118 | } |
119 | } |
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| Snippet ID: | #1029788 |
| Snippet name: | FileBasedLock (crash-safe, should work even over NFS) |
| Eternal ID of this version: | #1029788/44 |
| Text MD5: | 38f91f36d9d25d5119cdc81c262e7b1f |
| Author: | stefan |
| Category: | javax / io |
| Type: | JavaX fragment (include) |
| Public (visible to everyone): | Yes |
| Archived (hidden from active list): | No |
| Created/modified: | 2022-11-30 16:56:19 |
| Source code size: | 3082 bytes / 119 lines |
| Pitched / IR pitched: | No / No |
| Views / Downloads: | 375 / 847 |
| Version history: | 43 change(s) |
| Referenced in: | [show references] |