bool_t
LFLock_request(LockFileLock *self) {
Hash *file_data;
bool_t wrote_json;
bool_t success = false;
bool_t deletion_failed = false;
if (Folder_Exists(self->folder, self->lock_path)) {
Err_set_error((Err*)LockErr_new(CB_newf("Can't obtain lock: '%o' exists",
self->lock_path)));
return false;
}
// Create the "locks" subdirectory if necessary.
CharBuf *lock_dir_name = (CharBuf*)ZCB_WRAP_STR("locks", 5);
if (!Folder_Exists(self->folder, lock_dir_name)) {
if (!Folder_MkDir(self->folder, lock_dir_name)) {
Err *mkdir_err = (Err*)CERTIFY(Err_get_error(), ERR);
LockErr *err = LockErr_new(CB_newf("Can't create 'locks' directory: %o",
Err_Get_Mess(mkdir_err)));
// Maybe our attempt failed because another process succeeded.
if (Folder_Find_Folder(self->folder, lock_dir_name)) {
DECREF(err);
}
else {
// Nope, everything failed, so bail out.
Err_set_error((Err*)err);
return false;
}
}
}
// Prepare to write pid, lock name, and host to the lock file as JSON.
file_data = Hash_new(3);
Hash_Store_Str(file_data, "pid", 3,
(Obj*)CB_newf("%i32", (int32_t)PID_getpid()));
Hash_Store_Str(file_data, "host", 4, INCREF(self->host));
Hash_Store_Str(file_data, "name", 4, INCREF(self->name));
// Write to a temporary file, then use the creation of a hard link to
// ensure atomic but non-destructive creation of the lockfile with its
// complete contents.
wrote_json = Json_spew_json((Obj*)file_data, self->folder, self->link_path);
if (wrote_json) {
success = Folder_Hard_Link(self->folder, self->link_path,
self->lock_path);
if (!success) {
Err *hard_link_err = (Err*)CERTIFY(Err_get_error(), ERR);
Err_set_error((Err*)LockErr_new(CB_newf("Failed to obtain lock at '%o': %o",
self->lock_path,
Err_Get_Mess(hard_link_err))));
}
deletion_failed = !Folder_Delete(self->folder, self->link_path);
}
else {
Err *spew_json_err = (Err*)CERTIFY(Err_get_error(), ERR);
Err_set_error((Err*)LockErr_new(CB_newf("Failed to obtain lock at '%o': %o",
self->lock_path,
Err_Get_Mess(spew_json_err))));
}
DECREF(file_data);
// Verify that our temporary file got zapped.
if (wrote_json && deletion_failed) {
CharBuf *mess = MAKE_MESS("Failed to delete '%o'", self->link_path);
Err_throw_mess(ERR, mess);
}
return success;
}
LockErr*
LockErr_make(LockErr *self) {
UNUSED_VAR(self);
return LockErr_new(CB_new(0));
}
bool
LFLock_Request_IMP(LockFileLock *self) {
LockFileLockIVARS *const ivars = LFLock_IVARS(self);
bool success = false;
if (Folder_Exists(ivars->folder, ivars->lock_path)) {
Err_set_error((Err*)LockErr_new(Str_newf("Can't obtain lock: '%o' exists",
ivars->lock_path)));
return false;
}
// Create the "locks" subdirectory if necessary.
String *lock_dir_name = (String*)SSTR_WRAP_UTF8("locks", 5);
if (!Folder_Exists(ivars->folder, lock_dir_name)) {
if (!Folder_MkDir(ivars->folder, lock_dir_name)) {
Err *mkdir_err = (Err*)CERTIFY(Err_get_error(), ERR);
LockErr *err = LockErr_new(Str_newf("Can't create 'locks' directory: %o",
Err_Get_Mess(mkdir_err)));
// Maybe our attempt failed because another process succeeded.
if (Folder_Find_Folder(ivars->folder, lock_dir_name)) {
DECREF(err);
}
else {
// Nope, everything failed, so bail out.
Err_set_error((Err*)err);
return false;
}
}
}
// Prepare to write pid, lock name, and host to the lock file as JSON.
Hash *file_data = Hash_new(3);
Hash_Store_Utf8(file_data, "pid", 3,
(Obj*)Str_newf("%i32", (int32_t)PID_getpid()));
Hash_Store_Utf8(file_data, "host", 4, INCREF(ivars->host));
Hash_Store_Utf8(file_data, "name", 4, INCREF(ivars->name));
String *json = Json_to_json((Obj*)file_data);
DECREF(file_data);
// Write to a temporary file, then use the creation of a hard link to
// ensure atomic but non-destructive creation of the lockfile with its
// complete contents.
OutStream *outstream = Folder_Open_Out(ivars->folder, ivars->link_path);
if (!outstream) {
ERR_ADD_FRAME(Err_get_error());
DECREF(json);
return false;
}
struct lockfile_context context;
context.outstream = outstream;
context.json = json;
Err *json_error = Err_trap(S_write_lockfile_json, &context);
bool wrote_json = !json_error;
DECREF(outstream);
DECREF(json);
if (wrote_json) {
success = Folder_Hard_Link(ivars->folder, ivars->link_path,
ivars->lock_path);
if (!success) {
Err *hard_link_err = (Err*)CERTIFY(Err_get_error(), ERR);
Err_set_error((Err*)LockErr_new(Str_newf("Failed to obtain lock at '%o': %o",
ivars->lock_path,
Err_Get_Mess(hard_link_err))));
}
}
else {
Err_set_error((Err*)LockErr_new(Str_newf("Failed to obtain lock at '%o': %o",
ivars->lock_path,
Err_Get_Mess(json_error))));
DECREF(json_error);
}
// Verify that our temporary file got zapped.
bool deletion_failed = !Folder_Delete(ivars->folder, ivars->link_path);
if (deletion_failed) {
String *mess = MAKE_MESS("Failed to delete '%o'", ivars->link_path);
Err_throw_mess(ERR, mess);
}
return success;
}
