/** called during recovery (the error message text below assumes that)
*/
unsigned long long journalReadLSN() {
if( !debug ) {
// in nondebug build, for now, be conservative until more tests written, and apply the whole journal.
// however we will still write the lsn file to exercise that code, and use in _DEBUG build.
return 0;
}
if( !MemoryMappedFile::exists(lsnPath()) ) {
log() << "info no lsn file in journal/ directory" << endl;
return 0;
}
try {
// os can flush as it likes. if it flushes slowly, we will just do extra work on recovery.
// however, given we actually close the file when writing, that seems unlikely.
LSNFile L;
File f;
f.open(lsnPath().string().c_str());
assert(f.is_open());
f.read(0,(char*)&L, sizeof(L));
unsigned long long lsn = L.get();
return lsn;
}
catch(std::exception& e) {
uasserted(13611, str::stream() << "can't read lsn file in journal directory : " << e.what());
}
return 0;
}
/** remember "last sequence number" to speed recoveries
concurrency: called by durThread only.
*/
void Journal::updateLSNFile() {
if( !_writeToLSNNeeded )
return;
durThreadMain.assertWithin();
_writeToLSNNeeded = false;
try {
// os can flush as it likes. if it flushes slowly, we will just do extra work on recovery.
// however, given we actually close the file, that seems unlikely.
File f;
f.open(lsnPath().string().c_str());
if( !f.is_open() ) {
// can get 0 if an i/o error
log() << "warning: open of lsn file failed" << endl;
return;
}
log() << "lsn set " << _lastFlushTime << endl;
LSNFile lsnf;
lsnf.set(_lastFlushTime);
f.write(0, (char*)&lsnf, sizeof(lsnf));
}
catch(std::exception& e) {
log() << "warning: write to lsn file failed " << e.what() << endl;
// keep running (ignore the error). recovery will be slow.
}
}
/** called during recovery (the error message text below assumes that)
*/
unsigned long long journalReadLSN() {
if( !exists(lsnPath()) ) {
log() << "info no lsn file in journal/ directory" << endl;
return 0;
}
try {
// os can flush as it likes. if it flushes slowly, we will just do extra work on recovery.
// however, given we actually close the file when writing, that seems unlikely.
LSNFile L;
File f;
f.open(lsnPath().string().c_str());
assert(f.is_open());
if( f.len() == 0 ) {
// this could be 'normal' if we crashed at the right moment
log() << "info lsn file is zero bytes long" << endl;
return 0;
}
f.read(0,(char*)&L, sizeof(L));
unsigned long long lsn = L.get();
return lsn;
}
catch(std::exception& e) {
uasserted(13611, str::stream() << "can't read lsn file in journal directory : " << e.what());
}
return 0;
}
