bool PlanYieldPolicy::shouldYield() {
if (!allowedToYield())
return false;
invariant(!_planYielding->getOpCtx()->lockState()->inAWriteUnitOfWork());
if (_forceYield)
return true;
return _elapsedTracker.intervalHasElapsed();
}
bool PlanYieldPolicy::yield(RecordFetcher* fetcher) {
invariant(_planYielding);
invariant(allowedToYield());
_forceYield = false;
OperationContext* opCtx = _planYielding->getOpCtx();
invariant(opCtx);
invariant(!opCtx->lockState()->inAWriteUnitOfWork());
// Can't use MONGO_WRITE_CONFLICT_RETRY_LOOP_BEGIN/END since we need to call saveState
// before reseting the transaction.
for (int attempt = 1; true; attempt++) {
try {
// All YIELD_AUTO plans will get here eventually when the elapsed tracker triggers
// that it's time to yield. Whether or not we will actually yield, we need to check
// if this operation has been interrupted. Throws if the interrupt flag is set.
if (_policy == PlanExecutor::YIELD_AUTO) {
opCtx->checkForInterrupt();
}
// No need to yield if the collection is NULL.
if (NULL == _planYielding->collection()) {
return true;
}
try {
_planYielding->saveState();
}
catch (const WriteConflictException& wce) {
invariant(!"WriteConflictException not allowed in saveState");
}
if (_policy == PlanExecutor::WRITE_CONFLICT_RETRY_ONLY) {
// Just reset the snapshot. Leave all LockManager locks alone.
opCtx->recoveryUnit()->commitAndRestart();
}
else {
// Release and reacquire locks.
QueryYield::yieldAllLocks(opCtx, fetcher);
}
return _planYielding->restoreStateWithoutRetrying(opCtx);
}
catch (const WriteConflictException& wce) {
opCtx->getCurOp()->debug().writeConflicts++;
WriteConflictException::logAndBackoff(attempt,
"plan execution restoreState",
_planYielding->collection()->ns().ns());
// retry
}
}
}
