bool PlanYieldPolicy::shouldYield() {
if (!canAutoYield())
return false;
invariant(!_planYielding->getOpCtx()->lockState()->inAWriteUnitOfWork());
if (_forceYield)
return true;
return _elapsedTracker.intervalHasElapsed();
}
Status PlanYieldPolicy::yield(stdx::function<void()> beforeYieldingFn,
stdx::function<void()> whileYieldingFn) {
invariant(_planYielding);
invariant(canAutoYield());
// After we finish yielding (or in any early return), call resetTimer() to prevent yielding
// again right away. We delay the resetTimer() call so that the clock doesn't start ticking
// until after we return from the yield.
ON_BLOCK_EXIT([this]() { resetTimer(); });
_forceYield = false;
OperationContext* opCtx = _planYielding->getOpCtx();
invariant(opCtx);
invariant(!opCtx->lockState()->inAWriteUnitOfWork());
// Can't use writeConflictRetry 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.
if (_policy == PlanExecutor::YIELD_AUTO) {
MONGO_FAIL_POINT_PAUSE_WHILE_SET(setCheckForInterruptHang);
auto interruptStatus = opCtx->checkForInterruptNoAssert();
if (!interruptStatus.isOK()) {
return interruptStatus;
}
}
try {
_planYielding->saveState();
} catch (const WriteConflictException&) {
invariant(!"WriteConflictException not allowed in saveState");
}
if (_policy == PlanExecutor::WRITE_CONFLICT_RETRY_ONLY) {
// Just reset the snapshot. Leave all LockManager locks alone.
opCtx->recoveryUnit()->abandonSnapshot();
} else {
// Release and reacquire locks.
if (beforeYieldingFn)
beforeYieldingFn();
QueryYield::yieldAllLocks(opCtx, whileYieldingFn, _planYielding->nss());
}
return _planYielding->restoreStateWithoutRetrying();
} catch (const WriteConflictException&) {
CurOp::get(opCtx)->debug().writeConflicts++;
WriteConflictException::logAndBackoff(
attempt, "plan execution restoreState", _planYielding->nss().ns());
// retry
}
}
}
