Where is the code that changes the size of self.heap? How do we know that size(self.heap) is constant? My guess is that some thread changes this; but l is not recomputed.
On 18 Dec 2017 6:59 PM, "hubo" <h...@jiedaibao.com> wrote: > I'm reporting this issue in this mail group, though I don't know if it is > related with PyPy, because it is really strange, and is not able to > reproduce stably. But I hope someone may know the reason or have some > points. > > I'm running some SDN services written in Python with PyPy 5.3.0. The > related code is here: > > https://github.com/hubo1016/vlcp/blob/8022e3a3c67cf4305af503d507640a730ca3949d/vlcp/utils/indexedheap.py#L100 > > The full code is also in the repo, but may be too complex to describe. But > this related piece is quite simple: > > def _siftdown(self, pos): > temp = self.heap[pos] > l = len(self.heap) > while pos * 2 + 1 < l: > cindex = pos * 2 + 1 > pt = self.heap[cindex] > if cindex + 1 < l and self.heap[cindex+1][0] < pt[0]: > cindex = cindex + 1 > pt = self.heap[cindex] > if pt[0] < temp[0]: > self.heap[pos] = pt > self.index[pt[1]] = pos > else: > break > pos = cindex > self.heap[pos] = temp > self.index[temp[1]] = pos > It is a simple heap operation. The service uses a heap to process timers. > When the service is not busy, it usually runs this piece of code several > times per minute. > > I have 32 servers running this service. They are quite stable in about > three months, but one day one of the services crashes on line 100 reporting > IndexError: > pt = self.heap[cindex] > > As you can see, cindex = pos * 2 + 1, which is tested by the while > pre-conditon just two lines before. And there is not any multi-threading > issues here because this piece of code always runs in the same thread. So > it is not possible in theory for this to happen. > > Only the following facts are known about this issue: > > 1. It reproduces - through quite rarely. I've met this kind of > crashes 4 times, each with different machine, so it should not be related > to hardware issuess. Since I've got 32 servers, it might take more than one > year to reproduce with a single server. > 2. It seems not to be related to pressures. All of the crashes happens > at night, when there are little requests. Only some cleanup tasks are > running in fixed interval. > > The services are running with PyPy 5.3.0. I've upgraded a few of them to > 5.9, but it will take a long time to validate whether this still happens. > And It is not validated on CPython too. I'm also trying to collect more > debugging information for this issue, but it is very hard since it rarely > reproduces. > > It is not a serious issue. It could be workarounded with a auto-restart, > but I'm searching the cause. > > > 2017-12-18 > ------------------------------ > hubo > > _______________________________________________ > pypy-dev mailing list > pypy-dev@python.org > https://mail.python.org/mailman/listinfo/pypy-dev > >
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