On Tue, Feb 20, 2018 at 3:18 PM, Craig Ringer <cr...@2ndquadrant.com> wrote:
> On 20 February 2018 at 21:47, Magnus Hagander <mag...@hagander.net> wrote: > >> >> >> On Fri, Feb 16, 2018 at 8:28 AM, Tsunakawa, Takayuki < >> tsunakawa.ta...@jp.fujitsu.com> wrote: >> >>> Hello, >>> >>> postgres.exe on Windows doesn't output a crash dump when it crashes >>> before main() is called. The attached patch fixes this. I'd like this to >>> be back-patched. I'll add this to the next CF. >>> >>> The original problem happened on our customer's production system. >>> Their application sometimes failed to connect to the database. That was >>> because postgres.exe crashed due to access violation (exception code >>> C0000005). But there was no crash dump, so we had difficulty in finding >>> the cause. The frequency was low -- about ten times during half a year. >>> >>> What caused the access violation was Symantec's antivirus software. It >>> seems that sysfer.dll of the software intercepts registry access, during C >>> runtime library initialization, before main() is called. So, the direct >>> cause of this problem is not PostgreSQL. >>> >>> On the other hand, it's PostgreSQL's problem that we can't get the crash >>> dump, which makes the investigation difficult. The cause is that >>> postmaster calls SetErrorMode() to disable the outputing of crash dumps by >>> WER (Windows Error Reporting). This error mode is inherited from >>> postmaster to its children. If a crash happens before the child sets up >>> the exception handler, no crash dump is produced. >>> >> >> The original call to SetErrorMode() was put in there to make sure we >> didn't show a popup message which would then make everything freeze (see >> very old commit 27bff7502f04ee01237ed3f5a997748ae43d3a81). Doesn't this >> turn that back on, so that if you are not actually there to monitor >> something you can end up with stuck processes and exactly the issues we had >> before that one? >> > > Ha, I just went digging for the same. > > We should not disable WER when running as a service (no UI access), it > will not display an interactive dialog. > > I'm not convinced we should disable it at all personally. Things have come > a long way from drwatson.exe . Disabling WER makes it hard to debug > postgres by installing Visual Studio Debugger as the hander (I always > wondered why that didn't work!) and is generally just painful. It prevents > us from collecting data via Microsoft about crashes, should we wish to do > so. And who runs Pg on windows except as a service?! > > I've seen a number of usecases where apps start it alongside the app instead of as a service. I'm not sure how recent those apps are though, and I'm not sure it's better than using a service in the first place (but it does let you install things without being an admin). We really shouldn't *break* that scenario for people. But making it work well for the service usecase should definitely be the priority. -- Magnus Hagander Me: https://www.hagander.net/ <http://www.hagander.net/> Work: https://www.redpill-linpro.com/ <http://www.redpill-linpro.com/>
