On Thu, May 19, 2016 at 10:37 AM, Peter Juhasz <pjuh...@uhusystems.com> wrote:
> Hi all, > > this is somewhat involved so please bear with me. > > We've found a situation where canceling a query may cause the client to > hang, possibly indefinitely. This can happen if the network connection > fails in a specific way. > > The reason for this lies in the way the PQcancel function (which > eventually gets called from the higher level interface's cancel > function) is implemented. It works by opening a second connection to > the postmaster (on the same host/port as the existing connection), > send()-ing a cancellation message via the newly opened connection, then > calling recv() to receive an indication that the message was processed. > > However, if the network fails in a way that the connection appears to > have been established but subsequent packages are dropped silently, > this recv() call will block. > > My questions: > > Is this known? > Is this a bug? > What can be done to fix or work around it, apart from applying a > timeout wrapper the cancel operation as well? > > It does sound familiar. Providing the version number(s) on which you encountered this behavior would be helpful. Or HEAD if you have or are testing against current code. David J.
