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The API for WaitLatch and friends followed the Unix convention in which waiting for a socket connection to complete is identical to waiting for the socket to accept a write. While Windows provides a select(2) emulation that agrees with that, the native WaitForMultipleObjects API treats them as quite different --- and for some bizarre reason, it will report a not-yet-connected socket as write-ready. libpq itself has so far escaped dealing with this because it waits with select(), but in libpqwalreceiver.c we want to wait using WaitLatchOrSocket. The semantics mismatch resulted in replication connection failures on Windows, but only for remote connections (apparently, localhost connections complete immediately, or at least too fast for anyone to have noticed the problem in single-machine testing). To fix, introduce an additional WL_SOCKET_CONNECTED wait flag for WaitLatchOrSocket, which is identical to WL_SOCKET_WRITEABLE on non-Windows, but results in waiting for FD_CONNECT events on Windows. Ideally, we would also distinguish the two conditions in the API for PQconnectPoll(), but changing that API at this point seems infeasible. Instead, cheat by checking for PQstatus() == CONNECTION_STARTED to determine that we're still waiting for the connection to complete. (This is a cheat mainly because CONNECTION_STARTED is documented as an internal state rather than something callers should rely on. Perhaps we ought to change the documentation ... but this patch doesn't.) Per reports from Jobin Augustine and Igor Neyman. Back-patch to v10 where commit 1e8a85009 exposed this longstanding shortcoming. Andres Freund, minor fix and some code review/beautification by me Discussion: https://postgr.es/m/CAHBggj8g2T+ZDcACZ2FmzX9CTxkWjKBsHd6NkYB4i9Ojf6K1Fw@mail.gmail.com
PostgreSQL Database Management System ===================================== This directory contains the source code distribution of the PostgreSQL database management system. PostgreSQL is an advanced object-relational database management system that supports an extended subset of the SQL standard, including transactions, foreign keys, subqueries, triggers, user-defined types and functions. This distribution also contains C language bindings. PostgreSQL has many language interfaces, many of which are listed here: https://www.postgresql.org/download See the file INSTALL for instructions on how to build and install PostgreSQL. That file also lists supported operating systems and hardware platforms and contains information regarding any other software packages that are required to build or run the PostgreSQL system. Copyright and license information can be found in the file COPYRIGHT. A comprehensive documentation set is included in this distribution; it can be read as described in the installation instructions. The latest version of this software may be obtained at https://www.postgresql.org/download/. For more information look at our web site located at https://www.postgresql.org/.