From 14c794d9699f7b9f27d1a4ec026f748c6b7d8853 Mon Sep 17 00:00:00 2001 From: Tristan Partin Date: Tue, 30 Jan 2024 15:40:57 -0600 Subject: [PATCH v11 1/2] Expose PQsocketPoll for frontends PQsocketPoll should help with state machine processing when connecting to a database asynchronously via PQconnectStart(). --- doc/src/sgml/libpq.sgml | 40 +++++++++++++++++++++++++++++++- src/interfaces/libpq/exports.txt | 1 + src/interfaces/libpq/fe-misc.c | 7 +++--- src/interfaces/libpq/libpq-fe.h | 4 ++++ 4 files changed, 47 insertions(+), 5 deletions(-) diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml index d3e87056f2c..e69feacfe6a 100644 --- a/doc/src/sgml/libpq.sgml +++ b/doc/src/sgml/libpq.sgml @@ -262,6 +262,41 @@ PGconn *PQsetdb(char *pghost, + + PQsocketPollPQsocketPoll + + + nonblocking connection + Poll a connection's underlying socket descriptor retrieved with . + +int PQsocketPoll(int sock, int forRead, int forWrite, time_t end_time); + + + + + This function sets up polling of a file descriptor. The underlying function is either + poll(2) or select(2), depending on platform + support. The primary use of this function is iterating through the connection sequence + described in the documentation of . If + forRead is specified, the function waits for the socket to be ready + for reading. If forWrite is specified, the function waits for the + socket to be ready for write. See POLLIN and POLLOUT + from poll(2), or readfds and + writefds from select(2) for more information. If + end_time is not -1, it specifies the time at which + this function should stop waiting for the condition to be met. + + + + The function returns a value greater than 0 if the specified condition + is met, 0 if a timeout occurred, or -1 if an error + occurred. The error can be retrieved by checking the errno(3) value. In + the event forRead and forWrite are not set, the + function immediately returns a timeout condition. + + + + PQconnectStartParamsPQconnectStartParams PQconnectStartPQconnectStart @@ -358,7 +393,10 @@ PostgresPollingStatusType PQconnectPoll(PGconn *conn); Loop thus: If PQconnectPoll(conn) last returned PGRES_POLLING_READING, wait until the socket is ready to read (as indicated by select(), poll(), or - similar system function). + similar system function). Note that PQsocketPoll + can help reduce boilerplate by abstracting the setup of + select(2) or poll(2) if it is + available on your system. Then call PQconnectPoll(conn) again. Conversely, if PQconnectPoll(conn) last returned PGRES_POLLING_WRITING, wait until the socket is ready diff --git a/src/interfaces/libpq/exports.txt b/src/interfaces/libpq/exports.txt index 9fbd3d34074..1e48d37677d 100644 --- a/src/interfaces/libpq/exports.txt +++ b/src/interfaces/libpq/exports.txt @@ -202,3 +202,4 @@ PQcancelSocket 199 PQcancelErrorMessage 200 PQcancelReset 201 PQcancelFinish 202 +PQsocketPoll 203 diff --git a/src/interfaces/libpq/fe-misc.c b/src/interfaces/libpq/fe-misc.c index f2fc78a481c..f562cd8d344 100644 --- a/src/interfaces/libpq/fe-misc.c +++ b/src/interfaces/libpq/fe-misc.c @@ -55,7 +55,6 @@ static int pqPutMsgBytes(const void *buf, size_t len, PGconn *conn); static int pqSendSome(PGconn *conn, int len); static int pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time); -static int pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time); /* * PQlibVersion: return the libpq version number @@ -1059,7 +1058,7 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time) /* We will retry as long as we get EINTR */ do - result = pqSocketPoll(conn->sock, forRead, forWrite, end_time); + result = PQsocketPoll(conn->sock, forRead, forWrite, end_time); while (result < 0 && SOCK_ERRNO == EINTR); if (result < 0) @@ -1083,8 +1082,8 @@ pqSocketCheck(PGconn *conn, int forRead, int forWrite, time_t end_time) * Timeout is infinite if end_time is -1. Timeout is immediate (no blocking) * if end_time is 0 (or indeed, any time before now). */ -static int -pqSocketPoll(int sock, int forRead, int forWrite, time_t end_time) +int +PQsocketPoll(int sock, int forRead, int forWrite, time_t end_time) { /* We use poll(2) if available, otherwise select(2) */ #ifdef HAVE_POLL diff --git a/src/interfaces/libpq/libpq-fe.h b/src/interfaces/libpq/libpq-fe.h index 09b485bd2bc..8d3c5c6f662 100644 --- a/src/interfaces/libpq/libpq-fe.h +++ b/src/interfaces/libpq/libpq-fe.h @@ -21,6 +21,7 @@ extern "C" #endif #include +#include /* * postgres_ext.h defines the backend's externally visible types, @@ -670,6 +671,9 @@ extern int lo_export(PGconn *conn, Oid lobjId, const char *filename); /* Get the version of the libpq library in use */ extern int PQlibVersion(void); +/* Poll a socket for reading and/or writing with an optional timeout */ +extern int PQsocketPoll(int sock, int forRead, int forWrite, time_t end_time); + /* Determine length of multibyte encoded char at *s */ extern int PQmblen(const char *s, int encoding); -- Tristan Partin Neon (https://neon.tech)