Re: [HACKERS] LIBPQ patches ... - Mailing list pgsql-hackers

Looks fine.  I have talked to someone about doing no-blocking
connections in the past.  Maybe this the same person.

I will let someone else comment on whether the protocol changes are
correct.


> 
> Does anyone have anything against me applying this to the current source
> tree?  
> 
> 
> Marc G. Fournier                   ICQ#7615664               IRC Nick: Scrappy
> Systems Administrator @ hub.org 
> primary: scrappy@hub.org           secondary: scrappy@{freebsd|postgresql}.org 
> 
> ---------- Forwarded message ----------
> Date: Fri, 17 Dec 1999 13:51:50 -0800 (PST)
> From: Alfred Perlstein <bright@wintelcom.net>
> To: The Hermit Hacker <scrappy@hub.org>
> Subject: Re: pctrackd updates and such
> 
> On Fri, 17 Dec 1999, The Hermit Hacker wrote:
> 
> > 
> > Okay, first thing...can you redo these as context diffs?  We generally
> > refuse *any* patches that aren't context...
> 
> sure.
> 
> > 
> > Second, are these against a reasonably current snapshot of PostgreSQL
> > (aka. the upcoming v7), or v6.5.3 release?  If v6.5.3, we're gonna need to
> > get these v7.x ready before we can commit them...
> 
> they are against a checked out cvs copy as of a couple days ago,
> and should apply cleanly to what's in the current repo.
> 
> > Once both of the above conditions are in place, and after I get back from
> > BC, I'll work on  getting these into the v7.0 release...or, at least,
> > talked/commented about if there are any objections...
> > 
> > I'm outta here for 10 days...Happy Holidays and talk with ya when I get
> > back...
> 
> ok, cool see you soon. :)
> 
> -Alfred
> 
> don't forget the problem with sending queries that may occur:
> 
> i'm not sure if handlesendfailure() can cope with only sending
> a 'Q' to the backend, we may have to work out reservations or
> something for space, another idea would be to implement a 
> pqWritev() of some sort that would take an array of pointers
> and lengths to send to the backend and only allow any data to
> go into the backend if the entire string can fit.
> 
> then again, handlesendfailure may work, but doing reservations
> for the send buffer seems cleaner...
> 
> diff's contexted against pgsql-'current':
> 
> 
> Index: fe-connect.c
> ===================================================================
> RCS file: /home/pgcvs/pgsql/src/interfaces/libpq/fe-connect.c,v
> retrieving revision 1.108
> diff -u -c -r1.108 fe-connect.c
> cvs diff: conflicting specifications of output style
> *** fe-connect.c    1999/12/02 00:26:15    1.108
> --- fe-connect.c    1999/12/14 09:42:24
> ***************
> *** 595,625 ****
>       return 0;
>   }
>   
> - 
> - /* ----------
> -  * connectMakeNonblocking -
> -  * Make a connection non-blocking.
> -  * Returns 1 if successful, 0 if not.
> -  * ----------
> -  */
> - static int
> - connectMakeNonblocking(PGconn *conn)
> - {
> - #ifndef WIN32
> -     if (fcntl(conn->sock, F_SETFL, O_NONBLOCK) < 0)
> - #else
> -     if (ioctlsocket(conn->sock, FIONBIO, &on) != 0)
> - #endif
> -     {
> -         printfPQExpBuffer(&conn->errorMessage,
> -                           "connectMakeNonblocking -- fcntl() failed: errno=%d\n%s\n",
> -                           errno, strerror(errno));
> -         return 0;
> -     }
> - 
> -     return 1;
> - }
> - 
>   /* ----------
>    * connectNoDelay -
>    * Sets the TCP_NODELAY socket option.
> --- 595,600 ----
> ***************
> *** 792,798 ****
>        *   Ewan Mellor <eem21@cam.ac.uk>.
>        * ---------- */
>   #if (!defined(WIN32) || defined(WIN32_NON_BLOCKING_CONNECTIONS)) && !defined(USE_SSL)
> !     if (!connectMakeNonblocking(conn))
>           goto connect_errReturn;
>   #endif    
>   
> --- 767,773 ----
>        *   Ewan Mellor <eem21@cam.ac.uk>.
>        * ---------- */
>   #if (!defined(WIN32) || defined(WIN32_NON_BLOCKING_CONNECTIONS)) && !defined(USE_SSL)
> !     if (PQsetnonblocking(conn, TRUE) != 0)
>           goto connect_errReturn;
>   #endif    
>   
> ***************
> *** 904,910 ****
>       /* This makes the connection non-blocking, for all those cases which forced us
>          not to do it above. */
>   #if (defined(WIN32) && !defined(WIN32_NON_BLOCKING_CONNECTIONS)) || defined(USE_SSL)
> !     if (!connectMakeNonblocking(conn))
>           goto connect_errReturn;
>   #endif    
>   
> --- 879,885 ----
>       /* This makes the connection non-blocking, for all those cases which forced us
>          not to do it above. */
>   #if (defined(WIN32) && !defined(WIN32_NON_BLOCKING_CONNECTIONS)) || defined(USE_SSL)
> !     if (PQsetnonblocking(conn, TRUE) != 0)
>           goto connect_errReturn;
>   #endif    
>   
> ***************
> *** 1702,1707 ****
> --- 1677,1683 ----
>       conn->inBuffer = (char *) malloc(conn->inBufSize);
>       conn->outBufSize = 8 * 1024;
>       conn->outBuffer = (char *) malloc(conn->outBufSize);
> +     conn->nonblocking = FALSE;
>       initPQExpBuffer(&conn->errorMessage);
>       initPQExpBuffer(&conn->workBuffer);
>       if (conn->inBuffer == NULL ||
> ***************
> *** 1811,1816 ****
> --- 1787,1793 ----
>       conn->lobjfuncs = NULL;
>       conn->inStart = conn->inCursor = conn->inEnd = 0;
>       conn->outCount = 0;
> +     conn->nonblocking = FALSE;
>   
>   }
>   
> Index: fe-exec.c
> ===================================================================
> RCS file: /home/pgcvs/pgsql/src/interfaces/libpq/fe-exec.c,v
> retrieving revision 1.86
> diff -u -c -r1.86 fe-exec.c
> cvs diff: conflicting specifications of output style
> *** fe-exec.c    1999/11/11 00:10:14    1.86
> --- fe-exec.c    1999/12/14 05:55:11
> ***************
> *** 13,18 ****
> --- 13,19 ----
>    */
>   #include <errno.h>
>   #include <ctype.h>
> + #include <fcntl.h>
>   
>   #include "postgres.h"
>   #include "libpq-fe.h"
> ***************
> *** 24,30 ****
>   #include <unistd.h>
>   #endif
>   
> - 
>   /* keep this in same order as ExecStatusType in libpq-fe.h */
>   const char *const pgresStatus[] = {
>       "PGRES_EMPTY_QUERY",
> --- 25,30 ----
> ***************
> *** 574,580 ****
> --- 574,588 ----
>        * we will NOT block waiting for more input.
>        */
>       if (pqReadData(conn) < 0)
> +     {
> +         /*
> +          * try to flush the send-queue otherwise we may never get a 
> +          * resonce for something that may not have already been sent
> +          * because it's in our write buffer!
> +          */
> +         pqFlush(conn);
>           return 0;
> +     }
>       /* Parsing of the data waits till later. */
>       return 1;
>   }
> ***************
> *** 1088,1095 ****
> --- 1096,1112 ----
>   {
>       PGresult   *result;
>       PGresult   *lastResult;
> +     bool    savedblocking;
>   
>       /*
> +      * we assume anyone calling PQexec wants blocking behaviour,
> +      * we force the blocking status of the connection to blocking
> +      * for the duration of this function and restore it on return
> +      */
> +     savedblocking = PQisnonblocking(conn);
> +     PQsetnonblocking(conn, FALSE);
> + 
> +     /*
>        * Silently discard any prior query result that application didn't
>        * eat. This is probably poor design, but it's here for backward
>        * compatibility.
> ***************
> *** 1102,1115 ****
>               PQclear(result);
>               printfPQExpBuffer(&conn->errorMessage,
>                   "PQexec: you gotta get out of a COPY state yourself.\n");
> !             return NULL;
>           }
>           PQclear(result);
>       }
>   
>       /* OK to send the message */
>       if (!PQsendQuery(conn, query))
> !         return NULL;
>   
>       /*
>        * For backwards compatibility, return the last result if there are
> --- 1119,1133 ----
>               PQclear(result);
>               printfPQExpBuffer(&conn->errorMessage,
>                   "PQexec: you gotta get out of a COPY state yourself.\n");
> !             /* restore blocking status */
> !             goto errout;
>           }
>           PQclear(result);
>       }
>   
>       /* OK to send the message */
>       if (!PQsendQuery(conn, query))
> !         goto errout;
>   
>       /*
>        * For backwards compatibility, return the last result if there are
> ***************
> *** 1142,1148 ****
> --- 1160,1172 ----
>               result->resultStatus == PGRES_COPY_OUT)
>               break;
>       }
> + 
> +     PQsetnonblocking(conn, savedblocking);
>       return lastResult;
> + 
> + errout:
> +     PQsetnonblocking(conn, savedblocking);
> +     return NULL;
>   }
>   
>   
> ***************
> *** 1431,1438 ****
>                "PQendcopy() -- I don't think there's a copy in progress.\n");
>           return 1;
>       }
>   
> !     (void) pqFlush(conn);        /* make sure no data is waiting to be sent */
>   
>       /* Return to active duty */
>       conn->asyncStatus = PGASYNC_BUSY;
> --- 1455,1468 ----
>                "PQendcopy() -- I don't think there's a copy in progress.\n");
>           return 1;
>       }
> + 
> +     /* make sure no data is waiting to be sent */
> +     if (pqFlush(conn))
> +         return (1);
>   
> !     /* non blocking connections may have to abort at this point. */
> !     if (PQisnonblocking(conn) && PQisBusy(conn))
> !         return (1);
>   
>       /* Return to active duty */
>       conn->asyncStatus = PGASYNC_BUSY;
> ***************
> *** 2025,2028 ****
> --- 2055,2126 ----
>           return 1;
>       else
>           return 0;
> + }
> + 
> + /* PQsetnonblocking:
> +      sets the PGconn's database connection non-blocking if the arg is TRUE
> +      or makes it non-blocking if the arg is FALSE, this will not protect
> +      you from PQexec(), you'll only be safe when using the non-blocking
> +      API
> +      Needs to be called only on a connected database connection.
> + */
> + 
> + int
> + PQsetnonblocking(PGconn *conn, int arg)
> + {
> +     int    fcntlarg;
> + 
> +     arg = (arg == TRUE) ? 1 : 0;
> +     if (arg == conn->nonblocking)
> +         return (0);
> + 
> + #ifdef USE_SSL
> +     if (conn->ssl)
> +     {
> +         printfPQExpBuffer(&conn->errorMessage,
> +             "PQsetnonblocking() -- not supported when using SSL\n");
> +         return (-1);
> +     }
> + #endif /* USE_SSL */
> + 
> + #ifndef WIN32
> +     fcntlarg = fcntl(conn->sock, F_GETFL, 0);
> +     if (fcntlarg == -1)
> +         return (-1);
> + 
> +     if ((arg == TRUE && 
> +         fcntl(conn->sock, F_SETFL, fcntlarg | O_NONBLOCK) == -1) ||
> +         (arg == FALSE &&
> +         fcntl(conn->sock, F_SETFL, fcntlarg & ~O_NONBLOCK) == -1)) 
> + #else
> +     fcntlarg = arg;
> +     if (ioctlsocket(conn->sock, FIONBIO, &fcntlarg) != 0)
> + #endif
> +     {
> +         printfPQExpBuffer(&conn->errorMessage,
> +             "PQsetblocking() -- unable to set nonblocking status to %s\n",
> +             arg == TRUE ? "TRUE" : "FALSE");
> +         return (-1);
> +     }
> + 
> +     conn->nonblocking = arg;
> +     return (0);
> + }
> + 
> + /* return the blocking status of the database connection, TRUE == nonblocking,
> +      FALSE == blocking
> + */
> + int
> + PQisnonblocking(PGconn *conn)
> + {
> + 
> +     return (conn->nonblocking);
> + }
> + 
> + /* try to force data out, really only useful for non-blocking users */
> + int
> + PQflush(PGconn *conn)
> + {
> + 
> +     return (pqFlush(conn));
>   }
> Index: fe-misc.c
> ===================================================================
> RCS file: /home/pgcvs/pgsql/src/interfaces/libpq/fe-misc.c,v
> retrieving revision 1.33
> diff -u -c -r1.33 fe-misc.c
> cvs diff: conflicting specifications of output style
> *** fe-misc.c    1999/11/30 03:08:19    1.33
> --- fe-misc.c    1999/12/14 08:21:09
> ***************
> *** 86,91 ****
> --- 86,119 ----
>   {
>       size_t avail = Max(conn->outBufSize - conn->outCount, 0);
>   
> +     /*
> +      * if we are non-blocking and the send queue is too full to buffer this
> +      * request then try to flush some and return an error 
> +      */
> +     if (PQisnonblocking(conn) && nbytes > avail && pqFlush(conn))
> +     {
> +         /* 
> +          * even if the flush failed we may still have written some
> +          * data, recalculate the size of the send-queue relative
> +          * to the amount we have to send, we may be able to queue it
> +          * afterall even though it's not sent to the database it's
> +          * ok, any routines that check the data coming from the
> +          * database better call pqFlush() anyway.
> +          */
> +         if (nbytes > Max(conn->outBufSize - conn->outCount, 0))
> +         {
> +             printfPQExpBuffer(&conn->errorMessage,
> +                 "pqPutBytes --  pqFlush couldn't flush enough"
> +                 " data: space available: %d, space needed %d\n",
> +                 Max(conn->outBufSize - conn->outCount, 0), nbytes);
> +             return EOF;
> +         }
> +     }
> + 
> +     /* 
> +      * the non-blocking code above makes sure that this isn't true,
> +      * essentially this is no-op
> +      */
>       while (nbytes > avail)
>       {
>           memcpy(conn->outBuffer + conn->outCount, s, avail);
> ***************
> *** 548,553 ****
> --- 576,589 ----
>           return EOF;
>       }
>   
> +     /* 
> +      * don't try to send zero data, allows us to use this function
> +      * without too much worry about overhead
> +      */
> +     if (len == 0)
> +         return (0);
> + 
> +     /* while there's still data to send */
>       while (len > 0)
>       {
>           /* Prevent being SIGPIPEd if backend has closed the connection. */
> ***************
> *** 556,561 ****
> --- 592,598 ----
>   #endif
>   
>           int sent;
> + 
>   #ifdef USE_SSL
>           if (conn->ssl) 
>             sent = SSL_write(conn->ssl, ptr, len);
> ***************
> *** 585,590 ****
> --- 622,629 ----
>                   case EWOULDBLOCK:
>                       break;
>   #endif
> +                 case EINTR:
> +                     continue;
>   
>                   case EPIPE:
>   #ifdef ECONNRESET
> ***************
> *** 616,628 ****
>               ptr += sent;
>               len -= sent;
>           }
>           if (len > 0)
>           {
>               /* We didn't send it all, wait till we can send more */
>   
> -             /* At first glance this looks as though it should block.  I think
> -              * that it will be OK though, as long as the socket is
> -              * non-blocking. */
>               if (pqWait(FALSE, TRUE, conn))
>                   return EOF;
>           }
> --- 655,685 ----
>               ptr += sent;
>               len -= sent;
>           }
> + 
>           if (len > 0)
>           {
>               /* We didn't send it all, wait till we can send more */
> + 
> +             /* 
> +              * if the socket is in non-blocking mode we may need
> +              * to abort here 
> +              */
> + #ifdef USE_SSL
> +             /* can't do anything for our SSL users yet */
> +             if (conn->ssl == NULL)
> +             {
> + #endif
> +                 if (PQisnonblocking(conn))
> +                 {
> +                     /* shift the contents of the buffer */
> +                     memmove(conn->outBuffer, ptr, len);
> +                     conn->outCount = len;
> +                     return EOF;
> +                 }
> + #ifdef USE_SSL
> +             }
> + #endif
>   
>               if (pqWait(FALSE, TRUE, conn))
>                   return EOF;
>           }
> Index: libpq-fe.h
> ===================================================================
> RCS file: /home/pgcvs/pgsql/src/interfaces/libpq/libpq-fe.h,v
> retrieving revision 1.53
> diff -u -c -r1.53 libpq-fe.h
> cvs diff: conflicting specifications of output style
> *** libpq-fe.h    1999/11/30 03:08:19    1.53
> --- libpq-fe.h    1999/12/14 01:30:01
> ***************
> *** 269,274 ****
> --- 269,281 ----
>       extern int    PQputnbytes(PGconn *conn, const char *buffer, int nbytes);
>       extern int    PQendcopy(PGconn *conn);
>   
> +     /* Set blocking/nonblocking connection to the backend */
> +     extern int    PQsetnonblocking(PGconn *conn, int arg);
> +     extern int    PQisnonblocking(PGconn *conn);
> + 
> +     /* Force the write buffer to be written (or at least try) */
> +     extern int    PQflush(PGconn *conn);
> + 
>       /*
>        * "Fast path" interface --- not really recommended for application
>        * use
> Index: libpq-int.h
> ===================================================================
> RCS file: /home/pgcvs/pgsql/src/interfaces/libpq/libpq-int.h,v
> retrieving revision 1.14
> diff -u -c -r1.14 libpq-int.h
> cvs diff: conflicting specifications of output style
> *** libpq-int.h    1999/11/30 03:08:19    1.14
> --- libpq-int.h    1999/12/14 01:30:01
> ***************
> *** 215,220 ****
> --- 215,223 ----
>       int            inEnd;            /* offset to first position after avail
>                                    * data */
>   
> +     int            nonblocking;    /* whether this connection is using a blocking
> +                                  * socket to the backend or not */
> + 
>       /* Buffer for data not yet sent to backend */
>       char       *outBuffer;        /* currently allocated buffer */
>       int            outBufSize;        /* allocated size of buffer */
> 
> 
> 
> 
> 
> ************
> 


--  Bruce Momjian                        |  http://www.op.net/~candle maillist@candle.pha.pa.us            |  (610)
853-3000+  If your life is a hard drive,     |  830 Blythe Avenue +  Christ can be your backup.        |  Drexel Hill,
Pennsylvania19026