granicus.if.org Git - postgresql/blob - src/backend/replication/walsender.c

   1 /*-------------------------------------------------------------------------
   2  *
   3  * walsender.c
   4  *
   5  * The WAL sender process (walsender) is new as of Postgres 9.0. It takes
   6  * care of sending XLOG from the primary server to a single recipient.
   7  * (Note that there can be more than one walsender process concurrently.)
   8  * It is started by the postmaster when the walreceiver of a standby server
   9  * connects to the primary server and requests XLOG streaming replication.
  10  * It attempts to keep reading XLOG records from the disk and sending them
  11  * to the standby server, as long as the connection is alive (i.e., like
  12  * any backend, there is a one-to-one relationship between a connection
  13  * and a walsender process).
  14  *
  15  * Normal termination is by SIGTERM, which instructs the walsender to
  16  * close the connection and exit(0) at next convenient moment. Emergency
  17  * termination is by SIGQUIT; like any backend, the walsender will simply
  18  * abort and exit on SIGQUIT. A close of the connection and a FATAL error
  19  * are treated as not a crash but approximately normal termination;
  20  * the walsender will exit quickly without sending any more XLOG records.
  21  *
  22  * If the server is shut down, postmaster sends us SIGUSR2 after all
  23  * regular backends have exited and the shutdown checkpoint has been written.
  24  * This instruct walsender to send any outstanding WAL, including the
  25  * shutdown checkpoint record, and then exit.
  26  *
  27  *
  28  * Portions Copyright (c) 2010-2011, PostgreSQL Global Development Group
  29  *
  30  * IDENTIFICATION
  31  *        src/backend/replication/walsender.c
  32  *
  33  *-------------------------------------------------------------------------
  34  */
  35 #include "postgres.h"
  36
  37 #include <signal.h>
  38 #include <unistd.h>
  39
  40 #include "funcapi.h"
  41 #include "access/xlog_internal.h"
  42 #include "access/transam.h"
  43 #include "catalog/pg_type.h"
  44 #include "libpq/libpq.h"
  45 #include "libpq/pqformat.h"
  46 #include "libpq/pqsignal.h"
  47 #include "miscadmin.h"
  48 #include "replication/basebackup.h"
  49 #include "replication/replnodes.h"
  50 #include "replication/walprotocol.h"
  51 #include "replication/walsender.h"
  52 #include "storage/fd.h"
  53 #include "storage/ipc.h"
  54 #include "storage/pmsignal.h"
  55 #include "storage/proc.h"
  56 #include "tcop/tcopprot.h"
  57 #include "utils/builtins.h"
  58 #include "utils/guc.h"
  59 #include "utils/memutils.h"
  60 #include "utils/ps_status.h"
  61 #include "utils/resowner.h"
  62
  63
  64 /* Array of WalSnds in shared memory */
  65 WalSndCtlData *WalSndCtl = NULL;
  66
  67 /* My slot in the shared memory array */
  68 static WalSnd *MyWalSnd = NULL;
  69
  70 /* Global state */
  71 bool            am_walsender = false;           /* Am I a walsender process ? */
  72
  73 /* User-settable parameters for walsender */
  74 int                     max_wal_senders = 0;    /* the maximum number of concurrent walsenders */
  75 int                     WalSndDelay = 200;      /* max sleep time between some actions */
  76
  77 /*
  78  * These variables are used similarly to openLogFile/Id/Seg/Off,
  79  * but for walsender to read the XLOG.
  80  */
  81 static int      sendFile = -1;
  82 static uint32 sendId = 0;
  83 static uint32 sendSeg = 0;
  84 static uint32 sendOff = 0;
  85
  86 /*
  87  * How far have we sent WAL already? This is also advertised in
  88  * MyWalSnd->sentPtr.  (Actually, this is the next WAL location to send.)
  89  */
  90 static XLogRecPtr sentPtr = {0, 0};
  91
  92 /*
  93  * Buffer for processing reply messages.
  94  */
  95 static StringInfoData reply_message;
  96
  97 /* Flags set by signal handlers for later service in main loop */
  98 static volatile sig_atomic_t got_SIGHUP = false;
  99 volatile sig_atomic_t walsender_shutdown_requested = false;
 100 volatile sig_atomic_t walsender_ready_to_stop = false;
 101
 102 /* Signal handlers */
 103 static void WalSndSigHupHandler(SIGNAL_ARGS);
 104 static void WalSndShutdownHandler(SIGNAL_ARGS);
 105 static void WalSndQuickDieHandler(SIGNAL_ARGS);
 106 static void WalSndXLogSendHandler(SIGNAL_ARGS);
 107 static void WalSndLastCycleHandler(SIGNAL_ARGS);
 108
 109 /* Prototypes for private functions */
 110 static bool HandleReplicationCommand(const char *cmd_string);
 111 static int      WalSndLoop(void);
 112 static void InitWalSnd(void);
 113 static void WalSndHandshake(void);
 114 static void WalSndKill(int code, Datum arg);
 115 static bool XLogSend(char *msgbuf, bool *caughtup);
 116 static void IdentifySystem(void);
 117 static void StartReplication(StartReplicationCmd * cmd);
 118 static void ProcessStandbyReplyMessage(void);
 119 static void ProcessRepliesIfAny(void);
 120
 121
 122 /* Main entry point for walsender process */
 123 int
 124 WalSenderMain(void)
 125 {
 126         MemoryContext walsnd_context;
 127
 128         if (RecoveryInProgress())
 129                 ereport(FATAL,
 130                                 (errcode(ERRCODE_CANNOT_CONNECT_NOW),
 131                                  errmsg("recovery is still in progress, can't accept WAL streaming connections")));
 132
 133         /* Create a per-walsender data structure in shared memory */
 134         InitWalSnd();
 135
 136         /*
 137          * Create a memory context that we will do all our work in.  We do this so
 138          * that we can reset the context during error recovery and thereby avoid
 139          * possible memory leaks.  Formerly this code just ran in
 140          * TopMemoryContext, but resetting that would be a really bad idea.
 141          *
 142          * XXX: we don't actually attempt error recovery in walsender, we just
 143          * close the connection and exit.
 144          */
 145         walsnd_context = AllocSetContextCreate(TopMemoryContext,
 146                                                                                    "Wal Sender",
 147                                                                                    ALLOCSET_DEFAULT_MINSIZE,
 148                                                                                    ALLOCSET_DEFAULT_INITSIZE,
 149                                                                                    ALLOCSET_DEFAULT_MAXSIZE);
 150         MemoryContextSwitchTo(walsnd_context);
 151
 152         /* Set up resource owner */
 153         CurrentResourceOwner = ResourceOwnerCreate(NULL, "walsender top-level resource owner");
 154
 155         /* Unblock signals (they were blocked when the postmaster forked us) */
 156         PG_SETMASK(&UnBlockSig);
 157
 158         /* Tell the standby that walsender is ready for receiving commands */
 159         ReadyForQuery(DestRemote);
 160
 161         /* Handle handshake messages before streaming */
 162         WalSndHandshake();
 163
 164         /* Initialize shared memory status */
 165         {
 166                 /* use volatile pointer to prevent code rearrangement */
 167                 volatile WalSnd *walsnd = MyWalSnd;
 168
 169                 SpinLockAcquire(&walsnd->mutex);
 170                 walsnd->sentPtr = sentPtr;
 171                 SpinLockRelease(&walsnd->mutex);
 172         }
 173
 174         /* Main loop of walsender */
 175         return WalSndLoop();
 176 }
 177
 178 /*
 179  * Execute commands from walreceiver, until we enter streaming mode.
 180  */
 181 static void
 182 WalSndHandshake(void)
 183 {
 184         StringInfoData input_message;
 185         bool            replication_started = false;
 186
 187         initStringInfo(&input_message);
 188
 189         while (!replication_started)
 190         {
 191                 int                     firstchar;
 192
 193                 WalSndSetState(WALSNDSTATE_STARTUP);
 194                 set_ps_display("idle", false);
 195
 196                 /* Wait for a command to arrive */
 197                 firstchar = pq_getbyte();
 198
 199                 /*
 200                  * Emergency bailout if postmaster has died.  This is to avoid the
 201                  * necessity for manual cleanup of all postmaster children.
 202                  */
 203                 if (!PostmasterIsAlive(true))
 204                         exit(1);
 205
 206                 /*
 207                  * Check for any other interesting events that happened while we
 208                  * slept.
 209                  */
 210                 if (got_SIGHUP)
 211                 {
 212                         got_SIGHUP = false;
 213                         ProcessConfigFile(PGC_SIGHUP);
 214                 }
 215
 216                 if (firstchar != EOF)
 217                 {
 218                         /*
 219                          * Read the message contents. This is expected to be done without
 220                          * blocking because we've been able to get message type code.
 221                          */
 222                         if (pq_getmessage(&input_message, 0))
 223                                 firstchar = EOF;        /* suitable message already logged */
 224                 }
 225
 226                 /* Handle the very limited subset of commands expected in this phase */
 227                 switch (firstchar)
 228                 {
 229                         case 'Q':                       /* Query message */
 230                                 {
 231                                         const char *query_string;
 232
 233                                         query_string = pq_getmsgstring(&input_message);
 234                                         pq_getmsgend(&input_message);
 235
 236                                         if (HandleReplicationCommand(query_string))
 237                                                 replication_started = true;
 238                                 }
 239                                 break;
 240
 241                         case 'X':
 242                                 /* standby is closing the connection */
 243                                 proc_exit(0);
 244
 245                         case EOF:
 246                                 /* standby disconnected unexpectedly */
 247                                 ereport(COMMERROR,
 248                                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 249                                                  errmsg("unexpected EOF on standby connection")));
 250                                 proc_exit(0);
 251
 252                         default:
 253                                 ereport(FATAL,
 254                                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 255                                                  errmsg("invalid standby handshake message type %d", firstchar)));
 256                 }
 257         }
 258 }
 259
 260 /*
 261  * IDENTIFY_SYSTEM
 262  */
 263 static void
 264 IdentifySystem(void)
 265 {
 266         StringInfoData buf;
 267         char            sysid[32];
 268         char            tli[11];
 269         char            xpos[MAXFNAMELEN];
 270         XLogRecPtr      logptr;
 271
 272         /*
 273          * Reply with a result set with one row, three columns. First col is system
 274          * ID, second is timeline ID, and third is current xlog location.
 275          */
 276
 277         snprintf(sysid, sizeof(sysid), UINT64_FORMAT,
 278                          GetSystemIdentifier());
 279         snprintf(tli, sizeof(tli), "%u", ThisTimeLineID);
 280
 281         logptr = GetInsertRecPtr();
 282
 283         snprintf(xpos, sizeof(xpos), "%X/%X",
 284                          logptr.xlogid, logptr.xrecoff);
 285
 286         /* Send a RowDescription message */
 287         pq_beginmessage(&buf, 'T');
 288         pq_sendint(&buf, 3, 2);         /* 3 fields */
 289
 290         /* first field */
 291         pq_sendstring(&buf, "systemid");        /* col name */
 292         pq_sendint(&buf, 0, 4);         /* table oid */
 293         pq_sendint(&buf, 0, 2);         /* attnum */
 294         pq_sendint(&buf, TEXTOID, 4);           /* type oid */
 295         pq_sendint(&buf, -1, 2);        /* typlen */
 296         pq_sendint(&buf, 0, 4);         /* typmod */
 297         pq_sendint(&buf, 0, 2);         /* format code */
 298
 299         /* second field */
 300         pq_sendstring(&buf, "timeline");        /* col name */
 301         pq_sendint(&buf, 0, 4);         /* table oid */
 302         pq_sendint(&buf, 0, 2);         /* attnum */
 303         pq_sendint(&buf, INT4OID, 4);           /* type oid */
 304         pq_sendint(&buf, 4, 2);         /* typlen */
 305         pq_sendint(&buf, 0, 4);         /* typmod */
 306         pq_sendint(&buf, 0, 2);         /* format code */
 307
 308         /* third field */
 309         pq_sendstring(&buf, "xlogpos");
 310         pq_sendint(&buf, 0, 4);
 311         pq_sendint(&buf, 0, 2);
 312         pq_sendint(&buf, TEXTOID, 4);
 313         pq_sendint(&buf, -1, 2);
 314         pq_sendint(&buf, 0, 4);
 315         pq_sendint(&buf, 0, 2);
 316         pq_endmessage(&buf);
 317
 318         /* Send a DataRow message */
 319         pq_beginmessage(&buf, 'D');
 320         pq_sendint(&buf, 3, 2);         /* # of columns */
 321         pq_sendint(&buf, strlen(sysid), 4); /* col1 len */
 322         pq_sendbytes(&buf, (char *) &sysid, strlen(sysid));
 323         pq_sendint(&buf, strlen(tli), 4);       /* col2 len */
 324         pq_sendbytes(&buf, (char *) tli, strlen(tli));
 325         pq_sendint(&buf, strlen(xpos), 4);      /* col3 len */
 326         pq_sendbytes(&buf, (char *) xpos, strlen(xpos));
 327
 328         pq_endmessage(&buf);
 329
 330         /* Send CommandComplete and ReadyForQuery messages */
 331         EndCommand("SELECT", DestRemote);
 332         ReadyForQuery(DestRemote);
 333         /* ReadyForQuery did pq_flush for us */
 334 }
 335
 336 /*
 337  * START_REPLICATION
 338  */
 339 static void
 340 StartReplication(StartReplicationCmd * cmd)
 341 {
 342         StringInfoData buf;
 343
 344         /*
 345          * Let postmaster know that we're streaming. Once we've declared us as
 346          * a WAL sender process, postmaster will let us outlive the bgwriter and
 347          * kill us last in the shutdown sequence, so we get a chance to stream
 348          * all remaining WAL at shutdown, including the shutdown checkpoint.
 349          * Note that there's no going back, and we mustn't write any WAL records
 350          * after this.
 351          */
 352         MarkPostmasterChildWalSender();
 353
 354         /*
 355          * Check that we're logging enough information in the WAL for
 356          * log-shipping.
 357          *
 358          * NOTE: This only checks the current value of wal_level. Even if the
 359          * current setting is not 'minimal', there can be old WAL in the pg_xlog
 360          * directory that was created with 'minimal'. So this is not bulletproof,
 361          * the purpose is just to give a user-friendly error message that hints
 362          * how to configure the system correctly.
 363          */
 364         if (wal_level == WAL_LEVEL_MINIMAL)
 365                 ereport(FATAL,
 366                                 (errcode(ERRCODE_CANNOT_CONNECT_NOW),
 367                 errmsg("standby connections not allowed because wal_level=minimal")));
 368
 369         /* Send a CopyBothResponse message, and start streaming */
 370         pq_beginmessage(&buf, 'W');
 371         pq_sendbyte(&buf, 0);
 372         pq_sendint(&buf, 0, 2);
 373         pq_endmessage(&buf);
 374         pq_flush();
 375
 376         /*
 377          * Initialize position to the received one, then the xlog records begin to
 378          * be shipped from that position
 379          */
 380         sentPtr = cmd->startpoint;
 381 }
 382
 383 /*
 384  * Execute an incoming replication command.
 385  */
 386 static bool
 387 HandleReplicationCommand(const char *cmd_string)
 388 {
 389         bool            replication_started = false;
 390         int                     parse_rc;
 391         Node       *cmd_node;
 392         MemoryContext cmd_context;
 393         MemoryContext old_context;
 394
 395         elog(DEBUG1, "received replication command: %s", cmd_string);
 396
 397         cmd_context = AllocSetContextCreate(CurrentMemoryContext,
 398                                                                                 "Replication command context",
 399                                                                                 ALLOCSET_DEFAULT_MINSIZE,
 400                                                                                 ALLOCSET_DEFAULT_INITSIZE,
 401                                                                                 ALLOCSET_DEFAULT_MAXSIZE);
 402         old_context = MemoryContextSwitchTo(cmd_context);
 403
 404         replication_scanner_init(cmd_string);
 405         parse_rc = replication_yyparse();
 406         if (parse_rc != 0)
 407                 ereport(ERROR,
 408                                 (errcode(ERRCODE_SYNTAX_ERROR),
 409                                  (errmsg_internal("replication command parser returned %d",
 410                                                                   parse_rc))));
 411
 412         cmd_node = replication_parse_result;
 413
 414         switch (cmd_node->type)
 415         {
 416                 case T_IdentifySystemCmd:
 417                         IdentifySystem();
 418                         break;
 419
 420                 case T_StartReplicationCmd:
 421                         StartReplication((StartReplicationCmd *) cmd_node);
 422
 423                         /* break out of the loop */
 424                         replication_started = true;
 425                         break;
 426
 427                 case T_BaseBackupCmd:
 428                         SendBaseBackup((BaseBackupCmd *) cmd_node);
 429
 430                         /* Send CommandComplete and ReadyForQuery messages */
 431                         EndCommand("SELECT", DestRemote);
 432                         ReadyForQuery(DestRemote);
 433                         /* ReadyForQuery did pq_flush for us */
 434                         break;
 435
 436                 default:
 437                         ereport(FATAL,
 438                                         (errcode(ERRCODE_PROTOCOL_VIOLATION),
 439                                          errmsg("invalid standby query string: %s", cmd_string)));
 440         }
 441
 442         /* done */
 443         MemoryContextSwitchTo(old_context);
 444         MemoryContextDelete(cmd_context);
 445
 446         return replication_started;
 447 }
 448
 449 /*
 450  * Check if the remote end has closed the connection.
 451  */
 452 static void
 453 ProcessRepliesIfAny(void)
 454 {
 455         unsigned char firstchar;
 456         int                     r;
 457
 458         r = pq_getbyte_if_available(&firstchar);
 459         if (r < 0)
 460         {
 461                 /* unexpected error or EOF */
 462                 ereport(COMMERROR,
 463                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 464                                  errmsg("unexpected EOF on standby connection")));
 465                 proc_exit(0);
 466         }
 467         if (r == 0)
 468         {
 469                 /* no data available without blocking */
 470                 return;
 471         }
 472
 473         /* Handle the very limited subset of commands expected in this phase */
 474         switch (firstchar)
 475         {
 476                         /*
 477                          * 'd' means a standby reply wrapped in a CopyData packet.
 478                          */
 479                 case 'd':
 480                         ProcessStandbyReplyMessage();
 481                         break;
 482
 483                         /*
 484                          * 'X' means that the standby is closing down the socket.
 485                          */
 486                 case 'X':
 487                         proc_exit(0);
 488
 489                 default:
 490                         ereport(FATAL,
 491                                         (errcode(ERRCODE_PROTOCOL_VIOLATION),
 492                                          errmsg("invalid standby closing message type %d",
 493                                                         firstchar)));
 494         }
 495 }
 496
 497 /*
 498  * Process a status update message received from standby.
 499  */
 500 static void
 501 ProcessStandbyReplyMessage(void)
 502 {
 503         StandbyReplyMessage     reply;
 504         char msgtype;
 505
 506         resetStringInfo(&reply_message);
 507
 508         /*
 509          * Read the message contents.
 510          */
 511         if (pq_getmessage(&reply_message, 0))
 512         {
 513                 ereport(COMMERROR,
 514                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 515                                  errmsg("unexpected EOF on standby connection")));
 516                 proc_exit(0);
 517         }
 518
 519         /*
 520          * Check message type from the first byte. At the moment, there is only
 521          * one type.
 522          */
 523         msgtype = pq_getmsgbyte(&reply_message);
 524         if (msgtype != 'r')
 525         {
 526                 ereport(COMMERROR,
 527                                 (errcode(ERRCODE_PROTOCOL_VIOLATION),
 528                                  errmsg("unexpected message type %c", msgtype)));
 529                 proc_exit(0);
 530         }
 531
 532         pq_copymsgbytes(&reply_message, (char *) &reply, sizeof(StandbyReplyMessage));
 533
 534         elog(DEBUG2, "write %X/%X flush %X/%X apply %X/%X ",
 535                  reply.write.xlogid, reply.write.xrecoff,
 536                  reply.flush.xlogid, reply.flush.xrecoff,
 537                  reply.apply.xlogid, reply.apply.xrecoff);
 538
 539         /*
 540          * Update shared state for this WalSender process
 541          * based on reply data from standby.
 542          */
 543         {
 544                 /* use volatile pointer to prevent code rearrangement */
 545                 volatile WalSnd *walsnd = MyWalSnd;
 546
 547                 SpinLockAcquire(&walsnd->mutex);
 548                 walsnd->write = reply.write;
 549                 walsnd->flush = reply.flush;
 550                 walsnd->apply = reply.apply;
 551                 SpinLockRelease(&walsnd->mutex);
 552         }
 553 }
 554
 555 /* Main loop of walsender process */
 556 static int
 557 WalSndLoop(void)
 558 {
 559         char       *output_message;
 560         bool            caughtup = false;
 561
 562         /*
 563          * Allocate buffer that will be used for each output message.  We do this
 564          * just once to reduce palloc overhead.  The buffer must be made large
 565          * enough for maximum-sized messages.
 566          */
 567         output_message = palloc(1 + sizeof(WalDataMessageHeader) + MAX_SEND_SIZE);
 568
 569         /*
 570          * Allocate buffer that will be used for processing reply messages.  As
 571          * above, do this just once to reduce palloc overhead.
 572          */
 573         initStringInfo(&reply_message);
 574
 575         /* Loop forever, unless we get an error */
 576         for (;;)
 577         {
 578                 /*
 579                  * Emergency bailout if postmaster has died.  This is to avoid the
 580                  * necessity for manual cleanup of all postmaster children.
 581                  */
 582                 if (!PostmasterIsAlive(true))
 583                         exit(1);
 584
 585                 /* Process any requests or signals received recently */
 586                 if (got_SIGHUP)
 587                 {
 588                         got_SIGHUP = false;
 589                         ProcessConfigFile(PGC_SIGHUP);
 590                 }
 591
 592                 /*
 593                  * When SIGUSR2 arrives, we send all outstanding logs up to the
 594                  * shutdown checkpoint record (i.e., the latest record) and exit.
 595                  */
 596                 if (walsender_ready_to_stop)
 597                 {
 598                         if (!XLogSend(output_message, &caughtup))
 599                                 break;
 600                         ProcessRepliesIfAny();
 601                         if (caughtup)
 602                                 walsender_shutdown_requested = true;
 603                 }
 604
 605                 /* Normal exit from the walsender is here */
 606                 if (walsender_shutdown_requested)
 607                 {
 608                         /* Inform the standby that XLOG streaming was done */
 609                         pq_puttextmessage('C', "COPY 0");
 610                         pq_flush();
 611
 612                         proc_exit(0);
 613                 }
 614
 615                 /*
 616                  * If we had sent all accumulated WAL in last round, nap for the
 617                  * configured time before retrying.
 618                  */
 619                 if (caughtup)
 620                 {
 621                         /*
 622                          * Even if we wrote all the WAL that was available when we started
 623                          * sending, more might have arrived while we were sending this
 624                          * batch. We had the latch set while sending, so we have not
 625                          * received any signals from that time. Let's arm the latch
 626                          * again, and after that check that we're still up-to-date.
 627                          */
 628                         ResetLatch(&MyWalSnd->latch);
 629
 630                         if (!XLogSend(output_message, &caughtup))
 631                                 break;
 632                         if (caughtup && !got_SIGHUP && !walsender_ready_to_stop && !walsender_shutdown_requested)
 633                         {
 634                                 /*
 635                                  * XXX: We don't really need the periodic wakeups anymore,
 636                                  * WaitLatchOrSocket should reliably wake up as soon as
 637                                  * something interesting happens.
 638                                  */
 639
 640                                 /* Sleep */
 641                                 WaitLatchOrSocket(&MyWalSnd->latch, MyProcPort->sock,
 642                                                                   WalSndDelay * 1000L);
 643                         }
 644                 }
 645                 else
 646                 {
 647                         /* Attempt to send the log once every loop */
 648                         if (!XLogSend(output_message, &caughtup))
 649                                 break;
 650                 }
 651
 652                 /* Update our state to indicate if we're behind or not */
 653                 WalSndSetState(caughtup ? WALSNDSTATE_STREAMING : WALSNDSTATE_CATCHUP);
 654                 ProcessRepliesIfAny();
 655         }
 656
 657         /*
 658          * Get here on send failure.  Clean up and exit.
 659          *
 660          * Reset whereToSendOutput to prevent ereport from attempting to send any
 661          * more messages to the standby.
 662          */
 663         if (whereToSendOutput == DestRemote)
 664                 whereToSendOutput = DestNone;
 665
 666         proc_exit(0);
 667         return 1;                                       /* keep the compiler quiet */
 668 }
 669
 670 /* Initialize a per-walsender data structure for this walsender process */
 671 static void
 672 InitWalSnd(void)
 673 {
 674         int                     i;
 675
 676         /*
 677          * WalSndCtl should be set up already (we inherit this by fork() or
 678          * EXEC_BACKEND mechanism from the postmaster).
 679          */
 680         Assert(WalSndCtl != NULL);
 681         Assert(MyWalSnd == NULL);
 682
 683         /*
 684          * Find a free walsender slot and reserve it. If this fails, we must be
 685          * out of WalSnd structures.
 686          */
 687         for (i = 0; i < max_wal_senders; i++)
 688         {
 689                 /* use volatile pointer to prevent code rearrangement */
 690                 volatile WalSnd *walsnd = &WalSndCtl->walsnds[i];
 691
 692                 SpinLockAcquire(&walsnd->mutex);
 693
 694                 if (walsnd->pid != 0)
 695                 {
 696                         SpinLockRelease(&walsnd->mutex);
 697                         continue;
 698                 }
 699                 else
 700                 {
 701                         /*
 702                          * Found a free slot. Reserve it for us.
 703                          */
 704                         walsnd->pid = MyProcPid;
 705                         MemSet(&walsnd->sentPtr, 0, sizeof(XLogRecPtr));
 706                         walsnd->state = WALSNDSTATE_STARTUP;
 707                         SpinLockRelease(&walsnd->mutex);
 708                         /* don't need the lock anymore */
 709                         OwnLatch((Latch *) &walsnd->latch);
 710                         MyWalSnd = (WalSnd *) walsnd;
 711
 712                         break;
 713                 }
 714         }
 715         if (MyWalSnd == NULL)
 716                 ereport(FATAL,
 717                                 (errcode(ERRCODE_TOO_MANY_CONNECTIONS),
 718                                  errmsg("number of requested standby connections "
 719                                                 "exceeds max_wal_senders (currently %d)",
 720                                                 max_wal_senders)));
 721
 722         /* Arrange to clean up at walsender exit */
 723         on_shmem_exit(WalSndKill, 0);
 724 }
 725
 726 /* Destroy the per-walsender data structure for this walsender process */
 727 static void
 728 WalSndKill(int code, Datum arg)
 729 {
 730         Assert(MyWalSnd != NULL);
 731
 732         /*
 733          * Mark WalSnd struct no longer in use. Assume that no lock is required
 734          * for this.
 735          */
 736         MyWalSnd->pid = 0;
 737         DisownLatch(&MyWalSnd->latch);
 738
 739         /* WalSnd struct isn't mine anymore */
 740         MyWalSnd = NULL;
 741 }
 742
 743 /*
 744  * Read 'nbytes' bytes from WAL into 'buf', starting at location 'recptr'
 745  *
 746  * XXX probably this should be improved to suck data directly from the
 747  * WAL buffers when possible.
 748  *
 749  * Will open, and keep open, one WAL segment stored in the global file
 750  * descriptor sendFile. This means if XLogRead is used once, there will
 751  * always be one descriptor left open until the process ends, but never
 752  * more than one.
 753  */
 754 void
 755 XLogRead(char *buf, XLogRecPtr recptr, Size nbytes)
 756 {
 757         XLogRecPtr      startRecPtr = recptr;
 758         char            path[MAXPGPATH];
 759         uint32          lastRemovedLog;
 760         uint32          lastRemovedSeg;
 761         uint32          log;
 762         uint32          seg;
 763
 764         while (nbytes > 0)
 765         {
 766                 uint32          startoff;
 767                 int                     segbytes;
 768                 int                     readbytes;
 769
 770                 startoff = recptr.xrecoff % XLogSegSize;
 771
 772                 if (sendFile < 0 || !XLByteInSeg(recptr, sendId, sendSeg))
 773                 {
 774                         /* Switch to another logfile segment */
 775                         if (sendFile >= 0)
 776                                 close(sendFile);
 777
 778                         XLByteToSeg(recptr, sendId, sendSeg);
 779                         XLogFilePath(path, ThisTimeLineID, sendId, sendSeg);
 780
 781                         sendFile = BasicOpenFile(path, O_RDONLY | PG_BINARY, 0);
 782                         if (sendFile < 0)
 783                         {
 784                                 /*
 785                                  * If the file is not found, assume it's because the standby
 786                                  * asked for a too old WAL segment that has already been
 787                                  * removed or recycled.
 788                                  */
 789                                 if (errno == ENOENT)
 790                                 {
 791                                         char            filename[MAXFNAMELEN];
 792
 793                                         XLogFileName(filename, ThisTimeLineID, sendId, sendSeg);
 794                                         ereport(ERROR,
 795                                                         (errcode_for_file_access(),
 796                                                          errmsg("requested WAL segment %s has already been removed",
 797                                                                         filename)));
 798                                 }
 799                                 else
 800                                         ereport(ERROR,
 801                                                         (errcode_for_file_access(),
 802                                                          errmsg("could not open file \"%s\" (log file %u, segment %u): %m",
 803                                                                         path, sendId, sendSeg)));
 804                         }
 805                         sendOff = 0;
 806                 }
 807
 808                 /* Need to seek in the file? */
 809                 if (sendOff != startoff)
 810                 {
 811                         if (lseek(sendFile, (off_t) startoff, SEEK_SET) < 0)
 812                                 ereport(ERROR,
 813                                                 (errcode_for_file_access(),
 814                                                  errmsg("could not seek in log file %u, segment %u to offset %u: %m",
 815                                                                 sendId, sendSeg, startoff)));
 816                         sendOff = startoff;
 817                 }
 818
 819                 /* How many bytes are within this segment? */
 820                 if (nbytes > (XLogSegSize - startoff))
 821                         segbytes = XLogSegSize - startoff;
 822                 else
 823                         segbytes = nbytes;
 824
 825                 readbytes = read(sendFile, buf, segbytes);
 826                 if (readbytes <= 0)
 827                         ereport(ERROR,
 828                                         (errcode_for_file_access(),
 829                         errmsg("could not read from log file %u, segment %u, offset %u, "
 830                                    "length %lu: %m",
 831                                    sendId, sendSeg, sendOff, (unsigned long) segbytes)));
 832
 833                 /* Update state for read */
 834                 XLByteAdvance(recptr, readbytes);
 835
 836                 sendOff += readbytes;
 837                 nbytes -= readbytes;
 838                 buf += readbytes;
 839         }
 840
 841         /*
 842          * After reading into the buffer, check that what we read was valid. We do
 843          * this after reading, because even though the segment was present when we
 844          * opened it, it might get recycled or removed while we read it. The
 845          * read() succeeds in that case, but the data we tried to read might
 846          * already have been overwritten with new WAL records.
 847          */
 848         XLogGetLastRemoved(&lastRemovedLog, &lastRemovedSeg);
 849         XLByteToSeg(startRecPtr, log, seg);
 850         if (log < lastRemovedLog ||
 851                 (log == lastRemovedLog && seg <= lastRemovedSeg))
 852         {
 853                 char            filename[MAXFNAMELEN];
 854
 855                 XLogFileName(filename, ThisTimeLineID, log, seg);
 856                 ereport(ERROR,
 857                                 (errcode_for_file_access(),
 858                                  errmsg("requested WAL segment %s has already been removed",
 859                                                 filename)));
 860         }
 861 }
 862
 863 /*
 864  * Read up to MAX_SEND_SIZE bytes of WAL that's been flushed to disk,
 865  * but not yet sent to the client, and send it.
 866  *
 867  * msgbuf is a work area in which the output message is constructed.  It's
 868  * passed in just so we can avoid re-palloc'ing the buffer on each cycle.
 869  * It must be of size 1 + sizeof(WalDataMessageHeader) + MAX_SEND_SIZE.
 870  *
 871  * If there is no unsent WAL remaining, *caughtup is set to true, otherwise
 872  * *caughtup is set to false.
 873  *
 874  * Returns true if OK, false if trouble.
 875  */
 876 static bool
 877 XLogSend(char *msgbuf, bool *caughtup)
 878 {
 879         XLogRecPtr      SendRqstPtr;
 880         XLogRecPtr      startptr;
 881         XLogRecPtr      endptr;
 882         Size            nbytes;
 883         WalDataMessageHeader msghdr;
 884
 885         /*
 886          * Attempt to send all data that's already been written out and fsync'd to
 887          * disk.  We cannot go further than what's been written out given the
 888          * current implementation of XLogRead().  And in any case it's unsafe to
 889          * send WAL that is not securely down to disk on the master: if the master
 890          * subsequently crashes and restarts, slaves must not have applied any WAL
 891          * that gets lost on the master.
 892          */
 893         SendRqstPtr = GetFlushRecPtr();
 894
 895         /* Quick exit if nothing to do */
 896         if (XLByteLE(SendRqstPtr, sentPtr))
 897         {
 898                 *caughtup = true;
 899                 return true;
 900         }
 901
 902         /*
 903          * Figure out how much to send in one message. If there's no more than
 904          * MAX_SEND_SIZE bytes to send, send everything. Otherwise send
 905          * MAX_SEND_SIZE bytes, but round back to logfile or page boundary.
 906          *
 907          * The rounding is not only for performance reasons. Walreceiver relies on
 908          * the fact that we never split a WAL record across two messages. Since a
 909          * long WAL record is split at page boundary into continuation records,
 910          * page boundary is always a safe cut-off point. We also assume that
 911          * SendRqstPtr never points to the middle of a WAL record.
 912          */
 913         startptr = sentPtr;
 914         if (startptr.xrecoff >= XLogFileSize)
 915         {
 916                 /*
 917                  * crossing a logid boundary, skip the non-existent last log segment
 918                  * in previous logical log file.
 919                  */
 920                 startptr.xlogid += 1;
 921                 startptr.xrecoff = 0;
 922         }
 923
 924         endptr = startptr;
 925         XLByteAdvance(endptr, MAX_SEND_SIZE);
 926         if (endptr.xlogid != startptr.xlogid)
 927         {
 928                 /* Don't cross a logfile boundary within one message */
 929                 Assert(endptr.xlogid == startptr.xlogid + 1);
 930                 endptr.xlogid = startptr.xlogid;
 931                 endptr.xrecoff = XLogFileSize;
 932         }
 933
 934         /* if we went beyond SendRqstPtr, back off */
 935         if (XLByteLE(SendRqstPtr, endptr))
 936         {
 937                 endptr = SendRqstPtr;
 938                 *caughtup = true;
 939         }
 940         else
 941         {
 942                 /* round down to page boundary. */
 943                 endptr.xrecoff -= (endptr.xrecoff % XLOG_BLCKSZ);
 944                 *caughtup = false;
 945         }
 946
 947         nbytes = endptr.xrecoff - startptr.xrecoff;
 948         Assert(nbytes <= MAX_SEND_SIZE);
 949
 950         /*
 951          * OK to read and send the slice.
 952          */
 953         msgbuf[0] = 'w';
 954
 955         /*
 956          * Read the log directly into the output buffer to avoid extra memcpy
 957          * calls.
 958          */
 959         XLogRead(msgbuf + 1 + sizeof(WalDataMessageHeader), startptr, nbytes);
 960
 961         /*
 962          * We fill the message header last so that the send timestamp is taken as
 963          * late as possible.
 964          */
 965         msghdr.dataStart = startptr;
 966         msghdr.walEnd = SendRqstPtr;
 967         msghdr.sendTime = GetCurrentTimestamp();
 968
 969         memcpy(msgbuf + 1, &msghdr, sizeof(WalDataMessageHeader));
 970
 971         pq_putmessage('d', msgbuf, 1 + sizeof(WalDataMessageHeader) + nbytes);
 972
 973         /* Flush pending output to the client */
 974         if (pq_flush())
 975                 return false;
 976
 977         sentPtr = endptr;
 978
 979         /* Update shared memory status */
 980         {
 981                 /* use volatile pointer to prevent code rearrangement */
 982                 volatile WalSnd *walsnd = MyWalSnd;
 983
 984                 SpinLockAcquire(&walsnd->mutex);
 985                 walsnd->sentPtr = sentPtr;
 986                 SpinLockRelease(&walsnd->mutex);
 987         }
 988
 989         /* Report progress of XLOG streaming in PS display */
 990         if (update_process_title)
 991         {
 992                 char            activitymsg[50];
 993
 994                 snprintf(activitymsg, sizeof(activitymsg), "streaming %X/%X",
 995                                  sentPtr.xlogid, sentPtr.xrecoff);
 996                 set_ps_display(activitymsg, false);
 997         }
 998
 999         return true;
1000 }
1001
1002 /* SIGHUP: set flag to re-read config file at next convenient time */
1003 static void
1004 WalSndSigHupHandler(SIGNAL_ARGS)
1005 {
1006         got_SIGHUP = true;
1007         if (MyWalSnd)
1008                 SetLatch(&MyWalSnd->latch);
1009 }
1010
1011 /* SIGTERM: set flag to shut down */
1012 static void
1013 WalSndShutdownHandler(SIGNAL_ARGS)
1014 {
1015         walsender_shutdown_requested = true;
1016         if (MyWalSnd)
1017                 SetLatch(&MyWalSnd->latch);
1018 }
1019
1020 /*
1021  * WalSndQuickDieHandler() occurs when signalled SIGQUIT by the postmaster.
1022  *
1023  * Some backend has bought the farm,
1024  * so we need to stop what we're doing and exit.
1025  */
1026 static void
1027 WalSndQuickDieHandler(SIGNAL_ARGS)
1028 {
1029         PG_SETMASK(&BlockSig);
1030
1031         /*
1032          * We DO NOT want to run proc_exit() callbacks -- we're here because
1033          * shared memory may be corrupted, so we don't want to try to clean up our
1034          * transaction.  Just nail the windows shut and get out of town.  Now that
1035          * there's an atexit callback to prevent third-party code from breaking
1036          * things by calling exit() directly, we have to reset the callbacks
1037          * explicitly to make this work as intended.
1038          */
1039         on_exit_reset();
1040
1041         /*
1042          * Note we do exit(2) not exit(0).      This is to force the postmaster into a
1043          * system reset cycle if some idiot DBA sends a manual SIGQUIT to a random
1044          * backend.  This is necessary precisely because we don't clean up our
1045          * shared memory state.  (The "dead man switch" mechanism in pmsignal.c
1046          * should ensure the postmaster sees this as a crash, too, but no harm in
1047          * being doubly sure.)
1048          */
1049         exit(2);
1050 }
1051
1052 /* SIGUSR1: set flag to send WAL records */
1053 static void
1054 WalSndXLogSendHandler(SIGNAL_ARGS)
1055 {
1056         latch_sigusr1_handler();
1057 }
1058
1059 /* SIGUSR2: set flag to do a last cycle and shut down afterwards */
1060 static void
1061 WalSndLastCycleHandler(SIGNAL_ARGS)
1062 {
1063         walsender_ready_to_stop = true;
1064         if (MyWalSnd)
1065                 SetLatch(&MyWalSnd->latch);
1066 }
1067
1068 /* Set up signal handlers */
1069 void
1070 WalSndSignals(void)
1071 {
1072         /* Set up signal handlers */
1073         pqsignal(SIGHUP, WalSndSigHupHandler);          /* set flag to read config
1074                                                                                                  * file */
1075         pqsignal(SIGINT, SIG_IGN);      /* not used */
1076         pqsignal(SIGTERM, WalSndShutdownHandler);       /* request shutdown */
1077         pqsignal(SIGQUIT, WalSndQuickDieHandler);       /* hard crash time */
1078         pqsignal(SIGALRM, SIG_IGN);
1079         pqsignal(SIGPIPE, SIG_IGN);
1080         pqsignal(SIGUSR1, WalSndXLogSendHandler);       /* request WAL sending */
1081         pqsignal(SIGUSR2, WalSndLastCycleHandler);      /* request a last cycle and
1082                                                                                                  * shutdown */
1083
1084         /* Reset some signals that are accepted by postmaster but not here */
1085         pqsignal(SIGCHLD, SIG_DFL);
1086         pqsignal(SIGTTIN, SIG_DFL);
1087         pqsignal(SIGTTOU, SIG_DFL);
1088         pqsignal(SIGCONT, SIG_DFL);
1089         pqsignal(SIGWINCH, SIG_DFL);
1090 }
1091
1092 /* Report shared-memory space needed by WalSndShmemInit */
1093 Size
1094 WalSndShmemSize(void)
1095 {
1096         Size            size = 0;
1097
1098         size = offsetof(WalSndCtlData, walsnds);
1099         size = add_size(size, mul_size(max_wal_senders, sizeof(WalSnd)));
1100
1101         return size;
1102 }
1103
1104 /* Allocate and initialize walsender-related shared memory */
1105 void
1106 WalSndShmemInit(void)
1107 {
1108         bool            found;
1109         int                     i;
1110
1111         WalSndCtl = (WalSndCtlData *)
1112                 ShmemInitStruct("Wal Sender Ctl", WalSndShmemSize(), &found);
1113
1114         if (!found)
1115         {
1116                 /* First time through, so initialize */
1117                 MemSet(WalSndCtl, 0, WalSndShmemSize());
1118
1119                 for (i = 0; i < max_wal_senders; i++)
1120                 {
1121                         WalSnd     *walsnd = &WalSndCtl->walsnds[i];
1122
1123                         SpinLockInit(&walsnd->mutex);
1124                         InitSharedLatch(&walsnd->latch);
1125                 }
1126         }
1127 }
1128
1129 /* Wake up all walsenders */
1130 void
1131 WalSndWakeup(void)
1132 {
1133         int             i;
1134
1135         for (i = 0; i < max_wal_senders; i++)
1136                 SetLatch(&WalSndCtl->walsnds[i].latch);
1137 }
1138
1139 /* Set state for current walsender (only called in walsender) */
1140 void
1141 WalSndSetState(WalSndState state)
1142 {
1143         /* use volatile pointer to prevent code rearrangement */
1144         volatile WalSnd *walsnd = MyWalSnd;
1145
1146         Assert(am_walsender);
1147
1148         if (walsnd->state == state)
1149                 return;
1150
1151         SpinLockAcquire(&walsnd->mutex);
1152         walsnd->state = state;
1153         SpinLockRelease(&walsnd->mutex);
1154 }
1155
1156 /*
1157  * Return a string constant representing the state. This is used
1158  * in system views, and should *not* be translated.
1159  */
1160 static const char *
1161 WalSndGetStateString(WalSndState state)
1162 {
1163         switch (state)
1164         {
1165                 case WALSNDSTATE_STARTUP:
1166                         return "STARTUP";
1167                 case WALSNDSTATE_BACKUP:
1168                         return "BACKUP";
1169                 case WALSNDSTATE_CATCHUP:
1170                         return "CATCHUP";
1171                 case WALSNDSTATE_STREAMING:
1172                         return "STREAMING";
1173         }
1174         return "UNKNOWN";
1175 }
1176
1177
1178 /*
1179  * Returns activity of walsenders, including pids and xlog locations sent to
1180  * standby servers.
1181  */
1182 Datum
1183 pg_stat_get_wal_senders(PG_FUNCTION_ARGS)
1184 {
1185 #define PG_STAT_GET_WAL_SENDERS_COLS    6
1186         ReturnSetInfo      *rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
1187         TupleDesc                       tupdesc;
1188         Tuplestorestate    *tupstore;
1189         MemoryContext           per_query_ctx;
1190         MemoryContext           oldcontext;
1191         int                                     i;
1192
1193         /* check to see if caller supports us returning a tuplestore */
1194         if (rsinfo == NULL || !IsA(rsinfo, ReturnSetInfo))
1195                 ereport(ERROR,
1196                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1197                                  errmsg("set-valued function called in context that cannot accept a set")));
1198         if (!(rsinfo->allowedModes & SFRM_Materialize))
1199                 ereport(ERROR,
1200                                 (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
1201                                  errmsg("materialize mode required, but it is not " \
1202                                                 "allowed in this context")));
1203
1204         /* Build a tuple descriptor for our result type */
1205         if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
1206                 elog(ERROR, "return type must be a row type");
1207
1208         per_query_ctx = rsinfo->econtext->ecxt_per_query_memory;
1209         oldcontext = MemoryContextSwitchTo(per_query_ctx);
1210
1211         tupstore = tuplestore_begin_heap(true, false, work_mem);
1212         rsinfo->returnMode = SFRM_Materialize;
1213         rsinfo->setResult = tupstore;
1214         rsinfo->setDesc = tupdesc;
1215
1216         MemoryContextSwitchTo(oldcontext);
1217
1218         for (i = 0; i < max_wal_senders; i++)
1219         {
1220                 /* use volatile pointer to prevent code rearrangement */
1221                 volatile WalSnd *walsnd = &WalSndCtl->walsnds[i];
1222                 char            location[MAXFNAMELEN];
1223                 XLogRecPtr      sentPtr;
1224                 XLogRecPtr      write;
1225                 XLogRecPtr      flush;
1226                 XLogRecPtr      apply;
1227                 WalSndState     state;
1228                 Datum           values[PG_STAT_GET_WAL_SENDERS_COLS];
1229                 bool            nulls[PG_STAT_GET_WAL_SENDERS_COLS];
1230
1231                 if (walsnd->pid == 0)
1232                         continue;
1233
1234                 SpinLockAcquire(&walsnd->mutex);
1235                 sentPtr = walsnd->sentPtr;
1236                 state = walsnd->state;
1237                 write = walsnd->write;
1238                 flush = walsnd->flush;
1239                 apply = walsnd->apply;
1240                 SpinLockRelease(&walsnd->mutex);
1241
1242                 memset(nulls, 0, sizeof(nulls));
1243                 values[0] = Int32GetDatum(walsnd->pid);
1244
1245                 if (!superuser())
1246                 {
1247                         /*
1248                          * Only superusers can see details. Other users only get
1249                          * the pid value to know it's a walsender, but no details.
1250                          */
1251                         nulls[1] = true;
1252                         nulls[2] = true;
1253                         nulls[3] = true;
1254                         nulls[4] = true;
1255                         nulls[5] = true;
1256                 }
1257                 else
1258                 {
1259                         values[1] = CStringGetTextDatum(WalSndGetStateString(state));
1260
1261                         snprintf(location, sizeof(location), "%X/%X",
1262                                          sentPtr.xlogid, sentPtr.xrecoff);
1263                         values[2] = CStringGetTextDatum(location);
1264
1265                         if (write.xlogid == 0 && write.xrecoff == 0)
1266                                 nulls[3] = true;
1267                         snprintf(location, sizeof(location), "%X/%X",
1268                                          write.xlogid, write.xrecoff);
1269                         values[3] = CStringGetTextDatum(location);
1270
1271                         if (flush.xlogid == 0 && flush.xrecoff == 0)
1272                                 nulls[4] = true;
1273                         snprintf(location, sizeof(location), "%X/%X",
1274                                         flush.xlogid, flush.xrecoff);
1275                         values[4] = CStringGetTextDatum(location);
1276
1277                         if (apply.xlogid == 0 && apply.xrecoff == 0)
1278                                 nulls[5] = true;
1279                         snprintf(location, sizeof(location), "%X/%X",
1280                                          apply.xlogid, apply.xrecoff);
1281                         values[5] = CStringGetTextDatum(location);
1282                 }
1283
1284                 tuplestore_putvalues(tupstore, tupdesc, values, nulls);
1285         }
1286
1287         /* clean up and return the tuplestore */
1288         tuplestore_donestoring(tupstore);
1289
1290         return (Datum) 0;
1291 }
1292
1293 /*
1294  * This isn't currently used for anything. Monitoring tools might be
1295  * interested in the future, and we'll need something like this in the
1296  * future for synchronous replication.
1297  */
1298 #ifdef NOT_USED
1299 /*
1300  * Returns the oldest Send position among walsenders. Or InvalidXLogRecPtr
1301  * if none.
1302  */
1303 XLogRecPtr
1304 GetOldestWALSendPointer(void)
1305 {
1306         XLogRecPtr      oldest = {0, 0};
1307         int                     i;
1308         bool            found = false;
1309
1310         for (i = 0; i < max_wal_senders; i++)
1311         {
1312                 /* use volatile pointer to prevent code rearrangement */
1313                 volatile WalSnd *walsnd = &WalSndCtl->walsnds[i];
1314                 XLogRecPtr      recptr;
1315
1316                 if (walsnd->pid == 0)
1317                         continue;
1318
1319                 SpinLockAcquire(&walsnd->mutex);
1320                 recptr = walsnd->sentPtr;
1321                 SpinLockRelease(&walsnd->mutex);
1322
1323                 if (recptr.xlogid == 0 && recptr.xrecoff == 0)
1324                         continue;
1325
1326                 if (!found || XLByteLT(recptr, oldest))
1327                         oldest = recptr;
1328                 found = true;
1329         }
1330         return oldest;
1331 }
1332
1333 #endif