/*
* IDENTIFY_SYSTEM
*/
static void
IdentifySystem(void)
{
StringInfoData buf;
char sysid[32];
char tli[11];
/*
* Reply with a result set with one row, two columns. First col is system
* ID, and second is timeline ID
*/
snprintf(sysid, sizeof(sysid), UINT64_FORMAT,
GetSystemIdentifier());
snprintf(tli, sizeof(tli), "%u", ThisTimeLineID);
/* Send a RowDescription message */
pq_beginmessage(&buf, 'T');
pq_sendint(&buf, 2, 2); /* 2 fields */
/* first field */
pq_sendstring(&buf, "systemid"); /* col name */
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
pq_sendint(&buf, TEXTOID, 4); /* type oid */
pq_sendint(&buf, -1, 2); /* typlen */
pq_sendint(&buf, 0, 4); /* typmod */
pq_sendint(&buf, 0, 2); /* format code */
/* second field */
pq_sendstring(&buf, "timeline"); /* col name */
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
pq_sendint(&buf, INT4OID, 4); /* type oid */
pq_sendint(&buf, 4, 2); /* typlen */
pq_sendint(&buf, 0, 4); /* typmod */
pq_sendint(&buf, 0, 2); /* format code */
pq_endmessage(&buf);
/* Send a DataRow message */
pq_beginmessage(&buf, 'D');
pq_sendint(&buf, 2, 2); /* # of columns */
pq_sendint(&buf, strlen(sysid), 4); /* col1 len */
pq_sendbytes(&buf, (char *) &sysid, strlen(sysid));
pq_sendint(&buf, strlen(tli), 4); /* col2 len */
pq_sendbytes(&buf, (char *) tli, strlen(tli));
pq_endmessage(&buf);
/* Send CommandComplete and ReadyForQuery messages */
EndCommand("SELECT", DestRemote);
ReadyForQuery(DestRemote);
/* ReadyForQuery did pq_flush for us */
}
/*
* IDENTIFY_SYSTEM
*/
static void
IdentifySystem(void)
{
StringInfoData buf;
char sysid[32];
char tli[11];
char xpos[MAXFNAMELEN];
XLogRecPtr logptr;
/*
* Reply with a result set with one row, three columns. First col is
* system ID, second is timeline ID, and third is current xlog location.
*/
snprintf(sysid, sizeof(sysid), UINT64_FORMAT,
GetSystemIdentifier());
snprintf(tli, sizeof(tli), "%u", ThisTimeLineID);
logptr = am_cascading_walsender ? GetStandbyFlushRecPtr() : GetInsertRecPtr();
snprintf(xpos, sizeof(xpos), "%X/%X",
logptr.xlogid, logptr.xrecoff);
/* Send a RowDescription message */
pq_beginmessage(&buf, 'T');
pq_sendint(&buf, 3, 2); /* 3 fields */
/* first field */
pq_sendstring(&buf, "systemid"); /* col name */
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
pq_sendint(&buf, TEXTOID, 4); /* type oid */
pq_sendint(&buf, -1, 2); /* typlen */
pq_sendint(&buf, 0, 4); /* typmod */
pq_sendint(&buf, 0, 2); /* format code */
/* second field */
pq_sendstring(&buf, "timeline"); /* col name */
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
pq_sendint(&buf, INT4OID, 4); /* type oid */
pq_sendint(&buf, 4, 2); /* typlen */
pq_sendint(&buf, 0, 4); /* typmod */
pq_sendint(&buf, 0, 2); /* format code */
/* third field */
pq_sendstring(&buf, "xlogpos");
pq_sendint(&buf, 0, 4);
pq_sendint(&buf, 0, 2);
pq_sendint(&buf, TEXTOID, 4);
pq_sendint(&buf, -1, 2);
pq_sendint(&buf, 0, 4);
pq_sendint(&buf, 0, 2);
pq_endmessage(&buf);
/* Send a DataRow message */
pq_beginmessage(&buf, 'D');
pq_sendint(&buf, 3, 2); /* # of columns */
pq_sendint(&buf, strlen(sysid), 4); /* col1 len */
pq_sendbytes(&buf, (char *) &sysid, strlen(sysid));
pq_sendint(&buf, strlen(tli), 4); /* col2 len */
pq_sendbytes(&buf, (char *) tli, strlen(tli));
pq_sendint(&buf, strlen(xpos), 4); /* col3 len */
pq_sendbytes(&buf, (char *) xpos, strlen(xpos));
pq_endmessage(&buf);
/* Send CommandComplete and ReadyForQuery messages */
EndCommand("SELECT", DestRemote);
ReadyForQuery(DestRemote);
/* ReadyForQuery did pq_flush for us */
}
/*
* Establish the connection to the primary server for XLOG streaming
*/
static bool
libpqrcv_connect(char *conninfo, XLogRecPtr startpoint)
{
char conninfo_repl[MAXCONNINFO + 37];
char *primary_sysid;
char standby_sysid[32];
TimeLineID primary_tli;
TimeLineID standby_tli;
PGresult *res;
char cmd[64];
/*
* Connect using deliberately undocumented parameter: replication. The
* database name is ignored by the server in replication mode, but specify
* "replication" for .pgpass lookup.
*/
snprintf(conninfo_repl, sizeof(conninfo_repl),
"%s dbname=replication replication=true",
conninfo);
streamConn = PQconnectdb(conninfo_repl);
if (PQstatus(streamConn) != CONNECTION_OK)
ereport(ERROR,
(errmsg("could not connect to the primary server: %s",
PQerrorMessage(streamConn))));
/*
* Get the system identifier and timeline ID as a DataRow message from the
* primary server.
*/
res = libpqrcv_PQexec("IDENTIFY_SYSTEM");
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
PQclear(res);
ereport(ERROR,
(errmsg("could not receive database system identifier and timeline ID from "
"the primary server: %s",
PQerrorMessage(streamConn))));
}
if (PQnfields(res) != 2 || PQntuples(res) != 1)
{
int ntuples = PQntuples(res);
int nfields = PQnfields(res);
PQclear(res);
ereport(ERROR,
(errmsg("invalid response from primary server"),
errdetail("Expected 1 tuple with 2 fields, got %d tuples with %d fields.",
ntuples, nfields)));
}
primary_sysid = PQgetvalue(res, 0, 0);
primary_tli = pg_atoi(PQgetvalue(res, 0, 1), 4, 0);
/*
* Confirm that the system identifier of the primary is the same as ours.
*/
snprintf(standby_sysid, sizeof(standby_sysid), UINT64_FORMAT,
GetSystemIdentifier());
if (strcmp(primary_sysid, standby_sysid) != 0)
{
PQclear(res);
ereport(ERROR,
(errmsg("database system identifier differs between the primary and standby"),
errdetail("The primary's identifier is %s, the standby's identifier is %s.",
primary_sysid, standby_sysid)));
}
/*
* Confirm that the current timeline of the primary is the same as the
* recovery target timeline.
*/
standby_tli = GetRecoveryTargetTLI();
PQclear(res);
if (primary_tli != standby_tli)
ereport(ERROR,
(errmsg("timeline %u of the primary does not match recovery target timeline %u",
primary_tli, standby_tli)));
ThisTimeLineID = primary_tli;
/* Start streaming from the point requested by startup process */
snprintf(cmd, sizeof(cmd), "START_REPLICATION %X/%X",
startpoint.xlogid, startpoint.xrecoff);
res = libpqrcv_PQexec(cmd);
if (PQresultStatus(res) != PGRES_COPY_BOTH)
{
PQclear(res);
ereport(ERROR,
(errmsg("could not start WAL streaming: %s",
PQerrorMessage(streamConn))));
}
PQclear(res);
justconnected = true;
ereport(LOG,
(errmsg("streaming replication successfully connected to primary")));
return true;
}
/*
* Execute commands from walreceiver, until we enter streaming mode.
*/
static void
WalSndHandshake(void)
{
StringInfoData input_message;
bool replication_started = false;
initStringInfo(&input_message);
while (!replication_started)
{
int firstchar;
/* Wait for a command to arrive */
firstchar = pq_getbyte();
/*
* Emergency bailout if postmaster has died. This is to avoid the
* necessity for manual cleanup of all postmaster children.
*/
if (!PostmasterIsAlive(true))
exit(1);
/*
* Check for any other interesting events that happened while we
* slept.
*/
if (got_SIGHUP)
{
got_SIGHUP = false;
ProcessConfigFile(PGC_SIGHUP);
}
if (firstchar != EOF)
{
/*
* Read the message contents. This is expected to be done without
* blocking because we've been able to get message type code.
*/
if (pq_getmessage(&input_message, 0))
firstchar = EOF; /* suitable message already logged */
}
/* Handle the very limited subset of commands expected in this phase */
switch (firstchar)
{
case 'Q': /* Query message */
{
const char *query_string;
XLogRecPtr recptr;
query_string = pq_getmsgstring(&input_message);
pq_getmsgend(&input_message);
if (strcmp(query_string, "IDENTIFY_SYSTEM") == 0)
{
StringInfoData buf;
char sysid[32];
char tli[11];
/*
* Reply with a result set with one row, two columns.
* First col is system ID, and second is timeline ID
*/
snprintf(sysid, sizeof(sysid), UINT64_FORMAT,
GetSystemIdentifier());
snprintf(tli, sizeof(tli), "%u", ThisTimeLineID);
/* Send a RowDescription message */
pq_beginmessage(&buf, 'T');
pq_sendint(&buf, 2, 2); /* 2 fields */
/* first field */
pq_sendstring(&buf, "systemid"); /* col name */
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
pq_sendint(&buf, TEXTOID, 4); /* type oid */
pq_sendint(&buf, -1, 2); /* typlen */
pq_sendint(&buf, 0, 4); /* typmod */
pq_sendint(&buf, 0, 2); /* format code */
/* second field */
pq_sendstring(&buf, "timeline"); /* col name */
pq_sendint(&buf, 0, 4); /* table oid */
pq_sendint(&buf, 0, 2); /* attnum */
pq_sendint(&buf, INT4OID, 4); /* type oid */
pq_sendint(&buf, 4, 2); /* typlen */
pq_sendint(&buf, 0, 4); /* typmod */
pq_sendint(&buf, 0, 2); /* format code */
pq_endmessage(&buf);
/* Send a DataRow message */
pq_beginmessage(&buf, 'D');
pq_sendint(&buf, 2, 2); /* # of columns */
pq_sendint(&buf, strlen(sysid), 4); /* col1 len */
pq_sendbytes(&buf, (char *) &sysid, strlen(sysid));
pq_sendint(&buf, strlen(tli), 4); /* col2 len */
pq_sendbytes(&buf, (char *) tli, strlen(tli));
pq_endmessage(&buf);
/* Send CommandComplete and ReadyForQuery messages */
EndCommand("SELECT", DestRemote);
ReadyForQuery(DestRemote);
/* ReadyForQuery did pq_flush for us */
}
else if (sscanf(query_string, "START_REPLICATION %X/%X",
&recptr.xlogid, &recptr.xrecoff) == 2)
{
StringInfoData buf;
/*
* Check that we're logging enough information in the
* WAL for log-shipping.
*
* NOTE: This only checks the current value of
* wal_level. Even if the current setting is not
* 'minimal', there can be old WAL in the pg_xlog
* directory that was created with 'minimal'. So this
* is not bulletproof, the purpose is just to give a
* user-friendly error message that hints how to
* configure the system correctly.
*/
if (wal_level == WAL_LEVEL_MINIMAL)
ereport(FATAL,
(errcode(ERRCODE_CANNOT_CONNECT_NOW),
errmsg("standby connections not allowed because wal_level=minimal")));
/* Send a CopyOutResponse message, and start streaming */
pq_beginmessage(&buf, 'H');
pq_sendbyte(&buf, 0);
pq_sendint(&buf, 0, 2);
pq_endmessage(&buf);
pq_flush();
/*
* Initialize position to the received one, then the
* xlog records begin to be shipped from that position
*/
sentPtr = recptr;
/* break out of the loop */
replication_started = true;
}
else
{
ereport(FATAL,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("invalid standby query string: %s", query_string)));
}
break;
}
case 'X':
/* standby is closing the connection */
proc_exit(0);
case EOF:
/* standby disconnected unexpectedly */
ereport(COMMERROR,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("unexpected EOF on standby connection")));
proc_exit(0);
default:
ereport(FATAL,
(errcode(ERRCODE_PROTOCOL_VIOLATION),
errmsg("invalid standby handshake message type %d", firstchar)));
}
}
}