Refactor replication connection code of various pg_basebackup utilities.

Move some more code to manage replication connection command to
streamutil.c. A later patch will introduce replication slot via
pg_receivexlog and this avoid duplicating relevant code between
pg_receivexlog and pg_recvlogical.

Author: Michael Paquier, with some editing by me.

diff --git a/src/bin/pg_basebackup/pg_basebackup.c b/src/bin/pg_basebackup/pg_basebackup.c
index 8b9acea9f087516df589223fab4e351e4f12f354..0ebda9ae9e04f44bd2f7c6bf22454ed2f7095499 100644 (file)
--- a/src/bin/pg_basebackup/pg_basebackup.c
+++ b/src/bin/pg_basebackup/pg_basebackup.c
@@ -1569,8 +1569,8 @@ BaseBackup(void)
 {
    PGresult   *res;
    char       *sysidentifier;
-   uint32      latesttli;
-   uint32      starttli;
+   TimeLineID  latesttli;
+   TimeLineID  starttli;
    char       *basebkp;
    char        escaped_label[MAXPGPATH];
    char       *maxrate_clause = NULL;
@@ -1624,23 +1624,8 @@ BaseBackup(void)
    /*
     * Run IDENTIFY_SYSTEM so we can get the timeline
     */
-   res = PQexec(conn, "IDENTIFY_SYSTEM");
-   if (PQresultStatus(res) != PGRES_TUPLES_OK)
-   {
-       fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
-               progname, "IDENTIFY_SYSTEM", PQerrorMessage(conn));
+   if (!RunIdentifySystem(conn, &sysidentifier, &latesttli, NULL, NULL))
        disconnect_and_exit(1);
-   }
-   if (PQntuples(res) != 1 || PQnfields(res) < 3)
-   {
-       fprintf(stderr,
-               _("%s: could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields\n"),
-               progname, PQntuples(res), PQnfields(res), 1, 3);
-       disconnect_and_exit(1);
-   }
-   sysidentifier = pg_strdup(PQgetvalue(res, 0, 0));
-   latesttli = atoi(PQgetvalue(res, 0, 1));
-   PQclear(res);
 
    /*
     * Start the actual backup

diff --git a/src/bin/pg_basebackup/pg_receivexlog.c b/src/bin/pg_basebackup/pg_receivexlog.c
index a8b9ad3c05fe71935da0c3f1cd4c45c3dafbfeed..171cf431f57a65ddb9e35d527ce345d19f451da2 100644 (file)
--- a/src/bin/pg_basebackup/pg_receivexlog.c
+++ b/src/bin/pg_basebackup/pg_receivexlog.c
@@ -253,13 +253,8 @@ FindStreamingStart(uint32 *tli)
 static void
 StreamLog(void)
 {
-   PGresult   *res;
-   XLogRecPtr  startpos;
-   uint32      starttli;
-   XLogRecPtr  serverpos;
-   uint32      servertli;
-   uint32      hi,
-               lo;
+   XLogRecPtr  startpos, serverpos;
+   TimeLineID  starttli, servertli;
 
    /*
     * Connect in replication mode to the server
@@ -280,33 +275,12 @@ StreamLog(void)
    }
 
    /*
-    * Run IDENTIFY_SYSTEM so we can get the timeline and current xlog
-    * position.
+    * Identify server, obtaining start LSN position and current timeline ID
+    * at the same time, necessary if not valid data can be found in the
+    * existing output directory.
     */
-   res = PQexec(conn, "IDENTIFY_SYSTEM");
-   if (PQresultStatus(res) != PGRES_TUPLES_OK)
-   {
-       fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
-               progname, "IDENTIFY_SYSTEM", PQerrorMessage(conn));
-       disconnect_and_exit(1);
-   }
-   if (PQntuples(res) != 1 || PQnfields(res) < 3)
-   {
-       fprintf(stderr,
-               _("%s: could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields\n"),
-               progname, PQntuples(res), PQnfields(res), 1, 3);
+   if (!RunIdentifySystem(conn, NULL, &servertli, &serverpos, NULL))
        disconnect_and_exit(1);
-   }
-   servertli = atoi(PQgetvalue(res, 0, 1));
-   if (sscanf(PQgetvalue(res, 0, 2), "%X/%X", &hi, &lo) != 2)
-   {
-       fprintf(stderr,
-               _("%s: could not parse transaction log location \"%s\"\n"),
-               progname, PQgetvalue(res, 0, 2));
-       disconnect_and_exit(1);
-   }
-   serverpos = ((uint64) hi) << 32 | lo;
-   PQclear(res);
 
    /*
     * Figure out where to start streaming.

diff --git a/src/bin/pg_basebackup/pg_recvlogical.c b/src/bin/pg_basebackup/pg_recvlogical.c
index a88ffacc06df62fb2d812c1da7e3449afad57937..c48ceccf90164597e235d64980382ef85b13baae 100644 (file)
--- a/src/bin/pg_basebackup/pg_recvlogical.c
+++ b/src/bin/pg_basebackup/pg_recvlogical.c
@@ -596,7 +596,6 @@ sighup_handler(int signum)
 int
 main(int argc, char **argv)
 {
-   PGresult   *res;
    static struct option long_options[] = {
 /* general options */
        {"file", required_argument, NULL, 'f'},
@@ -628,6 +627,7 @@ main(int argc, char **argv)
    int         option_index;
    uint32      hi,
                lo;
+   char       *db_name;
 
    progname = get_progname(argv[0]);
    set_pglocale_pgservice(argv[0], PG_TEXTDOMAIN("pg_recvlogical"));
@@ -834,124 +834,62 @@ main(int argc, char **argv)
 #endif
 
    /*
-    * don't really need this but it actually helps to get more precise error
-    * messages about authentication, required GUCs and such without starting
-    * to loop around connection attempts lateron.
+    * Obtain a connection to server. This is not really necessary but it
+    * helps to get more precise error messages about authentification,
+    * required GUC parameters and such.
     */
-   {
-       conn = GetConnection();
-       if (!conn)
-           /* Error message already written in GetConnection() */
-           exit(1);
+   conn = GetConnection();
+   if (!conn)
+       /* Error message already written in GetConnection() */
+       exit(1);
 
-       /*
-        * Run IDENTIFY_SYSTEM so we can get the timeline and current xlog
-        * position.
-        */
-       res = PQexec(conn, "IDENTIFY_SYSTEM");
-       if (PQresultStatus(res) != PGRES_TUPLES_OK)
-       {
-           fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
-                   progname, "IDENTIFY_SYSTEM", PQerrorMessage(conn));
-           disconnect_and_exit(1);
-       }
+   /*
+    * Run IDENTIFY_SYSTEM to make sure we connected using a database specific
+    * replication connection.
+    */
+   if (!RunIdentifySystem(conn, NULL, NULL, NULL, &db_name))
+       disconnect_and_exit(1);
 
-       if (PQntuples(res) != 1 || PQnfields(res) < 4)
-       {
-           fprintf(stderr,
-                   _("%s: could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields\n"),
-                   progname, PQntuples(res), PQnfields(res), 1, 4);
-           disconnect_and_exit(1);
-       }
-       PQclear(res);
+   if (db_name == NULL)
+   {
+       fprintf(stderr,
+               _("%s: failed to establish database specific replication connection\n"),
+               progname);
+       disconnect_and_exit(1);
    }
 
-
-   /*
-    * drop a replication slot
-    */
+   /* Drop a replication slot. */
    if (do_drop_slot)
    {
-       char        query[256];
-
        if (verbose)
            fprintf(stderr,
                    _("%s: dropping replication slot \"%s\"\n"),
                    progname, replication_slot);
 
-       snprintf(query, sizeof(query), "DROP_REPLICATION_SLOT \"%s\"",
-                replication_slot);
-       res = PQexec(conn, query);
-       if (PQresultStatus(res) != PGRES_COMMAND_OK)
-       {
-           fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
-                   progname, query, PQerrorMessage(conn));
+       if (!DropReplicationSlot(conn, replication_slot))
            disconnect_and_exit(1);
-       }
-
-       if (PQntuples(res) != 0 || PQnfields(res) != 0)
-       {
-           fprintf(stderr,
-                   _("%s: could not drop replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields\n"),
-                   progname, replication_slot, PQntuples(res), PQnfields(res), 0, 0);
-           disconnect_and_exit(1);
-       }
-
-       PQclear(res);
-       disconnect_and_exit(0);
    }
 
-   /*
-    * create a replication slot
-    */
+   /* Create a replication slot. */
    if (do_create_slot)
    {
-       char        query[256];
-
        if (verbose)
            fprintf(stderr,
                    _("%s: creating replication slot \"%s\"\n"),
                    progname, replication_slot);
 
-       snprintf(query, sizeof(query), "CREATE_REPLICATION_SLOT \"%s\" LOGICAL \"%s\"",
-                replication_slot, plugin);
-
-       res = PQexec(conn, query);
-       if (PQresultStatus(res) != PGRES_TUPLES_OK)
-       {
-           fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
-                   progname, query, PQerrorMessage(conn));
+       if (!CreateReplicationSlot(conn, replication_slot, plugin,
+                                  &startpos, false))
            disconnect_and_exit(1);
-       }
-
-       if (PQntuples(res) != 1 || PQnfields(res) != 4)
-       {
-           fprintf(stderr,
-                   _("%s: could not create replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields\n"),
-                   progname, replication_slot, PQntuples(res), PQnfields(res), 1, 4);
-           disconnect_and_exit(1);
-       }
-
-       if (sscanf(PQgetvalue(res, 0, 1), "%X/%X", &hi, &lo) != 2)
-       {
-           fprintf(stderr,
-                   _("%s: could not parse transaction log location \"%s\"\n"),
-                   progname, PQgetvalue(res, 0, 1));
-           disconnect_and_exit(1);
-       }
-       startpos = ((uint64) hi) << 32 | lo;
-
-       replication_slot = strdup(PQgetvalue(res, 0, 0));
-       PQclear(res);
    }
 
-
    if (!do_start_slot)
        disconnect_and_exit(0);
 
+   /* Stream loop */
    while (true)
    {
-       StreamLog();
+       StreamLogicalLog();
        if (time_to_abort)
        {
            /*

diff --git a/src/bin/pg_basebackup/streamutil.c b/src/bin/pg_basebackup/streamutil.c
index 1100260c05abd83bbdc432a24d4c1d8bfbbad119..2f4bac95508cdc66a7be6e6b6cff66baa9e10362 100644 (file)
--- a/src/bin/pg_basebackup/streamutil.c
+++ b/src/bin/pg_basebackup/streamutil.c
@@ -27,6 +27,7 @@
 #include "receivelog.h"
 #include "streamutil.h"
 
+#include "pqexpbuffer.h"
 #include "common/fe_memutils.h"
 #include "datatype/timestamp.h"
 
@@ -227,11 +228,183 @@ GetConnection(void)
    return tmpconn;
 }
 
+/*
+ * Run IDENTIFY_SYSTEM through a given connection and give back to caller
+ * some result information if requested:
+ * - Start LSN position
+ * - Current timeline ID
+ * - System identifier
+ * - Plugin name
+ */
+bool
+RunIdentifySystem(PGconn *conn, char **sysid, TimeLineID *starttli,
+                 XLogRecPtr *startpos, char **db_name)
+{
+   PGresult   *res;
+   uint32      hi, lo;
+
+   /* Check connection existence */
+   Assert(conn != NULL);
+
+   res = PQexec(conn, "IDENTIFY_SYSTEM");
+   if (PQresultStatus(res) != PGRES_TUPLES_OK)
+   {
+       fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
+               progname, "IDENTIFY_SYSTEM", PQerrorMessage(conn));
+       return false;
+   }
+   if (PQntuples(res) != 1 || PQnfields(res) < 3)
+   {
+       fprintf(stderr,
+               _("%s: could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields\n"),
+               progname, PQntuples(res), PQnfields(res), 1, 3);
+       return false;
+   }
+
+   /* Get system identifier */
+   if (sysid != NULL)
+       *sysid = pg_strdup(PQgetvalue(res, 0, 0));
+
+   /* Get timeline ID to start streaming from */
+   if (starttli != NULL)
+       *starttli = atoi(PQgetvalue(res, 0, 1));
+
+   /* Get LSN start position if necessary */
+   if (startpos != NULL)
+   {
+       if (sscanf(PQgetvalue(res, 0, 2), "%X/%X", &hi, &lo) != 2)
+       {
+           fprintf(stderr,
+                   _("%s: could not parse transaction log location \"%s\"\n"),
+                   progname, PQgetvalue(res, 0, 2));
+           return false;
+       }
+       *startpos = ((uint64) hi) << 32 | lo;
+   }
+
+   /* Get database name, only available in 9.4 and newer versions */
+   if  (db_name != NULL)
+   {
+       if (PQnfields(res) < 4)
+           fprintf(stderr,
+                   _("%s: could not identify system: got %d rows and %d fields, expected %d rows and %d or more fields\n"),
+                   progname, PQntuples(res), PQnfields(res), 1, 4);
+
+       if (PQgetisnull(res, 0, 3))
+           *db_name =  NULL;
+       else
+           *db_name = pg_strdup(PQgetvalue(res, 0, 3));
+   }
+
+   PQclear(res);
+   return true;
+}
+
+/*
+ * Create a replication slot for the given connection. This function
+ * returns true in case of success as well as the start position
+ * obtained after the slot creation.
+ */
+bool
+CreateReplicationSlot(PGconn *conn, const char *slot_name, const char *plugin,
+                     XLogRecPtr *startpos, bool is_physical)
+{
+   PQExpBuffer query;
+   PGresult   *res;
+
+   query = createPQExpBuffer();
+
+   Assert((is_physical && plugin == NULL) ||
+          (!is_physical && plugin != NULL));
+   Assert(slot_name != NULL);
+
+   /* Build query */
+   if (is_physical)
+       appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" PHYSICAL",
+                         slot_name);
+   else
+       appendPQExpBuffer(query, "CREATE_REPLICATION_SLOT \"%s\" LOGICAL \"%s\"",
+                         slot_name, plugin);
+
+   res = PQexec(conn, query->data);
+   if (PQresultStatus(res) != PGRES_TUPLES_OK)
+   {
+       fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
+               progname, query->data, PQerrorMessage(conn));
+       return false;
+   }
+
+   if (PQntuples(res) != 1 || PQnfields(res) != 4)
+   {
+       fprintf(stderr,
+               _("%s: could not create replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields\n"),
+               progname, slot_name,
+               PQntuples(res), PQnfields(res), 1, 4);
+       return false;
+   }
+
+   /* Get LSN start position if necessary */
+   if (startpos != NULL)
+   {
+       uint32      hi, lo;
+
+       if (sscanf(PQgetvalue(res, 0, 1), "%X/%X", &hi, &lo) != 2)
+       {
+           fprintf(stderr,
+                   _("%s: could not parse transaction log location \"%s\"\n"),
+                   progname, PQgetvalue(res, 0, 1));
+           return false;
+       }
+       *startpos = ((uint64) hi) << 32 | lo;
+   }
+
+   PQclear(res);
+   return true;
+}
+
+/*
+ * Drop a replication slot for the given connection. This function
+ * returns true in case of success.
+ */
+bool
+DropReplicationSlot(PGconn *conn, const char *slot_name)
+{
+   PQExpBuffer query;
+   PGresult   *res;
+
+   Assert(slot_name != NULL);
+
+   query = createPQExpBuffer();
+
+   /* Build query */
+   appendPQExpBuffer(query, "DROP_REPLICATION_SLOT \"%s\"",
+                     slot_name);
+   res = PQexec(conn, query->data);
+   if (PQresultStatus(res) != PGRES_COMMAND_OK)
+   {
+       fprintf(stderr, _("%s: could not send replication command \"%s\": %s"),
+               progname, query->data, PQerrorMessage(conn));
+       return false;
+   }
+
+   if (PQntuples(res) != 0 || PQnfields(res) != 0)
+   {
+       fprintf(stderr,
+               _("%s: could not drop replication slot \"%s\": got %d rows and %d fields, expected %d rows and %d fields\n"),
+               progname, slot_name,
+               PQntuples(res), PQnfields(res), 0, 0);
+       return false;
+   }
+
+   PQclear(res);
+   return true;
+}
+
 
 /*
  * Frontend version of GetCurrentTimestamp(), since we are not linked with
- * backend code. The protocol always uses integer timestamps, regardless of
- * server setting.
+ * backend code. The replication protocol always uses integer timestamps,
+ * regardless of the server setting.
  */
 int64
 feGetCurrentTimestamp(void)

diff --git a/src/bin/pg_basebackup/streamutil.h b/src/bin/pg_basebackup/streamutil.h
index 8c6691f9c8c6d318a17961484af9b7774427abf5..ac66145c359e91783060e8368b334a5e4e707096 100644 (file)
--- a/src/bin/pg_basebackup/streamutil.h
+++ b/src/bin/pg_basebackup/streamutil.h
@@ -14,6 +14,8 @@
 
 #include "libpq-fe.h"
 
+#include "access/xlogdefs.h"
+
 extern const char *progname;
 extern char *connection_string;
 extern char *dbhost;
@@ -28,6 +30,15 @@ extern PGconn *conn;
 
 extern PGconn *GetConnection(void);
 
+/* Replication commands */
+extern bool CreateReplicationSlot(PGconn *conn, const char *slot_name,
+                                 const char *plugin, XLogRecPtr *startpos,
+                                 bool is_physical);
+extern bool DropReplicationSlot(PGconn *conn, const char *slot_name);
+extern bool RunIdentifySystem(PGconn *conn, char **sysid,
+                             TimeLineID *starttli,
+                             XLogRecPtr *startpos,
+                             char **db_name);
 extern int64 feGetCurrentTimestamp(void);
 extern void feTimestampDifference(int64 start_time, int64 stop_time,
                      long *secs, int *microsecs);