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repmgr: prevent a standby being cloned from a witness server

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Previously repmgr would happily clone from whatever server
it found at the provided source server address. We should
ensure that a standby can only be cloned from a node which
is part of the main replication cluster.

This check fetches a list of nodes from the source server,
connects to the first non-witness server it finds, and
compares the system identifiers of the source node and the
node it has connected to. If there is a mismatch, then the
source server is clearly not part of the main replication
cluster, and is most likely the witness server.
This commit is contained in:
Ian Barwick
2019-05-22 16:29:41 +09:00
parent fa66e72c2f
commit c9e85996f5
5 changed files with 124 additions and 2 deletions
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39
dbutils.c
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@@ -1551,12 +1551,12 @@ get_ready_archive_files(PGconn *conn, const char *data_directory)
}
bool
identify_system(PGconn *repl_conn, t_system_identification *identification)
{
PGresult *res = NULL;
/* semicolon required here */
res = PQexec(repl_conn, "IDENTIFY_SYSTEM;");
if (PQresultStatus(res) != PGRES_TUPLES_OK || !PQntuples(res))
@@ -1576,6 +1576,43 @@ identify_system(PGconn *repl_conn, t_system_identification *identification)
}
/*
* Return the system identifier by querying pg_control_system().
*
* Note there is a similar function in controldata.c ("get_system_identifier()")
* which reads the control file.
*/
uint64
system_identifier(PGconn *conn)
{
uint64 system_identifier = UNKNOWN_SYSTEM_IDENTIFIER;
PGresult *res = NULL;
/*
* pg_control_system() was introduced in PostgreSQL 9.6
*/
if (PQserverVersion(conn) < 90600)
{
return UNKNOWN_SYSTEM_IDENTIFIER;
}
res = PQexec(conn, "SELECT system_identifier FROM pg_catalog.pg_control_system()");
if (PQresultStatus(res) != PGRES_TUPLES_OK)
{
log_db_error(conn, NULL, _("get_system_identifier(): unable to query pg_control_system()"));
}
else
{
system_identifier = atol(PQgetvalue(res, 0, 0));
}
PQclear(res);
return system_identifier;
}
TimeLineHistoryEntry *
get_timeline_history(PGconn *repl_conn, TimeLineID tli)
{