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Allow multiple hostaddrs to go with multiple hostnames. 

Also fix two other issues, while we're at it:

* In error message on connection failure, if multiple network addresses
were given as the host option, as in "host=127.0.0.1,127.0.0.2", the
error message printed the address twice.

* If there were many more ports than hostnames, the error message would
always claim that there was one port too many, even if there was more than
one. For example, if you gave 2 hostnames and 5 ports, the error message
claimed that you gave 2 hostnames and 3 ports.

Discussion: https://www.postgresql.org/message-id/10badbc6-4d5a-a769-623a-f7ada43e14dd@iki.fi
This commit is contained in:
Heikki Linnakangas 2017-07-10 12:28:57 +03:00
parent 260ba8525a
commit 7b02ba62e9
3 changed files with 222 additions and 100 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

55
doc/src/sgml/libpq.sgml
View File

@ -887,6 +887,42 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
host will be tried in turn until a connection is successfully established.
</para>
</sect3>
<sect3 id="libpq-multiple-hosts">
<title>Specifying Multiple Hosts</title>
<para>
It is possible to specify multiple hosts to connect to, so that they are
tried in the given order. In the Keyword/Value format, the <literal>host</>,
<literal>hostaddr</>, and <literal>port</> options accept a comma-separated
list of values. The same number of elements must be given in each option, such
that e.g. the first <literal>hostaddr</> corresponds to the first host name,
the second <literal>hostaddr</> corresponds to the second host name, and so
forth. As an exception, if only one <literal>port</literal> is specified, it
applies to all the hosts.
</para>
<para>
In the connection URI format, you can list multiple <literal>host:port</> pairs
separated by commas, in the <literal>host</> component of the URI. In either
format, a single hostname can also translate to multiple network addresses. A
common example of this is a host that has both an IPv4 and an IPv6 address.
</para>
<para>
When multiple hosts are specified, or when a single hostname is
translated to multiple addresses, all the hosts and addresses will be
tried in order, until one succeeds. If none of the hosts can be reached,
the connection fails. If a connection is established successfully, but
authentication fails, the remaining hosts in the list are not tried.
</para>
<para>
If a password file is used, you can have different passwords for
different hosts. All the other connection options are the same for every
host, it is not possible to e.g. specify a different username for
different hosts.
</para>
</sect2>
<sect2 id="libpq-paramkeywords">
@ -900,7 +936,7 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
<term><literal>host</literal></term>
<listitem>
<para>
Comma-separated list of host names.<indexterm><primary>host name</></>
Name of host to connect to.<indexterm><primary>host name</></>
If a host name begins with a slash, it specifies Unix-domain
communication rather than TCP/IP communication; the value is the
name of the directory in which the socket file is stored. If
@ -912,6 +948,11 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
when <productname>PostgreSQL</> was built). On machines without
Unix-domain sockets, the default is to connect to <literal>localhost</>.
</para>
<para>
A comma-separated list of host names is also accepted, in which case
each host name in the list is tried in order. See
<xref linkend="libpq-multiple-hosts"> for details.
</para>
</listitem>
</varlistentry>
@ -965,6 +1006,11 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
<xref linkend="libpq-pgpass">).
</para>
<para>
A comma-separated list of <literal>hostaddrs</> is also accepted, in
which case each host in the list is tried in order. See
<xref linkend="libpq-multiple-hosts"> for details.
</para>
<para>
Without either a host name or host address,
<application>libpq</application> will connect using a
@ -981,9 +1027,10 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
Port number to connect to at the server host, or socket file
name extension for Unix-domain
connections.<indexterm><primary>port</></>
If the <literal>host</> parameter included multiple, comma-separated
hosts, this parameter may specify a list of ports of equal length,
or it may specify a single port number to be used for all hosts.
If multiple hosts were given in the <literal>host</literal> or
<literal>hostaddr</> parameters, this parameter may specify a list
of ports of equal length, or it may specify a single port number to
be used for all hosts.
</para>
</listitem>
</varlistentry>

264
src/interfaces/libpq/fe-connect.c
View File

@ -827,6 +827,62 @@ connectOptions1(PGconn *conn, const char *conninfo)
return true;
}
/*
* Count the number of elements in a simple comma-separated list.
*/
static int
count_comma_separated_elems(const char *input)
{
int n;
n = 1;
for (; *input != '\0'; input++)
{
if (*input == ',')
n++;
}
return n;
}
/*
* Parse a simple comma-separated list.
*
* On each call, returns a malloc'd copy of the next element, and sets *more
* to indicate whether there are any more elements in the list after this,
* and updates *startptr to point to the next element, if any.
*
* On out of memory, returns NULL.
*/
static char *
parse_comma_separated_list(char **startptr, bool *more)
{
char *p;
char *s = *startptr;
char *e;
int len;
/*
* Search for the end of the current element; a comma or end-of-string
* acts as a terminator.
*/
e = s;
while (*e != '\0' && *e != ',')
++e;
*more = (*e == ',');
len = e - s;
p = (char *) malloc(sizeof(char) * (len + 1));
if (p)
{
memcpy(p, s, len);
p[len] = '\0';
}
*startptr = e + 1;
return p;
}
/*
* connectOptions2
*
@ -840,21 +896,16 @@ connectOptions2(PGconn *conn)
{
/*
* Allocate memory for details about each host to which we might possibly
* try to connect. If pghostaddr is set, we're only going to try to
* connect to that one particular address. If it's not, we'll use pghost,
* which may contain multiple, comma-separated names.
* try to connect. For that, count the number of elements in the hostaddr
* or host options. If neither is given, assume one host.
*/
conn->nconnhost = 1;
conn->whichhost = 0;
if ((conn->pghostaddr == NULL || conn->pghostaddr[0] == '\0')
&& conn->pghost != NULL)
{
char *s;
for (s = conn->pghost; *s != '\0'; ++s)
if (*s == ',')
conn->nconnhost++;
}
if (conn->pghostaddr && conn->pghostaddr[0] != '\0')
conn->nconnhost = count_comma_separated_elems(conn->pghostaddr);
else if (conn->pghost && conn->pghost[0] != '\0')
conn->nconnhost = count_comma_separated_elems(conn->pghost);
else
conn->nconnhost = 1;
conn->connhost = (pg_conn_host *)
calloc(conn->nconnhost, sizeof(pg_conn_host));
if (conn->connhost == NULL)
@ -866,51 +917,67 @@ connectOptions2(PGconn *conn)
*/
if (conn->pghostaddr != NULL && conn->pghostaddr[0] != '\0')
{
conn->connhost[0].host = strdup(conn->pghostaddr);
if (conn->connhost[0].host == NULL)
goto oom_error;
conn->connhost[0].type = CHT_HOST_ADDRESS;
}
else if (conn->pghost != NULL && conn->pghost[0] != '\0')
{
int i = 0;
char *s = conn->pghost;
int i;
char *s = conn->pghostaddr;
bool more = true;
while (1)
for (i = 0; i < conn->nconnhost && more; i++)
{
char *e = s;
conn->connhost[i].hostaddr = parse_comma_separated_list(&s, &more);
if (conn->connhost[i].hostaddr == NULL)
goto oom_error;
/*
* Search for the end of the current hostname; a comma or
* end-of-string acts as a terminator.
*/
while (*e != '\0' && *e != ',')
++e;
conn->connhost[i].type = CHT_HOST_ADDRESS;
}
/* Copy the hostname whose bounds we just identified. */
conn->connhost[i].host =
(char *) malloc(sizeof(char) * (e - s + 1));
/*
* If hostaddr was given, the array was allocated according to the
* number of elements in the hostaddr list, so it really should be the
* right size.
*/
Assert(!more);
Assert(i == conn->nconnhost);
}
if (conn->pghost != NULL && conn->pghost[0] != '\0')
{
int i;
char *s = conn->pghost;
bool more = true;
for (i = 0; i < conn->nconnhost && more; i++)
{
conn->connhost[i].host = parse_comma_separated_list(&s, &more);
if (conn->connhost[i].host == NULL)
goto oom_error;
memcpy(conn->connhost[i].host, s, e - s);
conn->connhost[i].host[e - s] = '\0';
/* Identify the type of host. */
conn->connhost[i].type = CHT_HOST_NAME;
if (conn->pghostaddr == NULL || conn->pghostaddr[0] == '\0')
{
conn->connhost[i].type = CHT_HOST_NAME;
#ifdef HAVE_UNIX_SOCKETS
if (is_absolute_path(conn->connhost[i].host))
conn->connhost[i].type = CHT_UNIX_SOCKET;
if (is_absolute_path(conn->connhost[i].host))
conn->connhost[i].type = CHT_UNIX_SOCKET;
#endif
/* Prepare to find the next host (if any). */
if (*e == '\0')
break;
s = e + 1;
i++;
}
}
if (more || i != conn->nconnhost)
{
conn->status = CONNECTION_BAD;
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("could not match %d host names to %d hostaddrs\n"),
count_comma_separated_elems(conn->pghost), conn->nconnhost);
return false;
}
}
else
/*
* If neither host or hostaddr options was given, connect to default host.
*/
if ((conn->pghostaddr == NULL || conn->pghostaddr[0] == '\0') &&
(conn->pghost == NULL || conn->pghost[0] == '\0'))
{
Assert(conn->nconnhost == 1);
#ifdef HAVE_UNIX_SOCKETS
conn->connhost[0].host = strdup(DEFAULT_PGSOCKET_DIR);
conn->connhost[0].type = CHT_UNIX_SOCKET;
@ -927,54 +994,36 @@ connectOptions2(PGconn *conn)
*/
if (conn->pgport != NULL && conn->pgport[0] != '\0')
{
int i = 0;
int i;
char *s = conn->pgport;
int nports = 1;
bool more = true;
for (i = 0; i < conn->nconnhost; ++i)
for (i = 0; i < conn->nconnhost && more; i++)
{
char *e = s;
/* Search for the end of the current port number. */
while (*e != '\0' && *e != ',')
++e;
/*
* If we found a port number of non-zero length, copy it.
* Otherwise, insert the default port number.
*/
if (e > s)
{
conn->connhost[i].port =
(char *) malloc(sizeof(char) * (e - s + 1));
if (conn->connhost[i].port == NULL)
goto oom_error;
memcpy(conn->connhost[i].port, s, e - s);
conn->connhost[i].port[e - s] = '\0';
}
/*
* Move on to the next port number, unless there are no more. (If
* only one part number is specified, we reuse it for every host.)
*/
if (*e != '\0')
{
s = e + 1;
++nports;
}
conn->connhost[i].port = parse_comma_separated_list(&s, &more);
if (conn->connhost[i].port == NULL)
goto oom_error;
}
/*
* If multiple ports were specified, there must be exactly as many
* ports as there were hosts. Otherwise, we do not know how to match
* them up.
* If exactly one port was given, use it for every host. Otherwise,
* there must be exactly as many ports as there were hosts.
*/
if (nports != 1 && nports != conn->nconnhost)
if (i == 1 && !more)
{
for (i = 1; i < conn->nconnhost; i++)
{
conn->connhost[i].port = strdup(conn->connhost[0].port);
if (conn->connhost[i].port == NULL)
goto oom_error;
}
}
else if (more || i != conn->nconnhost)
{
conn->status = CONNECTION_BAD;
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("could not match %d port numbers to %d hosts\n"),
nports, conn->nconnhost);
count_comma_separated_elems(conn->pgport), conn->nconnhost);
return false;
}
}
@ -1048,8 +1097,8 @@ connectOptions2(PGconn *conn)
char *pwhost = conn->connhost[i].host;
if (conn->connhost[i].type == CHT_HOST_ADDRESS &&
conn->pghost != NULL && conn->pghost[0] != '\0')
pwhost = conn->pghost;
conn->connhost[i].host != NULL && conn->connhost[i].host != '\0')
pwhost = conn->connhost[i].hostaddr;
conn->connhost[i].password =
passwordFromFile(pwhost,
@ -1399,8 +1448,8 @@ connectFailureMessage(PGconn *conn, int errorno)
* Optionally display the network address with the hostname. This is
* useful to distinguish between IPv4 and IPv6 connections.
*/
if (conn->pghostaddr != NULL)
strlcpy(host_addr, conn->pghostaddr, NI_MAXHOST);
if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
strlcpy(host_addr, conn->connhost[conn->whichhost].hostaddr, NI_MAXHOST);
else if (addr->ss_family == AF_INET)
{
if (inet_net_ntop(AF_INET,
@ -1423,7 +1472,10 @@ connectFailureMessage(PGconn *conn, int errorno)
strcpy(host_addr, "???");
/* To which host and port were we actually connecting? */
displayed_host = conn->connhost[conn->whichhost].host;
if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
displayed_host = conn->connhost[conn->whichhost].hostaddr;
else
displayed_host = conn->connhost[conn->whichhost].host;
displayed_port = conn->connhost[conn->whichhost].port;
if (displayed_port == NULL || displayed_port[0] == '\0')
displayed_port = DEF_PGPORT_STR;
@ -1433,8 +1485,8 @@ connectFailureMessage(PGconn *conn, int errorno)
* 'host' was missing or does not match our lookup, display the
* looked-up IP address.
*/
if ((conn->pghostaddr == NULL) &&
(conn->pghost == NULL || strcmp(conn->pghost, host_addr) != 0))
if (conn->connhost[conn->whichhost].type != CHT_HOST_ADDRESS &&
strcmp(displayed_host, host_addr) != 0)
appendPQExpBuffer(&conn->errorMessage,
libpq_gettext("could not connect to server: %s\n"
"\tIs the server running on host \"%s\" (%s) and accepting\n"
@ -1659,7 +1711,7 @@ connectDBStart(PGconn *conn)
hint.ai_family = AF_UNSPEC;
/* Figure out the port number we're going to use. */
if (ch->port == NULL)
if (ch->port == NULL || ch->port[0] == '\0')
thisport = DEF_PGPORT;
else
{
@ -1689,7 +1741,7 @@ connectDBStart(PGconn *conn)
case CHT_HOST_ADDRESS:
hint.ai_flags = AI_NUMERICHOST;
ret = pg_getaddrinfo_all(ch->host, portstr, &hint, &ch->addrlist);
ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint, &ch->addrlist);
if (ret || !ch->addrlist)
appendPQExpBuffer(&conn->errorMessage,
libpq_gettext("could not parse network address \"%s\": %s\n"),
@ -3041,6 +3093,9 @@ keep_going: /* We will come back to here until there is
}
case CONNECTION_CHECK_WRITABLE:
{
const char *displayed_host;
const char *displayed_port;
if (!saveErrorMessage(conn, &savedMessage))
goto error_return;
@ -3067,6 +3122,17 @@ keep_going: /* We will come back to here until there is
val = PQgetvalue(res, 0, 0);
if (strncmp(val, "on", 2) == 0)
{
const char *displayed_host;
const char *displayed_port;
if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
displayed_host = conn->connhost[conn->whichhost].hostaddr;
else
displayed_host = conn->connhost[conn->whichhost].host;
displayed_port = conn->connhost[conn->whichhost].port;
if (displayed_port == NULL || displayed_port[0] == '\0')
displayed_port = DEF_PGPORT_STR;
PQclear(res);
restoreErrorMessage(conn, &savedMessage);
@ -3075,8 +3141,7 @@ keep_going: /* We will come back to here until there is
libpq_gettext("could not make a writable "
"connection to server "
"\"%s:%s\"\n"),
conn->connhost[conn->whichhost].host,
conn->connhost[conn->whichhost].port);
displayed_host, displayed_port);
conn->status = CONNECTION_OK;
sendTerminateConn(conn);
pqDropConnection(conn, true);
@ -3113,11 +3178,18 @@ keep_going: /* We will come back to here until there is
if (res)
PQclear(res);
restoreErrorMessage(conn, &savedMessage);
if (conn->connhost[conn->whichhost].type == CHT_HOST_ADDRESS)
displayed_host = conn->connhost[conn->whichhost].hostaddr;
else
displayed_host = conn->connhost[conn->whichhost].host;
displayed_port = conn->connhost[conn->whichhost].port;
if (displayed_port == NULL || displayed_port[0] == '\0')
displayed_port = DEF_PGPORT_STR;
appendPQExpBuffer(&conn->errorMessage,
libpq_gettext("test \"SHOW transaction_read_only\" failed "
"on server \"%s:%s\"\n"),
conn->connhost[conn->whichhost].host,
conn->connhost[conn->whichhost].port);
displayed_host, displayed_port);
conn->status = CONNECTION_OK;
sendTerminateConn(conn);
pqDropConnection(conn, true);
@ -3350,6 +3422,8 @@ freePGconn(PGconn *conn)
{
if (conn->connhost[i].host != NULL)
free(conn->connhost[i].host);
if (conn->connhost[i].hostaddr != NULL)
free(conn->connhost[i].hostaddr);
if (conn->connhost[i].port != NULL)
free(conn->connhost[i].port);
if (conn->connhost[i].password != NULL)

3
src/interfaces/libpq/libpq-int.h
View File

@ -304,8 +304,9 @@ typedef enum pg_conn_host_type
*/
typedef struct pg_conn_host
{
char *host; /* host name or address, or socket path */
pg_conn_host_type type; /* type of host */
char *host; /* host name or socket path */
char *hostaddr; /* host address */
char *port; /* port number for this host; if not NULL,
* overrides the PGConn's pgport */
char *password; /* password for this host, read from the