From 7b02ba62e9ffad5b14c24756a0c2aeae839c9d05 Mon Sep 17 00:00:00 2001 From: Heikki Linnakangas Date: Mon, 10 Jul 2017 12:28:57 +0300 Subject: [PATCH] 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 --- doc/src/sgml/libpq.sgml | 55 ++++++- src/interfaces/libpq/fe-connect.c | 258 +++++++++++++++++++----------- src/interfaces/libpq/libpq-int.h | 3 +- 3 files changed, 219 insertions(+), 97 deletions(-) diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml index f0167a64bc..124c21bed7 100644 --- a/doc/src/sgml/libpq.sgml +++ b/doc/src/sgml/libpq.sgml @@ -887,6 +887,42 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname host will be tried in turn until a connection is successfully established. + + + Specifying Multiple Hosts + + + 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 host, + hostaddr, and 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 hostaddr corresponds to the first host name, + the second hostaddr corresponds to the second host name, and so + forth. As an exception, if only one port is specified, it + applies to all the hosts. + + + + In the connection URI format, you can list multiple host:port pairs + separated by commas, in the 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. + + + + 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. + + + + 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. + @@ -900,7 +936,7 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname host - Comma-separated list of host names.host name + Name of host to connect to.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 PostgreSQL was built). On machines without Unix-domain sockets, the default is to connect to localhost. + + A comma-separated list of host names is also accepted, in which case + each host name in the list is tried in order. See + for details. + @@ -965,6 +1006,11 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname ). + + A comma-separated list of hostaddrs is also accepted, in + which case each host in the list is tried in order. See + for details. + Without either a host name or host address, libpq 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.port - If the 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 host or + 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. diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index 2f7b4060df..e548f3f062 100644 --- a/src/interfaces/libpq/fe-connect.c +++ b/src/interfaces/libpq/fe-connect.c @@ -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; + int i; + char *s = conn->pghostaddr; + bool more = true; + + for (i = 0; i < conn->nconnhost && more; i++) + { + conn->connhost[i].hostaddr = parse_comma_separated_list(&s, &more); + if (conn->connhost[i].hostaddr == NULL) + goto oom_error; + + conn->connhost[i].type = CHT_HOST_ADDRESS; + } + + /* + * 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); } - else if (conn->pghost != NULL && conn->pghost[0] != '\0') + + if (conn->pghost != NULL && conn->pghost[0] != '\0') { - int i = 0; + int i; char *s = conn->pghost; + bool more = true; - while (1) + for (i = 0; i < conn->nconnhost && more; i++) { - char *e = s; - - /* - * Search for the end of the current hostname; a comma or - * end-of-string acts as a terminator. - */ - while (*e != '\0' && *e != ',') - ++e; - - /* Copy the hostname whose bounds we just identified. */ - conn->connhost[i].host = - (char *) malloc(sizeof(char) * (e - s + 1)); + 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; + conn->connhost[i].port = parse_comma_separated_list(&s, &more); + if (conn->connhost[i].port == NULL) + goto oom_error; + } - /* - * If we found a port number of non-zero length, copy it. - * Otherwise, insert the default port number. - */ - if (e > s) + /* + * If exactly one port was given, use it for every host. Otherwise, + * there must be exactly as many ports as there were hosts. + */ + if (i == 1 && !more) + { + for (i = 1; i < conn->nconnhost; i++) { - conn->connhost[i].port = - (char *) malloc(sizeof(char) * (e - s + 1)); + conn->connhost[i].port = strdup(conn->connhost[0].port); 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; } } - - /* - * 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 (nports != 1 && nports != conn->nconnhost) + 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) diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h index ff5020fc0c..42913604e3 100644 --- a/src/interfaces/libpq/libpq-int.h +++ b/src/interfaces/libpq/libpq-int.h @@ -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 -- 2.40.0