From 6e20bb223012b666161521b5e7249c066467a5f3 Mon Sep 17 00:00:00 2001 From: Jelte Fennema Date: Mon, 12 Sep 2022 09:44:06 +0200 Subject: [PATCH v5] Support load balancing in libpq Load balancing connections across multiple read replicas is a pretty common way of scaling out read queries. There are two main ways of doing so, both with their own advantages and disadvantages: 1. Load balancing at the client level 2. Load balancing by connecting to an intermediary load balancer Both JBDC (Java) and Npgsql (C#) already support client level load balancing (option #1). This patch implements client level load balancing for libpq as well. To stay consistent with the JDBC and Npgsql part of the ecosystem, a similar implementation and name for the option are used. It contains two levels of load balancing: 1. The given hosts are randomly shuffled, before resolving them one-by-one. 2. Once a host its addresses get resolved, those addresses are shuffled, before trying to connect to them one-by-one. --- .cirrus.yml | 14 ++ doc/src/sgml/libpq.sgml | 48 +++++ src/include/libpq/pqcomm.h | 6 + src/interfaces/libpq/fe-connect.c | 231 +++++++++++++++++++--- src/interfaces/libpq/libpq-int.h | 12 +- src/interfaces/libpq/meson.build | 1 + src/interfaces/libpq/t/003_loadbalance.pl | 167 ++++++++++++++++ 7 files changed, 446 insertions(+), 33 deletions(-) create mode 100644 src/interfaces/libpq/t/003_loadbalance.pl diff --git a/.cirrus.yml b/.cirrus.yml index f31923333e..54c3c00e1b 100644 --- a/.cirrus.yml +++ b/.cirrus.yml @@ -293,6 +293,14 @@ task: mkdir -m 770 /tmp/cores chown root:postgres /tmp/cores sysctl kernel.core_pattern='/tmp/cores/%e-%s-%p.core' + + setup_hosts_file_script: | + cat >> /etc/hosts <<-EOF + 127.0.0.1 pg-loadbalancetest + 127.0.0.2 pg-loadbalancetest + 127.0.0.3 pg-loadbalancetest + EOF + setup_additional_packages_script: | #apt-get update #DEBIAN_FRONTEND=noninteractive apt-get -y install ... @@ -540,6 +548,12 @@ task: setup_additional_packages_script: | REM choco install -y --no-progress ... + setup_hosts_file_script: | + echo 127.0.0.1 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts + echo 127.0.0.2 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts + echo 127.0.0.3 pg-loadbalancetest >> c:\Windows\System32\Drivers\etc\hosts + type c:\Windows\System32\Drivers\etc\hosts + # Use /DEBUG:FASTLINK to avoid high memory usage during linking configure_script: | vcvarsall x64 diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml index f9558dec3b..6ce7a0c9cc 100644 --- a/doc/src/sgml/libpq.sgml +++ b/doc/src/sgml/libpq.sgml @@ -1316,6 +1316,54 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname + + load_balance_hosts + + + Controls whether the client load balances connections across hosts and + adresses. The default value is 0, meaning off, this means that hosts are + tried in order they are provided and addresses are tried in the order + they are received from DNS or a hosts file. If this value is set to 1, + meaning on, the hosts and addresses that they resolve to are tried in + random order. Subsequent queries once connected will still be sent to + the same server. Setting this to 1, is mostly useful when opening + multiple connections at the same time, possibly from different machines. + This way connections can be load balanced across multiple Postgres + servers. + + + When providing multiple hosts, these hosts are resolved in random order. + Then if that host resolves to multiple addresses, these addresses are + connected to in random order. Only once all addresses for a single host + have been tried, the addresses for the next random host will be + resolved. This behaviour can lead to non-uniform address selection in + certain cases. Such as when not all hosts resolve to the same number of + addresses, or when multiple hosts resolve to the same address. So if you + want uniform load balancing, this is something to keep in mind. However, + non-uniform load balancing also has usecases, e.g. providing the + hostname of a larger server multiple times in the host string so it gets + more requests. + + + When using this setting it's recommended to also configure a reasonable + value for . Because then, + if one of the nodes that are used for load balancing is not responding, + a new node will be tried. + + + + + + random_seed + + + Sets the random seed that is used by + to randomize the host order. This option is mostly useful when running + tests that require a stable random order. + + + + keepalives diff --git a/src/include/libpq/pqcomm.h b/src/include/libpq/pqcomm.h index fcf68df39b..39e93b1392 100644 --- a/src/include/libpq/pqcomm.h +++ b/src/include/libpq/pqcomm.h @@ -27,6 +27,12 @@ typedef struct socklen_t salen; } SockAddr; +typedef struct +{ + int family; + SockAddr addr; +} AddrInfo; + /* Configure the UNIX socket location for the well known port. */ #define UNIXSOCK_PATH(path, port, sockdir) \ diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c index f88d672c6c..b4d3613713 100644 --- a/src/interfaces/libpq/fe-connect.c +++ b/src/interfaces/libpq/fe-connect.c @@ -241,6 +241,14 @@ static const internalPQconninfoOption PQconninfoOptions[] = { "Fallback-Application-Name", "", 64, offsetof(struct pg_conn, fbappname)}, + {"load_balance_hosts", NULL, NULL, NULL, + "Load-Balance", "", 1, /* should be just '0' or '1' */ + offsetof(struct pg_conn, loadbalance)}, + + {"random_seed", NULL, NULL, NULL, + "Random-Seed", "", 10, /* strlen(INT32_MAX) == 10 */ + offsetof(struct pg_conn, randomseed)}, + {"keepalives", NULL, NULL, NULL, "TCP-Keepalives", "", 1, /* should be just '0' or '1' */ offsetof(struct pg_conn, keepalives)}, @@ -379,6 +387,7 @@ static bool fillPGconn(PGconn *conn, PQconninfoOption *connOptions); static void freePGconn(PGconn *conn); static void closePGconn(PGconn *conn); static void release_conn_addrinfo(PGconn *conn); +static bool store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist); static void sendTerminateConn(PGconn *conn); static PQconninfoOption *conninfo_init(PQExpBuffer errorMessage); static PQconninfoOption *parse_connection_string(const char *connstr, @@ -424,6 +433,9 @@ static void pgpassfileWarning(PGconn *conn); static void default_threadlock(int acquire); static bool sslVerifyProtocolVersion(const char *version); static bool sslVerifyProtocolRange(const char *min, const char *max); +static int loadBalance(PGconn *conn); +static bool parse_int_param(const char *value, int *result, PGconn *conn, + const char *context); /* global variable because fe-auth.c needs to access it */ @@ -1007,6 +1019,46 @@ parse_comma_separated_list(char **startptr, bool *more) return p; } +/* + * Initializes the prng_state field of the connection. We want something + * unpredictable, so if possible, use high-quality random bits for the + * seed. Otherwise, fall back to a seed based on timestamp and PID. + */ +static bool +libpq_prng_init(PGconn *conn) +{ + if (unlikely(conn->randomseed)) + { + int rseed; + + if (!parse_int_param(conn->randomseed, &rseed, conn, "random_seed")) + { + return false; + }; + pg_prng_seed(&conn->prng_state, rseed); + } + else if (unlikely(!pg_prng_strong_seed(&conn->prng_state))) + { + uint64 rseed; + time_t now = time(NULL); + + /* + * Since PIDs and timestamps tend to change more frequently in their + * least significant bits, shift the timestamp left to allow a larger + * total number of seeds in a given time period. Since that would + * leave only 20 bits of the timestamp that cycle every ~1 second, + * also mix in some higher bits. + */ + rseed = ((uint64) getpid()) ^ + ((uint64) now << 12) ^ + ((uint64) now >> 20); + + pg_prng_seed(&conn->prng_state, rseed); + } + return true; +} + + /* * connectOptions2 * @@ -1019,6 +1071,7 @@ static bool connectOptions2(PGconn *conn) { int i; + int loadbalancehosts = loadBalance(conn); /* * Allocate memory for details about each host to which we might possibly @@ -1164,6 +1217,36 @@ connectOptions2(PGconn *conn) } } + if (loadbalancehosts < 0) + { + appendPQExpBufferStr(&conn->errorMessage, + libpq_gettext("loadbalance parameter must be an integer\n")); + return false; + } + + if (loadbalancehosts) + { + if (!libpq_prng_init(conn)) + { + return false; + } + + /* + * Shuffle connhost with a Durstenfeld/Knuth version of the + * Fisher-Yates shuffle. Source: + * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm + */ + for (i = conn->nconnhost - 1; i > 0; i--) + { + int j = pg_prng_uint64_range(&conn->prng_state, 0, i); + pg_conn_host temp = conn->connhost[j]; + + conn->connhost[j] = conn->connhost[i]; + conn->connhost[i] = temp; + } + } + + /* * If user name was not given, fetch it. (Most likely, the fetch will * fail, since the only way we get here is if pg_fe_getauthname() failed @@ -1726,6 +1809,27 @@ connectFailureMessage(PGconn *conn, int errorno) libpq_append_conn_error(conn, "\tIs the server running on that host and accepting TCP/IP connections?"); } +/* + * Should we load balance across hosts? Returns 1 if yes, 0 if no, and -1 if + * conn->loadbalance is set to a value which is not parseable as an integer. + */ +static int +loadBalance(PGconn *conn) +{ + char *ep; + int val; + + if (conn->loadbalance == NULL) + { + return 0; + } + val = strtol(conn->loadbalance, &ep, 10); + if (*ep) + return -1; + return val != 0 ? 1 : 0; +} + + /* * Should we use keepalives? Returns 1 if yes, 0 if no, and -1 if * conn->keepalives is set to a value which is not parseable as an @@ -2077,7 +2181,7 @@ connectDBComplete(PGconn *conn) time_t finish_time = ((time_t) -1); int timeout = 0; int last_whichhost = -2; /* certainly different from whichhost */ - struct addrinfo *last_addr_cur = NULL; + int last_whichaddr = -2; /* certainly different from whichaddr */ if (conn == NULL || conn->status == CONNECTION_BAD) return 0; @@ -2121,11 +2225,11 @@ connectDBComplete(PGconn *conn) if (flag != PGRES_POLLING_OK && timeout > 0 && (conn->whichhost != last_whichhost || - conn->addr_cur != last_addr_cur)) + conn->whichaddr != last_whichaddr)) { finish_time = time(NULL) + timeout; last_whichhost = conn->whichhost; - last_addr_cur = conn->addr_cur; + last_whichaddr = conn->whichaddr; } /* @@ -2272,9 +2376,9 @@ keep_going: /* We will come back to here until there is /* Time to advance to next address, or next host if no more addresses? */ if (conn->try_next_addr) { - if (conn->addr_cur && conn->addr_cur->ai_next) + if (conn->whichaddr < conn->naddr) { - conn->addr_cur = conn->addr_cur->ai_next; + conn->whichaddr++; reset_connection_state_machine = true; } else @@ -2287,6 +2391,7 @@ keep_going: /* We will come back to here until there is { pg_conn_host *ch; struct addrinfo hint; + struct addrinfo *addrlist; int thisport; int ret; char portstr[MAXPGPATH]; @@ -2327,7 +2432,7 @@ keep_going: /* We will come back to here until there is /* Initialize hint structure */ MemSet(&hint, 0, sizeof(hint)); hint.ai_socktype = SOCK_STREAM; - conn->addrlist_family = hint.ai_family = AF_UNSPEC; + hint.ai_family = AF_UNSPEC; /* Figure out the port number we're going to use. */ if (ch->port == NULL || ch->port[0] == '\0') @@ -2350,8 +2455,8 @@ keep_going: /* We will come back to here until there is { case CHT_HOST_NAME: ret = pg_getaddrinfo_all(ch->host, portstr, &hint, - &conn->addrlist); - if (ret || !conn->addrlist) + &addrlist); + if (ret || !addrlist) { libpq_append_conn_error(conn, "could not translate host name \"%s\" to address: %s", ch->host, gai_strerror(ret)); @@ -2362,8 +2467,8 @@ keep_going: /* We will come back to here until there is case CHT_HOST_ADDRESS: hint.ai_flags = AI_NUMERICHOST; ret = pg_getaddrinfo_all(ch->hostaddr, portstr, &hint, - &conn->addrlist); - if (ret || !conn->addrlist) + &addrlist); + if (ret || !addrlist) { libpq_append_conn_error(conn, "could not parse network address \"%s\": %s", ch->hostaddr, gai_strerror(ret)); @@ -2372,7 +2477,7 @@ keep_going: /* We will come back to here until there is break; case CHT_UNIX_SOCKET: - conn->addrlist_family = hint.ai_family = AF_UNIX; + hint.ai_family = AF_UNIX; UNIXSOCK_PATH(portstr, thisport, ch->host); if (strlen(portstr) >= UNIXSOCK_PATH_BUFLEN) { @@ -2387,8 +2492,8 @@ keep_going: /* We will come back to here until there is * name as a Unix-domain socket path. */ ret = pg_getaddrinfo_all(NULL, portstr, &hint, - &conn->addrlist); - if (ret || !conn->addrlist) + &addrlist); + if (ret || !addrlist) { libpq_append_conn_error(conn, "could not translate Unix-domain socket path \"%s\" to address: %s", portstr, gai_strerror(ret)); @@ -2397,8 +2502,15 @@ keep_going: /* We will come back to here until there is break; } - /* OK, scan this addrlist for a working server address */ - conn->addr_cur = conn->addrlist; + if (!store_conn_addrinfo(conn, addrlist)) + { + pg_freeaddrinfo_all(hint.ai_family, addrlist); + appendPQExpBufferStr(&conn->errorMessage, + libpq_gettext("out of memory\n")); + goto error_return; + } + pg_freeaddrinfo_all(hint.ai_family, addrlist); + reset_connection_state_machine = true; conn->try_next_host = false; } @@ -2455,30 +2567,29 @@ keep_going: /* We will come back to here until there is { /* * Try to initiate a connection to one of the addresses - * returned by pg_getaddrinfo_all(). conn->addr_cur is the + * returned by pg_getaddrinfo_all(). conn->whichaddr is the * next one to try. * * The extra level of braces here is historical. It's not * worth reindenting this whole switch case to remove 'em. */ { - struct addrinfo *addr_cur = conn->addr_cur; char host_addr[NI_MAXHOST]; + AddrInfo *addr_cur; /* * Advance to next possible host, if we've tried all of * the addresses for the current host. */ - if (addr_cur == NULL) + if (conn->whichaddr == conn->naddr) { conn->try_next_host = true; goto keep_going; } + addr_cur = &conn->addr[conn->whichaddr]; /* Remember current address for possible use later */ - memcpy(&conn->raddr.addr, addr_cur->ai_addr, - addr_cur->ai_addrlen); - conn->raddr.salen = addr_cur->ai_addrlen; + memcpy(&conn->raddr, &addr_cur->addr, sizeof(SockAddr)); /* * Set connip, too. Note we purposely ignore strdup @@ -2494,7 +2605,7 @@ keep_going: /* We will come back to here until there is conn->connip = strdup(host_addr); /* Try to create the socket */ - conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0); + conn->sock = socket(addr_cur->family, SOCK_STREAM, 0); if (conn->sock == PGINVALID_SOCKET) { int errorno = SOCK_ERRNO; @@ -2505,7 +2616,7 @@ keep_going: /* We will come back to here until there is * cases where the address list includes both IPv4 and * IPv6 but kernel only accepts one family. */ - if (addr_cur->ai_next != NULL || + if (conn->whichaddr < conn->naddr || conn->whichhost + 1 < conn->nconnhost) { conn->try_next_addr = true; @@ -2531,7 +2642,7 @@ keep_going: /* We will come back to here until there is * TCP sockets, nonblock mode, close-on-exec. Try the * next address if any of this fails. */ - if (addr_cur->ai_family != AF_UNIX) + if (addr_cur->family != AF_UNIX) { if (!connectNoDelay(conn)) { @@ -2558,7 +2669,7 @@ keep_going: /* We will come back to here until there is } #endif /* F_SETFD */ - if (addr_cur->ai_family != AF_UNIX) + if (addr_cur->family != AF_UNIX) { #ifndef WIN32 int on = 1; @@ -2650,8 +2761,8 @@ keep_going: /* We will come back to here until there is * Start/make connection. This should not block, since we * are in nonblock mode. If it does, well, too bad. */ - if (connect(conn->sock, addr_cur->ai_addr, - addr_cur->ai_addrlen) < 0) + if (connect(conn->sock, (struct sockaddr *) &addr_cur->addr.addr, + addr_cur->addr.salen) < 0) { if (SOCK_ERRNO == EINPROGRESS || #ifdef WIN32 @@ -4005,6 +4116,8 @@ freePGconn(PGconn *conn) } free(conn->pgpassfile); free(conn->channel_binding); + free(conn->loadbalance); + free(conn->randomseed); free(conn->keepalives); free(conn->keepalives_idle); free(conn->keepalives_interval); @@ -4041,6 +4154,63 @@ freePGconn(PGconn *conn) free(conn); } + +/* + * Copies over the AddrInfos from addrlist to the PGconn. + */ +static bool +store_conn_addrinfo(PGconn *conn, struct addrinfo *addrlist) +{ + struct addrinfo *ai = addrlist; + + conn->whichaddr = 0; + + conn->naddr = 0; + while (ai) + { + ai = ai->ai_next; + conn->naddr++; + } + + conn->addr = calloc(conn->naddr, sizeof(AddrInfo)); + if (conn->addr == NULL) + { + return false; + } + + ai = addrlist; + for (int i = 0; i < conn->naddr; i++) + { + conn->addr[i].family = ai->ai_family; + + memcpy(&conn->addr[i].addr.addr, ai->ai_addr, + ai->ai_addrlen); + conn->addr[i].addr.salen = ai->ai_addrlen; + ai = ai->ai_next; + } + + if (loadBalance(conn)) + { + /* + * Shuffle addr with a Durstenfeld/Knuth version of the Fisher-Yates + * shuffle. Source: + * https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle#The_modern_algorithm + * + * We don't need to initialize conn->prng_state here, because that + * already happened in connectOptions2. + */ + for (int i = conn->naddr - 1; i > 0; i--) + { + int j = pg_prng_uint64_range(&conn->prng_state, 0, i); + AddrInfo temp = conn->addr[j]; + + conn->addr[j] = conn->addr[i]; + conn->addr[i] = temp; + } + } + return true; +} + /* * release_conn_addrinfo * - Free any addrinfo list in the PGconn. @@ -4048,11 +4218,10 @@ freePGconn(PGconn *conn) static void release_conn_addrinfo(PGconn *conn) { - if (conn->addrlist) + if (conn->addr) { - pg_freeaddrinfo_all(conn->addrlist_family, conn->addrlist); - conn->addrlist = NULL; - conn->addr_cur = NULL; /* for safety */ + free(conn->addr); + conn->addr = NULL; } } diff --git a/src/interfaces/libpq/libpq-int.h b/src/interfaces/libpq/libpq-int.h index 512762f999..76ee988038 100644 --- a/src/interfaces/libpq/libpq-int.h +++ b/src/interfaces/libpq/libpq-int.h @@ -82,6 +82,8 @@ typedef struct #endif #endif /* USE_OPENSSL */ +#include "common/pg_prng.h" + /* * POSTGRES backend dependent Constants. */ @@ -373,6 +375,8 @@ struct pg_conn char *pgpassfile; /* path to a file containing password(s) */ char *channel_binding; /* channel binding mode * (require,prefer,disable) */ + char *loadbalance; /* load balance over hosts */ + char *randomseed; /* seed for randomization of load balancing */ char *keepalives; /* use TCP keepalives? */ char *keepalives_idle; /* time between TCP keepalives */ char *keepalives_interval; /* time between TCP keepalive @@ -461,8 +465,10 @@ struct pg_conn PGTargetServerType target_server_type; /* desired session properties */ bool try_next_addr; /* time to advance to next address/host? */ bool try_next_host; /* time to advance to next connhost[]? */ - struct addrinfo *addrlist; /* list of addresses for current connhost */ - struct addrinfo *addr_cur; /* the one currently being tried */ + int naddr; /* number of addrs returned by getaddrinfo */ + int whichaddr; /* the addr currently being tried */ + AddrInfo *addr; /* the array of addresses for the currently + * tried host */ int addrlist_family; /* needed to know how to free addrlist */ bool send_appname; /* okay to send application_name? */ @@ -477,6 +483,8 @@ struct pg_conn PGVerbosity verbosity; /* error/notice message verbosity */ PGContextVisibility show_context; /* whether to show CONTEXT field */ PGlobjfuncs *lobjfuncs; /* private state for large-object access fns */ + pg_prng_state prng_state; /* prng state for load balancing connections */ + /* Buffer for data received from backend and not yet processed */ char *inBuffer; /* currently allocated buffer */ diff --git a/src/interfaces/libpq/meson.build b/src/interfaces/libpq/meson.build index 8e696f1183..8026398518 100644 --- a/src/interfaces/libpq/meson.build +++ b/src/interfaces/libpq/meson.build @@ -114,6 +114,7 @@ tests += { 'tests': [ 't/001_uri.pl', 't/002_api.pl', + 't/003_loadbalance.pl', ], 'env': {'with_ssl': get_option('ssl')}, }, diff --git a/src/interfaces/libpq/t/003_loadbalance.pl b/src/interfaces/libpq/t/003_loadbalance.pl new file mode 100644 index 0000000000..07eddbe9cc --- /dev/null +++ b/src/interfaces/libpq/t/003_loadbalance.pl @@ -0,0 +1,167 @@ +# Copyright (c) 2022, PostgreSQL Global Development Group +use strict; +use warnings; +use Config; +use PostgreSQL::Test::Utils; +use PostgreSQL::Test::Cluster; +use File::Spec::Functions 'catfile'; +use Test::More; + +# This tests two different methods of load balancing from libpq +# 1. Load balancing by providing multiple host and port combinations in the +# libpq connection string. +# 2. By using a hosts file where hostname maps to multiple different IP +# addresses. Regular Postgres users wouldn't usually use such a host file, +# but this is the easiest way to immitate behaviour of a DNS server that +# returns multiple IP addresses for the same DNS record. +# +# Testing method 1 is supported on all platforms and works out of the box. But +# testing method 2 has some more requirements, both on the platform and on the +# initial setup. If any of these requirements are not met, then method 2 is +# simply not tested. +# +# The requirements to test method 2 are as follows: +# 1. Windows or Linux should be used. +# 2. The OS hosts file at /etc/hosts or c:\Windows\System32\Drivers\etc\hosts +# should contain the following contents: +# +# 127.0.0.1 pg-loadbalancetest +# 127.0.0.2 pg-loadbalancetest +# 127.0.0.3 pg-loadbalancetest +# +# +# Windows or Linux are required to test method 2 because these OSes allow +# binding to 127.0.0.2 and 127.0.0.3 addresess by default, but other OSes +# don't. We need to bind to different IP addresses, so that we can use these +# different IP addresses in the hosts file. +# +# The hosts file needs to be prepared before running this test. We don't do it +# on the fly, because it requires root permissions to change the hosts file. In +# CI we set up the previously mentioned rules in the hosts file, so that this +# load balancing method is tested. + + +# Cluster setup which is shared for testing both load balancing methods +my $can_bind_to_127_0_0_2 = $Config{osname} eq 'linux' || $PostgreSQL::Test::Utils::windows_os; + +if ($can_bind_to_127_0_0_2) +{ + $PostgreSQL::Test::Cluster::use_tcp = 1; + $PostgreSQL::Test::Cluster::test_pghost = '127.0.0.1'; +} +my $port = PostgreSQL::Test::Cluster::get_free_port(); +my $node1 = PostgreSQL::Test::Cluster->new('node1', port => $port); +my $node2 = PostgreSQL::Test::Cluster->new('node2', port => $port, own_host => 1); +my $node3 = PostgreSQL::Test::Cluster->new('node3', port => $port, own_host => 1); + +# Create a data directory with initdb +$node1->init(); +$node2->init(); +$node3->init(); + +# Start the PostgreSQL server +$node1->start(); +$node2->start(); +$node3->start(); + +# Start the tests for load balancing method 1 +my $hostlist = $node1->host . ',' . $node2->host . ',' . $node3->host; +my $portlist = "$port,$port,$port"; + +$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=123", + "seed 123 selects node 1 first", + sql => "SELECT 'connect1'", + log_like => [qr/statement: SELECT 'connect1'/]); + +$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=123", + "seed 123 does not select node 2 first", + sql => "SELECT 'connect1'", + log_unlike => [qr/statement: SELECT 'connect1'/]); + +$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=123", + "seed 123 does not select node 3 first", + sql => "SELECT 'connect1'", + log_unlike => [qr/statement: SELECT 'connect1'/]); + +$node3->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42", + "seed 42 selects node 3 first", + sql => "SELECT 'connect2'", + log_like => [qr/statement: SELECT 'connect2'/]); + +$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42", + "seed 42 does not select node 1 first", + sql => "SELECT 'connect2'", + log_unlike => [qr/statement: SELECT 'connect2'/]); + +$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42", + "seed 42 does not select node 2 first", + sql => "SELECT 'connect2'", + log_unlike => [qr/statement: SELECT 'connect2'/]); + +$node3->stop(); + +$node1->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42", + "seed 42 does select node 1 second", + sql => "SELECT 'connect3'", + log_like => [qr/statement: SELECT 'connect3'/]); + +$node2->connect_ok("host=$hostlist port=$portlist load_balance_hosts=1 random_seed=42", + "seed 42 does not select node 2 second", + sql => "SELECT 'connect3'", + log_unlike => [qr/statement: SELECT 'connect3'/]); + +$node3->start(); + +# Checks for the requirements for testing load balancing method 2 +if (!$can_bind_to_127_0_0_2) { + # The OS requirement is not met + done_testing(); + exit; +} + +my $hosts_path; +if ($windows_os) { + $hosts_path = 'c:\Windows\System32\Drivers\etc\hosts'; +} +else +{ + $hosts_path = '/etc/hosts'; +} + +my $hosts_content = PostgreSQL::Test::Utils::slurp_file($hosts_path); + +if ($hosts_content !~ m/pg-loadbalancetest/) { + # Host file is not prepared for this test + done_testing(); + exit; +} + +# Start the tests for load balancing method 2 +$node2->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44", + "seed 44 selects node 2 first", + sql => "SELECT 'connect4'", + log_like => [qr/statement: SELECT 'connect4'/]); + +$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44", + "seed 44 does not select node 1 first", + sql => "SELECT 'connect4'", + log_unlike => [qr/statement: SELECT 'connect4'/]); + +$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44", + "seed 44 does not select node 3 first", + sql => "SELECT 'connect4'", + log_unlike => [qr/statement: SELECT 'connect4'/]); + +$node2->stop(); + +$node1->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44", + "seed 44 does select node 1 second", + sql => "SELECT 'connect5'", + log_like => [qr/statement: SELECT 'connect5'/]); + +$node3->connect_ok("host=pg-loadbalancetest port=$port load_balance_hosts=1 random_seed=44", + "seed 44 does not select node 3 second", + sql => "SELECT 'connect5'", + log_unlike => [qr/statement: SELECT 'connect5'/]); + +done_testing(); -- 2.34.1