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Merge pull request #5697 from BOINC/dpa_replica
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PHP DB code: clean up the logic, and allow for > 1 readonly replica
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@davidpanderson
davidpanderson authored Aug 31, 2024
2 parents 8ae0805 + da1727c commit 66440f9
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Showing 3 changed files with 136 additions and 211 deletions.
193 changes: 93 additions & 100 deletions html/inc/boinc_db.inc
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Original file line number Diff line number Diff line change
@@ -1,7 +1,7 @@
<?php
// This file is part of BOINC.
// http://boinc.berkeley.edu
// Copyright (C) 2008 University of California
// https://boinc.berkeley.edu
// Copyright (C) 2024 University of California
//
// BOINC is free software; you can redistribute it and/or modify it
// under the terms of the GNU Lesser General Public License
Expand All @@ -16,6 +16,19 @@
// You should have received a copy of the GNU Lesser General Public License
// along with BOINC. If not, see <http://www.gnu.org/licenses/>.

// A project can have one or more BOINC databases:
// DB 0:
// the main DB; read/write
// identified in config file by db_host, db_name, db_user, db_passwd
// db_host defaults to localhost
// DB 1:
// read-only replica; identified by
// replica_db_host/name/user/passwd (must include all)
// DB 2:
// read-only replica; identified by
// replica2_db_host/name/user/passwd (must include all)
// ... and potentially more

function incs() {
$d = dirname(__FILE__);
require_once("$d/db_conn.inc");
Expand All @@ -24,122 +37,102 @@ function incs() {

incs();

class BoincDb extends DbConn {
static $instance;
// class BoincDb represents a connection to a BOINC database.
// All its members are static, so there's only 1 connection at a time.
// get(n) establishes a connection to DB n,
// or DB 0 if that fails or doesn't exit.
// close() closes the connection.

// connect to the database (possibly to a read-only replica)
// NOTE: choice of replica can be made only at the page level.
// If there's a page that's guaranteed to do only reads, put
// BoincDb::get(true);
// at the top of it.
//
// Specify a $fallback_mode that is used when $readonly is true:
// 0: default, use db_user if no replica_db_user is specified,
// first try replica_db_host (if specified) then db_host
// 1: only use replica_db_user, first try replica_db_host then db_host
// 2: only use replica_db_user, only try replica_db_host
// can be set projectwide using <replica_fallback_mode>
class BoincDb {
static $instance; // a DbConn object, or null
static $dbnum; // which replica we're connected to

// connect to DB $dbnum (0, 1, ...)
// If the requested DB doesn't exist or connection fails, connect to DB 0.
// Set self::$instance; no return value
//
static function get_aux($readonly, $fallback_mode = 0) {
$config = get_config();
$user = parse_config($config, '<db_user>');
$passwd = parse_config($config, '<db_passwd>');
$host = parse_config($config, '<db_host>');
$replica_host = parse_config($config, '<replica_db_host>');
$name = parse_config($config, '<db_name>');
$fm = parse_config($config, '<replica_fallback_mode>');
if ($fm) {
// override parameter with config.xml setting
$fallback_mode = $fm;
}
if ($host == null) {
$host = "localhost";
}
static function get_aux($dbnum) {
$instance = new DbConn();
if ($readonly) {
if (($fallback_mode > 0) && (!$replica_host)) {
error_log("BoincDb::get_aux(): <replica_db_host> required for \$fallback_mode > 0 (giving up)");
$instance = null;
self::$instance = $instance;
return $instance;
}
$u = parse_config($config, '<replica_db_user>');
$p = parse_config($config, '<replica_db_passwd>');
$n = parse_config($config, '<replica_db_name>');
if (($fallback_mode > 0) && (!$u || !$p || !$n)) {
error_log("BoincDb::get_aux(): <replica_db_*> required for \$fallback_mode > 0 (giving up)");
$instance = null;
self::$instance = $instance;
return $instance;
} else {
// use replica user if given or use normal user for $fallback_mode == 0
if ($u) $user = $u;
if ($p) $passwd = $p;
if ($n) $name = $n;
}
// skip this block if no $replica_host is specified for $fallback_mode == 0
if ($replica_host) {
$retval = $instance->init_conn(
$user, $passwd, $replica_host, $name, true
);
self::$instance = null;
$config = get_config();
if ($dbnum) {
$r = $dbnum==1?'':strval($dbnum);
$host = parse_config($config, sprintf('<replica%s_db_host>', $r));
$name = parse_config($config, sprintf('<replica%s_db_name>', $r));
$user = parse_config($config, sprintf('<replica%s_db_user>', $r));
$passwd = parse_config($config, sprintf('<replica%s_db_passwd>', $r));
if ($host && $name && $user && $passwd) {
$retval = $instance->init_conn($user, $passwd, $host, $name);
if ($retval) {
// needed for places where we do direct queries
if (!$instance->do_query("use $name")) {
error_log("BoincDb::get_aux(): Couldn't select database $name on $replica_host (giving up)");
$instance = null;
}
self::$instance = $instance;
return $instance;
} elseif ($fallback_mode == 2) {
// no fallback to master in this case
error_log("BoincDb::get_aux(): Couldn't connect to $user@$replica_host (giving up)");
$instance = null;
//error_log("BoincDb::get_aux(): connected to replica DB $dbnum");
self::$instance = $instance;
return $instance;
} else {
error_log("BoincDb::get_aux(): Couldn't connect to $user@$replica_host (trying $user@$host next)");
self::$dbnum = $dbnum;
return;
}
}
// if can't connect to replica, fall through and try DB 0
}
$retval = $instance->init_conn($user, $passwd, $host, $name, false);
if (!$retval) {
$instance = null;
error_log("BoincDb::get_aux(): Couldn't connect to $user@$host (giving up)");
} else {
// needed for places where we do direct queries
if (!$instance->do_query("use $name")) {
error_log("BoincDb::get_aux(): Couldn't select database $name on $host (giving up)");
$instance = null;
}
$host = parse_config($config, '<db_host>');
if (!$host) $host = 'localhost';
$user = parse_config($config, '<db_user>');
$name = parse_config($config, '<db_name>');
$passwd = parse_config($config, '<db_passwd>');
if (!$name || !$user || !$passwd) {
error_log("BoincDb::get_aux(): must specify DB name, user, passwd");
return;
}
$retval = $instance->init_conn($user, $passwd, $host, $name);
if ($retval) {
//error_log("BoincDb::get_aux(): connected to DB $dbnum");
self::$instance = $instance;
self::$dbnum = 0;
return;
}
self::$instance = $instance;
return $instance;
error_log("BoincDb::get_aux(): Couldn't connect to DB $dbnum");
}

// same, but
// connect to DB $dbnum, but first:
// 1) check for a cached connection
// 2) check whether the "stop_web" trigger file is present
//
static function get($readonly = false, $fallback_mode = 0) {
// If there's a page that's guaranteed to do only reads, put
// BoincDb::get(true);
// at the top of it.
//
// Note: true == 1.
// You can also use 2, 3... to select other replicas
//
static function get($dbnum = 0) {
global $generating_xml;
if (!isset(self::$instance)) {
if (web_stopped()) {
if ($generating_xml) {
xml_error(-183, "project down for maintenance");
} else {
show_project_down();
}
if (isset(self::$instance)) {
if (self::$dbnum == $dbnum) {
return self::$instance;
}
self::get_aux($readonly, $fallback_mode);
if (!self::$instance) {
if ($generating_xml) {
xml_error(-138, "Can't connect to database");
} else {
error_page("Can't connect to database");
}
close();
}
if (web_stopped()) {
if ($generating_xml) {
xml_error(-183, "project down for maintenance");
} else {
show_project_down();
}
}
return self::$instance;
self::get_aux($dbnum);
if (self::$instance) {
return self::$instance;
}
if ($generating_xml) {
xml_error(-138, "Can't connect to database");
} else {
error_page("Can't connect to database");
}
}

static function close() {
if (isset(self::$instance)) {
self::$instance->close();
self::$instance = null;
}
}

static function escape_string($string) {
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15 changes: 1 addition & 14 deletions html/inc/db.inc
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Original file line number Diff line number Diff line change
Expand Up @@ -22,20 +22,7 @@ require_once("../inc/util_basic.inc");
// When possible, use the classes in boinc_db.inc instead.
// Lots of old code uses these functions, e.g. in ops/

// use mysqli if available,
// but let projects not use it if they want
// (put <no_mysqli/> in config.xml)
//
if (parse_bool(get_config(), "no_mysqli")) {
define("MYSQLI", false);
} else {
if (class_exists("mysqli")) {
define("MYSQLI", true);
$mysqli = null;
} else {
define("MYSQLI", false);
}
}
define("MYSQLI", true);

if (MYSQLI) {
function _mysql_connect($host, $user, $pass, $dbname) {
Expand Down
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