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proxysql
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DNS Cache Fixes

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* If a MySQL connection fails or times out for a specific hostname, the
corresponding DNS record will be removed from DNS Cache. This ensures that outdated DNS
records are not retained. (Rest of the DNS resolution process remains unchanged)
* DNS cache functionality will automatically be disabled when ProxySQL is
run with the -M or --no-monitor option.
pull/4656/head
Rahim Kanji 2 years ago
parent bd7bd3571b
commit c5bc9ed2c6
7 changed files with 76 additions and 11 deletions
Show Stats Download Patch File Download Diff File

6
include/MySQL_Monitor.hpp
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@ -398,7 +398,9 @@ struct DNS_Cache_Record {
class DNS_Cache {
public:
DNS_Cache() : enabled(true) {
// By default, the DNS cache is disabled.
// This handles the case when ProxySQL is executed with the -M/--no-monitor option.
DNS_Cache() : enabled(false) {
int rc = pthread_rwlock_init(&rwlock_, NULL);
assert(rc == 0);
}
@ -445,6 +447,7 @@ class MySQL_Monitor {
static std::string dns_lookup(const std::string& hostname, bool return_hostname_if_lookup_fails = true, size_t* ip_count = NULL);
static std::string dns_lookup(const char* hostname, bool return_hostname_if_lookup_fails = true, size_t* ip_count = NULL);
static bool update_dns_cache_from_mysql_conn(const MYSQL* mysql);
static void remove_dns_record_from_dns_cache(const std::string& hostname);
static void trigger_dns_cache_update();
void process_discovered_topology(const std::string& originating_server_hostname, const vector<MYSQL_ROW>& discovered_servers, int reader_hostgroup);
@ -457,6 +460,7 @@ class MySQL_Monitor {
void drop_tables_defs(std::vector<table_def_t *> *tables_defs);
void check_and_build_standard_tables(SQLite3DB *db, std::vector<table_def_t *> *tables_defs);
static bool _dns_cache_update(const std::string& hostname, std::vector<std::string>&& ip_address);
static void _remove_dns_record_from_dns_cache(const std::string& hostname);
public:
pthread_mutex_t group_replication_mutex; // for simplicity, a mutex instead of a rwlock

2
include/MySQL_Session.h
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@ -473,6 +473,8 @@ public:
KillArgs(char *u, char *p, char *h, unsigned int P, unsigned int _hid, unsigned long i, int kt, int _use_ssl, MySQL_Thread* _mt, char *ip);
~KillArgs();
const char* get_host_address() const;
void resolve_hostname();
void remove_dns_record();
private:
char* ip_addr;

1
include/ProxySQL_Cluster.hpp
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@ -104,6 +104,7 @@ public:
~ProxySQL_Node_Address();
const char* get_host_address() const;
void resolve_hostname();
void remove_dns_record();
private:
char* ip_addr;
};

30
lib/MySQL_Monitor.cpp
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@ -1549,6 +1549,10 @@ bool MySQL_Monitor_State_Data::create_new_connection() {
myrc=mysql_real_connect(mysql, "localhost", mysql_thread___monitor_username, mysql_thread___monitor_password, NULL, 0, hostname, 0);
}
if (myrc==NULL) {
// port == 0 means we are connecting to a unix socket
if (port) {
MySQL_Monitor::remove_dns_record_from_dns_cache(hostname);
}
mysql_error_msg=strdup(mysql_error(mysql));
int myerrno=mysql_errno(mysql);
MyHGM->p_update_mysql_error_counter(p_mysql_error_type::proxysql, hostgroup_id, hostname, port, myerrno);
@ -6653,6 +6657,15 @@ bool MySQL_Monitor::update_dns_cache_from_mysql_conn(const MYSQL* mysql)
return result;
}
void MySQL_Monitor::remove_dns_record_from_dns_cache(const std::string& hostname) {
// if IP was provided, no need to update dns cache
if (hostname.empty() || validate_ip(hostname))
return;
_remove_dns_record_from_dns_cache(hostname);
}
bool MySQL_Monitor::_dns_cache_update(const std::string &hostname, std::vector<std::string>&& ip_address) {
static thread_local std::shared_ptr<DNS_Cache> dns_cache_thread;
@ -6669,6 +6682,18 @@ bool MySQL_Monitor::_dns_cache_update(const std::string &hostname, std::vector<s
return false;
}
void MySQL_Monitor::_remove_dns_record_from_dns_cache(const std::string& hostname) {
static thread_local std::shared_ptr<DNS_Cache> dns_cache_thread;
if (!dns_cache_thread && GloMyMon)
dns_cache_thread = GloMyMon->dns_cache;
if (dns_cache_thread) {
dns_cache_thread->remove(trim(hostname));
proxy_debug(PROXY_DEBUG_MYSQL_CONNECTION, 5, "Direct DNS cache record removed. (Hostname:[%s])\n", hostname.c_str());
}
}
void MySQL_Monitor::trigger_dns_cache_update() {
if (GloMyMon) {
GloMyMon->force_dns_cache_update = true;
@ -6697,7 +6722,7 @@ bool DNS_Cache::add(const std::string& hostname, std::vector<std::string>&& ips)
bool DNS_Cache::add_if_not_exist(const std::string& hostname, std::vector<std::string>&& ips) {
if (!enabled) return false;
bool item_added = false;
int rc = pthread_rwlock_wrlock(&rwlock_);
assert(rc == 0);
if (records.find(hostname) == records.end()) {
@ -6705,11 +6730,12 @@ bool DNS_Cache::add_if_not_exist(const std::string& hostname, std::vector<std::s
auto& ip_addr = records[hostname];
ip_addr.ips = std::move(ips);
__sync_fetch_and_and(&ip_addr.counter, 0);
item_added = true;
}
rc = pthread_rwlock_unlock(&rwlock_);
assert(rc == 0);
if (GloMyMon)
if (item_added && GloMyMon)
__sync_fetch_and_add(&GloMyMon->dns_cache_record_updated, 1);
return true;

29
lib/MySQL_Session.cpp
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@ -209,13 +209,7 @@ bool Session_Regex::match(char *m) {
KillArgs::KillArgs(char* u, char* p, char* h, unsigned int P, unsigned int _hid, unsigned long i, int kt, int _use_ssl, MySQL_Thread* _mt) :
KillArgs(u, p, h, P, _hid, i, kt, _use_ssl, _mt, NULL) {
// resolving DNS if available in Cache
if (h && P) {
const std::string& ip = MySQL_Monitor::dns_lookup(h, false);
if (ip.empty() == false) {
ip_addr = strdup(ip.c_str());
}
}
resolve_hostname();
}
KillArgs::KillArgs(char* u, char* p, char* h, unsigned int P, unsigned int _hid, unsigned long i, int kt, int _use_ssl, MySQL_Thread *_mt, char *ip) {
@ -250,6 +244,25 @@ const char* KillArgs::get_host_address() const {
return host_address;
}
void KillArgs::resolve_hostname() {
if (ip_addr) {
free(ip_addr);
ip_addr = NULL;
}
if (hostname && port) {
const std::string& ip = MySQL_Monitor::dns_lookup(hostname, false);
if (ip.empty() == false) {
ip_addr = strdup(ip.c_str());
}
}
}
void KillArgs::remove_dns_record() {
if (hostname && port) {
MySQL_Monitor::remove_dns_record_from_dns_cache(hostname);
}
}
/**
* @brief Thread function to kill a query or connection on a MySQL server.
@ -324,6 +337,8 @@ void* kill_query_thread(void *arg) {
ret=mysql_real_connect(mysql,"localhost",ka->username,ka->password,NULL,0,ka->hostname,0);
}
if (!ret) {
ka->remove_dns_record();
//ka->resolve_hostname();
int myerr = mysql_errno(mysql);
if (ssl_params != NULL && myerr == 2026) {
proxy_error("Failed to connect to server %s:%d to run KILL %s %lu. SSL Params: %s , %s , %s , %s , %s , %s , %s , %s\n",

9
lib/ProxySQL_Cluster.cpp
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@ -241,6 +241,7 @@ void * ProxySQL_Cluster_Monitor_thread(void *args) {
}
} else {
proxy_warning("Cluster: unable to connect to peer %s:%d . Error: %s\n", node->hostname, node->port, mysql_error(conn));
node->remove_dns_record();
node->resolve_hostname();
mysql_close(conn);
conn = mysql_init(NULL);
@ -4481,3 +4482,11 @@ void ProxySQL_Node_Address::resolve_hostname() {
}
}
}
void ProxySQL_Node_Address::remove_dns_record() {
// make sure hostname is not NULL and port is not 0 (UNIX socket)
if (hostname && port) {
MySQL_Monitor::remove_dns_record_from_dns_cache(hostname);
}
}

10
lib/mysql_connection.cpp
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@ -1278,11 +1278,19 @@ handler_again:
//}
MySQL_Monitor::update_dns_cache_from_mysql_conn(mysql);
break;
case ASYNC_CONNECT_FAILED:
case ASYNC_CONNECT_FAILED:
// port == 0 means we are connecting to a unix socket
if (parent->port) {
MySQL_Monitor::remove_dns_record_from_dns_cache(parent->address);
}
MyHGM->p_update_mysql_error_counter(p_mysql_error_type::mysql, parent->myhgc->hid, parent->address, parent->port, mysql_errno(mysql));
parent->connect_error(mysql_errno(mysql));
break;
case ASYNC_CONNECT_TIMEOUT:
// port == 0 means we are connecting to a unix socket
if (parent->port) {
MySQL_Monitor::remove_dns_record_from_dns_cache(parent->address);
}
//proxy_error("Connect timeout on %s:%d : %llu - %llu = %llu\n", parent->address, parent->port, myds->sess->thread->curtime , myds->wait_until, myds->sess->thread->curtime - myds->wait_until);
proxy_error("Connect timeout on %s:%d : exceeded by %lluus\n", parent->address, parent->port, myds->sess->thread->curtime - myds->wait_until);
MyHGM->p_update_mysql_error_counter(p_mysql_error_type::mysql, parent->myhgc->hid, parent->address, parent->port, mysql_errno(mysql));

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