> For the complete documentation index, see [llms.txt](https://docs.starrocks.io/llms.txt). This page is also available as Markdown at its `.md` URL.

# Load Balancing

When deploying multiple FE nodes, users can deploy a load balancing layer on top of the FEs to achieve high availability.

The following are some high availability options:

## Code approach[​](#code-approach "Direct link to Code approach")

One way is to implement code at the application layer to perform retry and load balancing. For example, if a connection is broken, it will automatically retry on other connections. This approach requires users to configure multiple FE node addresses.

## JDBC Connector[​](#jdbc-connector "Direct link to JDBC Connector")

JDBC connector supports automatic retry:

```sql
jdbc:mysql:loadbalance://[host1][:port],[host2][:port][,[host3][:port]]...[/[database]][?propertyName1=propertyValue1[&propertyName2=propertyValue2]...]

```

## ProxySQL[​](#proxysql "Direct link to ProxySQL")

ProxySQL is a MySQL proxy layer that supports read/write separation, query routing, SQL caching, dynamic load configuration, failover, and SQL filtering.

StarRocks FE is responsible for receiving connection and query requests, and it’s horizontally scalable and highly available. However FE requires users to set up a proxy layer on top of it to achieve automatic load balancing. See the following steps for setup:

### 1. Install relevant dependencies[​](#1-install-relevant-dependencies "Direct link to 1. Install relevant dependencies")

```shell
yum install -y gnutls perl-DBD-MySQL perl-DBI perl-devel

```

### 2. Download the installation package[​](#2-download-the-installation-package "Direct link to 2. Download the installation package")

```shell
wget https://github.com/sysown/proxysql/releases/download/v2.0.14/proxysql-2.0.14-1-centos7.x86_64.rpm

```

### 3. Decompress to the current directory[​](#3-decompress-to-the-current-directory "Direct link to 3. Decompress to the current directory")

```shell
rpm2cpio proxysql-2.0.14-1-centos7.x86_64.rpm | cpio -ivdm

```

### 4. Modify the configuration file[​](#4-modify-the-configuration-file "Direct link to 4. Modify the configuration file")

```shell
vim ./etc/proxysql.cnf 

```

Direct to a directory that the user has privilege to access (absolute path):

```vim
datadir="/var/lib/proxysql"
errorlog="/var/lib/proxysql/proxysql.log"

```

### 5. Start[​](#5-start "Direct link to 5. Start")

```shell
./usr/bin/proxysql -c ./etc/proxysql.cnf --no-monitor

```

### 6. Log in[​](#6-log-in "Direct link to 6. Log in")

```shell
mysql -u admin -padmin -h 127.0.0.1 -P6032

```

### 7. Configure the global log[​](#7-configure-the-global-log "Direct link to 7. Configure the global log")

```shell
SET mysql-eventslog_filename='proxysql_queries.log';
SET mysql-eventslog_default_log=1;
SET mysql-eventslog_format=2;
LOAD MYSQL VARIABLES TO RUNTIME;
SAVE MYSQL VARIABLES TO DISK;

```

### 8. Insert into the leader node[​](#8-insert-into-the-leader-node "Direct link to 8. Insert into the leader node")

```sql
insert into mysql_servers(hostgroup_id, hostname, port) values(1, '172.xx.xx.139', 9030);

```

### 9. Insert the observer nodes[​](#9-insert-the-observer-nodes "Direct link to 9. Insert the observer nodes")

```sql
insert into mysql_servers(hostgroup_id, hostname, port) values(2, '172.xx.xx.139', 9030);
insert into mysql_servers(hostgroup_id, hostname, port) values(2, '172.xx.xx.140', 9030);

```

### 10. Load the configuration[​](#10-load-the-configuration "Direct link to 10. Load the configuration")

```sql
load mysql servers to runtime;
save mysql servers to disk;

```

### 11. Configure the username and password[​](#11-configure-the-username-and-password "Direct link to 11. Configure the username and password")

```sql
insert into mysql_users(username, password, active, default_hostgroup, backend, frontend) values('root', '*94BDCEBE19083CE2A1F959FD02F964C7AF4CFC29', 1, 1, 1, 1);

```

### 12. Load the configuration[​](#12-load-the-configuration "Direct link to 12. Load the configuration")

```sql
load mysql users to runtime; 
save mysql users to disk;

```

### 13. Write to the proxy rules[​](#13-write-to-the-proxy-rules "Direct link to 13. Write to the proxy rules")

```sql
insert into mysql_query_rules(rule_id, active, match_digest, destination_hostgroup, mirror_hostgroup, apply) values(1, 1, '.', 1, 2, 1);

```

### 14. Load the configuration[​](#14-load-the-configuration "Direct link to 14. Load the configuration")

```sql
load mysql query rules to runtime; 
save mysql query rules to disk;

```