docs/faq/en/how_to_use_mysql_as_alpha_backend

Problem: How to use MySQL as alpha's backend database?

Solution: To replace the default database from postgreSQL to MySQL:

add dependency of mysql-connector-java in alpha/alpha-server/pom.xml

    <dependency>
      <groupId>mysql</groupId>
      <artifactId>mysql-connector-java</artifactId>
    </dependency>

install Saga
```
mvn clean package -Pdocker -DskipTests
```
After that, you will find the generated docker image alpha-server and executable file alpha/alpha-server/target/saga/alpha-server-${version}-exec.jar.
Notice: If you do not want to build the docker image, run mvn clean package -DskipTests is enough.
Notice: If you have installed saga with docker before, you need to remove the alpha-server's docker image first.
```
docker rmi -f $(docker images | grep alpha-server | awk '{print $3}')
```

run MySQL

docker run -d -e "MYSQL_ROOT_PASSWORD=password" -e "MYSQL_DATABASE=saga" -e "MYSQL_USER=saga" -e "MYSQL_PASSWORD=password" -p 3306:3306 mysql/mysql-server:5.7

Run alpha. Please make sure MySQL is up before this step. You can run alpha through docker or executable file.
- via docker
```
docker run -d -p 8080:8080 -p 8090:8090 -e "JAVA_OPTS=-Dspring.profiles.active=mysql -Dspring.datasource.url=jdbc:mysql://${host_address}:3306/saga?useSSL=false" alpha-server:${saga_version}
```
- via executable file
```
java -Dspring.profiles.active=mysql -D"spring.datasource.url=jdbc:mysql://${host_address}:3306/saga?useSSL=false" -jar alpha-server-${saga_version}-exec.jar
```
Notice: Please change ${saga_version} and ${host_address} to the actual value before you execute the command.
Note: By default, port 8080 is used to serve omega's request via gRPC while port 8090 is used to query the events stored in alpha.