This article describes a method to create a mysqld
Process
managed by the Spring Boot Application conditioned on the definition of an application.properties
property, ${mysqld.home}
. If the property is defined, the corresponding bean @Configuration
with invoke mysqld
with the --initialize-insecure
option to create the database and then create and manage the mysqld
Process
for the life of the Spring Boot application including graceful shutdown at application shutdown.
Complete javadoc is provided.
Theory of Operation
The MysqldConfiguration
is @ConditionalOnProperty
annotation for ${mysqld.home}
; if the property is defined, the Process
@Bean
is created running the MySQL server. If the ${mysqld.datadir}
does not exist, mysqld
is invoked with the --initialize-insecure
option to create the database first. A @PreDestroy
method is defined to destroy the mysqld
Process
at application shutdown.
@Configuration
@ConditionalOnProperty(name = "mysqld.home", havingValue = "")
@NoArgsConstructor @ToString @Log4j2
public class MysqldConfiguration {
@Value("${mysqld.home}")
private File home;
@Value("${mysqld.defaults.file:${mysqld.home}/my.cnf}")
private File defaults;
@Value("${mysqld.datadir:${mysqld.home}/data}")
private File datadir;
@Value("${mysqld.port}")
private Integer port;
@Value("${mysqld.socket:${mysqld.home}/socket}")
private File socket;
@Value("${logging.path}/mysqld.log")
private File console;
private volatile Process mysqld = null;
...
@Bean
public Process mysqld() throws IOException {
if (mysqld == null) {
synchronized (this) {
if (mysqld == null) {
Files.createDirectories(home.toPath());
Files.createDirectories(datadir.toPath().getParent());
Files.createDirectories(console.toPath().getParent());
String defaultsArg = "--no-defaults";
if (defaults.exists()) {
defaultsArg = "--defaults-file=" + defaults.getAbsolutePath();
}
String datadirArg = "--datadir=" + datadir.getAbsolutePath();
String socketArg = "--socket=" + socket.getAbsolutePath();
String portArg = "--port=" + port;
if (! datadir.exists()) {
try {
new ProcessBuilder("mysqld", defaultsArg, datadirArg, "--initialize-insecure")
.directory(home)
.inheritIO()
.redirectOutput(Redirect.to(console))
.redirectErrorStream(true)
.start()
.waitFor();
} catch (InterruptedException exception) {
}
}
if (datadir.exists()) {
socket.delete();
mysqld =
new ProcessBuilder("mysqld", defaultsArg, datadirArg, socketArg, portArg)
.directory(home)
.inheritIO()
.redirectOutput(Redirect.appendTo(console))
.redirectErrorStream(true)
.start();
while (! socket.exists()) {
try {
mysqld.waitFor(15, SECONDS);
} catch (InterruptedException exception) {
}
if (mysqld.isAlive()) {
continue;
} else {
throw new IllegalStateException("mysqld not started");
}
}
} else {
throw new IllegalStateException("mysqld datadir does not exist");
}
}
}
}
return mysqld;
}
@PreDestroy
public void destroy() {
if (mysqld != null) {
try {
for (int i = 0; i < 8; i+= 1) {
if (mysqld.isAlive()) {
mysqld.destroy();
mysqld.waitFor(15, SECONDS);
} else {
break;
}
}
} catch (InterruptedException exception) {
}
try {
if (mysqld.isAlive()) {
mysqld.destroyForcibly().waitFor(60, SECONDS);
}
} catch (InterruptedException exception) {
}
}
}
}
The mysqld
server is configured with the --socket=${mysqld.socket}
option for the purpose of notifying the Spring Boot Application that the server has started: While the MySQL Connector/J does not support UNIX domain sockets, the above code waits for the mysqld
server to create the socket to be sure the server is running before continuing. The MysqldComponent
will simply monitor that the Process
is still alive. This @Component
is dependent on the mysqld
@Bean
which in turn is dependent on the ${mysqld.home}
property.
@Component
@ConditionalOnBean(name = { "mysqld" })
@NoArgsConstructor @ToString @Log4j2
public class MysqldComponent {
@Autowired private Process mysqld;
@Scheduled(fixedRate = 15 * 1000)
public void run() {
if (mysqld != null) {
if (mysqld.isAlive()) {
try {
mysqld.waitFor(15, SECONDS);
} catch (InterruptedException exception) {
}
} else {
throw new IllegalStateException("mysqld is not running");
}
}
}
}
Per the direction of the Spring Boot Reference Guide, EntityManagerFactoryComponent
is provided to indicate the mysqld
Process
is required by JPA.
@Component
@ConditionalOnProperty(name = "mysqld.home", havingValue = "")
@ToString @Log4j2
public class EntityManagerFactoryComponent extends EntityManagerFactoryDependsOnPostProcessor {
@Autowired private Process mysqld;
public EntityManagerFactoryComponent() { super("mysqld"); }
}
An application may integrate this functionality by annotating some component (presumably one that depends on a Repository
or JpaRepository
) with:
@Component
@ComponentScan(basePackageClasses = { ball.spring.mysqld.MysqldComponent.class })
public class SomeComponent {
...
}
Shell Script
The following shell script may be dropped into the ${mysqld.home}
directory to conveniently start a MySQL server from the shell.
#!/bin/bash
PRG="$0"
while [ -h "$PRG" ]; do
ls=$(ls -ld "$PRG")
link=$(expr "$ls" : '.*-> \(.*\)$')
if expr "$link" : '/.*' > /dev/null; then
PRG="$link"
else
PRG=$(dirname "$PRG")"/$link"
fi
done
cd $(dirname "$PRG")
MYCNF=$(pwd)/my.cnf
DATADIR=$(pwd)/data
SOCKET=$(pwd)/socket
if [ ! -f "${MYCNF}" ]; then
cat > "${MYCNF}" <<EOF
[mysqld]
general_log = ON
log_output = TABLE
EOF
fi
DEFAULTS_OPT=--no-defaults
DATADIR_OPT=--datadir="${DATADIR}"
if [ -f "${MYCNF}" ]; then
DEFAULTS_OPT=--defaults-file="${MYCNF}"
fi
if [ ! -d "${DATADIR}" ]; then
mysqld "${DEFAULTS_OPT}" "${DATADIR_OPT}" --initialize-insecure
fi
exec mysqld "${DEFAULTS_OPT}" "${DATADIR_OPT}" --socket="${SOCKET}"
Summary
The technique described here may be used with with other database applications (e.g., PostgreSQL).
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