SpringBoot druid配置datasource启动初始化数据库连接
1、问题场景：
1.1、服务在启动之后的第一笔或者几笔请求，处理时间较长，对于调用方来说超时，引发技术保底。
1.2、数据库连接信息配置错误，项目启动过程中却不产生任何异常，等到实际功能用到数据库了才抛出异常。
2、问题分析：
2.1、调用发系统通过http请求调用服务，设置超时时间为1s，超时时间过短，调整为3s；
2.2、应用启动之后的初始几笔请求处理时间过长，超过1s，跟踪日志发现在init-datasource中等待时间占用过多；
2.3、经过本地测试发现，在应用启动之后，在jvisualvm中查看mbeans中的druid.pool中的读写datasource的属性，启动之后的creatCount为0。在有请求进入之后才初始化了配置文件中的init连接数，导致了线上的问题；
3、解决方案：在数据库配置文件中配置读写datasource的bean中增加init-method=init的配置即可。druid官方文档中介绍，如果想要在项目启动的时候初始化配置的数据库连接数，需要显示配置或者调用init-method。
具体实现，如下图：
你可以在bean中增加init-method=init的配置，
也可以创建 dataSource 后，显示的调用 init 方法。
附 init 方法源码：
public void init() throws SQLException {
if (inited) {
return;
}
final ReentrantLock lock = this.lock;
try {
lock.lockInterruptibly();
} catch (InterruptedException e) {
throw new SQLException("interrupt", e);
}
boolean init = false;
try {
if (inited) {
return;
}
initStackTrace = Utils.toString(Thread.currentThread().getStackTrace());
this.id = DruidDriver.createDataSourceId();
if (this.id > 1) {
long delta = (this.id - 1) * 100000;
this.connectionIdSeed.addAndGet(delta);
this.statementIdSeed.addAndGet(delta);
this.resultSetIdSeed.addAndGet(delta);
this.transactionIdSeed.addAndGet(delta);
}
if (this.jdbcUrl != null) {
this.jdbcUrl = this.jdbcUrl.trim();
initFromWrapDriverUrl();
}
for (Filter filter : filters) {
filter.init(this);
}
if (this.dbType == null || this.dbType.length() == 0) {
this.dbType = JdbcUtils.getDbType(jdbcUrl, null);
}
if (JdbcConstants.MYSQL.equals(this.dbType) || //
JdbcConstants.MARIADB.equals(this.dbType)) {
boolean cacheServerConfigurationSet = false;
if (this.connectProperties.containsKey("cacheServerConfiguration")) {
cacheServerConfigurationSet = true;
} else if (this.jdbcUrl.indexOf("cacheServerConfiguration") != -1) {
cacheServerConfigurationSet = true;
}
if (cacheServerConfigurationSet) {
this.connectProperties.put("cacheServerConfiguration", "true");
}
}
if (maxActive <= 0) {
throw new IllegalArgumentException("illegal maxActive " + maxActive);
}
if (maxActive < minIdle) {
throw new IllegalArgumentException("illegal maxActive " + maxActive);
}
if (getInitialSize() > maxActive) {
throw new IllegalArgumentException("illegal initialSize " + this.initialSize + ", maxActieve " + maxActive);
}
if (timeBetweenLogStatsMillis > 0 && useGlobalDataSourceStat) {
throw new IllegalArgumentException("timeBetweenLogStatsMillis not support useGlobalDataSourceStat=true");
}
if (maxEvictableIdleTimeMillis < minEvictableIdleTimeMillis) {
throw new SQLException("maxEvictableIdleTimeMillis must be grater than minEvictableIdleTimeMillis");
}
if (this.driverClass != null) {
this.driverClass = driverClass.trim();
}
initFromSPIServiceLoader();
if (this.driver == null) {
if (this.driverClass == null || this.driverClass.isEmpty()) {
this.driverClass = JdbcUtils.getDriverClassName(this.jdbcUrl);
}
if (MockDriver.class.getName().equals(driverClass)) {
driver = MockDriver.instance;
} else {
driver = JdbcUtils.createDriver(driverClassLoader, driverClass);
}
} else {
if (this.driverClass == null) {
this.driverClass = driver.getClass().getName();
}
}
initCheck();
initExceptionSorter();
initValidConnectionChecker();
validationQueryCheck();
if (isUseGlobalDataSourceStat()) {
dataSourceStat = JdbcDataSourceStat.getGlobal();
if (dataSourceStat == null) {
dataSourceStat = new JdbcDataSourceStat("Global", "Global", this.dbType);
JdbcDataSourceStat.setGlobal(dataSourceStat);
}
if (dataSourceStat.getDbType() == null) {
dataSourceStat.setDbType(this.getDbType());
}
} else {
dataSourceStat = new JdbcDataSourceStat(this.name, this.jdbcUrl, this.dbType, this.connectProperties);
}
dataSourceStat.setResetStatEnable(this.resetStatEnable);
connections = new DruidConnectionHolder[maxActive];
SQLException connectError = null;
try {
// init connections
for (int i = 0, size = getInitialSize(); i < size; ++i) {
PhysicalConnectionInfo pyConnectInfo = createPhysicalConnection();
DruidConnectionHolder holder = new DruidConnectionHolder(this, pyConnectInfo);
connections[poolingCount] = holder;
incrementPoolingCount();
}
if (poolingCount > 0) {
poolingPeak = poolingCount;
poolingPeakTime = System.currentTimeMillis();
}
} catch (SQLException ex) {
LOG.error("init datasource error, url: " + this.getUrl(), ex);
connectError = ex;
}
createAndLogThread();
createAndStartCreatorThread();
createAndStartDestroyThread();
initedLatch.await();
init = true;
initedTime = new Date();
registerMbean();
if (connectError != null && poolingCount == 0) {
throw connectError;
}
} catch (SQLException e) {
LOG.error("{dataSource-" + this.getID() + "} init error", e);
throw e;
} catch (InterruptedException e) {
throw new SQLException(e.getMessage(), e);
} finally {
inited = true;
lock.unlock();
if (init && LOG.isInfoEnabled()) {
LOG.info("{dataSource-" + this.getID() + "} inited");
}
}
}在 init 里调用 createPhysicalConnection() 创建物理连接
public PhysicalConnectionInfo createPhysicalConnection() throws SQLException {
String url = this.getUrl();
Properties connectProperties = getConnectProperties();
String user;
if (getUserCallback() != null) {
user = getUserCallback().getName();
} else {
user = getUsername();
}
String password = getPassword();
PasswordCallback passwordCallback = getPasswordCallback();
if (passwordCallback != null) {
if (passwordCallback instanceof DruidPasswordCallback) {
DruidPasswordCallback druidPasswordCallback = (DruidPasswordCallback) passwordCallback;
druidPasswordCallback.setUrl(url);
druidPasswordCallback.setProperties(connectProperties);
}
char[] chars = passwordCallback.getPassword();
if (chars != null) {
password = new String(chars);
}
}
Properties physicalConnectProperties = new Properties();
if (connectProperties != null) {
physicalConnectProperties.putAll(connectProperties);
}
if (user != null && user.length() != 0) {
physicalConnectProperties.put("user", user);
}
if (password != null && password.length() != 0) {
physicalConnectProperties.put("password", password);
}
Connection conn;
long connectStartNanos = System.nanoTime();
long connectedNanos, initedNanos, validatedNanos;
try {
conn = createPhysicalConnection(url, physicalConnectProperties);
connectedNanos = System.nanoTime();
if (conn == null) {
throw new SQLException("connect error, url " + url + ", driverClass " + this.driverClass);
}
initPhysicalConnection(conn);
initedNanos = System.nanoTime();
validateConnection(conn);
validatedNanos = System.nanoTime();
setCreateError(null);
} catch (SQLException ex) {
setCreateError(ex);
throw ex;
} catch (RuntimeException ex) {
setCreateError(ex);
throw ex;
} catch (Error ex) {
createErrorCount.incrementAndGet();
throw ex;
} finally {
long nano = System.nanoTime() - connectStartNanos;
createTimespan += nano;
}
return new PhysicalConnectionInfo(conn, connectStartNanos, connectedNanos, initedNanos, validatedNanos);
}