HikariCP源码简洁剖析——HikariConfig

• HikariConfig的作用
• 链接池大小
• 各种timeout
• HikariConfig中的配置

HikariConfig的作用

HikariConfig是HikariDataSource的父类，维护链接池的各种参数，如数据库用户名密码、链接池大小、查询超时时间等等。

整体上HikariConfig的实现仍然非常简单，只是提供了这些参数的基本校验和get/set方法。

链接池大小

HikariCP中只有两个值来控制连接池的大小：maxPoolSize和minIdle，且HikariCP中建议将这两个值设置为相同的数字。

• maxPoolSize
  • 链接池中链接的最大数量
  • 默认为10；超过minIdle，则设置为与minIdle相同
• minIdle
  • 默认为10；若小于0或大于maxPoolSize，则设置为与maxPoolSize相同

各种timeout

• initializationFailTimeout
  • 单位ms，初始化时设置为1。大于1的值即为初始化链接池时执行FailFast的超时时间。
  • 若值小于0，则不执行链接池FailFast检查。
  • FailFast检查就是尝试创建链接，并执行sql检查
• maxLifetime
  • 默认30s，至少30s
• idleTimeout
  • 默认10s。当maxLifetime大于0时，至少比maxLifetime小1s以上
• connectionTimeout
  • 默认为30s，不能低于250ms
• validationTimeout
  • 默认为5s，不能低于250ms

HikariConfig中的配置

   //默认值
   private static final long CONNECTION_TIMEOUT = SECONDS.toMillis(30);
   private static final long VALIDATION_TIMEOUT = SECONDS.toMillis(5);
   private static final long IDLE_TIMEOUT = MINUTES.toMillis(10);
   private static final long MAX_LIFETIME = MINUTES.toMillis(30);
   private static final int DEFAULT_POOL_SIZE = 10;
   
   // Properties changeable at runtime through the MBean
   //
   private volatile long connectionTimeout;
   private volatile long validationTimeout;
   private volatile long idleTimeout;
   private volatile long leakDetectionThreshold;
   private volatile long maxLifetime;
   //HikariCP中只有最大链接数和最小链接数两个值，没有max_active等。
   //而且会默认将maxPoolSize和minIdle设置为相同的值
   private volatile int maxPoolSize;
   private volatile int minIdle;

   // Properties NOT changeable at runtime
   //
   private long initializationFailTimeout;
   private String catalog;
   private String connectionInitSql;
   private String connectionTestQuery;
   private String dataSourceClassName;
   private String dataSourceJndiName;
   private String driverClassName;
   private String jdbcUrl;
   private String password;
   private String poolName;
   private String transactionIsolationName;
   private String username;
   private boolean isAutoCommit;
   private boolean isReadOnly;
   private boolean isIsolateInternalQueries;
   private boolean isRegisterMbeans;
   private boolean isAllowPoolSuspension;
   private DataSource dataSource;
   private Properties dataSourceProperties;
   private ThreadFactory threadFactory;
   private ScheduledExecutorService scheduledExecutor;
   private MetricsTrackerFactory metricsTrackerFactory;
   private Object metricRegistry;
   private Object healthCheckRegistry;
   private Properties healthCheckProperties;