重试逻辑直到数据库出现

Question

通过我的java代码，我使用连接池连接到多个数据库。如果我的数据库出现故障，我需要处理重试逻辑来获取连接，直到它返回一个连接对象。

Answer 1

如果您的数据库连接抛出某种异常，那么您可以休眠一会儿，然后再次重试该操作。

在下面的示例中，worker 是一个执行一些工作的对象，例如连接到数据库等。它非常通用，因此您可以重试任何类型的操作，例如从文件中读取等。

请注意，捕获 Throwable< /code> 可能不一定是个好主意。

    boolean success = false;
    int i = 0;
    long delay = retryDelay;

    LOGGER.info("Starting operation");

    /*
     * Loop until you cannot retry anymore or the operation completed successfully
     * The catch block has a nested try catch to ensure that nothing goes wrong
     * while trying to sleep
     * 
     * In case of failure the last retry exception is propagated up to the calling
     * class.
     */
    while (i++ < retryMax && !success)
    {
        try
        {
            worker.work();
            success = true;
        }
        catch (Throwable t)
        {
            try
            {
                LOGGER.warn("Caught throwable", t);

                if (i == retryMax) 
                {
                    LOGGER.warn("Retry maximum reached, propagating error");
                    throw t;
                }

                if (retryPolicy == RetryPolicy.ESCALATING) 
                {
                    delay *= 2;
                }

                LOGGER.info("Sleeping for " + delay + " milliseconds");

                Thread.sleep(delay);
            }
            catch (Throwable tt)
            {
                /*
                 * Quick check to see if the maximum has been hit, so we don't log twice
                 * 
                 * t is the original error, and tt is the error we got while retrying
                 * tt would most likely be a InterruptedException or something
                 */
                if (i == retryMax) 
                {
                    throw t;
                }

                LOGGER.warn("Error while retrying, propagating original error up", tt);

                throw t;
            }
        }

    } // end retry loop