apollo-configservice/src/main/java/com/ctrip/framework/apollo/configservice/filter/ClientAuthenticationFilter.java/ClientAuthenticationFilter/checkTimestamp
class ClientAuthenticationFilter:  private boolean checkTimestamp(String timestamp) {
    long requestTimeMillis = 0L;
    try {
      requestTimeMillis = Long.parseLong(timestamp);
    } catch (NumberFormatException e) {
      // nothing to do
    }

    long x = System.currentTimeMillis() - requestTimeMillis;
    long authTimeDiffToleranceInMillis = bizConfig.accessKeyAuthTimeDiffTolerance() * 1000L;
    return Math.abs(x) < authTimeDiffToleranceInMillis;
  }