Configure degradation policies - - Alibaba Cloud Documentation Center

Configure a downgrade policy

You can configure a degradation policy to switch the domain name resolution method to native DNS resolution.

Important

The degradation policy determines which domain names require native DNS resolution. For these domain names, the SDK provides empty resolution results. The business code completes the specific degradation operation after receiving these empty results, following the same logic as when the SDK cannot resolve domain names. The SDK does not employ the local DNS server for resolution.

Interface Definition

void setDegradationFilter(DegradationFilter filter);
public interface DegradationFilter {
    /**
     * Degradation filter
     *
     * @param hostName The domain name that you want to resolve, such as www.aliyun.com. You can filter the domain names that are not resolved by HTTPDNS.
     * @return Specify whether to perform native DNS resolution.
     */
    boolean shouldDegradeHttpDNS(String hostName);
}

Parameter Description

Parameter	Type	Required	Description
filter	DegradationFilter	Yes	Downgrade proxy

Code Example

// httpdns is the service instance obtained during initialization
DegradationFilter filter = new DegradationFilter() {
  @Override
  public boolean shouldDegradeHttpDNS(String hostName) {
    // You can specify custom degradation logic. In this example, HTTPDNS resolution is not used for www.aliyuno.com
    // Refer to the HTTPDNS API documentation. If an intermediate HTTP proxy exists, use the local DNS server for resolution.
    return hostName.equals("www.aliyuno.com");
  }
};
// Import the filter to HTTPDNS. The shouldDegradeHTTPDNS method is called during resolution to check whether HTTPDNS is used
httpdns.setDegradationFilter(filter);

Configure a degradation filter

Apply a degradation filter to domain names.

Interface Definition

boolean shouldDegradeHttpDNS(String hostName);

Parameter Description

Parameter	Type	Required	Description
hostname	String	Yes	The domain name that you want to resolve, such as www.aliyun.com. You can filter the domain names that are not resolved by HTTPDNS.
return	Boolean	No	Specifies whether to perform native DNS resolution.

Code Example

DegradationFilter filter = new DegradationFilter() {
  @Override
  public boolean shouldDegradeHttpDNS(String hostName) {
    // You can specify custom degradation logic. In this example, HTTPDNS resolution is not used for www.aliyuno.com
    // Refer to the HTTPDNS API documentation. If an intermediate HTTP proxy exists, use the local DNS server for resolution.
    return hostName.equals("www.aliyuno.com");
  }
};