io.netty.resolver.dns

Interface DnsQueryLifecycleObserver

@UnstableApi
public interface DnsQueryLifecycleObserver

This interface provides visibility into individual DNS queries. The lifecycle of an objects is as follows:

1. Object creation
2. queryCancelled(int)

OR

1. Object creation
2. queryWritten(InetSocketAddress, ChannelFuture)
3. queryRedirected(List) or queryCNAMEd(DnsQuestion) or queryNoAnswer(DnsResponseCode) or queryCancelled(int) or queryFailed(Throwable) or querySucceed()

This interface can be used to track metrics for individual DNS servers. Methods which may lead to another DNS query return an object of type DnsQueryLifecycleObserver. Implementations may use this to build a query tree to understand the "sub queries" generated by a single query.

Method Summary

Modifier and Type	Method and Description
void	queryCancelled(int queriesRemaining) The query may have been written but it was cancelled at some point.
DnsQueryLifecycleObserver	queryCNAMEd(DnsQuestion cnameQuestion) The query returned a CNAME which we may attempt to follow with a new query.
void	queryFailed(Throwable cause) The following criteria are possible: IO Error Server responded with an invalid DNS response Server responded with a valid DNS response, but it didn't progress the resolution
DnsQueryLifecycleObserver	queryNoAnswer(DnsResponseCode code) The response to the query didn't provide the expected response code, but it didn't return DnsResponseCode.NXDOMAIN so we may try to query again.
DnsQueryLifecycleObserver	queryRedirected(List<InetSocketAddress> nameServers) The query has been redirected to another list of DNS servers.
void	querySucceed() The query received the expected results.
void	queryWritten(InetSocketAddress dnsServerAddress, ChannelFuture future) The query has been written.

Method Detail

queryWritten

void queryWritten(InetSocketAddress dnsServerAddress,
                  ChannelFuture future)

The query has been written.

Parameters:

dnsServerAddress - The DNS server address which the query was sent to.

future - The future which represents the status of the write operation for the DNS query.

queryCancelled

void queryCancelled(int queriesRemaining)

The query may have been written but it was cancelled at some point.

Parameters:

queriesRemaining - The number of queries remaining.

queryRedirected

DnsQueryLifecycleObserver queryRedirected(List<InetSocketAddress> nameServers)

The query has been redirected to another list of DNS servers.

Parameters:

nameServers - The name servers the query has been redirected to.

Returns:

An observer for the new query which we may issue.

queryCNAMEd

DnsQueryLifecycleObserver queryCNAMEd(DnsQuestion cnameQuestion)

The query returned a CNAME which we may attempt to follow with a new query.

Note that multiple queries may be encountering a CNAME. For example a if both DnsRecordType.AAAA and DnsRecordType.A are supported we may query for both.

Parameters:

cnameQuestion - the question we would use if we issue a new query.

Returns:

An observer for the new query which we may issue.

queryNoAnswer

DnsQueryLifecycleObserver queryNoAnswer(DnsResponseCode code)

The response to the query didn't provide the expected response code, but it didn't return DnsResponseCode.NXDOMAIN so we may try to query again.

Parameters:

code - the unexpected response code.

Returns:

An observer for the new query which we may issue.

queryFailed

void queryFailed(Throwable cause)

The following criteria are possible:

• IO Error
• Server responded with an invalid DNS response
• Server responded with a valid DNS response, but it didn't progress the resolution

Parameters:

cause - The cause which for the failure.

querySucceed

void querySucceed()

The query received the expected results.