Package com.linkedin.venice.httpclient

Class CachedDnsResolver

java.lang.Object

com.linkedin.venice.httpclient.CachedDnsResolver

All Implemented Interfaces:

Closeable, AutoCloseable, org.apache.http.conn.DnsResolver

public class CachedDnsResolver
extends Object
implements org.apache.http.conn.DnsResolver, Closeable

CachedDnsResolver caches the dns entries for hosts, which matches the specified host pattern. In the meantime, there is a asynchronous task running to refresh the cached entries periodically. The reason to have this customized DnsResolver: 1. If the DNS lookup is slow, AbstractNIOConnPool.lease(Object, Object) will be blocked by the slow DNS lookup, which will cause a lot of requests being blocked since the slow DNS lookup will grab the per-connection-pool lock until it is done; 2. Here we choose to use a asynchronous task to refresh the cached entries is that the synchronous refresh with TTL will still cause latency spike because of #1;

Constructor Summary

Constructors

Constructor	Description
CachedDnsResolver(String cachedHostPattern, long refreshIntervalInMs, DnsLookupStats stats)

Method Summary

Modifier and Type	Method	Description
void	close()
protected Optional<InetAddress[]>	getEntryFromDnsCache(String host)
InetAddress[]	resolve(String host)
protected InetAddress[]	systemGetAllByName(String host)

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Details

CachedDnsResolver

public CachedDnsResolver(String cachedHostPattern,
 long refreshIntervalInMs,
 DnsLookupStats stats)

Method Details

resolve

public InetAddress[] resolve(String host)
                      throws UnknownHostException

Specified by:

resolve in interface org.apache.http.conn.DnsResolver

Throws:

UnknownHostException

getEntryFromDnsCache

protected Optional<InetAddress[]> getEntryFromDnsCache(String host)

systemGetAllByName

protected InetAddress[] systemGetAllByName(String host)
                                    throws UnknownHostException

Throws:

UnknownHostException

close

public void close()
           throws IOException

Specified by:

close in interface AutoCloseable

Specified by:

close in interface Closeable

Throws:

IOException