sijie commented on a change in pull request #425: BOOKKEEPER-1105:
RackAwarePolicy: Failure to map node into rack may result in failure to add
other nodes.
URL: https://github.com/apache/bookkeeper/pull/425#discussion_r132529923
##########
File path:
bookkeeper-server/src/main/java/org/apache/bookkeeper/net/DNSToSwitchMapping.java
##########
@@ -41,14 +41,14 @@
* <p/>
*
* If a name cannot be resolved to a rack, the implementation
- * should return {@link NetworkTopology#DEFAULT_RACK}. This
+ * should return {@link NetworkTopology#DEFAULT_REGION_AND_RACK}. This
* is what the bundled implementations do, though it is not a formal
requirement
*
* @param names the list of hosts to resolve (can be empty)
* @return list of resolved network paths.
* If <i>names</i> is empty, the returned list is also empty
*/
- public List<String> resolve(List<String> names);
+ public List<String> resolve(List<String> names, String defaultRack);
Review comment:
This would break the binary compatibility for any people who implemented
DNSToSwitchMapping.
The main problem is
```java
public static String resolveNetworkLocation(DNSToSwitchMapping
dnsResolver, InetSocketAddress addr) {
List<String> names = new ArrayList<String>(1);
if (dnsResolver instanceof CachedDNSToSwitchMapping) {
names.add(addr.getAddress().getHostAddress());
} else {
names.add(addr.getHostName());
}
// resolve network addresses
List<String> rNames = dnsResolver.resolve(names);
String netLoc;
if (null == rNames) {
logger.warn("Failed to resolve network location for {}, using
default rack for them : {}.", names,
NetworkTopology.DEFAULT_RACK);
netLoc = NetworkTopology.DEFAULT_RACK;
} else {
netLoc = rNames.get(0);
}
return netLoc;
}
```
I think a clean solution without breaking the binary compatibility is
- Fix the DefaultResolver to allow passing in a `defaultRack`
```java
class DefaultResolver {
final String defaultRack = ...;
DefaultResolver() {
this(...);
}
DefaultResolver(String defaultRack) {
this.defaultRack = defaultRack;
}
}
```
the rackware can use new DefaultResolver(`/default-rack`) and regionaware
can use new DefaultResolver(`/default-region/default-rack`)
- create a DNSResolverDelegator with default-rack and remove the logic
`NetUtils#resolveNetworkLocation` to this delegator.
```java
class DNSResolverDelegator extends DefaultResolver {
DNSToSwitchMapping resolver;
DNSResolverDelegator(DNSToSwitchMapping resolver, String defaultRack) {
super(defaultRack);
this.resolver= resolver;
}
List<String> resolve(List<String> names) {
List<String> resolvedNames = resolver.resolve(names);
if (null == resolvedNames) {
// return default rack
}
}
}
```
- on initialization
```java
if (optionalDnsResolver.isPresent()) {
dnsResolver = optionalDnsResolver.get();
} else {
String dnsResolverName = conf.getString(REPP_DNS_RESOLVER_CLASS,
ScriptBasedMapping.class.getName());
try {
dnsResolver = ReflectionUtils.newInstance(dnsResolverName,
DNSToSwitchMapping.class);
if (dnsResolver instanceof Configurable) {
((Configurable) dnsResolver).setConf(conf);
}
} catch (RuntimeException re) {
LOG.info("Failed to initialize DNS Resolver {}, used default
subnet resolver.", dnsResolverName, re);
dnsResolver = new DefaultResolver(`default-rack`); // <= add
default rack
}
}
this.dnsResolver = new DNSResolverDelegator(dnsResolver,
defaultRack);
```
In this way you don't need to change the signature of the methods. How does
that sound?
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