Motivation:
DnsCache (an interface) is coupled to DnsCacheEntry (a final class). This means that DnsCache implementations can't implement their own DnsCacheEntry objects if the default behavior isn't appropriate.
Modifications:
- DnsCacheEntry should be moved to DefaultDnsCache as it is an implementation detail
- DnsCache#cache(..) should return a new DnsCacheEntry
- The methods which from DnsCacheEntry that were used outside the scope of DefaultDnsCache should be moved into an interface
Result:
DnsCache is more extensible and not tightly coupled to a default implementation of DnsCacheEntry.
Motivation:
Some codecs should be considered unstable as these are relative new. For this purpose we should introduce an annotation which these codecs should us to be marked as unstable in terms of API.
Modifications:
- Add UnstableApi annotation and use it on codecs that are not stable
- Move http2.hpack to http2.internal.hpack as it is internal.
Result:
Better document unstable APIs.
Motivation:
Caching is currently nested in DnsResolver.
It should also be possible to extend DnsResolver to ba able to pass a different cache on each resolution attemp.
Modifications:
* Introduce DnsCache, NoopDnsCache and DefaultDnsCache. The latter contains all the current caching logic that was extracted.
* Introduce protected versions of doResolve and doResolveAll that can be used as extension points to build resolvers that bypass the main cache and use a different one on each resolution.
Result:
Isolated caching logic. Better extensibility.
Related issues:
- #3971
- #3973
- #3976
- #4035
Motivation:
1. Previously, DnsNameResolver.query() retried the request query by its
own. It prevents a user from deciding when to retry or stop. It is also
impossible to get the response object whose code is not NOERROR.
2. NameResolver does not have an operation that resolves a host name
into multiple addresses, like InetAddress.getAllByName()
Modifications:
- Changes related with DnsNameResolver.query()
- Make query() not retry
- Move the retry logic to DnsNameResolver.resolve() instead.
- Make query() fail the promise only when I/O error occurred or it
failed to get a response
- Add DnsNameResolverException and use it when query() fails so that
the resolver can give more information about the failure
- query() does not cache anymore.
- Changes related with NameResolver.resolveAll()
- Add NameResolver.resolveAll()
- Add SimpleNameResolver.doResolveAll()
- Changes related with DnsNameResolver.resolve() and resolveAll()
- Make DnsNameResolveContext abstract so that DnsNameResolver can
decide to get single or multiple addresses from it
- Re-implement cache so that the cache works for resolve() and
resolveAll()
- Add 'traceEnabled' property to enable/disable trace information
- Miscellaneous changes
- Use ObjectUtil.checkNotNull() wherever possible
- Add InternetProtocolFamily.addressType() to remove repetitive
switch-case blocks in DnsNameResolver(Context)
- Do not raise an exception when decoding a truncated DNS response
Result:
- Full control over query()
- A user can now retrieve all addresses via (Dns)NameResolver.resolveAll()
- DNS cache works only for resolve() and resolveAll() now.
Related: #3797
Motivation:
There is a race condition where DnsNameResolver.query() can attempt to
increase the reference count of the DNS response which was released
already by other thread.
Modifications:
- Make DnsCacheEntry a top-level class for clear access control
- Use 'synchronized' to avoid the race condition
- Add DnsCacheEntry.retainedResponse() to make sure that the response
is never released while it is retained
- Make retainedResponse() return null when the response has been
released already, so that DnsNameResolver.query() knows that the
cached entry has been released
Result:
The forementioned race condition has been fixed.
