Github user afine commented on a diff in the pull request: https://github.com/apache/zookeeper/pull/150#discussion_r96512625 --- Diff: src/java/main/org/apache/zookeeper/client/StaticHostProvider.java --- @@ -87,15 +73,69 @@ public StaticHostProvider(Collection<InetSocketAddress> serverAddresses) Collections.shuffle(this.serverAddresses); } + /** + * In Java 7, we have a method getHostString, but earlier versions do not support it. + * This method is to provide a replacement for InetSocketAddress.getHostString(). + * + * It evaluates to a hostname if one is available and otherwise it returns the + * string representation of the IP address. + * + * @param addr + * @return Hostname string of address parameter + */ + private String getHostString(InetSocketAddress addr) { + String hostString; + InetAddress ia = addr.getAddress(); + + if (ia != null) { + // If the string starts with '/', then it has no hostname + // and we want to avoid the reverse lookup, so we return + // the string representation of the address. + if (ia.toString().startsWith("/")) { + hostString = ia.getHostAddress(); + } else { + hostString = addr.getHostName(); + } + } else { + // According to the Java 6 documentation, if the hostname is + // unresolved, then the string before the colon is the hostname. + String addrString = addr.toString(); + hostString = addrString.substring(0, addrString.lastIndexOf(':')); + } + + return hostString; + } + public int size() { return serverAddresses.size(); } public InetSocketAddress next(long spinDelay) { - ++currentIndex; - if (currentIndex == serverAddresses.size()) { - currentIndex = 0; + // Handle possible connection error by re-resolving hostname if possible + if (!connectedSinceNext) { + InetSocketAddress curAddr = serverAddresses.get(currentIndex); + if (!curAddr.getHostString().equals(curAddr.getAddress().getHostAddress())) { + try { + int thePort = curAddr.getPort(); + InetAddress resolvedAddresses[] = InetAddress.getAllByName(getHostString(curAddr)); + if (resolvedAddresses.length == 1) { + serverAddresses.set(currentIndex, new InetSocketAddress(resolvedAddresses[0], thePort)); + } else { + serverAddresses.remove(currentIndex); --- End diff -- In the case where during the construction of the `StaticHostProvider` we add a host H1 which resolves to addresses A,B,C. Then at some point in the future A goes offline and the DNS system has changed H1 to resolve to hosts D,E,F. With the current code wouldn't `serverAddresses` now contain hosts B,C,D,E,F instead of only hosts D,E,F? Is this something even worth fixing?
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