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From fpj <...@git.apache.org>
Subject [GitHub] zookeeper pull request #150: ZOOKEEPER-2184: Zookeeper Client should re-reso...
Date Mon, 23 Jan 2017 23:00:22 GMT
Github user fpj commented on a diff in the pull request:

    https://github.com/apache/zookeeper/pull/150#discussion_r97437693
  
    --- Diff: src/java/main/org/apache/zookeeper/client/StaticHostProvider.java ---
    @@ -87,15 +86,69 @@ 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);
    +                        for (InetAddress resolvedAddress : resolvedAddresses) {
    +                            InetSocketAddress newAddr = new InetSocketAddress(resolvedAddress,
thePort);
    +                            if (!serverAddresses.contains(newAddr)) {
    +                                serverAddresses.add(newAddr);
    +                            }
    +                        }
    --- End diff --
    
    We shuffle initially to avoid having all clients connecting to the same server in the
case they are all given the same connect string. If the array of addresses has already been
shuffled (in the constructor), then the order followed in this method will be the shuffled
one. I don't see a strong reason for re-shuffling, as we are not bringing it back to the original
order by resolving again.


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