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https://issues.apache.org/jira/browse/ZOOKEEPER-2691?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15873701#comment-15873701
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ASF GitHub Bot commented on ZOOKEEPER-2691:
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Github user eribeiro commented on the issue:
https://github.com/apache/zookeeper/pull/173
@jiangjiafu glad to help. :) Thanks for driving this change. Great work.
> recreateSocketAddresses may recreate the unreachable IP address
> ---------------------------------------------------------------
>
> Key: ZOOKEEPER-2691
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2691
> Project: ZooKeeper
> Issue Type: Bug
> Affects Versions: 3.4.8
> Environment: Centos6.5
> Java8
> ZooKeeper3.4.8
> Reporter: JiangJiafu
> Priority: Minor
>
> The QuorumPeer$QuorumServer.recreateSocketAddress() is used to resolved the
> hostname to a new IP address(InetAddress) when any exception happens to the
> socket. It will be very useful when a hostname can be resolved to more than
> one IP address.
> But the problem is Java API InetAddress.getByName(String hostname) will
> always return the first IP address when the hostname can be resolved to more
> than one IP address, and the first IP address may be unreachable forever. For
> example, if a machine has two network interfaces: eth0, eth1, say eth0 has
> ip1, eth1 has ip2, the relationship between hostname and the IP addresses is
> set in /etc/hosts. When I "close" the eth0 by command "ifdown eth0", the
> InetAddress.getByName(String hostname) will still return ip1, which is
> unreachable forever.
> So I think it will be better to check the IP address by
> InetAddress.isReachable(long) and choose the reachable IP address.
> I have modified the ZooKeeper source code, and test the new code in my own
> environment, and it can work very well when I turn down some network
> interfaces using "ifdown" command.
> The original code is:
> {code:title=QuorumPeer.java|borderStyle=solid}
> public void recreateSocketAddresses() {
> InetAddress address = null;
> try {
> address = InetAddress.getByName(this.hostname);
> LOG.info("Resolved hostname: {} to address: {}",
> this.hostname, address);
> this.addr = new InetSocketAddress(address, this.port);
> if (this.electionPort > 0){
> this.electionAddr = new InetSocketAddress(address,
> this.electionPort);
> }
> } catch (UnknownHostException ex) {
> LOG.warn("Failed to resolve address: {}", this.hostname, ex);
> // Have we succeeded in the past?
> if (this.addr != null) {
> // Yes, previously the lookup succeeded. Leave things as
> they are
> return;
> }
> // The hostname has never resolved. Create our
> InetSocketAddress(es) as unresolved
> this.addr = InetSocketAddress.createUnresolved(this.hostname,
> this.port);
> if (this.electionPort > 0){
> this.electionAddr =
> InetSocketAddress.createUnresolved(this.hostname,
>
> this.electionPort);
> }
> }
> }
> {code}
> After my modification:
> {code:title=QuorumPeer.java|borderStyle=solid}
> public void recreateSocketAddresses() {
> InetAddress address = null;
> try {
> address = getReachableAddress(this.hostname);
> LOG.info("Resolved hostname: {} to address: {}",
> this.hostname, address);
> this.addr = new InetSocketAddress(address, this.port);
> if (this.electionPort > 0){
> this.electionAddr = new InetSocketAddress(address,
> this.electionPort);
> }
> } catch (UnknownHostException ex) {
> LOG.warn("Failed to resolve address: {}", this.hostname, ex);
> // Have we succeeded in the past?
> if (this.addr != null) {
> // Yes, previously the lookup succeeded. Leave things as
> they are
> return;
> }
> // The hostname has never resolved. Create our
> InetSocketAddress(es) as unresolved
> this.addr = InetSocketAddress.createUnresolved(this.hostname,
> this.port);
> if (this.electionPort > 0){
> this.electionAddr =
> InetSocketAddress.createUnresolved(this.hostname,
>
> this.electionPort);
> }
> }
> }
> public InetAddress getReachableAddress(String hostname) throws
> UnknownHostException {
> InetAddress[] addresses = InetAddress.getAllByName(hostname);
> for (InetAddress a : addresses) {
> try {
> if (a.isReachable(5000)) {
> return a;
> }
> } catch (IOException e) {
> LOG.warn("IP address {} is unreachable", a);
> }
> }
> // All the IP address is unreachable, just return the first one.
> return addresses[0];
> }
> {code}
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