JiangJiafu created ZOOKEEPER-2691:
-------------------------------------
Summary: 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. 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:
{quote}
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);
}
}
}
{quote}
After my modification:
{quote}
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];
}
{quote}
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