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https://issues.apache.org/jira/browse/ZOOKEEPER-2184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15826845#comment-15826845
]
ASF GitHub Bot commented on ZOOKEEPER-2184:
-------------------------------------------
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?
> Zookeeper Client should re-resolve hosts when connection attempts fail
> ----------------------------------------------------------------------
>
> Key: ZOOKEEPER-2184
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2184
> Project: ZooKeeper
> Issue Type: Bug
> Components: java client
> Affects Versions: 3.4.6, 3.5.0
> Environment: Ubuntu 14.04 host, Docker containers for Zookeeper &
> Kafka
> Reporter: Robert P. Thille
> Assignee: Flavio Junqueira
> Labels: easyfix, patch
> Fix For: 3.4.10, 3.5.3
>
> Attachments: ZOOKEEPER-2184.patch
>
>
> Testing in a Docker environment with a single Kafka instance using a single
> Zookeeper instance. Restarting the Zookeeper container will cause it to
> receive a new IP address. Kafka will never be able to reconnect to Zookeeper
> and will hang indefinitely. Updating DNS or /etc/hosts with the new IP
> address will not help the client to reconnect as the
> zookeeper/client/StaticHostProvider resolves the connection string hosts at
> creation time and never re-resolves.
> A solution would be for the client to notice that connection attempts fail
> and attempt to re-resolve the hostnames in the connectString.
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