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https://issues.apache.org/jira/browse/ZOOKEEPER-2184?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16366132#comment-16366132
]
ASF GitHub Bot commented on ZOOKEEPER-2184:
-------------------------------------------
Github user afine commented on a diff in the pull request:
https://github.com/apache/zookeeper/pull/451#discussion_r168578617
--- Diff: src/java/main/org/apache/zookeeper/client/StaticHostProvider.java
---
@@ -58,48 +61,122 @@
public StaticHostProvider(Collection<InetSocketAddress>
serverAddresses) {
for (InetSocketAddress address : serverAddresses) {
try {
- InetAddress ia = address.getAddress();
- InetAddress resolvedAddresses[] =
InetAddress.getAllByName((ia != null) ? ia.getHostAddress() :
- address.getHostName());
+ InetAddress resolvedAddresses[] =
InetAddress.getAllByName(getHostString(address));
for (InetAddress resolvedAddress : resolvedAddresses) {
- // If hostName is null but the address is not, we can
tell that
- // the hostName is an literal IP address. Then we can
set the host string as the hostname
- // safely to avoid reverse DNS lookup.
- // As far as i know, the only way to check if the
hostName is null is use toString().
- // Both the two implementations of InetAddress are
final class, so we can trust the return value of
- // the toString() method.
- if (resolvedAddress.toString().startsWith("/")
- && resolvedAddress.getAddress() != null) {
- this.serverAddresses.add(
- new
InetSocketAddress(InetAddress.getByAddress(
- address.getHostName(),
- resolvedAddress.getAddress()),
- address.getPort()));
- } else {
- this.serverAddresses.add(new
InetSocketAddress(resolvedAddress.getHostAddress(), address.getPort()));
- }
+ this.serverAddresses.add(new
InetSocketAddress(resolvedAddress, address.getPort()));
}
} catch (UnknownHostException e) {
LOG.error("Unable to connect to server: {}", address, e);
}
}
-
+
if (this.serverAddresses.isEmpty()) {
throw new IllegalArgumentException(
"A HostProvider may not be empty!");
}
Collections.shuffle(this.serverAddresses);
}
+ /**
+ * Evaluate to a hostname if one is available and otherwise it returns
the
+ * string representation of the IP address.
+ *
+ * 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().
+ *
+ * @param addr
+ * @return Hostname string of address parameter
+ */
+ private String getHostString(InetSocketAddress addr) {
+ String hostString = "";
+
+ if (addr == null) {
+ return hostString;
+ }
+ if (!addr.isUnresolved()) {
+ InetAddress ia = addr.getAddress();
+
+ // 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();
}
+ // Counts the number of addresses added and removed during
+ // the last call to next. Used mainly for test purposes.
+ // See StasticHostProviderTest.
+ private int nextAdded = 0;
+ private int nextRemoved = 0;
+
+ public int getNextAdded() {
+ return nextAdded;
+ }
+
+ public int getNextRemoved() {
+ return nextRemoved;
+ }
+
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);
+ String curHostString = getHostString(curAddr);
+ if
(!curHostString.equals(curAddr.getAddress().getHostAddress())) {
+ LOG.info("Resolving again hostname: {}",
getHostString(curAddr));
+ try {
+ int thePort = curAddr.getPort();
+ InetAddress resolvedAddresses[] =
InetAddress.getAllByName(curHostString);
+ nextAdded = 0;
+ nextRemoved = 0;
+ if (resolvedAddresses.length == 1) {
+ serverAddresses.set(currentIndex, new
InetSocketAddress(resolvedAddresses[0], thePort));
+ nextAdded = nextRemoved = 1;
+ LOG.debug("Newly resolved address: {}",
resolvedAddresses[0]);
+ } else {
+ int i = 0;
+ while (i < serverAddresses.size()) {
+ if
(getHostString(serverAddresses.get(i)).equals(curHostString) &&
--- End diff --
Why don't we simplify things and just do this always? In other words,
always remove all serverAddresses that correspond to the curHostString. That
way if curHostString goes from resolving to many addresses to just 1, we remove
all of them?
> 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, 3.4.7, 3.4.8, 3.4.9, 3.4.10, 3.5.0, 3.5.1, 3.5.2,
> 3.5.3, 3.4.11
> Environment: Ubuntu 14.04 host, Docker containers for Zookeeper &
> Kafka
> Reporter: Robert P. Thille
> Assignee: Flavio Junqueira
> Priority: Blocker
> Labels: easyfix, patch
> Fix For: 3.5.4, 3.4.12
>
> 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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