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The following commit(s) were added to refs/heads/9.0.x by this push:
new 963711cb64 Expand the Javadoc for DNSMembershipProvider
963711cb64 is described below
commit 963711cb64e720bd38f55e64566cb940f3516fa0
Author: Mark Thomas <[email protected]>
AuthorDate: Wed Jul 8 11:46:27 2026 +0100
Expand the Javadoc for DNSMembershipProvider
---
.../membership/cloud/CloudMembershipService.java | 5 +++--
.../tribes/membership/cloud/DNSMembershipProvider.java | 18 ++++++++++++++++--
webapps/docs/changelog.xml | 5 +++++
3 files changed, 24 insertions(+), 4 deletions(-)
diff --git
a/java/org/apache/catalina/tribes/membership/cloud/CloudMembershipService.java
b/java/org/apache/catalina/tribes/membership/cloud/CloudMembershipService.java
index 1b1d96be92..737503dd50 100644
---
a/java/org/apache/catalina/tribes/membership/cloud/CloudMembershipService.java
+++
b/java/org/apache/catalina/tribes/membership/cloud/CloudMembershipService.java
@@ -33,8 +33,9 @@ import org.apache.juli.logging.LogFactory;
* A {@link org.apache.catalina.tribes.MembershipService} that uses Kubernetes
API(default) or DNS to retrieve the
* members of a cluster.<br>
* <p>
- * The default implementation of the MembershipProvider component is the
{@link KubernetesMembershipProvider}. The
- * MembershipProvider can be configured by the
<code>membershipProviderClassName</code> property. Possible shortcuts are
+ * The default (and recommended) implementation of the MembershipProvider
component is the
+ * {@link KubernetesMembershipProvider}. The MembershipProvider can be
configured by the
+ * <code>membershipProviderClassName</code> property. Possible shortcuts are
* {@code kubernetes} and {@code dns}. For dns look at the {@link
DNSMembershipProvider}.
* </p>
* <p>
diff --git
a/java/org/apache/catalina/tribes/membership/cloud/DNSMembershipProvider.java
b/java/org/apache/catalina/tribes/membership/cloud/DNSMembershipProvider.java
index c3731aceb0..d9be130e9f 100644
---
a/java/org/apache/catalina/tribes/membership/cloud/DNSMembershipProvider.java
+++
b/java/org/apache/catalina/tribes/membership/cloud/DNSMembershipProvider.java
@@ -32,7 +32,21 @@ import org.apache.juli.logging.Log;
import org.apache.juli.logging.LogFactory;
/**
- * A {@link org.apache.catalina.tribes.MembershipProvider} that uses DNS to
retrieve the members of a cluster.<br>
+ * A {@link org.apache.catalina.tribes.MembershipProvider} that uses DNS to
retrieve the members of a cluster.
+ * <p>
+ * Relying solely on DNS to determine cluster membership requires that all DNS
caching between the cluster nodes and the
+ * authoritative name server must honour the TTL set by the authoritative name
server. Experience has shown that that is
+ * often not the case. Therefore, to ensure that new cluster members are not
excluded from the cluster due to a stale
+ * DNS cache, this membership service accepts messages from any node
regardless of whether it or not is listed as a
+ * cluster member in DNS and adds that node to the cluster. The DNS entry is,
effectively, used by new nodes to identify
+ * the other nodes in the cluster to which cluster messages should be sent.
+ * <p>
+ * If more control is required over cluster membership, users are strongly
encouraged to use
+ * {@link KubernetesMembershipProvider} instead. Alternatively, the
+ * {@link org.apache.catalina.tribes.group.interceptors.EncryptInterceptor}
may be used to ensure that only nodes with
+ * knowledge of the shared key are able to participate in the cluster.
+ * <p>
+ * TODO: Make the "accept messages from any node and add that node to the
cluster" behaviour optional.
* <p>
* <strong>Configuration example for Kubernetes</strong>
* </p>
@@ -202,7 +216,7 @@ public class DNSMembershipProvider extends
CloudMembershipProvider {
byte[] host = sender.getHost();
int i = 0;
StringBuilder buf = new StringBuilder();
- if (host.length > 0 ) {
+ if (host.length > 0) {
buf.append(host[i++] & 0xff);
for (; i < host.length; i++) {
buf.append('.').append(host[i] & 0xff);
diff --git a/webapps/docs/changelog.xml b/webapps/docs/changelog.xml
index fe9a8b548a..1a684483b6 100644
--- a/webapps/docs/changelog.xml
+++ b/webapps/docs/changelog.xml
@@ -137,6 +137,11 @@
algorithms. Also explicitly state that the replay protection is only
effective for non-malleable algorithms. (markt)
</add>
+ <add>
+ Expand the Javadoc for the <code>DNSMembershipProvider</code> in
+ particular explaining its behaviour and providing configuration advice
+ if control more over cluster membership is required. (markt)
+ </add>
</changelog>
</subsection>
</section>
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