Sandor Molnar created KNOX-3246:
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Summary: Make Java discovery deterministic on hosts with multiple
JDKs
Key: KNOX-3246
URL: https://issues.apache.org/jira/browse/KNOX-3246
Project: Apache Knox
Issue Type: Improvement
Components: Startup Scripts
Affects Versions: 2.1.0, 3.0.0
Reporter: Sandor Molnar
Assignee: Sandor Molnar
Fix For: 3.0.0
h3. *Problem*
Knox Java discovery is non-deterministic on hosts with multiple JDK
installations.
In environments where both Java 11 and Java 17 are installed, neither version
is matched by the current {{{}JAVA_VERSION_PATTERNS{}}}. As a result, Java
detection falls back to the generic {{/bin/java$}} pattern and selects the
first match returned by {{{}find{}}}.
Because the order of results from {{find}} is not guaranteed, different hosts
in the same cluster may select different Java versions, leading to inconsistent
and unpredictable behavior.
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h3. *Root Cause*
* {{JAVA_VERSION_PATTERNS}} does not include patterns for Java 11 or Java 17
installations.
* {{{}/usr/java/default/bin/java{}}}, commonly used to define the
system-preferred Java, is not recognized.
* {{find}} is executed without {{{}-L{}}}, so symlinks are not followed.
* The fallback selection uses {{head -n 1}} without stabilizing the result
order.
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h3. *Example*
On different hosts in the same cluster:
/usr/lib/jvm/jdk1.17.0.11.0-openjdk/bin/java
/usr/java/jdk1.11.70.15-z.0_lu/bin/java
or
/usr/java/jdk1.11.70.15-z.0_lu/bin/java
/usr/lib/jvm/jdk1.17.0.11.0-openjdk/bin/java
Depending on the host, Knox may start with Java 11 or Java 17.
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h3. *Proposed Fix*
* Extend {{JAVA_VERSION_PATTERNS}} to explicitly recognize Java 11 and Java 17
layouts.
* Add support for {{/usr/java/default/bin/java}} to honor the system default
Java.
* Use {{find -L}} to follow symlinks.
* Sort Java candidates before selecting the first match to ensure
deterministic behavior.
----
h3. *Impact*
Ensures consistent Java version selection across all nodes in a cluster,
prevents unpredictable startup behavior, and aligns Knox Java discovery with
common enterprise JDK layouts.
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