tuhaihe commented on issue #150:
URL: https://github.com/apache/cloudberry-pxf/issues/150#issuecomment-5581957930
Root-caused this. Not a source or build-script bug -- two separate causes
stacked on top of
each other, which is why it looked so stubborn.
### Cause 1: on Debian/Ubuntu, `apt install maven` does not give you a JDK
Both distros got their Java the same way, as a side effect of installing
Maven, but the
dependency chains are not equivalent:
| | Java dependency of the `maven` package | `javac`? |
|---|---|---|
| Ubuntu 22.04 / 24.04 | `default-jre-headless \| <java7-runtime-headless>`
-- every alternative is a **`-jre-headless`** package | **no** |
| Rocky 9 / 10 | `maven-jdk-binding`, provided by `maven-openjdkNN`, which
pulls `java-NN-openjdk-devel` | yes |
So `dnf install maven` drags in a full JDK and the build passes on the first
try, while
`apt install maven` installs only a runtime. Confirmed against the project's
own CI images:
```
cbdb-build-rocky9 -> java-11-openjdk-devel
javac: yes
cbdb-build-rocky10 -> java-21-openjdk-devel
javac: yes
cbdb-build-ubuntu22.04-> openjdk-11-jre-headless, default-jre-headless
(auto) javac: NO
cbdb-build-ubuntu24.04-> (no java at all)
javac: NO
```
Two details make the Ubuntu side genuinely hard to spot:
- Debian/Ubuntu install the JRE into `/usr/lib/jvm/java-11-openjdk-amd64`,
the *same*
directory a JDK would occupy, so `ls /usr/lib/jvm` and `java -version`
both look healthy.
- Gradle's error names that very directory, which reinforces the impression
that Java 11 is
installed and fine.
There is simply no `bin/javac` in it, so `:pxf-api:compileJava` cannot
resolve a
`javaCompiler`. Note that
`ci/docker/pxf-cbdb-dev/common/script/build_pxf.sh:42` already
compensates -- it explicitly installs `openjdk-11-jdk` on apt systems and
`java-11-openjdk-devel` on dnf systems. CI therefore never hits this; only
people following
`README.md` do.
### Cause 2: after installing the JDK, a stale Gradle daemon replays the old
verdict
`server/gradle.properties` sets `org.gradle.daemon=true`. Gradle probes each
JVM
installation once and caches the result for the **lifetime of the daemon
process**, without
ever re-checking the filesystem. The failed first build leaves behind a
daemon that has
recorded `/usr/lib/jvm/java-11-openjdk-amd64` as having no `JAVA_COMPILER`.
Installing
`openjdk-11-jdk` then adds `javac` to that same directory -- but the *path*
is unchanged, so
Gradle treats it as the same JVM, reuses the existing daemon, and replays
the stale verdict.
Hence the identical error, in 2 seconds, without touching the disk.
### Reproduction
Clean `ubuntu:22.04` container, `2.2.0-incubating-rc1` source tree:
| Phase | Environment | Result |
|---|---|---|
| 1 | `openjdk-11-jre-headless` only | `Toolchain installation
'/usr/lib/jvm/java-11-openjdk-amd64' does not provide the required
capabilities: [JAVA_COMPILER]` |
| 2 | `openjdk-11-jdk` installed (`javac 11.0.32` present), daemon **not**
stopped | identical error, `BUILD FAILED in 2s` |
| 3 | same, after `./gradlew --stop` | `BUILD SUCCESSFUL in 23s` |
Phase 1 reproduces the first report, phase 2 the second. A clean Ubuntu
22.04 that installs
`openjdk-11-jdk` *before* the first build succeeds outright (`BUILD
SUCCESSFUL in 6m 10s`).
### Workaround
```bash
sudo apt-get install -y openjdk-11-jdk
export JAVA_HOME=/usr/lib/jvm/java-11-openjdk-amd64
cd server && ./gradlew --stop # required: the failed build left a
daemon behind
cd .. && make
```
Confirmed on both the Ubuntu 22.04 (JDK 11) and Ubuntu 24.04 (JDK 21) hosts
from the report.
### Proposed improvements
1. **The first failure is unhelpful.** Gradle starts happily on a JRE and
only fails later
at `:pxf-api:compileJava` with a message about toolchain capabilities
that never says
"you need a JDK". A preflight check in `server/Makefile` verifying
`$JAVA_HOME/bin/javac`
(or `javac` on `PATH`) before invoking Gradle turns this into an
actionable error.
2. **`README.md` is misleading on Debian/Ubuntu.** It says "JDK 1.8 or JDK
11" and suggests
`export JAVA_HOME=/usr/lib/jvm/java-11-openjdk` -- a RHEL-style path that
does not exist
on Debian/Ubuntu (`-amd64` suffix). It should say a JRE is insufficient,
give the package
names for apt and dnf, warn that `apt install maven` does **not** pull a
JDK (while
`dnf install maven` does), note that on Debian/Ubuntu a JRE occupies the
same
`/usr/lib/jvm/java-N-openjdk-amd64` path a JDK would, and mention that
installing the JDK
after a failed build requires `./gradlew --stop`.
I will open a PR with both.
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