[SPARK-10359][PROJECT-INFRA] Use more random number in dev/test-depen…

…dencies.sh; fix version switching

This patch aims to fix another potential source of flakiness in the `dev/test-dependencies.sh` script.

pwendell's original patch and my version used `$(date +%s | tail -c6)` to generate a suffix to use when installing temporary Spark versions into the local Maven cache, but this value only changes once per second and thus is highly collision-prone when concurrent builds launch on AMPLab Jenkins. In order to reduce the potential for conflicts, this patch updates the script to call Python's random number generator instead.

I also fixed a bug in how we captured the original project version; the bug was causing the exit handler code to fail.

Author: Josh Rosen <[email protected]>

Closes apache#10558 from JoshRosen/build-dep-tests-round-3.

dev/test-dependencies.sh

@@ -41,9 +41,19 @@ HADOOP_PROFILES=(
 # the old version. We need to do this because the `dependency:build-classpath` task needs to
 # resolve Spark's internal submodule dependencies.
 
-# See http://stackoverflow.com/a/3545363 for an explanation of this one-liner:
-OLD_VERSION=$($MVN help:evaluate -Dexpression=project.version|grep -Ev '(^\[|Download\w+:)')
-TEMP_VERSION="spark-$(date +%s | tail -c6)"
+# From http://stackoverflow.com/a/26514030
+set +e
+OLD_VERSION=$($MVN -q \
+    -Dexec.executable="echo" \
+    -Dexec.args='${project.version}' \
+    --non-recursive \
+    org.codehaus.mojo:exec-maven-plugin:1.3.1:exec)
+if [ $? != 0 ]; then
+    echo -e "Error while getting version string from Maven:\n$OLD_VERSION"
+    exit 1
+fi
+set -e
+TEMP_VERSION="spark-$(python -S -c "import random; print(random.randrange(100000, 999999))")"
 
 function reset_version {
   # Delete the temporary POMs that we wrote to the local Maven repo: