fix gcp build with latest maven (#750)

* script to help check for the issue

* pom that pins good version of maven-assembly-plugin (3.6.0)

* more correct uber-jar assembly pom

* revert assembly plugin version to latest, although leave pinned

java/impl/gcp/check-grpc-services.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+# helper script to quickly check the gRPC services in a jar file, which seems to be root cause
+# of the gRPC issue in the cloud function
+
+# determine the jar file to check
+VERSION=$1
+JAR_FILE=target/psoxy-gcp-${VERSION}.jar
+
+BLUE='\e[34m'
+NC='\e[0m' # No Color
+
+printf "Checking grpc load balancer services in jar file: ${BLUE}${JAR_FILE}${NC}\n"
+printf " (as of 2024-07-10, good one contains 3 files, including 'io.grpc.internal.PickFirstLoadBalancerProvider')\n"
+jar xf $JAR_FILE META-INF/services/io.grpc.LoadBalancerProvider
+
+cat META-INF/services/io.grpc.LoadBalancerProvider
+rm -rf META-INF

java/impl/gcp/pom.xml

@@ -182,15 +182,16 @@
             <!-- produces an 'uber' JAR, with all deps pkg'd -->
             <plugin>
                 <artifactId>maven-assembly-plugin</artifactId>
+                <version>3.7.1</version>
                 <configuration>
                     <archive>
                         <manifest>
                             <mainClass>co.worklytics.psoxy.Route</mainClass>
                         </manifest>
                     </archive>
-                    <descriptorRefs>
-                        <descriptorRef>jar-with-dependencies</descriptorRef>
-                    </descriptorRefs>
+                    <descriptors>
+                        <descriptor>uber-jar.xml</descriptor>
+                    </descriptors>
                     <appendAssemblyId>false</appendAssemblyId>
                 </configuration>
                 <executions>
@@ -251,7 +252,7 @@
 
             <!-- add license plugin -->
             <!-- use mvn goal license:aggregate-third-party-report to get report on licenses about
-                 dependencies, to facillitate eventual distribution of built JAR -->
+                 dependencies, to facilitate eventual distribution of built JAR -->
             <plugin>
                 <groupId>org.codehaus.mojo</groupId>
                 <artifactId>license-maven-plugin</artifactId>

java/impl/gcp/uber-jar.xml

@@ -0,0 +1,25 @@
+<assembly xmlns="http://maven.apache.org/ASSEMBLY/2.2.0"
+          xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+          xsi:schemaLocation="http://maven.apache.org/ASSEMBLY/2.2.0 http://maven.apache.org/xsd/assembly-2.2.0.xsd">
+
+    <id>uber-jar</id>
+    <formats>
+        <format>jar</format>
+    </formats>
+    <includeBaseDirectory>false</includeBaseDirectory>
+    <dependencySets>
+        <dependencySet>
+            <outputDirectory>/</outputDirectory>
+            <useProjectArtifact>true</useProjectArtifact>
+            <unpack>true</unpack>
+            <scope>runtime</scope>
+        </dependencySet>
+    </dependencySets>
+    <!-- above from https://maven.apache.org/plugins/maven-assembly-plugin/descriptor-refs.html#jar-with-dependencies -->
+    <!-- what we need is below, to merge all the META-INF/services files -->
+    <containerDescriptorHandlers>
+        <containerDescriptorHandler>
+            <handlerName>metaInf-services</handlerName>
+        </containerDescriptorHandler>
+    </containerDescriptorHandlers>
+</assembly>