[pulsar-client] fix protobuf dependency with shaded pulsar-client

[rdhabalia]

Motivation

Right now, pulsar-client doesn't include classes of pulsar::protobuf-shaded and because of that it throws below runtime error

Exception in thread "main" java.lang.NoClassDefFoundError: org/apache/pulsar/shaded/com/google/protobuf/v241/UninitializedMessageException
	at java.lang.Class.getDeclaredConstructors0(Native Method)
	at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671)
	at java.lang.Class.getConstructor0(Class.java:3075)
	at java.lang.Class.getConstructor(Class.java:1825)
	at org.apache.pulsar.client.internal.ReflectionUtils.getConstructor(ReflectionUtils.java:52)
	at org.apache.pulsar.client.internal.DefaultImplementation.<clinit>(DefaultImplementation.java:55)
	at org.apache.pulsar.client.api.Schema.<clinit>(Schema.java:117)
Caused by: java.lang.ClassNotFoundException: org.apache.pulsar.shaded.com.google.protobuf.v241.UninitializedMessageException
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 11 more

[sijie]

@rdhabalia not sure if I understand the problem here. If protobuf-shaded is not added, the shaded client should be always not usable, no?

[rdhabalia]

If protobuf-shaded is not added, the shaded client should be always not usable, no?

it doesn't work when we try to exclude all transitive dependencies from it. pulsar-client is a shaded jar so, we don't want to fetch any transitive dependencies from it. So, it throws above RunTimeException when we exclude all the dependencies from it because it excludes protobuf and client-api as well..

  <dependency>
	<groupId>${cms.groupId}</groupId>
	<artifactId>pulsar-client</artifactId>
	<exclusions>
		<exclusion>
			<!-- Exclude all dependencies since we're fetching the shaded jar -->
			<groupId>*</groupId>
			<artifactId>*</artifactId>
		</exclusion>
	</exclusions>
</dependency>                  

[sijie]

@rdhabalia okay. but how about other transitive dependencies? Is protobuf-shaded the only transitive dependency?

This doesn't sounds like a correct approach to me.

[merlimat]

pulsar-client is a shaded jar so, we don't want to fetch any transitive dependencies from it

There are still some of the dependencies that are not being shaded (eg: lz4-java because the JNI would not work if shaded)

[sijie]

@rdhabalia my feeling this issue is not a blocker for 2.4.0. Can we move it to 2.5.0? If we come to an agreement before 2.4.0 release, we can still include it in 2.4.0.

[rdhabalia]

yes moving to 2.5 for now and I will see if it's possible to create a shaded jar without fetching any transitive dependecies.

[aahmed-se]

@rdhabalia is this ready for review ?