[Issue 9549] Add friendly comment for topic compactor tool. (apache#9563

)

fix apache#9549 

when `pulsar topic compact -t topic` without setting `--broker-conf`

origin logic will read the `current path + /conf/broker.conf`.

which can cause zookeeperServers blank and throw NPE.

pulsar-broker/src/main/java/org/apache/pulsar/compaction/CompactorTool.java

@@ -73,10 +73,21 @@ public static void main(String[] args) throws Exception {
             jcommander.usage();
             throw new IllegalArgumentException("Need to specify a configuration file for broker");
         } else {
+            log.info(String.format("read configuration file %s", arguments.brokerConfigFile));
             brokerConfig = PulsarConfigurationLoader.create(
                     arguments.brokerConfigFile, ServiceConfiguration.class);
         }
 
+
+        if (isBlank(brokerConfig.getZookeeperServers())) {
+            throw new IllegalArgumentException(
+                    String.format("Need to specify `zookeeperServers` in configuration file \n"
+                                    + "or specify configuration file path from command line.\n"
+                                    + "now configuration file path is=[%s]\n",
+                            arguments.brokerConfigFile)
+            );
+        }
+
         ClientBuilder clientBuilder = PulsarClient.builder();
 
         if (isNotBlank(brokerConfig.getBrokerClientAuthenticationPlugin())) {
@@ -86,6 +97,8 @@ public static void main(String[] args) throws Exception {
 
 
         if (brokerConfig.getBrokerServicePortTls().isPresent()) {
+            log.info("Found `brokerServicePortTls` in configuration file. \n"
+                    + "Will connect pulsar use TLS.");
             clientBuilder
                     .serviceUrl(PulsarService.brokerUrlTls(PulsarService.advertisedAddress(brokerConfig),
                             brokerConfig.getBrokerServicePortTls().get()))