KAFKA-9337: Simplify MirrorMaker2 sample config (#7872)

Reviewers: Mickael Maison <mickael.maison@gmail.com>, Ryanne Dolan <ryannedolan@gmail.com>, Robert Požarickij

config/connect-mirror-maker.properties

@@ -18,18 +18,40 @@
 # Run with ./bin/connect-mirror-maker.sh connect-mirror-maker.properties 
 
 # specify any number of cluster aliases
-clusters = A, B, C
+clusters = A, B
 
 # connection information for each cluster
+# This is a comma separated host:port pairs for each cluster
+# for e.g. "A_host1:9092, A_host2:9092, A_host3:9092"
 A.bootstrap.servers = A_host1:9092, A_host2:9092, A_host3:9092
 B.bootstrap.servers = B_host1:9092, B_host2:9092, B_host3:9092
-C.bootstrap.servers = C_host1:9092, C_host2:9092, C_host3:9092
 
 # enable and configure individual replication flows
 A->B.enabled = true
-A->B.topics = foo-.*
-B->C.enabled = true
-B->C.topics = bar-.*
+
+# regex which defines which topics gets replicated. For eg "foo-.*"
+A->B.topics = .*
+
+B->A.enabled = true
+B->A.topics = .*
+
+# Setting replication factor of newly created remote topics
+replication.factor=1
+
+############################# Internal Topic Settings  #############################
+# The replication factor for mm2 internal topics "heartbeats", "B.checkpoints.internal" and
+# "mm2-offset-syncs.B.internal"
+# For anything other than development testing, a value greater than 1 is recommended to ensure availability such as 3.
+checkpoints.topic.replication.factor=1
+heartbeats.topic.replication.factor=1
+offset-syncs.topic.replication.factor=1
+
+# The replication factor for connect internal topics "mm2-configs.B.internal", "mm2-offsets.B.internal" and
+# "mm2-status.B.internal"
+# For anything other than development testing, a value greater than 1 is recommended to ensure availability such as 3.
+offset.storage.replication.factor=1
+status.storage.replication.factor=1
+config.storage.replication.factor=1
 
 # customize as needed
 # replication.policy.separator = _