private void ensureSecondaryInstancesIsMutable() {
        if (!((bitField0_ & 0x00000002) != 0)) {
          secondaryInstances_ =
              new java.util.ArrayList<
                  com.google.cloud.memorystore.v1.CrossInstanceReplicationConfig.RemoteInstance>(
                  secondaryInstances_);
          bitField0_ |= 0x00000002;
        }
      }
<pre>
Output only. The primary instance that acts as the source of replication
for the secondary instances.
</pre>

<code>
.google.cloud.memorystore.v1.CrossInstanceReplicationConfig.RemoteInstance primary_instance = 1 [(.google.api.field_behavior) = OUTPUT_ONLY];
</code>
java-valkey/proto-google-cloud-valkey-v1/src/main/java/com/google/cloud/memorystore/v1/CrossInstanceReplicationConfig.java