我试图建立一个包含3个节点的小型cassandra集群。群集将具有一个种子节点。种子节点首先被购买。一旦启动，我就会“同时”调出另外两个节点。我看到的是只有一个节点被添加到集群中。我在另一个节点上得到以下异常。
ERROR [main] 2013-03-20 11:44:57,146 CassandraDaemon.java (line 387) Exception encountered during startup
java.lang.RuntimeException: Every node is a bootstrap source! **Please specify an initial token manually or wait for an existing bootstrap operation to finish.**
at org.apache.cassandra.dht.BootStrapper.getBootstrapSource(BootStrapper.java:180)
at org.apache.cassandra.dht.BootStrapper.getBalancedToken(BootStrapper.java:135)
at org.apache.cassandra.dht.BootStrapper.getBootstrapTokens(BootStrapper.java:115)
at org.apache.cassandra.service.StorageService.joinTokenRing(StorageService.java:620)
at org.apache.cassandra.service.StorageService.initServer(StorageService.java:508)
at org.apache.cassandra.service.StorageService.initServer(StorageService.java:406)
at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:282)
at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:370)
at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:413)
cassandra（种子节点）在处理来自多个节点的同步引导时遇到问题吗？这是一个限制吗？如果是这样，任何方式克服它？