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運行Cassandra守護進程時，我遇到以下異常。我從1.2主幹運行。在啓動Cassandra時讀取已保存的緩存和系統表時出錯
WARN 14:47:51,038 error reading saved cache /home/manuzhang/cassandra/saved_caches/system-local-KeyCache-b.db
java.lang.NullPointerException
at org.apache.cassandra.cache.AutoSavingCache.loadSaved(AutoSavingCache.java:141)
at org.apache.cassandra.db.ColumnFamilyStore.<init>(ColumnFamilyStore.java:237)
at org.apache.cassandra.db.ColumnFamilyStore.createColumnFamilyStore(ColumnFamilyStore.java:340)
at org.apache.cassandra.db.ColumnFamilyStore.createColumnFamilyStore(ColumnFamilyStore.java:312)
at org.apache.cassandra.db.Table.initCf(Table.java:332)
at org.apache.cassandra.db.Table.<init>(Table.java:265)
at org.apache.cassandra.db.Table.open(Table.java:110)
at org.apache.cassandra.db.Table.open(Table.java:88)
at org.apache.cassandra.db.SystemTable.checkHealth(SystemTable.java:284)
at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:168)
at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:318)
at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:361)
這裏的地方緩存保存：
[email protected]:~/cassandra/saved_caches$ ls -l
total 12
-rw-rw-r-- 1 manuzhang manuzhang 156 Aug 7 13:09 system-local-KeyCache-b.db
-rw-rw-r-- 1 manuzhang manuzhang 60 Aug 7 13:09 system-schema_columnfamilies-KeyCache-b.db
-rw-rw-r-- 1 manuzhang manuzhang 60 Aug 7 13:09 system-schema_columns-KeyCache-b.db
此外，無法加載系統表文件。
ERROR 17:03:16,637 Fatal exception during initialization
org.apache.cassandra.config.ConfigurationException: Found system table files, but they couldn't be loaded!
at org.apache.cassandra.db.SystemTable.checkHealth(SystemTable.java:303)
at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:201)
at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:349)
at org.apache.cassandra.service.CassandraDaemon.main(CassandraDaemon.java:392)
現在我能夠重現裝載系統故障表爲每個卡桑德拉的運行（我事後清理所有文件）。這裏拋出異常：
/**
* One of three things will happen if you try to read the system table:
* 1. files are present and you can read them: great
* 2. no files are there: great (new node is assumed)
* 3. files are present but you can't read them: bad
* @throws ConfigurationException
*/
public static void checkHealth() throws ConfigurationException
{
Table table;
try
{
table = Table.open(Table.SYSTEM_TABLE);
}
catch (AssertionError err)
{
// this happens when a user switches from OPP to RP.
ConfigurationException ex = new ConfigurationException("Could not read system table!");
ex.initCause(err);
throw ex;
}
ColumnFamilyStore cfs = table.getColumnFamilyStore(LOCAL_CF);
String req = "SELECT cluster_name FROM system.%s WHERE key='%s'";
UntypedResultSet result = processInternal(String.format(req, LOCAL_CF, LOCAL_KEY));
if (result.isEmpty() || !result.one().has("cluster_name"))
{
// this is a brand new node
if (!cfs.getSSTables().isEmpty())
throw new ConfigurationException("Found system table files, but they couldn't be loaded!");
// no system files. this is a new node.
req = "INSERT INTO system.%s (key, cluster_name) VALUES ('%s', '%s')";
processInternal(String.format(req, LOCAL_CF, LOCAL_KEY, DatabaseDescriptor.getClusterName()));
return;
}
String savedClusterName = result.one().getString("cluster_name");
if (!DatabaseDescriptor.getClusterName().equals(savedClusterName))
throw new ConfigurationException("Saved cluster name " + savedClusterName + " != configured name " + DatabaseDescriptor.getClusterName());
}
這三次運行完全符合註釋中的三個條件。
「沒有文件存在」在第一次運行，因爲它是一個全新的節點。
在第二次運行「文件在那裏，你可以看到他們。」
在第三次運行中，「文件存在但您無法讀取它們」，並且我檢查了result.isEmpty()和result.one.has("cluster_name")都返回false。
其實，我很困惑與異常「無法加載」。這是什麼意思？我不認爲這是文件系統權限問題，因爲r/w權限授予當前用戶。
上述問題消失後，我刪除所有相關文件，但我不希望運行卡桑德拉每次都做到這一點。
這一直困擾着我很長一段時間。
一個不相關的問題是，我不認爲卡桑德拉@計算器已經得到足夠的重視從社會。你同意嗎？
任何意見或建議，將不勝感激。
謝謝。
你爲什麼運行cassandra主幹，而不是發佈的版本？ – sbridges 2012-09-03 13:14:40
@sbridges如果您按照Cassandra wiki下載代碼庫，那就是您得到的;並且我還可以閱讀有關虛擬節點的新內容 – manuzhang 2012-09-03 23:29:03
您是否可以通過官方發佈重現您的問題：http：//cassandra.apache.org/download/ – sbridges 2012-09-04 02:26:35