Hadoop之安全模式
this.safeMode = new SafeModeInfo(conf);在启动时创建SafeModeInfo实例时，其参数如下:
this.threshold =conf.getFloat("dfs.safemode.threshold.pct", 0.95f);
this.extension =conf.getInt("dfs.safemode.extension", 0);
this.safeReplication =conf.getInt("dfs.replication.min", 1);
//namenode启动时创建SafeModeInfo实例
SafeModeInfo(Configuration conf) {
this.threshold =conf.getFloat("dfs.safemode.threshold.pct", 0.95f);
this.extension =conf.getInt("dfs.safemode.extension", 0);
this.safeReplication =conf.getInt("dfs.replication.min", 1);
this.blockTotal = 0;
this.blockSafe = 0;
}
//手动进入安全模式的实例构造方法
private SafeModeInfo() {
this.threshold = 1.5f;//this threshold can never be reached
this.extension = Integer.MAX_VALUE;
this.safeReplication = Short.MAX_VALUE +1; // more than maxReplication
this.blockTotal = -1;
this.blockSafe = -1;
this.reached = -1;
enter();
reportStatus("STATE* Safe mode isON.", true);
}
//手动触发的方法入口如下：
synchronized void enterSafeMode() throws IOException {
if (!isInSafeMode()) {
safeMode = new SafeModeInfo();
return;
}
safeMode.setManual();
getEditLog().logSync();
NameNode.stateChangeLog.info("STATE* Safe modeis ON. "
+ safeMode.getTurnOffTip());
}
SafeModeMonitor安全模式监控类，1000毫秒监控状态。
核心代码：
public void run() {
while (fsRunning && (safeMode !=null && !safeMode.canLeave())) {
try {
Thread.sleep(recheckInterval);
} catch(InterruptedException ie) {
}
}
// leave safe mode and stop the monitor
try {
leaveSafeMode(true);
} catch(SafeModeException es) { //should never happen
String msg ="SafeModeMonitor may not run during distributed upgrade.";
assert false : msg;
throw newRuntimeException(msg, es);
}
smmthread = null;
}
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