hbase中balance的status一会儿为true,一会儿为false

balance_switch status 是将balance状态强制转换为false, 无论之前是true还是false, 返回的是之前的状态。 查看balance_switch 状态的命令是使用balancer_enabled

首先看balance_switch命令对应的rb文件源码：
module Shell
module Commands

class BalanceSwitch < Command
def help

<<-EOF

Enable/Disable balancer. Returns previous balancer state.
Examples:

hbase> balance_switch true
hbase> balance_switch false
EOF

end

def command(enableDisable)

prev_state = admin.balance_switch(enableDisable) ? 'true' : 'false'
formatter.row(["Previous balancer state : #{prev_state}"])
prev_state

end
end

end
end
该命令输出的是之前balancer的状态，其次再看balance_switch的处理源码：
public SetBalancerRunningResponse setBalancerRunning(RpcController c,

SetBalancerRunningRequest req) throws ServiceException {
try {
master.checkInitialized();
boolean prevValue = (req.getSynchronous())?

synchronousBalanceSwitch(req.getOn()) : master.balanceSwitch(req.getOn());

return SetBalancerRunningResponse.newBuilder().setPrevBalanceValue(prevValue).build();
} catch (IOException ioe) {
throw new ServiceException(ioe);
}

}

public boolean balanceSwitch(final boolean b) throws IOException {

return getMasterRpcServices().switchBalancer(b, BalanceSwitchMode.ASYNC);

}

/**

Assigns balancer switch according to BalanceSwitchMode
@param b new balancer switch
@param mode BalanceSwitchMode
@return old balancer switch
*/

boolean switchBalancer(final boolean b, BalanceSwitchMode mode) throws IOException {

boolean oldValue = master.loadBalancerTracker.isBalancerOn();
boolean newValue = b;
try {
if (master.cpHost != null) {

master.cpHost.preBalanceSwitch(newValue);

}
try {

if (mode == BalanceSwitchMode.SYNC) {
  synchronized (master.getLoadBalancer()) {
    master.loadBalancerTracker.setBalancerOn(newValue);
  }
} else {
  master.loadBalancerTracker.setBalancerOn(newValue);
}

} catch (KeeperException ke) {

throw new IOException(ke);

}
LOG.info(master.getClientIdAuditPrefix() " set balanceSwitch=" newValue);
if (master.cpHost != null) {

master.cpHost.postBalanceSwitch(oldValue, newValue);

}
} catch (IOException ioe) {
LOG.warn("Error flipping balance switch", ioe);
}
return oldValue;

}
从switchBalancer方法也能看到返回的是之前balancer的状态值。
至于status参数设置的balanceSwitch为false是因为admin.rb文件在处理参数的时候如果传status则
java.lang.Boolean.valueOf(enableDisable)为false，并且shell.rb文件指定了哪些参数是符合要求的，status是其中之一，而其他的譬如state这种参数会报异常。
----------------------------------------------------------------------------------------------Enable/disable balancerReturns previous balancer switch setting.

def balance_switch(enableDisable)

@admin.setBalancerRunning(

java.lang.Boolean.valueOf(enableDisable), java.lang.Boolean.valueOf(false)

)

end
Load all commands

Shell.load_command_group(
'general',
full_name: 'GENERAL HBASE SHELL COMMANDS',
commands: %w[

status
version
table_help
whoami
processlist

]
)