4
我正在为MongoDB编写一个维护脚本，它将按照计划压缩来自副本集的集合。迄今为止，我所看到的脚本看起来不错，可以完成它针对主节点和次节点所做的工作。然而，存在一个问题：MongoDB维护
使用MongoDB副本集的系统是一个高可用性Web队列，它不断被写入和读取。因此，即使调用rs.StepDown（）几秒钟的停机时间也绝对不可接受。有没有一种方法可以安全降级数百个客户端的没有MongoException的主节点？
谢谢！
p.s.这里是一个应该通过一个cron作业，在低负载时每月一次
// assuming we are a replica set ;-)
if(rs.isMaster().setName){
try {
//check if the script is run against a master
if(rs.isMaster().ismaster){ //if so, step down as master
print("Connected to a PRIMARY node")
print("Will try to step down as primary");
rs.stepDown();
// after stepdown connections are dropped. do an operation to cause reconnect:
rs.isMaster();
// now ready to go.
// wait for another node to become primary -- it may need data from us for the last
// small sliver of time, and if we are already compacting it cannot get it while the
// compaction is running.
var counter = 1;
while(1) {
var m = rs.isMaster();
if(m.ismaster) {
print("ERROR: no one took over during our stepDown duration. we are primary again!");
assert(false);
}
if(m.primary){ // someone else is, great
print("new master host is: "+m.primary);
break;
}
print("waiting "+counter+" seconds");
sleep(1000);
counter++;
}
}else{
print("Connected to a SECONDARY node");
print("Going into Recovery Mode and Compacting");
}
// someone else is primary, so we are ready to proceed with a compaction
print(" ");
print("Compacting...");
print("- queue");
printjson(db.runCommand({compact:"queue"}));
print(" ");
} catch(e) {
print(" ");
print("ACHTUNG! Exception:" + e);
print(" ");
}
}else{
print('This script works with replica sets only');
}