【问题描述】
zkui报错
2016-04-07 16:30:27 ERROR Home:103 - [org.apache.zookeeper.KeeperException.create(KeeperException.java:99), org.apache.zookeeper.KeeperException.create(KeeperException.java:51), org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1468), org.apache.zookeeper.ZooKeeper.getChildren(ZooKeeper.java:1496), com.deem.zkui.utils.ZooKeeperUtil.listNodeEntries(ZooKeeperUtil.java:255), com.deem.zkui.controller.Home.doGet(Home.java:71), javax.servlet.http.HttpServlet.service(HttpServlet.java:687), javax.servlet.http.HttpServlet.service(HttpServlet.java:790), org.eclipse.jetty.servlet.ServletHolder.handle(ServletHolder.java:698), org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1564), com.deem.zkui.filter.AuthFilter.doFilter(AuthFilter.java:63), org.eclipse.jetty.servlet.ServletHandler$CachedChain.doFilter(ServletHandler.java:1544), org.eclipse.jetty.servlet.ServletHandler.doHandle(ServletHandler.java:524), org.eclipse.jetty.se

分析：

java程序启动后，默认（请注意是默认）会在/tmp/hsperfdata_userName目录下以该进程的id为文件名新建文件，并在该文件中存储jvm运行的相关信息，其中的userName为当前的用户名，/tmp/hsperfdata_userName目录会存放该用户所有已经启动的java进程信息。对于windows机器/tmp用Windows存放临时文件目录代替。

 

而jps、jconsole、jvisualvm等工具的数据来源就是这个文件（/tmp/hsperfdata_userName/pid)。所以当该文件不存在或是无法读取时就会出现jps无法查看该进程号，jconsole无法监控等问题

zk的进程找不到了，就是因为误删了这个目录下的文件导致。

group by是一个‘一行命令’
distinct 是一个‘多行命令’
做统计就需区分：分类项和指标项。


select pc.category_id,
sum(case when t.so_month between 3 and 5 then t.order_item_num else 0 end) as spring,
sum(case when t.so_month between 6 and 8 then t.order_item_num else 0 end) as summer,
sum(case when t.so_month between 9 and 11 then t.order_item_num else 0 end) as autumn,
sum(case when t.so_month=12 or t.so_month<=2 then t.order_item_num else 0 end) as winnter
from product_category pc join (select si.product_id, si.order_item_num, month(si.order_create_time) as so_month from so_item si where si.ds between '2013-05-01' and '2014-04-30' and si.is_gift=0) t on pc.product_id=t.product_id
group by pc.category_id;

把else后面的0改为0L即可

select pc.category_id,  
sum(case when t.so_month between 3 and 5 then t.order_item_num else 0L end) as spring,  
sum(case when t.so_month between

  【异常描述】 这个程序跑了n天了，没有问题，从1.4号开始出现各种失败，这是其中一种： 

  2015-01-15 09:43:12,250 WARN [main] org.apache.hadoop.conf.Configuration: job.xml:an attempt to override final parameter: mapreduce.job.end-notification.max.retry.interval;  Ignoring. 2015-01-15 09:43:12,252 WARN [main] org.apache.hadoop.conf.Configuration: job.xml:an attempt to override final parameter: mapreduce.job.end-notification.max.attempts;  Ignoring. 2015-01-15 09:43:12,412 INFO [main] org.apache.hadoop.metrics2.impl.MetricsConfig: loaded properties from hadoop-metrics2.properties 2015-01-15 09:43:12,471 INFO [main] org.apache.hadoop.metrics2.impl.MetricsSystemImpl: Scheduled snapshot period at 10 s