clickhouse（十二、踩坑之路）

• Q1
  DB::Exception: Cannot create table from metadata file /data/clickhouse/metadata/default/dwd_test.sql, error: DB::Exception: The local set of parts of table default.dwd_test doesn’t look like the set of parts in ZooKeeper: 65.88 million rows of 85.04 million total rows in filesystem are suspicious. There are 545 unexpected parts with 65883643 rows (191 of them is not just-written with 65883643 rows), 0 missing parts (with 0 blocks).
  
• A1
  这是由于truncate、alter等ddl语句用了on cluster，偶尔导致zookeeper同步异常。解决方法1：删除有问题节点的本地表数据 rm -r /data/clickhouse/data/default/dwd_test，再重新启动CK，副本会自动重新同步该表数据。(如果没有副本请不要使用此方法。)
  解决方法2：命令行执行sudo -u clickhouse touch /data/clickhouse/flags/force_restore_data 然后手动恢复有问题的partition
  
• Q2
  Connected to ClickHouse server version 20.3.8 revision 54433.
  Poco::Exception. Code: 1000, e.code() = 13, e.displayText() = Access to file denied: /home/qspace/.clickhouse-client-history (version 20.3.8.53 (official build))
  
• A2
  
  创建该文件、并设置开放权限。
  chown clickhouse:clickhouse /home/qspace/.clickhouse-client-history (没有则创建)
  
• Q3
  Application: DB::Exception: Listen [::]:8124 failed: Poco::Exception. Code: 1000, e.code() = 0, e.displayText() = DNS error: EAI: Address family for hostname not supported (version 20.5.2.7 (official build))
  
• A3
  本机没有开放ipv6，只能对ipv4生效。在/etc/click-house/config.xml中，把<listen_host> 改成0.0.0.0 或者 ::
  
• Q4
  Code: 32, e.displayText() = DB::Exception: Received from hadoop8:9900. DB::Exception: Attempt to read after eof: Cannot parse Int32 from String, because value is too short. (version 20.3.8.53 (official build))
  字符串转数字异常，有些为空或者非数字的字符导致转换失败
  
• A4
  使用toUInt64OrZero函数、转换失败则为0。
• Q5
  Application: DB::Exception: Suspiciously many (125) broken parts to remove.: Cannot attach table default.test
  Code: 231. DB::Exception: Received from ck10:9000. DB::Exception: Suspiciously many (125) broken parts to remove…
  
• A5
  因为写入数据造成的元数据和数据不一致问题。先删除磁盘数据、再重启节点删除本地表，如果是复制表再上zookeeper删除副本，然后重新建表。复制表的话数据会同步其他副本的。
• Q6
  Cannot execute replicated DDL query on leader.
• A6
  由于分布式ddl语句比较耗时会超时响应、改为本地执行或者减少作用的数据范围。如ALTER、OPTIMIZE全表改为具体的partition.
• Q7
  Code: 76. DB::Exception: Received from 0.0.0.0:9900. DB::Exception: Cannot open file /data/clickhouse/data/default/test/tmp_insert_20200523_55575_55575_0/f0560_deep_conversion_optimization_goal.mrk2, errno: 24, strerror: Too many open files.
  
• A7
  修改/etc/security/limits.conf 添加：
  clickhouse soft nofile 262144
  clickhouse hard nofile 262144
  使用ulimit -n 查询、看到的是所有用户可打开的总数，而ck能打开的大小只是系统的默认值，所以不要被这个命令干扰，重启ck后、获取ck的进程、再通过cat /proc/${pid}/limits |grep open ，判断配置是否生效