(?m)

centos6.5:/root/sbin#cat -n vv
     1	192.168.11.186,192.168.11.187	35199,3306	Dec  7, 2016 11:40:02.750520978		SELECT
     2	    r.trx_id waiting_trx_id,\x0a    r.trx_mysql_thread_id waiting_thread,\x0a   r.trx_query waiting_query,\x0a    b.trx_id blocking_trx_id,\x0a    b.trx_mysql_thread_id blocking_thread,\x0a    b.trx_query blocking_query\x0aFROM\x0a    information_schema.innodb_lock_waits w\x0a        INNER JOIN\x0a    information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id\x0a        INNER JOIN\x0a    information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id

此时分为2行

%{IPORHOST:clientip},%{IPORHOST:serverip}\s+(?<client_port>\S+),(?<server_port>\S+)\s+(?<time>(\S+\s+).*?[0-9]{2}:[0-9]{2}:[0-9]{2}\.\d+)\s+(?<running_sql>(\S+\s+).*)

{
  "clientip": [
    [
      "192.168.11.186"
    ]
  ],
  "serverip": [
    [
      "192.168.11.187"
    ]
  ],
  "client_port": [
    [
      "35199"
    ]
  ],
  "server_port": [
    [
      "3306"
    ]
  ],
  "time": [
    [
      "Dec  7, 2016 11:40:02.750520978"
    ]
  ],
  "running_sql": [
    [
      "SELECT \n    r.trx_id waiting_trx_id,\\x0a    r.trx_mysql_thread_id waiting_thread,\\x0a   r.trx_query waiting_query,\\x0a    b.trx_id blocking_trx_id,\\x0a    b.trx_mysql_thread_id blocking_thread,\\x0a    b.trx_query blocking_query\\x0aFROM\\x0a    information_schema.innodb_lock_waits w\\x0a        INNER JOIN\\x0a    information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id\\x0a        INNER JOIN\\x0a    information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id"
    ]
  ]
}

此时可以玩转匹配

/*************
centos6.5:/root/sbin#cat -n dd
     1	192.168.11.186,192.168.11.187	35199,3306	Dec  7, 2016 11:40:02.750520978		SELECT
     2	    r.trx_id waiting_trx_id,\x0a    r.trx_mysql_thread_id waiting_thread,\x0a   r.trx_query waiting_query,\x0a    b.trx_id blocking_trx_id,\x0a    b.trx_mysql_thread_id blocking_thread,\x0a    b.trx_query blocking_query\x0aFROM\x0a
     3	 information_schema.innodb_lock_waits w\x0a        INNER JOIN\x0a    information_schema.innodb_trx b ON b.trx_id = w.blocking_trx_id\x0a        INNER JOIN\x0a    information_schema.innodb_trx r ON r.trx_id = w.requesting_trx_id

换成3行

此时
{
  "clientip": [
    [
      "192.168.11.186"
    ]
  ],
  "serverip": [
    [
      "192.168.11.187"
    ]
  ],
  "client_port": [
    [
      "35199"
    ]
  ],
  "server_port": [
    [
      "3306"
    ]
  ],
  "time": [
    [
      "Dec  7, 2016 11:40:02.750520978"
    ]
  ],
  "running_sql": [
    [
      "SELECT \n    r.trx_id waiting_trx_id,\\x0a    r.trx_mysql_thread_id waiting_thread,\\x0a   r.trx_query waiting_query,\\x0a    b.trx_id blocking_trx_id,\\x0a    b.trx_mysql_thread_id blocking_thread,\\x0a    b.trx_query blocking_query\\x0aFROM\\x0a   "
    ]
  ]
}

匹配不完整了

需要
(?m)%{IPORHOST:clientip},%{IPORHOST:serverip}\s+(?<client_port>\S+),(?<server_port>\S+)\s+(?<time>(\S+\s+).*?[0-9]{2}:[0-9]{2}:[0-9]{2}\.\d+)\s+(?<running_sql>(\S+\s+).*)

在和 codec/multiline 搭配使用的时候，需要注意一个问题，

grok 正则和普通正则一样，默认是不支持匹配回车换行的。

就像你需要 =~ //m 一样也需要单独指定，具体写法是在表达式开始位置加 (?m) 标记。如下所示：