flink 使用问题汇总

罗列一下bug，备注一下，后续不断完善

1. 注册表时，请勿使用result

tableEnv.registerTable("result_agg", talbe);

如上，若是你写为

tableEnv.registerTable("result", talbe);

那么会报如下错误

org.apache.flink.client.program.ProgramInvocationException: The main method caused an error: SQL parse failed. Encountered "from result" at line 1, column 13.
Was expecting one of:
    <EOF> 
    "ORDER" ...
    "LIMIT" ...
    "OFFSET" ...
    "FETCH" ...
    "FROM" <IDENTIFIER> ...
    "FROM" <QUOTED_IDENTIFIER> ...
    "FROM" <BACK_QUOTED_IDENTIFIER> ...
    "FROM" <BRACKET_QUOTED_IDENTIFIER> ...
    "FROM" <UNICODE_QUOTED_IDENTIFIER> ...
    "FROM" "LATERAL" ...
    "FROM" "(" ...
    "FROM" "UNNEST" ...
    "FROM" "TABLE" ...
    "," ...
    "AS" ...
    <IDENTIFIER> ...
    <QUOTED_IDENTIFIER> ...
    <BACK_QUOTED_IDENTIFIER> ...
    <BRACKET_QUOTED_IDENTIFIER> ...
    <UNICODE_QUOTED_IDENTIFIER> ...

2. 若是mysql 类型是tinyint 要转如下，不然flink会报错

Caused by: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String
    at org.apache.flink.api.common.typeutils.base.StringSerializer.serialize(StringSerializer.java:33)
    at org.apache.flink.api.java.typeutils.runtime.RowSerializer.serialize(RowSerializer.java:161)

转的方式很简单好比

select project_fid, cast(project_info_type as CHAR) as type from table

3. join的时候若是有一侧为map类型的数据（好比你使用了collect方法，相似于mysql的group_concat）,回报空指针，相似于

org.apache.flink.client.program.ProgramInvocationException: The main method caused an error: Error while applying rule FlinkLogicalJoinConverter, args [rel#56:LogicalJoin.NONE(left=rel#52:Subset#0.NONE,right=rel#55:Subset#2.NONE,condition==($0, $2),joinType=inner)]

这个bug目前尚未修复，链接以下 https://issues.apache.org/jira/browse/FLINK-11433

只能想办法绕过去，把map类型的数据，变成字符串，方法是自定义函数

public class MapToString extends ScalarFunction {

    public String eval(Map<String, Integer> map) {
        if(map==null || map.size()==0) {
            return "";
        }
        StringBuffer sb=new StringBuffer();
        for(Map.Entry<String, Integer> entity : map.entrySet()) {
            sb.append(entity.getKey()+",");
        }
        String result=sb.toString();
        return result.substring(0, result.length()-1);
      }
}

调用的时候使用

select id, mapToString(collect(type)) as type from table  group by id

固然你还须要注册一下

tableEnv.registerFunction("mapToString", new MapToString());

4. 类型转化错误

最近总遇到类型转化错误的提示，目前发现了两个， 作个记录

a 若是是tiny（1） 会自动转为 boolean， 除了上面的解决方案，更优雅的是修改mysql 的链接，加上参数 tinyInt1isBit=false， 注意大小写

b 有时候mysql数据库id字段明明是int，但flink却认定为long。 貌似之前mybatis也有此问题（https://blog.csdn.net/ahwsk/article/details/81975117）。
后来我又认真的看了一下表设计（别人的表）发现 勾选了“无符号” 这个选项，当我去掉这个选项，再次运行，竟然不报错了，看来是无符号，让flink转化错误的，无符号比有符号在范围上多了一位， 多出的这一位，有可能已经超过了java中int 的范围（java中int 都是有符号的），因此自动转为long型了。

5. Could not find a suitable table factory for 'org.apache.flink.table.factories.StreamTableSourceFactory'

虽然fatjar已经有对应的类了，可是依然报错，最后的解决办法是在flink的lib目录中再次加入相关的类，问题解决。

6. cannot assign instance of org.apache.commons.collections.map.LinkedMap to field org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumerBase.pendingOffsetsToCommit of type org.apache.commons.collections.map.LinkedMap in instance of org.apache.flink.streaming.connectors.kafka.FlinkKafkaConsumer011

这个错误须要在flink-conf.yaml 加入 classloader.resolve-order: parent-first

7. Caused by: java.util.concurrent.CompletionException: akka.pattern.AskTimeoutException: Ask timed out on [Actor[akka.tcp://flink@flink88:15265/user/taskmanager_0#66653408]] after [10000 ms]. Sender[null] sent message of type "org.apache.flink.runtime.rpc.messages.RemoteRpcInvocation".

出现此错误，在flink的配置中增长

akka.ask.timeout: 120s
web.timeout: 120000

8.Exception while invoking ApplicationClientProtocolPBClientImpl.forceKillApplication over null. Retrying after sleeping for 30000ms

发生此错误是提交任务时出错，使用 yarn logs -applicationId application_1565600987111 查看错误，找到缘由，我遇到的缘由是： akka.watch.heartbeat.pause 值小于 akka.watch.heartbeat.interval。修改后错误消失
或者kill 掉 CliFrontend 的进程

9. Exception while invoking ApplicationClientProtocolPBClientImpl.forceKillApplication over null. Retrying after sleeping for 30000ms.
   java.io.IOException: The client is stopped
   at org.apache.hadoop.ipc.Client.getConnection(Client.java:1519)
   at org.apache.hadoop.ipc.Client.call(Client.java:1381)
   at org.apache.hadoop.ipc.Client.call(Client.java:1345)
   at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:227)
   at org.apache.hadoop.ipc.ProtobufRpcEngine$Invoker.invoke(ProtobufRpcEngine.java:116)

出现此异常仍是内存的问题，检查一下内存是否足够，必须是free的不能是available， 若是发现后者很高， 请执行 如下两条命令释放内存

sync
echo 3 > /proc/sys/vm/drop_caches

10
Caused by: java.net.BindException: Could not start rest endpoint on any port in port range 8081
at org.apache.flink.runtime.rest.RestServerEndpoint.start(RestServerEndpoint.java:219)
at org.apache.flink.runtime.entrypoint.component.AbstractDispatcherResourceManagerComponentFactory.create(AbstractDispatcherResourceManagerComponentFactory.java:161)
... 9 more

此错误是说端口被占用。查看源代码：

Iterator<Integer> portsIterator;
            try {
                portsIterator = NetUtils.getPortRangeFromString(restBindPortRange);
            } catch (IllegalConfigurationException e) {
                throw e;
            } catch (Exception e) {
                throw new IllegalArgumentException("Invalid port range definition: " + restBindPortRange);
            }

对应的配置是 flink-conf.yaml中的rest.bind-port。rest.bind-port不设置，则Rest Server默认绑定到rest.port端口(8081)。rest.bind-port能够设置成列表格式如50100,50101，也可设置成范围格式如50100-50200。推荐范围格式，避免端口冲突。