问题背景
- 问题描述
基于Flink-CDC ，Flink SQL的实时计算作业在运行一段时间后，突然发现插入数据库的计算结果发生部分主键属性发生失败，导致后续计算结果无法插入，
超过失败次数失败的情况
- 问题报错
Caused by: java.sql.BatchUpdateException: Batch entry 0 INSERT INTO dm_hljy.dws_table_name (op_date, school_year, campus_name, school_name, depart_name, total_opfare, ids, update_time) VALUES ('2024-03-11 00:00:00+08', '2023', 'xxxx', 'xxxx学校', 'xxxx小学部', '203333300000', '57', '2024-03-21 09:31:08.47+08') ON DUPLICATE KEY UPDATE school_year=VALUES(school_year), total_opfare=VALUES(total_opfare), ids=VALUES(ids), update_time=VALUES(update_time) was aborted: ERROR: dn_6007_6008: null value in column "depart_name" violates not-null constraint Call getNextException to see other errors in the batch.
at com.huawei.gauss200.jdbc.jdbc.BatchResultHandler.handleCompletion(BatchResultHandler.java:171) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at com.huawei.gauss200.jdbc.core.v3.QueryExecutorImpl.executeBatch(QueryExecutorImpl.java:586) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at com.huawei.gauss200.jdbc.jdbc.PgStatement.executeBatch(PgStatement.java:883) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at com.huawei.gauss200.jdbc.jdbc.PgPreparedStatement.executeBatch(PgPreparedStatement.java:1580) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at org.apache.flink.connector.jdbc.statement.FieldNamedPreparedStatementImpl.executeBatch(FieldNamedPreparedStatementImpl.java:65) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.executor.TableSimpleStatementExecutor.executeBatch(TableSimpleStatementExecutor.java:64) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.executor.TableBufferReducedStatementExecutor.executeBatch(TableBufferReducedStatementExecutor.java:101) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.JdbcOutputFormat.attemptFlush(JdbcOutputFormat.java:266) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.JdbcOutputFormat.flush(JdbcOutputFormat.java:236) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.JdbcOutputFormat.lambda$open$0(JdbcOutputFormat.java:159) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_332]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) ~[?:1.8.0_332]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) ~[?:1.8.0_332]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) ~[?:1.8.0_332]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_332]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_332]
... 1 more
Caused by: com.huawei.gauss200.jdbc.util.PSQLException: ERROR: dn_6007_6008: null value in column "depart_name" violates not-null constraint
at com.huawei.gauss200.jdbc.core.v3.QueryExecutorImpl.receiveErrorResponse(QueryExecutorImpl.java:2856) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at com.huawei.gauss200.jdbc.core.v3.QueryExecutorImpl.processResults(QueryExecutorImpl.java:2587) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at com.huawei.gauss200.jdbc.core.v3.QueryExecutorImpl.executeBatch(QueryExecutorImpl.java:575) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at com.huawei.gauss200.jdbc.jdbc.PgStatement.executeBatch(PgStatement.java:883) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at com.huawei.gauss200.jdbc.jdbc.PgPreparedStatement.executeBatch(PgPreparedStatement.java:1580) ~[huaweicloud-dws-jdbc-8.1.1.1-200.jar:?]
at org.apache.flink.connector.jdbc.statement.FieldNamedPreparedStatementImpl.executeBatch(FieldNamedPreparedStatementImpl.java:65) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.executor.TableSimpleStatementExecutor.executeBatch(TableSimpleStatementExecutor.java:64) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.executor.TableBufferReducedStatementExecutor.executeBatch(TableBufferReducedStatementExecutor.java:101) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.JdbcOutputFormat.attemptFlush(JdbcOutputFormat.java:266) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.JdbcOutputFormat.flush(JdbcOutputFormat.java:236) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at org.apache.flink.connector.jdbc.internal.JdbcOutputFormat.lambda$open$0(JdbcOutputFormat.java:159) ~[flink-connector-jdbc-1.15.0-h0.cbu.mrs.320.r33.jar:1.15.0-h0.cbu.mrs.320.r33]
at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) ~[?:1.8.0_332]
at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:308) ~[?:1.8.0_332]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$301(ScheduledThreadPoolExecutor.java:180) ~[?:1.8.0_332]
at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:294) ~[?:1.8.0_332]
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[?:1.8.0_332]
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[?:1.8.0_332
定位
定位思路
1.方向一：怀疑数据库插入存在数据处理时，造成数据处理出现空值的情况，即数据本身不为空，但是数据插入却出现了空
2.方向二：Flink-SQL在消费kafka数据时存在了空值，故加工的数据计算结果存在空值
定位过程
- 因插入数据库定位比较麻烦，且数据库已经设置该字段为主属性，故出现插入时处理为空值的概率较小。故先从较为简单的Flink SQL查询数据
- 定位方法一，查询该字段为空的记录,待作业执行完成后，未查询到空值对应记录
select select * from table_name where depart_name is null or depart_name = '' or char_length(depart_name) = 0;
- 因考虑到使用Flink-CDC进行变更数据捕获，故对应的update流存在-U,+U,-D,+I记录，因此随着插入记录存在空值被记录进去的情况，故采用view的方式，先将宽表的加工、关联方式创建为view，然后进行空值的过滤。实施如下
create view view_prd as
select a.* ,b.* from a join b on a.id = b.id
select * from view_prd where depart_name is null or depart_name = '' or char_length(depart_name) = 0;
- 通过查询结果，发现存在最后一条记录存在空值的原因，往源头定位，发现该字段之前为空，后面进行更新填充到值出现-U记录，导致数据插入持续失败
原因
- 因为flink-SQL消费的数据时kafka topic，flink以upsert-kafka形式的connector进行写入，故存在changelog 流中数据更新存在-U，+U的记录（按照Key进行区分唯一条记录），value 为空(-U)的记录kafka也，导致出现空值，
解决
通过在DWS宽表创建一层View（如上)，在写入DWS宽表的kafka topic之前，现将该字段空值过滤，即可排除空值涉及记录被纳入结果指标计算的范围中
