Kafka-connect-jdbc: JDBC Kafka Connector Not Sending Messages in Timestamp mode, only in Bulk

[aleks-myplanet]

Hi,

I'm encountering an issue where for a specific query when deployed with a JDBC kafka connector in timestamp mode, it never sends any messages. That exact same connector, with the exact same query, with the exact same connector config works perfectly fine when deployed in bulk mode.

I believe it is the query causing this since changing the query to something I know works in timestamp mode resolves the problem.

An example of the query causing the issue (removing sensitive data such as table names, column names, etc):
SELECT * FROM (SELECT COLUMN1, COLUMN2, COLUMN3, COLUMN4, COLUMN5, COLUMN6, COLUMN7, COLUMN8, COLUMN9
FROM TABLE1
INNER JOIN (SELECT COLUMN1, COLUMN5 FROM TABLE2) ON TABLE2.COLUMN1 = TABLE1.COLUMN1
INNER JOIN (SELECT COLUMN5, COLUMN3, COLUMN10, STATUS FROM TABLE3) ON TABLE3.COLUMN5 = TABLE2.COLUMN5 AND TABLE3.COLUMN3 = TABLE1.COLUMN11
INNER JOIN (SELECT COLUMN5, COLUMN10 FROM TABLE4) ON TABLE4.COLUMN5 = TABLE3.COLUMN5
INNER JOIN (SELECT COLUMN12, COLUMN8, COLUMN3 FROM TABLE5) ON TABLE5.COLUMN12 = TABLE4.COLUMN12 AND TABLE5.COLUMN3 = TABLE3.COLUMN10
INNER JOIN (SELECT COLUMN12, COLUMN2, COLUMN5 FROM TABLE6) ON TABLE6.COLUMN12 = TABLE5.COLUMN12
WHERE TABLE6.COLUMN2 = 'VALUE')

I don't believe the query is the issue since it executes correctly and sends messages to the topic when deploy with a connector in bulk mode.

Some things I've already tried:

1. Increase log level in kafka connect to look for errors. No errors or relevant logs. The connector just flushes 0 messages always, nothing special.
2. Double check the connector offsets in case those timestamps are wrong and resulting in no messages. According to the extra logs the timestamps are correct.
3. Testing every single documented kafka connect connector parameter. Spent a long time trying out different options that kafka connect provides for configuration. Can't find anything that seems to address the problem
4. Reducing the number of joins in the connector query. This did have an impact, and messages began to be sent after limiting it to just a single inner join. BUT I have other connectors with over 8 inner joins but those do send messages in timestamp mode. The issue doesn’t appear to be linked to data size or joins then.
5. Increasing resources to kafka connect. No difference
6. No github issues on the kafka connect repo, so this problem doesn’t appear to be documented as far as I can tell
7. Trying different topics in case it was limited to a specific topic, issue happens no matter the topic.
8. Updating drivers. I assumed it may be an issue on the database the connector is connecting to, maybe outdated drivers. No difference

Has anyone encountered a similar problem before? Any suggestions on how to resolve it?

[vtypal]

I also had the same issue with both timestamp and timestamp+incrementing mode. Only bulk mode worked properly.

[zak-n]

I am also experiencing the exact issue on a project of mine. We're also using Kafka to poll an Oracle DB. And it seems like, at some point, it just stops polling messages in Timestamp mode. Currently, we're running that same connector in Bulk, which seems to have mitigated the issue. However, it's not really ideal for us to run that connector in Bulk and so we're hoping to get any input that may help us eliminate this problem altogether.

[SpenserZC]

we also use timestamp mode in polling an Oracle DB,It not work. but the bulk is ok. Is there anyone can resolve it.

[SpenserZC]

we also use timestamp mode in polling an Oracle DB,It not work. but the bulk is ok. Is there anyone can resolve it.

we also use timestamp mode in polling an Oracle DB,It not work. but the bulk is ok. Is there anyone can resolve it.
it worked for me, use this post: https://github.com/confluentinc/kafka-connect-jdbc/issues/408#issuecomment-389176015

[harshrajsinha]

I am also facing same issue, used mode as timestamp. Topic offset does not on inserting new row.

[evertonpavan]

same issue here, only mode=bulk works correctly.

[ferchu]

i had the same problem and in my case the issue was that the timestamp column had the type INT instead of TIMESTAMP.

[atrbgithub]

@zak-n was you able to resolve this?

We're seeing exactly the same. We even have 2 connectors setup querying the same table, both incrementing mode. Suddenly one of them will stop producing new messages to the topic.

[aakashchhabra1989]

I setup a JDBC source connector using timestamp mode. configuration is straight forward as below:
This is working fine in postgres. but when using MSSQL with datetime type column. instead of picking of cdc all data is getting picked up from table just like bulk mode. there is no error in log as well

{
"name": "JdbcSourceConnector_1",
"config":
{
"connector.class": "io.confluent.connect.jdbc.JdbcSourceConnector",
"connection.user": "postgres",
"connection.password": "xxxxxxx",
"connection.url": "jdbc:postgresql://postgres:5432/postgres",
"tasks.max": "1",
"topic.prefix": "connect_bulk_",
"table.whitelist": "timestamp_table",
"mode": "timestamp",
"timestamp.column.name": "last_updated_time",
"value.converter": "org.apache.kafka.connect.json.JsonConverter",
"value.converter.schema.enable": "false",
"poll.interval.ms": "12000"
}
}

[aleks-myplanet]

Nope, this hasn't been solved in any way.

Aleksandar Stefanovic
Myplanet
myplanet.com http://www.myplanet.com
P: +1.866.232.7456

On Mon, Aug 2, 2021 at 12:42 PM aakashchhabra1989 @.*>
wrote:

I setup a JDBC source connector using timestamp mode. configuration is
straight forward as below:
This is working fine in postgres. but when using MSSQL with datetime type
column. instead of picking of cdc all data is getting picked up from table
just like bulk mode. there is no error in log as well

{
"name": "JdbcSourceConnector_1",
"config":
{
"connector.class": "io.confluent.connect.jdbc.JdbcSourceConnector",
"connection.user": "postgres",
"connection.password": "xxxxxxx",
"connection.url": "jdbc:postgresql://postgres:5432/postgres",
"tasks.max": "1",
"topic.prefix": "connect_bulk_",
"table.whitelist": "timestamp_table",
"mode": "timestamp",
"timestamp.column.name": "last_updated_time",
"value.converter": "org.apache.kafka.connect.json.JsonConverter",
"value.converter.schema.enable": "false",
"poll.interval.ms": "12000"
}
}

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