pingcap / pingcap/ticdc

In `avro-enable-watermark=true` using AWS Glue Schema Registry, "DELETE" event and normal event has colliding magic byte

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Dominant language
Go
Stars
56
Forks
63
Avg merge
2d 20h
Merged PRs (30d)
34

Description

deleteByte is 3

https://github.com/pingcap/ticdc/blob/41b855b10b129a6b4af681a6f1b02362f6e4f104/pkg/sink/codec/avro/helper.go#L48-L55

The headerVersionByte of a Glue message is also 3

https://github.com/pingcap/ticdc/blob/41b855b10b129a6b4af681a6f1b02362f6e4f104/pkg/sink/codec/avro/glue_schema_registry.go#L325-L332

This will lead to mis-identification when both avro-enable-watermark and AWS Glue Schema Registry are used, e.g.

https://github.com/pingcap/ticdc/blob/41b855b10b129a6b4af681a6f1b02362f6e4f104/pkg/sink/codec/avro/decoder.go#L194-L199

I suggest changing the 3 internal-use bytes to some value far away from these magic bytes, and probably don't occupy three slots for internal use. Maybe change to e.g. cd c1, cd c2, cd c3.

(Internal reference: GTOC-8564/NAID-12126)

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Research direction

Start with the referenced byte definitions in pkg/sink/codec/avro/helper.go and pkg/sink/codec/avro/glue_schema_registry.go, then trace the identification logic in pkg/sink/codec/avro/decoder.go. Confirm which internal-use bytes collide with AWS Glue's header version byte, update the internal values without overlapping Glue messages, and verify that DELETE and normal events are distinguished when avro-enable-watermark and AWS Glue Schema Registry are both enabled.

Written by the indexing model from the issue text.

Assessment

Tech stack
aws, go
Domain
backend, data-engineering
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Quiet
Clarity
Clearly specified
Newbie friendliness
72/100

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