Debezium Won't Start? The Whitespace Bug That Stumped Our Client

We recently got a support ticket that looked simple at first. A client's Debezium MySQL connector kept failing at startup. The error pointed to message.key.columns. The config looked reasonable. But nothing worked.

Here's what happened — and how we fixed it without touching the database schema.

The Problem

The client had a MySQL table with a space in its name: dbo.Sourcing Id Master.

They configured the connector like this:

"message.key.columns": "dbo.Sourcing Id Master:id"

Connector validation failed immediately. They tried escaping — backslashes, quotes, every combination. Same error every time.

Why Escaping Doesn't Work Here

The problem isn't at runtime. It's at config validation time.

Debezium's validator for message.key.columns requires the fully-qualified table identifier to contain no whitespace. The validator rejects it before the connector even connects to MySQL. No escaping fixes this.

The Fix

Step 1 — capture the table via table.include.list (accepts spaces fine):

"table.include.list": "dbo\.Sourcing Id Master"

Step 2 — build the message key with a ValueToKey SMT:

"transforms": "ValueToKey",
"transforms.ValueToKey.type": "org.apache.kafka.connect.transforms.ValueToKey",
"transforms.ValueToKey.fields": "id"

Debezium includes primary key fields in the record value anyway — the SMT pulls id from there and sets it as the Kafka message key, bypassing the validator entirely.

Result

Connector starts. Table captured. Keys work. Zero schema changes.

At Hossted, we help enterprises run open source in production — Kafka, Debezium, PostgreSQL, Kubernetes and more. Follow us on LinkedIn for more cases like this.