The latest articles on DEV Community by Marta @ Hossted (@marta-hossted). https://dev.to/marta-hossted https://media2.dev.to/dynamic/image/width=90,height=90,fit=cover,gravity=auto,format=auto/https:%2F%2Fdev-to-uploads.s3.amazonaws.com%2Fuploads%2Fuser%2Fprofile_image%2F3929328%2F7696a04b-6caf-4db8-bb4a-9e5877870e62.png https://dev.to/marta-hossted en Marta @ Hossted Wed, 13 May 2026 13:02:58 +0000 https://dev.to/marta-hossted/debezium-wont-start-the-whitespace-bug-that-stumped-our-client-2k73 https://dev.to/marta-hossted/debezium-wont-start-the-whitespace-bug-that-stumped-our-client-2k73 <h1> Debezium Won't Start? The Whitespace Bug That Stumped Our Client </h1> <p>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 <code>message.key.columns</code>. The config looked reasonable. But nothing worked.</p> <p>Here's what happened — and how we fixed it without touching the database schema.</p> <h2> The Problem </h2> <p>The client had a MySQL table with a space in its name: <code>dbo.Sourcing Id Master</code>.</p> <p>They configured the connector like this:<br> </p> <div class="highlight js-code-highlight"> <pre class="highlight json"><code><span class="nl">"message.key.columns"</span><span class="p">:</span><span class="w"> </span><span class="s2">"dbo.Sourcing Id Master:id"</span><span class="w"> </span></code></pre> </div> <p>Connector validation failed immediately. They tried escaping — backslashes, quotes, every combination. Same error every time.</p> <h2> Why Escaping Doesn't Work Here </h2> <p>The problem isn't at runtime. It's at config validation time.</p> <p>Debezium's validator for <code>message.key.columns</code> 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.</p> <h2> The Fix </h2> <p><strong>Step 1 — capture the table via table.include.list</strong> (accepts spaces fine):</p> <p>"table.include.list": "dbo\.Sourcing Id Master"</p> <p><strong>Step 2 — build the message key with a ValueToKey SMT:</strong></p> <p>"transforms": "ValueToKey",<br> "transforms.ValueToKey.type": "org.apache.kafka.connect.transforms.ValueToKey",<br> "transforms.ValueToKey.fields": "id"</p> <p>Debezium includes primary key fields in the record value anyway — the SMT pulls <code>id</code> from there and sets it as the Kafka message key, bypassing the validator entirely.</p> <h2> Result </h2> <p>Connector starts. Table captured. Keys work. Zero schema changes.</p> <p><em>At <a href="https://hossted.com/?utm_source=devto&amp;utm_medium=article" rel="noopener noreferrer">Hossted</a>, we help enterprises run open source in production — Kafka, Debezium, PostgreSQL, Kubernetes and more. Follow us on <a href="https://www.linkedin.com/company/hossted" rel="noopener noreferrer">LinkedIn</a> for more cases like this.</em></p> devops kafka opensource database