What causes "${type} is required" in cube-js/cube?

Include the database type in the request variables, e.g. { variables: { CUBEJS_DB_TYPE: 'postgres', ... } }

cube-js/cube · error · Error

${type} is required

Error message

${type} is required

What it means

The Dev Server's /playground/test-connection endpoint resolves the env variable name that must hold the database type (CUBEJS_DB_TYPE, or CUBEJS_DS_<dataSource>_DB_TYPE for multiple data sources) via keyByDataSource, then requires the submitted `variables` object to contain a value for that key. If the variables map is missing/empty or lacks that key, it throws `${type} is required` before attempting to instantiate and test the driver. Cube needs the db type to know which driver package to load and which env keys to read.

Source

Thrown at packages/cubejs-server-core/src/core/DevServer.ts:508

          [env: string]: string,
        },
      },
    };

    app.post('/playground/test-connection', catchErrors(
      async (req: TestConnectionRequest, res) => {
        const { dataSource, variables } = req.body || {};

        // With multiple data sources enabled, we need to use
        // CUBEJS_DS_<dataSource>_DB_TYPE environment variable
        // instead of CUBEJS_DB_TYPE.
        const type = keyByDataSource('CUBEJS_DB_TYPE', dataSource);

        let driver: BaseDriver | null = null;

        try {
          if (!variables || !variables[type]) {
            throw new Error(`${type} is required`);
          }

          // Backup env variables and set new ones in-place.
          // We must mutate the existing process.env object (not replace it)
          // because env-var holds a reference to the original object.
          const backup: Record<string, string | undefined> = {};

          for (const [envName, envValue] of Object.entries(variables)) {
            backup[envName] = process.env[envName];
            process.env[envName] = <string>envValue;
          }

          // With multiple data sources enabled, we need to put the dataSource
          // parameter to the driver instance to read an appropriate set of
          // driver configuration parameters. It can be undefined if multiple
          // data source is disabled.
          driver = CubejsServerCore.createDriver(
            <DatabaseType>variables[type],

View on GitHub (pinned to 7d981676b3)

Solutions

Include the database type in the request variables, e.g. { variables: { CUBEJS_DB_TYPE: 'postgres', ... } }
For multiple data sources, send the dataSource-specific key, e.g. { variables: { CUBEJS_DS_MYDS_DB_TYPE: 'mysql' } } together with dataSource in the body
Fix the client/UI to always populate the db type field before calling the endpoint
Set CUBEJS_DB_TYPE in the environment as a baseline so tooling can default to it

Example fix

// before
curl -X POST /playground/test-connection -d '{"variables":{"CUBEJS_DB_HOST":"localhost"}}'
// after
curl -X POST /playground/test-connection -d '{"variables":{"CUBEJS_DB_TYPE":"postgres","CUBEJS_DB_HOST":"localhost"}}'

Defensive patterns

Strategy: validation

Validate before calling

async function testConnectionSafe(body) {
  const { dataSource, variables } = body || {};
  const type = dataSource ? `CUBEJS_DS_${dataSource.toUpperCase()}_DB_TYPE` : 'CUBEJS_DB_TYPE';
  if (!variables || !variables[type]) {
    throw new Error(`${type} is required by /playground/test-connection`);
  }
  return fetch('/playground/test-connection', { method: 'POST', body: JSON.stringify(body) });
}

Type guard

function hasDbTypeVariables(v) {
  return typeof v === 'object' && v !== null && typeof v.CUBEJS_DB_TYPE === 'string' && v.CUBEJS_DB_TYPE.length > 0;
}

Try / catch

try {
  const res = await fetch('/playground/test-connection', {...});
  if (!res.ok) throw new Error((await res.json()).error);
} catch (e) {
  if (/DB_TYPE is required/.test(String(e))) {
    // prompt the user to pick a database type before retrying
  }
}

Prevention

Always include CUBEJS_DB_TYPE in the variables payload sent to the test-connection endpoint
For multiple data sources, compute the per-source key CUBEJS_DS_<DS>_DB_TYPE before sending
Validate the request body client-side before posting
Default the db type from the server environment when the form field is empty

When it happens

Trigger: POSTing to /playground/test-connection with a body whose `variables` is undefined, or variables lacking the key 'CUBEJS_DB_TYPE' (or 'CUBEJS_DS_<ds>_DB_TYPE' when a dataSource is passed and multiple data sources are enabled). This happens from the Developer Playground 'Test connection' UI when the database type field was not filled in.

Common situations: Using the Playground's connection-test form without selecting a database type; custom tooling calling the endpoint without the variables payload; multi-data-source setups where the request omits the per-data-source DB type variable; typos in the env variable key sent by the client.

Understand the failure class

Background: "environment variable is not set" and "Missing keys in environment" errors: what missing required env var messages mean and how to fix them — this error's family across 28 libraries.

Related errors

AI-assisted analysis of cube-js/cube@7d981676b3 (2026-09-02). Data as JSON: /api/errors/f91adf1aaa8be2d2. Report an issue: GitHub.