How can I diagnose a failed ember-cli-deploy deployment by examining its log output?

Where ember-cli-deploy writes its logs

By default ember-cli-deploy streams its output to the process’ stdout and stderr. The terminal you see when you run ember deploy is therefore the combined log of all pipeline steps.

Identifying the failing step

1. Look for the first line that begins with ERROR: or contains the word Failed. That line names the plugin (e.g., ember-cli-deploy-s3) and the error message.
2. The lines immediately above it (usually prefixed with INFO: or DEBUG:) show the command the plugin executed and any non‑zero exit code it returned.
3. If a stack trace follows the error line, copy the whole trace; the module name in the trace points to the specific plugin or dependency that threw.

Increasing verbosity

Set the environment variable EMBER_CLI_DEPLOY_LOG_LEVEL to debug before running the deploy command:

EMBER_CLI_DEPLOY_LOG_LEVEL=debug ember deploy production

This forces ember-cli-deploy to emit DEBUG: lines for every internal step, making it easier to see which plugin initialization or API call failed.

Redirecting logs to a file

When you need to preserve the output for later inspection (e.g., in CI), pipe the streams to a file:

ember deploy production 2>&1 | tee deploy.log

Or, if you prefer to keep stdout and stderr separate:

ember deploy production > deploy.out 2> deploy.err

Verifying the fix

• After correcting the suspected issue (e.g., adding a missing AWS key), re‑run the deploy with the same log level.
• Confirm that the previous ERROR: line is gone and the pipeline ends with Deploy finished with exit code 0.
• Compare the successful log with the failed one; the step that previously showed ERROR: should now display an INFO: success message.

If the log still ends with a generic Deploy finished with exit code 1 and no explicit error, repeat the run with EMBER_CLI_DEPLOY_LOG_LEVEL=debug to uncover the hidden failure.