Silent deployment failures in Travis CI when credentials are missing

Identifying Missing Credential Signatures

Silent failures in Travis CI deployment jobs typically occur when a command expects an environment variable that is either unset or empty, leading to a generic non-zero exit code. To isolate these from permission or network errors, look for these specific log signatures:

• Interpolation Errors: The phrase Variable not defined appearing during the script expansion phase.
• Unbound Variables: If set -u is enabled in your shell, look for variable_name: unbound variable.
• Empty Parameter Substitution: Commands that appear in the log with empty quotes where a key should be (e.g., --access-key "").
• DPL Provider Errors: For those using the dpl tool, search for Error: Missing required option: [option_name] near the end of the deployment phase.

Differentiating Credentials from Other Failures

You can distinguish missing credentials from other deployment errors by analyzing the timing and the nature of the error message:

Failure Type	Log Signature	Timing
Missing Credential	"Missing required option" or empty strings in command line.	Immediate; occurs at the start of the deploy command.
Incorrect Permission	AccessDenied, 403 Forbidden, or "Unauthorized".	Post-authentication; occurs after the tool connects to the provider.
Network/Transient	Connection timeout, 502 Bad Gateway, or retry loops.	Intermittent; often shows multiple attempts before failing.

Mapping Failures via the Travis API

There is no single API field that explicitly flags a "missing variable" failure. Instead, you must correlate data from two endpoints using the Job ID:

1. Fetch Job Configuration: Call GET /job/{id}/config. Examine the env array. This list shows which variables were passed to the job (secure values are redacted, but the keys are visible).
2. Fetch Job Logs: Call GET /job/{id}/log. Search for the "unbound variable" or "Missing required option" signatures mentioned above.
3. Cross-Reference: If the log mentions a missing option (e.g., AWS_SECRET_ACCESS_KEY) and that key is absent from the env array in the config, you have confirmed a missing credential.

Recommended Verification Step

To prevent future silent failures, add the following to your deployment script to force the shell to exit immediately when an undefined variable is referenced:

set -euo pipefail

Diagnostic Detail Needed: Are you using the built-in dpl deployment tool or a custom shell script for your deployment? The log signatures differ significantly between the two.