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Logging

RustMailer uses the tracing framework for structured logging. Logging can be configured via command-line arguments or environment variables. We recommend using environment variables for production environments.

Supported Configuration Options​

Variable NameTypeDefaultDescription
RUSTMAILER_LOG_LEVELstringinfoSets the log level. Options: trace, debug, info, warn, error.
RUSTMAILER_ANSI_LOGSbooleanfalseEnables ANSI colored log output.
RUSTMAILER_JSON_LOGSbooleanfalseOutputs logs in JSON format (one JSON object per line).
RUSTMAILER_LOG_TO_FILEbooleanfalseEnables writing logs to a file. Recommended in production.
RUSTMAILER_MAX_SERVER_LOG_FILESinteger5Number of daily rotated log files to retain.
RUSTMAILER_ROOT_DIRpath.Root directory for log files; logs are stored in the logs/ subdirectory.

Example: Setting via Environment Variables​

You can set these variables in a .env file or export them before running RustMailer:

export RUSTMAILER_LOG_LEVEL=warn
export RUSTMAILER_JSON_LOGS=true
export RUSTMAILER_LOG_TO_FILE=true
export RUSTMAILER_MAX_SERVER_LOG_FILES=14
export RUSTMAILER_ROOT_DIR=/var/lib/rustmailer

Log Output Examples​

  • Default (stdout):
2025-07-15T15:01:23Z  INFO rustmailer::server: server started on 0.0.0.0:8000
  • JSON log format:
{"timestamp":"2025-07-15T15:01:23Z","level":"INFO","target":"rustmailer::server","message":"server started on 0.0.0.0:8000"}
  • Log file location:

If RUSTMAILER_LOG_TO_FILE=true, logs are written to:

{RUSTMAILER_ROOT_DIR}/logs/server-2025-07-15.log

And old files are rotated daily, based on RUSTMAILER_MAX_SERVER_LOG_FILES.

tip
  • Enable RUSTMAILER_LOG_TO_FILE in production to persist logs.
  • Use RUSTMAILER_JSON_LOGS for machine-readable logs (e.g., ELK/ClickHouse ingestion).
  • Make sure RUSTMAILER_ROOT_DIR points to a persistent volume (especially in containers).