Logging

zero handles logging in well strucutred manner to provide ongoing state of the application and services that it attached to. The logs are tidy and visualque to understand the app status.

The framework allows to customize and know only the needed information on any given time.

Through LOG_LEVEL config one can adjust the app logging and know more of underlying state. The least level is debug and that let start see logs all above.

Levels in order (highest to lowest) - fatal, error, warn, info and debug.

Remote log level

LOG_LEVEL can also be driven at runtime from a remote endpoint.

When REMOTE_LOG_URL is configured, zero registers an outbound HTTP client and a cron job that fetches the level (JSON { "level": "info" }) every REMOTE_LOG_FETCH_INTERVAL seconds (default 15) and applies it in-process.

The feature is opt-in — leave REMOTE_LOG_URL empty to disable it.

See Configuration → Remote Log for the keys.

JSON structured logging

Set LOG_FORMAT=json (env or .env) to emit one JSON object per log line instead of the colorized text format:

{ "ts": "14:22:05", "level": "info", "msg": "connected to database" }

Fields:

• ts (timestamp, see Log timezone),
• level (debug|info|warn|error|fatal)
• msg. Non-string arguments are still serialized (via {any}).

You can also flip the format in code through the logger:

zero.logger.setJsonFormat(true);   // or false for text

Log timezone

Log timestamps use the system local zone by default. Override with ZERO_LOG_TIMEZONE:

Value	Behavior
local (default) / empty	System zone from /etc/localtime
utc	Force UTC
IANA name (e.g. America/New_York)	Pin a specific zone, resolved from the embedded tz database

Resolution failure on an IANA name falls back to the system local zone, and ultimately to UTC. The timezone is resolved before the first log line (e.g. "Loaded config from file"), so it applies to startup logs too.

When zero app runs, it starts reading log level, allow us to know more

• log level of statement
• database/kv/mq connection status
• authentication setup
• static directory attachments,
• request trace id, response status, response handling time
• possibly errors that occured.

Visual cue

Method signature

ctx.info("message");

ctx.debug([]const u8);

ctx.err([]const u8);

ctx.warn([]const u8);

ctx.fatal([]const u8);

ctx.any(struct);