go-log

This logging library used by go-log

zap-log wraps zap to provide a logging facade. go-log manages logging instances and allows for their levels to be controlled individually.

Install

go get github.com/ngchain/zap-log

Usage

Once the package is imported under the name logging, an instance of EventLogger can be created like so:

var log = logging.Logger("subsystem name")

It can then be used to emit log messages in plain printf-style messages at seven standard levels:

Levels may be set for all loggers:

lvl, err := logging.LevelFromString("error")
if err != nil {
	panic(err)
}
logging.SetAllLoggers(lvl)

or individually:

err := logging.SetLogLevel("net:pubsub", "info")
if err != nil {
	panic(err)
}

or by regular expression:

err := logging.SetLogLevelRegex("net:.*", "info")
if err != nil {
	panic(err)
}

Environment Variables

This package can be configured through various environment variables.

ZAP_LOG_LEVEL

Specifies the log-level, both globally and on a per-subsystem basis.

For example, the following will set the global minimum log level to error, but reduce the minimum log level for subsystem1 to info and reduce the minimum log level for subsystem2 to debug.

export ZAP_LOG_LEVEL="error,subsystem1=info,subsystem2=debug"

ZAP_FILE

Specifies that logs should be written to the specified file. If this option is not specified, logs are written to standard error.

export ZAP_FILE="/path/to/my/file.log"

ZAP_OUTPUT

Specifies where logging output should be written. Can take one or more of the following values, combined with +:

• stdout -- write logs to standard out.
• stderr -- write logs to standard error.
• file -- write logs to the file specified by ZAP_FILE

For example, if you want to log to both a file and standard error:

export ZAP_FILE="/path/to/my/file.log"
export ZAP_OUTPUT="stderr+file"

Setting only ZAP_FILE will prevent logs from being written to standard error.

ZAP_LOG_FMT

Specifies the log message format. It supports the following values:

• color -- human readable, colorized (ANSI) output
• nocolor -- human readable, plain-text output.
• json -- structured JSON.

For example, to log structured JSON (for easier parsing):

export ZAP_LOG_FMT="json"

The logging format defaults to color when the output is a terminal, and nocolor otherwise.

ZAP_LOG_LABELS

Specifies a set of labels that should be added to all log messages as comma-separated key-value pairs. For example, the following add {"app": "example_app", "dc": "sjc-1"} to every log entry.

export ZAP_LOG_LABELS="app=example_app,dc=sjc-1"

Contribute

Feel free to join in. All welcome. Open an issue!

License

MIT