README.md

Log

Handle global logging with context. Based on logrus incorporating golang's context.context

It uses logfmt by default but can also output json using a &logrus.JSONFormatter()

$ go get github.com/graze/golang-service/log

Set global properties

Setting these will mean any use of the global logging context or log.New() will use these properties

log.SetFormatter(&logrus.TextFormatter()) // default
log.SetOutput(os.Stderr) // default
log.SetLevel(log.InfoLevel) // default
log.AddFields(log.KV{"service":"super_service"}) // apply `service=super_service` to each log message

logging using the global logger

log.With(log.KV{
    "module": "request_handler",
    "tag":    "received_request"
    "method": "GET",
    "path":   "/path"
}).Info("Received request");

Example:

time="2016-10-28T10:51:32Z" level=info msg="Received request" module="request_handler" tag="received_request" method=GET path=/path service="super_service"

Log using a local field store

logger := log.New()
logger.Add(log.KV{
    "module": "request_handler"
})
logger.With(log.KV{
    "tag":    "received_request",
    "method": "GET",
    "path":   "/path"
}).Info("Received GET /path")
logger.Err(err).Error("Failed to handle input request")

time="2016-10-28T10:51:32Z" level=info msg="Received GET /path" tag="received_request" method=GET path=/path module="request_handler"

Log using a context

The logger can use golang's context to pass around fields

logger := log.New()
logger.Add(log.KV{"module": "request_handler"})
ctx := logger.NewContext(context.Background())
log.Ctx(ctx).
    With(log.KV{"tag": "received_request"}).
    Info("Received request")

time="2016-10-28T10:51:32Z" level=info msg="Received request" tag="received_request" module="request_handler"

The context can be applied to another local logger

logger := log.New()
logger.Add(log.KV{"module": "request_handler"})
ctx := logger.NewContext(context.Background())

logger2 := log.New()
logger2.SetOutput(os.Stderr)
logger2.Add(log.KV{"tag": "received_request"})
logger2.Ctx(ctx).Info("Received request")

time="2016-10-28T10:51:32Z" level=info msg="Received request" tag="received_request" module="request_handler"

Modifying a loggers properties

logger := log.New()
logger.SetFormatter(&logrus.JSONFormatter{})
logger.SetLevel(log.DebugLevel)
logger.SetOutput(os.Stdout)

logger.Debug("some debug output printed")

logger implements the log.Logger interface which includes SetFormatter, SetLevel, SetOutput, Level and AddHook

{"time":"2016-10-28T10:51:32Z","level":"debug","msg":"some debug output printed"}