From 77c172b823b64ebface655681ab0749b9d2f7081 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Ra=C3=BAl=20Benencia?= Date: Fri, 13 Apr 2018 16:30:31 -0700 Subject: First public commit --- vendor/github.com/go-kit/kit/log/doc.go | 116 ++++++++++++++++++++++++++++++++ 1 file changed, 116 insertions(+) create mode 100644 vendor/github.com/go-kit/kit/log/doc.go (limited to 'vendor/github.com/go-kit/kit/log/doc.go') diff --git a/vendor/github.com/go-kit/kit/log/doc.go b/vendor/github.com/go-kit/kit/log/doc.go new file mode 100644 index 0000000..918c0af --- /dev/null +++ b/vendor/github.com/go-kit/kit/log/doc.go @@ -0,0 +1,116 @@ +// Package log provides a structured logger. +// +// Structured logging produces logs easily consumed later by humans or +// machines. Humans might be interested in debugging errors, or tracing +// specific requests. Machines might be interested in counting interesting +// events, or aggregating information for off-line processing. In both cases, +// it is important that the log messages are structured and actionable. +// Package log is designed to encourage both of these best practices. +// +// Basic Usage +// +// The fundamental interface is Logger. Loggers create log events from +// key/value data. The Logger interface has a single method, Log, which +// accepts a sequence of alternating key/value pairs, which this package names +// keyvals. +// +// type Logger interface { +// Log(keyvals ...interface{}) error +// } +// +// Here is an example of a function using a Logger to create log events. +// +// func RunTask(task Task, logger log.Logger) string { +// logger.Log("taskID", task.ID, "event", "starting task") +// ... +// logger.Log("taskID", task.ID, "event", "task complete") +// } +// +// The keys in the above example are "taskID" and "event". The values are +// task.ID, "starting task", and "task complete". Every key is followed +// immediately by its value. +// +// Keys are usually plain strings. Values may be any type that has a sensible +// encoding in the chosen log format. With structured logging it is a good +// idea to log simple values without formatting them. This practice allows +// the chosen logger to encode values in the most appropriate way. +// +// Contextual Loggers +// +// A contextual logger stores keyvals that it includes in all log events. +// Building appropriate contextual loggers reduces repetition and aids +// consistency in the resulting log output. With and WithPrefix add context to +// a logger. We can use With to improve the RunTask example. +// +// func RunTask(task Task, logger log.Logger) string { +// logger = log.With(logger, "taskID", task.ID) +// logger.Log("event", "starting task") +// ... +// taskHelper(task.Cmd, logger) +// ... +// logger.Log("event", "task complete") +// } +// +// The improved version emits the same log events as the original for the +// first and last calls to Log. Passing the contextual logger to taskHelper +// enables each log event created by taskHelper to include the task.ID even +// though taskHelper does not have access to that value. Using contextual +// loggers this way simplifies producing log output that enables tracing the +// life cycle of individual tasks. (See the Contextual example for the full +// code of the above snippet.) +// +// Dynamic Contextual Values +// +// A Valuer function stored in a contextual logger generates a new value each +// time an event is logged. The Valuer example demonstrates how this feature +// works. +// +// Valuers provide the basis for consistently logging timestamps and source +// code location. The log package defines several valuers for that purpose. +// See Timestamp, DefaultTimestamp, DefaultTimestampUTC, Caller, and +// DefaultCaller. A common logger initialization sequence that ensures all log +// entries contain a timestamp and source location looks like this: +// +// logger := log.NewLogfmtLogger(log.NewSyncWriter(os.Stdout)) +// logger = log.With(logger, "ts", log.DefaultTimestampUTC, "caller", log.DefaultCaller) +// +// Concurrent Safety +// +// Applications with multiple goroutines want each log event written to the +// same logger to remain separate from other log events. Package log provides +// two simple solutions for concurrent safe logging. +// +// NewSyncWriter wraps an io.Writer and serializes each call to its Write +// method. Using a SyncWriter has the benefit that the smallest practical +// portion of the logging logic is performed within a mutex, but it requires +// the formatting Logger to make only one call to Write per log event. +// +// NewSyncLogger wraps any Logger and serializes each call to its Log method. +// Using a SyncLogger has the benefit that it guarantees each log event is +// handled atomically within the wrapped logger, but it typically serializes +// both the formatting and output logic. Use a SyncLogger if the formatting +// logger may perform multiple writes per log event. +// +// Error Handling +// +// This package relies on the practice of wrapping or decorating loggers with +// other loggers to provide composable pieces of functionality. It also means +// that Logger.Log must return an error because some +// implementations—especially those that output log data to an io.Writer—may +// encounter errors that cannot be handled locally. This in turn means that +// Loggers that wrap other loggers should return errors from the wrapped +// logger up the stack. +// +// Fortunately, the decorator pattern also provides a way to avoid the +// necessity to check for errors every time an application calls Logger.Log. +// An application required to panic whenever its Logger encounters +// an error could initialize its logger as follows. +// +// fmtlogger := log.NewLogfmtLogger(log.NewSyncWriter(os.Stdout)) +// logger := log.LoggerFunc(func(keyvals ...interface{}) error { +// if err := fmtlogger.Log(keyvals...); err != nil { +// panic(err) +// } +// return nil +// }) +package log -- cgit v1.2.3