bump(vendor)

vendor/github.com/go-kit/log/log.go

@@ -0,0 +1,179 @@
+package log
+
+import "errors"
+
+// Logger is the fundamental interface for all log operations. Log creates a
+// log event from keyvals, a variadic sequence of alternating keys and values.
+// Implementations must be safe for concurrent use by multiple goroutines. In
+// particular, any implementation of Logger that appends to keyvals or
+// modifies or retains any of its elements must make a copy first.
+type Logger interface {
+	Log(keyvals ...interface{}) error
+}
+
+// ErrMissingValue is appended to keyvals slices with odd length to substitute
+// the missing value.
+var ErrMissingValue = errors.New("(MISSING)")
+
+// With returns a new contextual logger with keyvals prepended to those passed
+// to calls to Log. If logger is also a contextual logger created by With,
+// WithPrefix, or WithSuffix, keyvals is appended to the existing context.
+//
+// The returned Logger replaces all value elements (odd indexes) containing a
+// Valuer with their generated value for each call to its Log method.
+func With(logger Logger, keyvals ...interface{}) Logger {
+	if len(keyvals) == 0 {
+		return logger
+	}
+	l := newContext(logger)
+	kvs := append(l.keyvals, keyvals...)
+	if len(kvs)%2 != 0 {
+		kvs = append(kvs, ErrMissingValue)
+	}
+	return &context{
+		logger: l.logger,
+		// Limiting the capacity of the stored keyvals ensures that a new
+		// backing array is created if the slice must grow in Log or With.
+		// Using the extra capacity without copying risks a data race that
+		// would violate the Logger interface contract.
+		keyvals:    kvs[:len(kvs):len(kvs)],
+		hasValuer:  l.hasValuer || containsValuer(keyvals),
+		sKeyvals:   l.sKeyvals,
+		sHasValuer: l.sHasValuer,
+	}
+}
+
+// WithPrefix returns a new contextual logger with keyvals prepended to those
+// passed to calls to Log. If logger is also a contextual logger created by
+// With, WithPrefix, or WithSuffix, keyvals is prepended to the existing context.
+//
+// The returned Logger replaces all value elements (odd indexes) containing a
+// Valuer with their generated value for each call to its Log method.
+func WithPrefix(logger Logger, keyvals ...interface{}) Logger {
+	if len(keyvals) == 0 {
+		return logger
+	}
+	l := newContext(logger)
+	// Limiting the capacity of the stored keyvals ensures that a new
+	// backing array is created if the slice must grow in Log or With.
+	// Using the extra capacity without copying risks a data race that
+	// would violate the Logger interface contract.
+	n := len(l.keyvals) + len(keyvals)
+	if len(keyvals)%2 != 0 {
+		n++
+	}
+	kvs := make([]interface{}, 0, n)
+	kvs = append(kvs, keyvals...)
+	if len(kvs)%2 != 0 {
+		kvs = append(kvs, ErrMissingValue)
+	}
+	kvs = append(kvs, l.keyvals...)
+	return &context{
+		logger:     l.logger,
+		keyvals:    kvs,
+		hasValuer:  l.hasValuer || containsValuer(keyvals),
+		sKeyvals:   l.sKeyvals,
+		sHasValuer: l.sHasValuer,
+	}
+}
+
+// WithSuffix returns a new contextual logger with keyvals appended to those
+// passed to calls to Log. If logger is also a contextual logger created by
+// With, WithPrefix, or WithSuffix, keyvals is appended to the existing context.
+//
+// The returned Logger replaces all value elements (odd indexes) containing a
+// Valuer with their generated value for each call to its Log method.
+func WithSuffix(logger Logger, keyvals ...interface{}) Logger {
+	if len(keyvals) == 0 {
+		return logger
+	}
+	l := newContext(logger)
+	// Limiting the capacity of the stored keyvals ensures that a new
+	// backing array is created if the slice must grow in Log or With.
+	// Using the extra capacity without copying risks a data race that
+	// would violate the Logger interface contract.
+	n := len(l.sKeyvals) + len(keyvals)
+	if len(keyvals)%2 != 0 {
+		n++
+	}
+	kvs := make([]interface{}, 0, n)
+	kvs = append(kvs, keyvals...)
+	if len(kvs)%2 != 0 {
+		kvs = append(kvs, ErrMissingValue)
+	}
+	kvs = append(l.sKeyvals, kvs...)
+	return &context{
+		logger:     l.logger,
+		keyvals:    l.keyvals,
+		hasValuer:  l.hasValuer,
+		sKeyvals:   kvs,
+		sHasValuer: l.sHasValuer || containsValuer(keyvals),
+	}
+}
+
+// context is the Logger implementation returned by With, WithPrefix, and
+// WithSuffix. It wraps a Logger and holds keyvals that it includes in all
+// log events. Its Log method calls bindValues to generate values for each
+// Valuer in the context keyvals.
+//
+// A context must always have the same number of stack frames between calls to
+// its Log method and the eventual binding of Valuers to their value. This
+// requirement comes from the functional requirement to allow a context to
+// resolve application call site information for a Caller stored in the
+// context. To do this we must be able to predict the number of logging
+// functions on the stack when bindValues is called.
+//
+// Two implementation details provide the needed stack depth consistency.
+//
+//    1. newContext avoids introducing an additional layer when asked to
+//       wrap another context.
+//    2. With, WithPrefix, and WithSuffix avoid introducing an additional
+//       layer by returning a newly constructed context with a merged keyvals
+//       rather than simply wrapping the existing context.
+type context struct {
+	logger     Logger
+	keyvals    []interface{}
+	sKeyvals   []interface{} // suffixes
+	hasValuer  bool
+	sHasValuer bool
+}
+
+func newContext(logger Logger) *context {
+	if c, ok := logger.(*context); ok {
+		return c
+	}
+	return &context{logger: logger}
+}
+
+// Log replaces all value elements (odd indexes) containing a Valuer in the
+// stored context with their generated value, appends keyvals, and passes the
+// result to the wrapped Logger.
+func (l *context) Log(keyvals ...interface{}) error {
+	kvs := append(l.keyvals, keyvals...)
+	if len(kvs)%2 != 0 {
+		kvs = append(kvs, ErrMissingValue)
+	}
+	if l.hasValuer {
+		// If no keyvals were appended above then we must copy l.keyvals so
+		// that future log events will reevaluate the stored Valuers.
+		if len(keyvals) == 0 {
+			kvs = append([]interface{}{}, l.keyvals...)
+		}
+		bindValues(kvs[:(len(l.keyvals))])
+	}
+	kvs = append(kvs, l.sKeyvals...)
+	if l.sHasValuer {
+		bindValues(kvs[len(kvs)-len(l.sKeyvals):])
+	}
+	return l.logger.Log(kvs...)
+}
+
+// LoggerFunc is an adapter to allow use of ordinary functions as Loggers. If
+// f is a function with the appropriate signature, LoggerFunc(f) is a Logger
+// object that calls f.
+type LoggerFunc func(...interface{}) error
+
+// Log implements Logger by calling f(keyvals...).
+func (f LoggerFunc) Log(keyvals ...interface{}) error {
+	return f(keyvals...)
+}