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Diffstat (limited to 'vendor/github.com/go-kit/kit/log/log.go')
-rw-r--r-- | vendor/github.com/go-kit/kit/log/log.go | 135 |
1 files changed, 135 insertions, 0 deletions
diff --git a/vendor/github.com/go-kit/kit/log/log.go b/vendor/github.com/go-kit/kit/log/log.go new file mode 100644 index 0000000..66a9e2f --- /dev/null +++ b/vendor/github.com/go-kit/kit/log/log.go @@ -0,0 +1,135 @@ +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 or +// WithPrefix, 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), + } +} + +// 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 or WithPrefix, 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), + } +} + +// context is the Logger implementation returned by With and WithPrefix. 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 and WithPrefix 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{} + hasValuer 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)]) + } + 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...) +} |