log, vendor: vendor in log15 inline into our codebase
This commit is contained in:
Péter Szilágyi
356
log/handler.go
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356
log/handler.go
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@ -0,0 +1,356 @@
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package log
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import (
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"fmt"
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"io"
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"net"
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"os"
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"reflect"
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"sync"
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"github.com/go-stack/stack"
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)
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// A Logger prints its log records by writing to a Handler.
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// The Handler interface defines where and how log records are written.
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// Handlers are composable, providing you great flexibility in combining
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// them to achieve the logging structure that suits your applications.
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type Handler interface {
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Log(r *Record) error
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}
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// FuncHandler returns a Handler that logs records with the given
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// function.
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func FuncHandler(fn func(r *Record) error) Handler {
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return funcHandler(fn)
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}
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type funcHandler func(r *Record) error
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func (h funcHandler) Log(r *Record) error {
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return h(r)
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}
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// StreamHandler writes log records to an io.Writer
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// with the given format. StreamHandler can be used
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// to easily begin writing log records to other
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// outputs.
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//
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// StreamHandler wraps itself with LazyHandler and SyncHandler
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// to evaluate Lazy objects and perform safe concurrent writes.
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func StreamHandler(wr io.Writer, fmtr Format) Handler {
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h := FuncHandler(func(r *Record) error {
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_, err := wr.Write(fmtr.Format(r))
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return err
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})
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return LazyHandler(SyncHandler(h))
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}
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// SyncHandler can be wrapped around a handler to guarantee that
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// only a single Log operation can proceed at a time. It's necessary
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// for thread-safe concurrent writes.
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func SyncHandler(h Handler) Handler {
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var mu sync.Mutex
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return FuncHandler(func(r *Record) error {
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defer mu.Unlock()
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mu.Lock()
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return h.Log(r)
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})
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}
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// FileHandler returns a handler which writes log records to the give file
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// using the given format. If the path
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// already exists, FileHandler will append to the given file. If it does not,
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// FileHandler will create the file with mode 0644.
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func FileHandler(path string, fmtr Format) (Handler, error) {
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f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
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if err != nil {
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return nil, err
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}
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return closingHandler{f, StreamHandler(f, fmtr)}, nil
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}
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// NetHandler opens a socket to the given address and writes records
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// over the connection.
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func NetHandler(network, addr string, fmtr Format) (Handler, error) {
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conn, err := net.Dial(network, addr)
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if err != nil {
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return nil, err
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}
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return closingHandler{conn, StreamHandler(conn, fmtr)}, nil
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}
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// XXX: closingHandler is essentially unused at the moment
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// it's meant for a future time when the Handler interface supports
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// a possible Close() operation
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type closingHandler struct {
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io.WriteCloser
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Handler
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}
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func (h *closingHandler) Close() error {
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return h.WriteCloser.Close()
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}
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// CallerFileHandler returns a Handler that adds the line number and file of
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// the calling function to the context with key "caller".
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func CallerFileHandler(h Handler) Handler {
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return FuncHandler(func(r *Record) error {
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r.Ctx = append(r.Ctx, "caller", fmt.Sprint(r.Call))
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return h.Log(r)
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})
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}
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// CallerFuncHandler returns a Handler that adds the calling function name to
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// the context with key "fn".
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func CallerFuncHandler(h Handler) Handler {
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return FuncHandler(func(r *Record) error {
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r.Ctx = append(r.Ctx, "fn", fmt.Sprintf("%+n", r.Call))
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return h.Log(r)
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})
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}
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// CallerStackHandler returns a Handler that adds a stack trace to the context
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// with key "stack". The stack trace is formated as a space separated list of
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// call sites inside matching []'s. The most recent call site is listed first.
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// Each call site is formatted according to format. See the documentation of
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// package github.com/go-stack/stack for the list of supported formats.
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func CallerStackHandler(format string, h Handler) Handler {
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return FuncHandler(func(r *Record) error {
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s := stack.Trace().TrimBelow(r.Call).TrimRuntime()
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if len(s) > 0 {
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r.Ctx = append(r.Ctx, "stack", fmt.Sprintf(format, s))
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}
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return h.Log(r)
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})
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}
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// FilterHandler returns a Handler that only writes records to the
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// wrapped Handler if the given function evaluates true. For example,
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// to only log records where the 'err' key is not nil:
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//
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// logger.SetHandler(FilterHandler(func(r *Record) bool {
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// for i := 0; i < len(r.Ctx); i += 2 {
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// if r.Ctx[i] == "err" {
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// return r.Ctx[i+1] != nil
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// }
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// }
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// return false
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// }, h))
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//
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func FilterHandler(fn func(r *Record) bool, h Handler) Handler {
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return FuncHandler(func(r *Record) error {
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if fn(r) {
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return h.Log(r)
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}
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return nil
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})
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}
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// MatchFilterHandler returns a Handler that only writes records
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// to the wrapped Handler if the given key in the logged
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// context matches the value. For example, to only log records
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// from your ui package:
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//
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// log.MatchFilterHandler("pkg", "app/ui", log.StdoutHandler)
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//
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func MatchFilterHandler(key string, value interface{}, h Handler) Handler {
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return FilterHandler(func(r *Record) (pass bool) {
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switch key {
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case r.KeyNames.Lvl:
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return r.Lvl == value
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case r.KeyNames.Time:
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return r.Time == value
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case r.KeyNames.Msg:
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return r.Msg == value
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}
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for i := 0; i < len(r.Ctx); i += 2 {
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if r.Ctx[i] == key {
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return r.Ctx[i+1] == value
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}
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}
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return false
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}, h)
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}
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// LvlFilterHandler returns a Handler that only writes
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// records which are less than the given verbosity
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// level to the wrapped Handler. For example, to only
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// log Error/Crit records:
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//
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// log.LvlFilterHandler(log.LvlError, log.StdoutHandler)
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//
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func LvlFilterHandler(maxLvl Lvl, h Handler) Handler {
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return FilterHandler(func(r *Record) (pass bool) {
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return r.Lvl <= maxLvl
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}, h)
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}
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// A MultiHandler dispatches any write to each of its handlers.
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// This is useful for writing different types of log information
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// to different locations. For example, to log to a file and
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// standard error:
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//
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// log.MultiHandler(
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// log.Must.FileHandler("/var/log/app.log", log.LogfmtFormat()),
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// log.StderrHandler)
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//
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func MultiHandler(hs ...Handler) Handler {
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return FuncHandler(func(r *Record) error {
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for _, h := range hs {
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// what to do about failures?
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h.Log(r)
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}
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return nil
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})
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}
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// A FailoverHandler writes all log records to the first handler
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// specified, but will failover and write to the second handler if
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// the first handler has failed, and so on for all handlers specified.
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// For example you might want to log to a network socket, but failover
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// to writing to a file if the network fails, and then to
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// standard out if the file write fails:
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//
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// log.FailoverHandler(
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// log.Must.NetHandler("tcp", ":9090", log.JsonFormat()),
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// log.Must.FileHandler("/var/log/app.log", log.LogfmtFormat()),
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// log.StdoutHandler)
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//
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// All writes that do not go to the first handler will add context with keys of
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// the form "failover_err_{idx}" which explain the error encountered while
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// trying to write to the handlers before them in the list.
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func FailoverHandler(hs ...Handler) Handler {
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return FuncHandler(func(r *Record) error {
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var err error
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for i, h := range hs {
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err = h.Log(r)
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if err == nil {
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return nil
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} else {
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r.Ctx = append(r.Ctx, fmt.Sprintf("failover_err_%d", i), err)
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}
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}
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return err
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})
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}
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// ChannelHandler writes all records to the given channel.
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// It blocks if the channel is full. Useful for async processing
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// of log messages, it's used by BufferedHandler.
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func ChannelHandler(recs chan<- *Record) Handler {
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return FuncHandler(func(r *Record) error {
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recs <- r
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return nil
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})
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}
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// BufferedHandler writes all records to a buffered
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// channel of the given size which flushes into the wrapped
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// handler whenever it is available for writing. Since these
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// writes happen asynchronously, all writes to a BufferedHandler
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// never return an error and any errors from the wrapped handler are ignored.
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func BufferedHandler(bufSize int, h Handler) Handler {
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recs := make(chan *Record, bufSize)
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go func() {
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for m := range recs {
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_ = h.Log(m)
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}
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}()
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return ChannelHandler(recs)
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}
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// LazyHandler writes all values to the wrapped handler after evaluating
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// any lazy functions in the record's context. It is already wrapped
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// around StreamHandler and SyslogHandler in this library, you'll only need
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// it if you write your own Handler.
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func LazyHandler(h Handler) Handler {
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return FuncHandler(func(r *Record) error {
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// go through the values (odd indices) and reassign
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// the values of any lazy fn to the result of its execution
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hadErr := false
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for i := 1; i < len(r.Ctx); i += 2 {
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lz, ok := r.Ctx[i].(Lazy)
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if ok {
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v, err := evaluateLazy(lz)
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if err != nil {
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hadErr = true
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r.Ctx[i] = err
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} else {
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if cs, ok := v.(stack.CallStack); ok {
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v = cs.TrimBelow(r.Call).TrimRuntime()
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}
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r.Ctx[i] = v
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}
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}
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}
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if hadErr {
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r.Ctx = append(r.Ctx, errorKey, "bad lazy")
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}
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return h.Log(r)
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})
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}
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func evaluateLazy(lz Lazy) (interface{}, error) {
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t := reflect.TypeOf(lz.Fn)
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if t.Kind() != reflect.Func {
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return nil, fmt.Errorf("INVALID_LAZY, not func: %+v", lz.Fn)
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}
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if t.NumIn() > 0 {
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return nil, fmt.Errorf("INVALID_LAZY, func takes args: %+v", lz.Fn)
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}
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if t.NumOut() == 0 {
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return nil, fmt.Errorf("INVALID_LAZY, no func return val: %+v", lz.Fn)
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}
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value := reflect.ValueOf(lz.Fn)
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results := value.Call([]reflect.Value{})
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if len(results) == 1 {
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return results[0].Interface(), nil
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} else {
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values := make([]interface{}, len(results))
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for i, v := range results {
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values[i] = v.Interface()
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}
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return values, nil
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}
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}
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// DiscardHandler reports success for all writes but does nothing.
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// It is useful for dynamically disabling logging at runtime via
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// a Logger's SetHandler method.
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func DiscardHandler() Handler {
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return FuncHandler(func(r *Record) error {
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return nil
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})
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}
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// The Must object provides the following Handler creation functions
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// which instead of returning an error parameter only return a Handler
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// and panic on failure: FileHandler, NetHandler, SyslogHandler, SyslogNetHandler
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var Must muster
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func must(h Handler, err error) Handler {
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if err != nil {
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panic(err)
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}
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return h
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}
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type muster struct{}
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func (m muster) FileHandler(path string, fmtr Format) Handler {
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return must(FileHandler(path, fmtr))
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}
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func (m muster) NetHandler(network, addr string, fmtr Format) Handler {
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return must(NetHandler(network, addr, fmtr))
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}
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