-
-
Notifications
You must be signed in to change notification settings - Fork 39
/
handler.go
234 lines (204 loc) · 6.19 KB
/
handler.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
package log
import (
"fmt"
"io"
"net"
"os"
"reflect"
"sync"
"github.com/go-stack/stack"
)
// A Logger prints its log records by writing to a Handler.
// The Handler interface defines where and how log records are written.
// Handlers are composable, providing you great flexibility in combining
// them to achieve the logging structure that suits your applications.
type Handler interface {
Log(r *Record) error
// IsLogging returns true if global logging for level is enabled.
IsLogging(Lvl) bool
}
// FuncHandler returns a Handler that logs records with the given
// functions.
func FuncHandler(log func(r *Record) error, isLogging func(Lvl) bool) Handler {
return &funcHandler{
log: log,
isLogging: isLogging,
}
}
type funcHandler struct {
log func(r *Record) error
isLogging func(Lvl) bool
}
func (h funcHandler) Log(r *Record) error {
return h.log(r)
}
func (h funcHandler) IsLogging(level Lvl) bool {
return h.isLogging(level)
}
// StreamHandler writes log records to an io.Writer
// with the given format. StreamHandler can be used
// to easily begin writing log records to other
// outputs.
//
// StreamHandler wraps itself with LazyHandler and SyncHandler
// to evaluate Lazy objects and perform safe concurrent writes.
func StreamHandler(wr io.Writer, fmtr Format) Handler {
h := FuncHandler(func(r *Record) error {
_, err := wr.Write(fmtr.Format(r))
return err
}, func(Lvl) bool { return true })
return LazyHandler(SyncHandler(h))
}
// SyncHandler can be wrapped around a handler to guarantee that
// only a single Log operation can proceed at a time. It's necessary
// for thread-safe concurrent writes.
func SyncHandler(h Handler) Handler {
var mu sync.Mutex
return FuncHandler(func(r *Record) error {
mu.Lock()
err := h.Log(r)
mu.Unlock()
return err
}, h.IsLogging)
}
// FileHandler returns a handler which writes log records to the give file
// using the given format. If the path
// already exists, FileHandler will append to the given file. If it does not,
// FileHandler will create the file with mode 0644.
func FileHandler(path string, fmtr Format) (Handler, error) {
f, err := os.OpenFile(path, os.O_CREATE|os.O_APPEND|os.O_WRONLY, 0644)
if err != nil {
return nil, err
}
return closingHandler{f, StreamHandler(f, fmtr)}, nil
}
// NetHandler opens a socket to the given address and writes records
// over the connection.
func NetHandler(network, addr string, fmtr Format) (Handler, error) {
conn, err := net.Dial(network, addr)
if err != nil {
return nil, err
}
return closingHandler{conn, StreamHandler(conn, fmtr)}, nil
}
// XXX: closingHandler is essentially unused at the moment
// it's meant for a future time when the Handler interface supports
// a possible Close() operation
type closingHandler struct {
io.WriteCloser
Handler
}
func (h *closingHandler) Close() error {
return h.WriteCloser.Close()
}
// FilterHandler returns a Handler that only writes records to the
// wrapped Handler if the given function evaluates true. For example,
// to only log records where the 'err' key is not nil:
//
// logger.SetHandler(FilterHandler(func(r *Record) bool {
// for i := 0; i < len(r.Ctx); i += 2 {
// if r.Ctx[i] == "err" {
// return r.Ctx[i+1] != nil
// }
// }
// return false
// }, h))
//
func FilterHandler(fn func(r *Record) bool, h Handler) Handler {
return FuncHandler(func(r *Record) error {
if fn(r) {
return h.Log(r)
}
return nil
}, h.IsLogging)
}
// LvlFilterHandler returns a Handler that only writes
// records which are less than the given verbosity
// level to the wrapped Handler. For example, to only
// log Error/Crit records:
//
// log.LvlFilterHandler(log.LvlError, log.StdoutHandler)
//
func LvlFilterHandler(maxLvl Lvl, h Handler) Handler {
return FilterHandler(func(r *Record) (pass bool) {
return r.Lvl <= maxLvl
}, h)
}
// LazyHandler writes all values to the wrapped handler after evaluating
// any lazy functions in the record's context. It is already wrapped
// around StreamHandler and SyslogHandler in this library, you'll only need
// it if you write your own Handler.
func LazyHandler(h Handler) Handler {
return FuncHandler(func(r *Record) error {
// go through the values (odd indices) and reassign
// the values of any lazy fn to the result of its execution
hadErr := false
for i := 1; i < len(r.Ctx); i += 2 {
lz, ok := r.Ctx[i].(Lazy)
if ok {
v, err := evaluateLazy(lz)
if err != nil {
hadErr = true
r.Ctx[i] = err
} else {
if cs, ok := v.(stack.CallStack); ok {
v = cs.TrimBelow(r.Call).TrimRuntime()
}
r.Ctx[i] = v
}
}
}
if hadErr {
r.Ctx = append(r.Ctx, errorKey, "bad lazy")
}
return h.Log(r)
}, h.IsLogging)
}
func evaluateLazy(lz Lazy) (interface{}, error) {
t := reflect.TypeOf(lz.Fn)
if t.Kind() != reflect.Func {
return nil, fmt.Errorf("INVALID_LAZY, not func: %+v", lz.Fn)
}
if t.NumIn() > 0 {
return nil, fmt.Errorf("INVALID_LAZY, func takes args: %+v", lz.Fn)
}
if t.NumOut() == 0 {
return nil, fmt.Errorf("INVALID_LAZY, no func return val: %+v", lz.Fn)
}
value := reflect.ValueOf(lz.Fn)
results := value.Call([]reflect.Value{})
if len(results) == 1 {
return results[0].Interface(), nil
} else {
values := make([]interface{}, len(results))
for i, v := range results {
values[i] = v.Interface()
}
return values, nil
}
}
// DiscardHandler reports success for all writes but does nothing.
// It is useful for dynamically disabling logging at runtime via
// a Logger's SetHandler method.
func DiscardHandler() Handler {
return FuncHandler(func(r *Record) error {
return nil
}, func(Lvl) bool { return false })
}
// The Must object provides the following Handler creation functions
// which instead of returning an error parameter only return a Handler
// and panic on failure: FileHandler, NetHandler, SyslogHandler, SyslogNetHandler
var Must muster
func must(h Handler, err error) Handler {
if err != nil {
panic(err)
}
return h
}
type muster struct{}
func (m muster) FileHandler(path string, fmtr Format) Handler {
return must(FileHandler(path, fmtr))
}
func (m muster) NetHandler(network, addr string, fmtr Format) Handler {
return must(NetHandler(network, addr, fmtr))
}