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Add zapio.Writer #971
Add zapio.Writer #971
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// Copyright (c) 2021 Uber Technologies, Inc. | ||
// | ||
// Permission is hereby granted, free of charge, to any person obtaining a copy | ||
// of this software and associated documentation files (the "Software"), to deal | ||
// in the Software without restriction, including without limitation the rights | ||
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
// copies of the Software, and to permit persons to whom the Software is | ||
// furnished to do so, subject to the following conditions: | ||
// | ||
// The above copyright notice and this permission notice shall be included in | ||
// all copies or substantial portions of the Software. | ||
// | ||
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
// THE SOFTWARE. | ||
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package zapio | ||
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import ( | ||
"bytes" | ||
"io" | ||
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"go.uber.org/zap" | ||
"go.uber.org/zap/zapcore" | ||
) | ||
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// Writer is an io.Writer that writes to the provided Zap logger, splitting log | ||
// messages on line boundaries. | ||
// | ||
// Writer must be closed when finished to flush buffered data to the logger. | ||
type Writer struct { | ||
Log *zap.Logger // log to write to | ||
Level zapcore.Level // log level to write at | ||
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buff bytes.Buffer | ||
} | ||
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var ( | ||
_ zapcore.WriteSyncer = (*Writer)(nil) | ||
_ io.Closer = (*Writer)(nil) | ||
) | ||
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// Write writes the provided bytes to the underlying logger at the configured | ||
// log level and returns the length of the bytes. | ||
func (w *Writer) Write(bs []byte) (n int, err error) { | ||
// Skip all checks if the level isn't enabled. | ||
if !w.Log.Core().Enabled(w.Level) { | ||
return len(bs), nil | ||
} | ||
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n = len(bs) | ||
for len(bs) > 0 { | ||
bs = w.writeLine(bs) | ||
} | ||
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return n, nil | ||
} | ||
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// writeLine writes a single line from the input, returning the remaining, | ||
// unconsumed bytes. | ||
func (w *Writer) writeLine(line []byte) (remaining []byte) { | ||
idx := bytes.IndexByte(line, '\n') | ||
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if idx < 0 { | ||
// If there are no newlines, buffer the entire string. | ||
w.buff.Write(line) | ||
return nil | ||
} | ||
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// Split on the newline, buffer and flush the left. | ||
line, remaining = line[:idx], line[idx+1:] | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. if There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Na, subslicing like |
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w.buff.Write(line) | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. optional performance optimization: There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. Oh, that's a good idea. That'll be the case a majority of the time anyway. |
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// Log empty messages in the middle of the stream so that we don't lose | ||
// information when the user writes "foo\n\nbar". | ||
w.flush(true /* allowEmpty */) | ||
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return remaining | ||
} | ||
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// Close closes the writer, flushing any buffered data in the process. | ||
func (w *Writer) Close() error { | ||
return w.Sync() | ||
} | ||
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// Sync flushes the buffered data from the writer, even if it doesn't end with | ||
// a newline. | ||
func (w *Writer) Sync() error { | ||
// Don't allow empty messages on explicit Sync calls or on Close | ||
// because we don't want an extraneous empty message at the end of the | ||
// stream -- it's common for files to end with a newline. | ||
w.flush(false /* allowEmpty */) | ||
return nil | ||
} | ||
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// flush flushes the buffered data to the logger, allowing empty messages only | ||
// if the bool is set. | ||
func (w *Writer) flush(allowEmpty bool) { | ||
if allowEmpty || w.buff.Len() > 0 { | ||
if ce := w.Log.Check(w.Level, w.buff.String()); ce != nil { | ||
There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. can we save some allocations using a There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. I wrote a benchmark and tested that. strings.Builder performs the same because it throws away the buffer on each Reset. Given that Zap will not use the string given to Check once we call ce.Write, it might be okay for us to cast the There was a problem hiding this comment. Choose a reason for hiding this commentThe reason will be displayed to describe this comment to others. Learn more. So I tried the unsafe cast. Turns out we can't do that after all. |
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ce.Write() | ||
} | ||
} | ||
w.buff.Reset() | ||
} |
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// Copyright (c) 2021 Uber Technologies, Inc. | ||
// | ||
// Permission is hereby granted, free of charge, to any person obtaining a copy | ||
// of this software and associated documentation files (the "Software"), to deal | ||
// in the Software without restriction, including without limitation the rights | ||
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | ||
// copies of the Software, and to permit persons to whom the Software is | ||
// furnished to do so, subject to the following conditions: | ||
// | ||
// The above copyright notice and this permission notice shall be included in | ||
// all copies or substantial portions of the Software. | ||
// | ||
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | ||
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | ||
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | ||
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | ||
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | ||
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN | ||
// THE SOFTWARE. | ||
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package zapio | ||
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import ( | ||
"io" | ||
"testing" | ||
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"github.com/stretchr/testify/assert" | ||
"github.com/stretchr/testify/require" | ||
"go.uber.org/zap" | ||
"go.uber.org/zap/zapcore" | ||
"go.uber.org/zap/zaptest/observer" | ||
) | ||
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func TestWriter(t *testing.T) { | ||
t.Parallel() | ||
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tests := []struct { | ||
desc string | ||
level zapcore.Level // defaults to info | ||
writes []string | ||
want []zapcore.Entry | ||
}{ | ||
{ | ||
desc: "simple", | ||
writes: []string{ | ||
"foo\n", | ||
"bar\n", | ||
"baz\n", | ||
}, | ||
want: []zapcore.Entry{ | ||
{Level: zap.InfoLevel, Message: "foo"}, | ||
{Level: zap.InfoLevel, Message: "bar"}, | ||
{Level: zap.InfoLevel, Message: "baz"}, | ||
}, | ||
}, | ||
{ | ||
desc: "level too low", | ||
level: zap.DebugLevel, | ||
writes: []string{ | ||
"foo\n", | ||
"bar\n", | ||
}, | ||
want: []zapcore.Entry{}, | ||
}, | ||
{ | ||
desc: "multiple newlines in a message", | ||
level: zap.WarnLevel, | ||
writes: []string{ | ||
"foo\nbar\n", | ||
"baz\n", | ||
"qux\nquux\n", | ||
}, | ||
want: []zapcore.Entry{ | ||
{Level: zap.WarnLevel, Message: "foo"}, | ||
{Level: zap.WarnLevel, Message: "bar"}, | ||
{Level: zap.WarnLevel, Message: "baz"}, | ||
{Level: zap.WarnLevel, Message: "qux"}, | ||
{Level: zap.WarnLevel, Message: "quux"}, | ||
}, | ||
}, | ||
{ | ||
desc: "message split across multiple writes", | ||
level: zap.ErrorLevel, | ||
writes: []string{ | ||
"foo", | ||
"bar\nbaz", | ||
"qux", | ||
}, | ||
want: []zapcore.Entry{ | ||
{Level: zap.ErrorLevel, Message: "foobar"}, | ||
{Level: zap.ErrorLevel, Message: "bazqux"}, | ||
}, | ||
}, | ||
{ | ||
desc: "blank lines in the middle", | ||
writes: []string{ | ||
"foo\n\nbar\nbaz", | ||
}, | ||
want: []zapcore.Entry{ | ||
{Level: zap.InfoLevel, Message: "foo"}, | ||
{Level: zap.InfoLevel, Message: ""}, | ||
{Level: zap.InfoLevel, Message: "bar"}, | ||
{Level: zap.InfoLevel, Message: "baz"}, | ||
}, | ||
}, | ||
{ | ||
desc: "blank line at the end", | ||
writes: []string{ | ||
"foo\nbar\nbaz\n", | ||
}, | ||
want: []zapcore.Entry{ | ||
{Level: zap.InfoLevel, Message: "foo"}, | ||
{Level: zap.InfoLevel, Message: "bar"}, | ||
{Level: zap.InfoLevel, Message: "baz"}, | ||
}, | ||
}, | ||
{ | ||
desc: "multiple blank line at the end", | ||
writes: []string{ | ||
"foo\nbar\nbaz\n\n", | ||
}, | ||
want: []zapcore.Entry{ | ||
{Level: zap.InfoLevel, Message: "foo"}, | ||
{Level: zap.InfoLevel, Message: "bar"}, | ||
{Level: zap.InfoLevel, Message: "baz"}, | ||
{Level: zap.InfoLevel, Message: ""}, | ||
}, | ||
}, | ||
} | ||
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for _, tt := range tests { | ||
tt := tt // for t.Parallel | ||
t.Run(tt.desc, func(t *testing.T) { | ||
t.Parallel() | ||
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core, observed := observer.New(zap.InfoLevel) | ||
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w := Writer{ | ||
Log: zap.New(core), | ||
Level: tt.level, | ||
} | ||
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for _, s := range tt.writes { | ||
_, err := io.WriteString(&w, s) | ||
require.NoError(t, err, "Writer.Write failed.") | ||
} | ||
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assert.NoError(t, w.Close(), "Writer.Close failed.") | ||
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// Turn []observer.LoggedEntry => []zapcore.Entry | ||
got := make([]zapcore.Entry, observed.Len()) | ||
for i, ent := range observed.AllUntimed() { | ||
got[i] = ent.Entry | ||
} | ||
assert.Equal(t, tt.want, got, "Logged entries do not match.") | ||
}) | ||
} | ||
} |
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Doesn't Write usually return len of bytes written? If so, shouldn't this be 0?
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That's a valid point, in that we're not actually writing those bytes, but per https://golang.org/pkg/io/#Writer
So this is less to detect "how much you wrote in reality" but more "how much were you able to write before it failed". If the logger is configured to not log at this level, it's a no-op, but we're still consuming the text, so I figured we'd want to tell the caller we consumed everything.
The alternative here is to return an error stating that the logger is not configured to log at this level, but I suspect that's undesirable.
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Ok, that makes sense. I agree that telling the caller that we consumed everything would be better than returning an error. Thanks!