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Bugfix for log lines without or delayed newlines results in a file truncated detection and reading the file again #164

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Bugfix for log lines without or delayed newlines results in a file truncated detection and reading the file again #164

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2c7d915
Bugfix for logging lines without or delayed newlines
Feb 14, 2014
41e4a4d
Fixing some more issues (offset calculation, removing CR,...)
tzahari Feb 28, 2014
eb6309a
Small optimizations
tzahari Feb 28, 2014
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49 changes: 34 additions & 15 deletions harvester.go
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Original file line number Diff line number Diff line change
Expand Up @@ -38,11 +38,12 @@ func (h *Harvester) Harvest(output chan *FileEvent) {

// TODO(sissel): Make the buffer size tunable at start-time
reader := bufio.NewReaderSize(h.file, 16<<10) // 16kb buffer by default
buffer := new(bytes.Buffer)

var read_timeout = 10 * time.Second
last_read_time := time.Now()
for {
text, err := h.readline(reader, read_timeout)
text, bytesread, err := h.readline(reader, buffer, read_timeout)

if err != nil {
if err == io.EOF {
Expand Down Expand Up @@ -78,7 +79,7 @@ func (h *Harvester) Harvest(output chan *FileEvent) {
Fields: &h.Fields,
fileinfo: &info,
}
offset += int64(len(*event.Text)) + 1 // +1 because of the line terminator
offset += int64(bytesread)

output <- event // ship the new event downstream
} /* forever */
Expand Down Expand Up @@ -116,38 +117,56 @@ func (h *Harvester) open() *os.File {
return h.file
}

func (h *Harvester) readline(reader *bufio.Reader, eof_timeout time.Duration) (*string, error) {
var buffer bytes.Buffer
func (h *Harvester) readline(reader *bufio.Reader, buffer *bytes.Buffer, eof_timeout time.Duration) (*string, int, error) {
var is_partial bool = true
var newline_length int = 1
start_time := time.Now()

for {
segment, is_partial, err := reader.ReadLine()
segment, err := reader.ReadBytes('\n')
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I haven't fully read this patch, but it looks like this reimplements go's ReadLine() method with respect to partial detection. Is there a bug we should file upstream to the Go developers? Put differently, what caused this to need reimplementing of is_partial?

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As described in #149 we discovered ReadLine() actually treats EOF as an end-of-line delimiter (I checked the pkg source) - which is the root cause of the issue.
So if you have data at the end of the log, with no new line, ReadLine() returns normally with is_partial set to false and you can never know if there was a new line or not - and LSF assumes there was (the +1 we have for offset). So we end up offset too far ahead of the Size() and detect truncation, wrongly.

It's also worth noting http://golang.org/pkg/bufio/#Reader.ReadLine

ReadLine is a low-level line-reading primitive. Most callers should use ReadBytes('\n') or ReadString('\n') instead or use a Scanner.

Using ReadBytes('\n') we can safely ensure that we don't treat EOF as a line delimiter and properly count the \r\n bytes at the end.

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I also think Go have documented the behaviour at EOF. Note the second sentence.

The text returned from ReadLine does not include the line end ("\r\n" or "\n"). No indication or error is given if the input ends without a final line end.

So an upstream patch is probably not viable as it's the defined behaviour.


if segment != nil && len(segment) > 0 {
if segment[len(segment)-1] == '\n' {
// Found a complete line
is_partial = false

// Check if also a CR present
if len(segment) > 1 && segment[len(segment)-2] == '\r' {
newline_length++
}
}

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Line 145. Just needs blank line removing here and at end of block - forget what I said about moved - got it now, needed bufferSize earlier ^^ Coolios

// TODO(sissel): if buffer exceeds a certain length, maybe report an error condition? chop it?
buffer.Write(segment)
}

if err != nil {
if err == io.EOF {
if err == io.EOF && is_partial {
time.Sleep(1 * time.Second) // TODO(sissel): Implement backoff

// Give up waiting for data after a certain amount of time.
// If we time out, return the error (eof)
if time.Since(start_time) > eof_timeout {
return nil, err
return nil, 0, err
}
continue
} else {
log.Println(err)
return nil, err // TODO(sissel): don't do this?
return nil, 0, err // TODO(sissel): don't do this?
}
}

// TODO(sissel): if buffer exceeds a certain length, maybe report an error condition? chop it?
buffer.Write(segment)

// If we got a full line, return the whole line without the EOL chars (CRLF or LF)
if !is_partial {
// If we got a full line, return the whole line.
// Get the str length with the EOL chars (LF or CRLF)
bufferSize := buffer.Len()
str := new(string)
*str = buffer.String()
return str, nil
*str = buffer.String()[:bufferSize - newline_length]
// Reset the buffer for the next line
buffer.Reset()
return str, bufferSize, nil
}
} /* forever read chunks */

return nil, nil
return nil, 0, nil
}
1 change: 1 addition & 0 deletions registrar.go
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Original file line number Diff line number Diff line change
Expand Up @@ -22,6 +22,7 @@ func Registrar(input chan []*FileEvent) {
Source: event.Source,
// take the offset + length of the line + newline char and
// save it as the new starting offset.
// This issues a problem, if the EOL is a CRLF! Then on start it read the LF again and generates a event with an empty line
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This is easy fix. In Harvester just needs offset updating before passing the event down. Then we don't need to do this calculation here at all and can just use event.Offset. Might be easier to do after merge.

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Hi Driskell,
I am too facing this duplicate events pushed.
I tried your https://github.com/driskell/logstash-forwarder.
With the following config

"files": [
{
"paths": [
"/path/to/log1.log"
],
"fields": { "type": "log1" }
},
{
"paths": [
"/path/to/log2.log"
],
"fields": { "type": "log2" }
}
]

I see the messages with the type flag getting misplaced. For instance log1.log gets the log2 type.

Also, is this patch is committed in to the main git repo?
https://github.com/elasticsearch/logstash-forwarder?

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Hi,

This isn't merged yet. I believe @alphazero-es was testing a merge if this with one of my PR but not sure where he got.

I'm not working on my fork of the logstash-forwarder repo anymore. I moved everything to http://github.com/driskell/log-courier and started maintaining it as my own shipper. It has it's own protocol and logstash plugins and there's docs on how to install them to logstash.

Your specific issue was reported at driskell/log-courier#9 and it's now fixed in the develop branch. Hoping to merge to stable at the weekend.

Jason

Offset: event.Offset + int64(len(*event.Text)) + 1,
Inode: ino,
Device: dev,
Expand Down