live loading from stdin

[gitlw]

Adding the support of live loader reading from standard input
Refactored the code around chunk processing, mainly because the checking of
if err == io.EOF
is supposed to be checking the err returned by the ck.Chunk function, however in the current code, the err variable can be overwriten by the ck.Parse function.

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This change is 

[codexnull]

Reviewed 3 of 3 files at r1.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @gitlw)

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chunker/chunk.go, line 283 at r1 (raw file):

	var err error
	if file == "-" {
		f = os.Stdin

Data can already be loaded from standard input by using /dev/stdin as the filename, but is useful on systems that may not have that device (Windows).

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dgraph/cmd/live/run.go, line 226 at r1 (raw file):

// to the loader.reqs channel
func (l *loader) processChunk(chunkBuf *bytes.Buffer, ck chunker.Chunker) {
	if chunkBuf != nil && chunkBuf.Len() > 0 {

Is the entire function body wrapped by this if statement? I the code would be clearer written like:

if chunBuf == nil || chunkBuf.Len() == 0 {
    return
}

<function body>

[gitlw]

Reviewable status: 2 of 3 files reviewed, 2 unresolved discussions (waiting on @codexnull)

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chunker/chunk.go, line 283 at r1 (raw file):

Previously, codexnull (Javier Alvarado) wrote…

Data can already be loaded from standard input by using /dev/stdin as the filename, but is useful on systems that may not have that device (Windows).

Done.

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dgraph/cmd/live/run.go, line 226 at r1 (raw file):

Previously, codexnull (Javier Alvarado) wrote…

Is the entire function body wrapped by this if statement? I the code would be clearer written like:

if chunBuf == nil || chunkBuf.Len() == 0 {
    return
}

<function body>

Done.

[manishrjain]

Got a comment. See if it would be worth doing. Will leave it to @codexnull for the final approval.

Reviewed 2 of 3 files at r1, 1 of 1 files at r2.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @codexnull)

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chunker/chunk.go, line 283 at r1 (raw file):

Previously, gitlw (Lucas Wang) wrote…

Done.

A file named dash can cause confusion for command line args. Why not just have a boolean arg in live loader to accept input from stdin?

[codexnull]

Reviewable status: all files reviewed, 2 unresolved discussions (waiting on @codexnull and @manishrjain)

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chunker/chunk.go, line 283 at r1 (raw file):

Previously, manishrjain (Manish R Jain) wrote…

A file named dash can cause confusion for command line args. Why not just have a boolean arg in live loader to accept input from stdin?

A file named dash to represent stdin/stdout is a Unix/Linux convention. (For example, I used this earlier today: curl -SsL 'https://github.com/dgraph-io/dgraph/releases/download/v1.0.13/dgraph-linux-amd64.tar.gz' | tar zxf -)

I don't think it's worth adding another flag for that, especially since you can already use /dev/stdin as the file if you don't want to use a dash.