feature: dgraph_txn_aborts metric for prometheus

[darkn3rd]

This adds new metric and unit test for the metric so that txnAborts can be tracked.

Testing

cd dgraph/dgraph/cmd/alpha
go test -v -run TestMetricTxnAborts

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This change is 

[danielmai]

Reviewed 3 of 11 files at r2.
Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @darkn3rd, @manishrjain, and @vvbalaji-dgraph)

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dgraph/cmd/alpha/metrics_test.go, line 39 at r2 (raw file):

ts

What's ts, here? I don't see it set in this test. You should

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dgraph/cmd/alpha/metrics_test.go, line 54 at r2 (raw file):

	txnAbort1, _ := strconv.Atoi(txnAbort.(string))
	require.True(t, ok, "the required metric %s is not found", requiredMetric)

These two lines should be switched. If ok is false, then the strconv panics since the metric isn't there:

$ go test -v -run TestMetricTxnAborts
[Decoder]: Using assembly version of decoder
=== RUN   TestMetricTxnAborts
--- FAIL: TestMetricTxnAborts (0.13s)
panic: interface conversion: interface {} is nil, not string [recovered]
	panic: interface conversion: interface {} is nil, not string

goroutine 53 [running]:
testing.tRunner.func1.1(0x199b600, 0xc000656030)
	/usr/local/go/src/testing/testing.go:940 +0x2f5
testing.tRunner.func1(0xc0003e3b00)
	/usr/local/go/src/testing/testing.go:943 +0x3f9
panic(0x199b600, 0xc000656030)
	/usr/local/go/src/runtime/panic.go:969 +0x166
github.com/dgraph-io/dgraph/dgraph/cmd/alpha.TestMetricTxnAborts(0xc0003e3b00)
	/home/dmai/go/src/github.com/dgraph-io/dgraph/dgraph/cmd/alpha/metrics_test.go:54 +0xb22
testing.tRunner(0xc0003e3b00, 0x1bbb808)
	/usr/local/go/src/testing/testing.go:991 +0xdc
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:1042 +0x357
exit status 2
FAIL	github.com/dgraph-io/dgraph/dgraph/cmd/alpha	0.295s

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dgraph/cmd/alpha/metrics_test.go, line 119 at r2 (raw file):

		matches := metricRegex.FindAllString(line, -1)
		if len(matches) > 0 {
			metricsMap[matches[0]] = matches[1]

Why was this change needed?

[darkn3rd]

Reviewable status: all files reviewed, 3 unresolved discussions (waiting on @danielmai, @manishrjain, and @vvbalaji-dgraph)

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dgraph/cmd/alpha/metrics_test.go, line 39 at r2 (raw file):

Previously, danielmai (Daniel Mai) wrote…

ts

What's ts, here? I don't see it set in this test. You should

It is set to 0 by default, and mutationWithTs() checks if non-zero and append it to the /mutation params.

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dgraph/cmd/alpha/metrics_test.go, line 54 at r2 (raw file):

Previously, danielmai (Daniel Mai) wrote…

	txnAbort1, _ := strconv.Atoi(txnAbort.(string))
	require.True(t, ok, "the required metric %s is not found", requiredMetric)

These two lines should be switched. If ok is false, then the strconv panics since the metric isn't there:

$ go test -v -run TestMetricTxnAborts
[Decoder]: Using assembly version of decoder
=== RUN   TestMetricTxnAborts
--- FAIL: TestMetricTxnAborts (0.13s)
panic: interface conversion: interface {} is nil, not string [recovered]
	panic: interface conversion: interface {} is nil, not string

goroutine 53 [running]:
testing.tRunner.func1.1(0x199b600, 0xc000656030)
	/usr/local/go/src/testing/testing.go:940 +0x2f5
testing.tRunner.func1(0xc0003e3b00)
	/usr/local/go/src/testing/testing.go:943 +0x3f9
panic(0x199b600, 0xc000656030)
	/usr/local/go/src/runtime/panic.go:969 +0x166
github.com/dgraph-io/dgraph/dgraph/cmd/alpha.TestMetricTxnAborts(0xc0003e3b00)
	/home/dmai/go/src/github.com/dgraph-io/dgraph/dgraph/cmd/alpha/metrics_test.go:54 +0xb22
testing.tRunner(0xc0003e3b00, 0x1bbb808)
	/usr/local/go/src/testing/testing.go:991 +0xdc
created by testing.(*T).Run
	/usr/local/go/src/testing/testing.go:1042 +0x357
exit status 2
FAIL	github.com/dgraph-io/dgraph/dgraph/cmd/alpha	0.295s

Got it. Will fix this.

---

dgraph/cmd/alpha/metrics_test.go, line 119 at r2 (raw file):

Previously, danielmai (Daniel Mai) wrote…

		matches := metricRegex.FindAllString(line, -1)
		if len(matches) > 0 {
			metricsMap[matches[0]] = matches[1]

Why was this change needed?

The original code only got the keys. I needed the value for testing, so I added this code to get the values.

[darkn3rd]

Reviewable status: 2 of 3 files reviewed, 3 unresolved discussions (waiting on @danielmai, @manishrjain, and @vvbalaji-dgraph)

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dgraph/cmd/alpha/metrics_test.go, line 39 at r2 (raw file):

Previously, darkn3rd (Joaquin Menchaca) wrote…

It is set to 0 by default, and mutationWithTs() checks if non-zero and append it to the /mutation params.

Done.

---

dgraph/cmd/alpha/metrics_test.go, line 54 at r2 (raw file):

Previously, darkn3rd (Joaquin Menchaca) wrote…

Got it. Will fix this.

Done.

---

dgraph/cmd/alpha/metrics_test.go, line 119 at r2 (raw file):

Previously, darkn3rd (Joaquin Menchaca) wrote…

The original code only got the keys. I needed the value for testing, so I added this code to get the values.

Done.

[danielmai]

Reviewed 1 of 1 files at r3.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @manishrjain and @vvbalaji-dgraph)