Metrics - Cloudwatch v2 by nelz9999 · Pull Request #668 · go-kit/kit

nelz9999 · 2018-02-25T20:40:33Z

Per the conversation in the Slack channel: https://gophers.slack.com/archives/C04S3T99A/p1519410405000323

I have created the metrics/cloudwatch2 package.

This package targets using the V2 SDK (https://github.com/aws/aws-sdk-go-v2). It also opts for using the CloudWatch native client-side aggregation into "StatisticsSet" -
https://docs.aws.amazon.com/AmazonCloudWatch/latest/APIReference/API_StatisticSet.html. (Whereas the existing metrics/cloudwatch package does addition lossy aggregations and just emits a single "Value".) Also, as per CloudWatch idiom, Counters / Histograms / Gauges are all sent to CloudWatch in exactly the same way.

(I mostly cribbed from the existing cloudwatch package, simplified the work it does, and touched up around the edges to adjust to the delta in API between v1 and v2 versions of the AWS SDK.)

Since Histograms/Gauges all reduce down to the exact same behavior as Counters, I created the convert package to easily swap in Histogram/Gauge API semantics. I made it its own package in case any other metrics systems have a need for similar generification... Though if this is an overshoot, I could dumb that down and just isolate it into the cloudwatch2 package.

groob

A few nits.

groob · 2018-02-25T23:24:30Z

metrics/cloudwatch2/cloudwatch2.go

+
+type option func(*CloudWatch)
+
+func (cw *CloudWatch) apply(opt option) {


this method is never used.

Ahh, yup. That's what I get for doin' a copypasta.

groob · 2018-02-25T23:25:22Z

metrics/cloudwatch2/cloudwatch2.go

+		svc:                   svc,
+		counters:              lv.NewSpace(),
+		numConcurrentRequests: 10,
+		logger:                log.NewLogfmtLogger(os.Stderr),


default should be NewNopLogger

groob · 2018-02-25T23:26:03Z

metrics/cloudwatch2/cloudwatch2.go

+// manually or with one of the helper methods.
+func New(namespace string, svc cloudwatchiface.CloudWatchAPI, options ...option) *CloudWatch {
+	cw := &CloudWatch{
+		sem:                   nil, // set below


Should this field be omitted since it's set below?

groob · 2018-02-26T01:59:52Z

metrics/cloudwatch2/cloudwatch2.go

+}
+
+var zero = float64(0.0)
+var zeros = cloudwatch.StatisticSet{


this is only used once, any reason it should be a package var?

My intent was to avoid paying the "construction costs" every time a zero set is needed.

... Should I do something different to make that apparent?

Maybe just a light comment could work.

Sure thing!

groob · 2018-02-26T02:06:22Z

metrics/cloudwatch2/cloudwatch2.go

+
+	var errors = make(chan error, len(batches))
+	for _, batch := range batches {
+		go func(batch []cloudwatch.MetricDatum) {


the goroutines could run as an errorgroup

Oooh, cool! I hadn't yet added errorgroup to my toolbelt. Added!

nelz9999 · 2018-02-28T23:06:16Z

@peterbourgon How are you feeling about this PR?

peterbourgon

Lovely bit of code to read. A few nits.

peterbourgon · 2018-03-02T17:28:37Z

metrics/cloudwatch2/cloudwatch2.go

+	numConcurrentRequests int
+}
+
+type option func(*CloudWatch)


Since this is returned by exported functions, it's nicer to also make it exported. (And commented, etc.)

peterbourgon · 2018-03-02T17:29:38Z

metrics/cloudwatch2/cloudwatch2.go

+
+// WithLogger sets the Logger that will recieve error messages generated
+// during the WriteLoop
+func WithLogger(logger log.Logger) option {


I find it's nice if functional options describe the default behavior if the option isn't invoked. In this case, it might be nice to add: "By default, no logger is used."

peterbourgon · 2018-03-02T17:29:51Z

metrics/cloudwatch2/cloudwatch2.go

+// WithConcurrentRequests sets the upper limit on how many
+// cloudwatch.PutMetricDataRequest may be under way at any
+// given time. If n is greater than 20, 20 is used.
+func WithConcurrentRequests(n int) option {


Similarly: "By default, 10 concurrent requests are used."

peterbourgon · 2018-03-02T17:31:12Z

metrics/cloudwatch2/cloudwatch2.go

+
+	"github.com/aws/aws-sdk-go-v2/aws"
+	"github.com/aws/aws-sdk-go-v2/service/cloudwatch"
+	"github.com/aws/aws-sdk-go-v2/service/cloudwatch/cloudwatchiface"


package cloudwatchiface 🤦‍♂️

Yah. It's supposed to be in support of mocking out their service... But it feels so icky.

peterbourgon · 2018-03-02T17:33:12Z

metrics/cloudwatch2/cloudwatch2.go

+
+func makeDimensions(labelValues ...string) []cloudwatch.Dimension {
+	dimensions := make([]cloudwatch.Dimension, len(labelValues)/2)
+	for i, j := 0, 0; i < len(labelValues); i, j = i+2, j+1 {


Ha! Wild. Nice.

I can't take credit for this... I lifted this directly from the existing cloudwatch package.

peterbourgon · 2018-03-02T17:34:48Z

metrics/convert/convert.go

@@ -0,0 +1,135 @@
+// Package convert provides a way to use Counters, Histograms, or Gauges
+// as one of the other types
+package convert


It feels like this is tailor-made to cloudwatch2, and I'm a little bit scared that folks will see it and think it's something they should be doing in their own code. Would you be OK with moving this underneath the internal/ dir?

peterbourgon · 2018-03-02T17:34:58Z

metrics/cloudwatch2/cloudwatch2_test.go

+	}
+}
+
+type mockCloudWatch struct {


peterbourgon · 2018-03-02T17:35:25Z

metrics/convert/convert_test.go

+	h := NewCounterAsHistogram(c)
+	top := NewHistogramAsCounter(h).With("label", "counter").(histogramCounter)
+	mid := top.h.(counterHistogram)
+	low := mid.c.(*generic.Counter)


Hehe, nice!

nelz9999 · 2018-03-03T19:40:38Z

@peterbourgon Back atcha! 😄

peterbourgon · 2018-03-06T05:08:45Z

Nice! Thanks!

Nelz added 3 commits February 17, 2018 12:51

Enable using counters as the other types

7702703

For completeness - gauge<->histogram

ebc199f

Create metrics/cloudwatch2 pkg

f261280

groob reviewed Feb 26, 2018

View reviewed changes

Nelz added 2 commits February 25, 2018 18:43

Address PR comments

7ba11af

Comment around prebuilt zeros StatisticsSet

9c0b674

peterbourgon reviewed Mar 2, 2018

View reviewed changes

Address PR comments

904b106

peterbourgon merged commit 7b0e27d into go-kit:master Mar 6, 2018

nelz9999 deleted the cloudwatch-v2 branch March 6, 2018 19:37


		type option func(*CloudWatch)

		func (cw *CloudWatch) apply(opt option) {

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nelz9999 commented Feb 25, 2018

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nelz9999 commented Feb 28, 2018

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peterbourgon Mar 2, 2018 • edited Loading Uh oh! There was an error while loading. Please reload this page.

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nelz9999 commented Mar 3, 2018

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peterbourgon commented Mar 6, 2018

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peterbourgon Mar 2, 2018 •

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