Category Archives: golang

How go code is being compiled to assembler code

https://go.godbolt.org/z/31FyJ3 I was interested in comparing line 15 vs line 17 of the following code:

package main

import "fmt"

type kv struct {
	key   []byte
	value []byte
}

type sliceMap []kv

func (sm *sliceMap) Add(k, v []byte) {
	kvs := *sm
	if cap(kvs) > len(kvs) {
		kvs = kvs[:len(kvs)+1]
	} else {
		kvs = append(kvs, kv{})
	}
	kv := &kvs[len(kvs)-1]
	kv.key = append(kv.key[:0], k...)
	kv.value = append(kv.value[:0], v...)
	*sm = kvs
}

func main() {
	sm := sliceMap{}
	sm.Add([]byte("foo"), []byte("bar"))
	fmt.Println(sm)
}

package main

import "fmt"

type kv struct {

key []byte

value []byte

}

type sliceMap []kv

func (sm *sliceMap) Add(k, v []byte) {

kvs := *sm

if cap(kvs) > len(kvs) {

kvs = kvs[:len(kvs)+1]

} else {

kvs = append(kvs, kv{})

}

kv := &kvs[len(kvs)-1]

kv.key = append(kv.key[:0], k...)

kv.value = append(kv.value[:0], v...)

*sm = kvs

}

func main() {

sm := sliceMap{}

sm.Add([]byte("foo"), []byte("bar"))

fmt.Println(sm)

}

E2E tests in go

I tried it via ginkgo and gomega. It has Agouti with WebDriver support out of the box, but I didn’t use it as we have grpc API. That’s the example (table tests):

var _ = Describe("GetRoute", func() {
	var (
		srClient sr.Client
		srErr    error
	)

	JustBeforeEach(func() {
		srClient, srErr = GetClient()
	})

	DescribeTable("positive cases",
		func(fromGeoPointID, toGeoPointID int, expectedUID string, expectedCostGreaterThan float64) {
			Expect(srErr).NotTo(HaveOccurred())
			Expect(srClient).NotTo(BeNil())

			response, err := srClient.GetRoute(context.TODO(), &sr.GetRouteRequest{
				FromGeoPointId: int64(fromGeoPointID),
				ToGeoPointId:   int64(toGeoPointID),
				Quantity:       1,
				Volume:         1,
				Weight:         1,
			})

			Expect(err).To(Succeed())
			Expect(response).NotTo(BeNil())
			Expect(response.RouteCost).NotTo(BeNil())
			Expect(response.RouteCost.RouteUid).To(HaveSuffix(expectedUID))
			Expect(response.RouteCost.GetCost()).To(BeNumerically(">", expectedCostGreaterThan))
		},
		Entry("from(geo=3)->to(geo=2)", 3, 2, "-3-2", float64(10)),
	)

var _ = Describe("GetRoute", func() {

var (

srClient sr.Client

srErr error

)

JustBeforeEach(func() {

srClient, srErr = GetClient()

})

DescribeTable("positive cases",

func(fromGeoPointID, toGeoPointID int, expectedUID string, expectedCostGreaterThan float64) {

Expect(srErr).NotTo(HaveOccurred())

Expect(srClient).NotTo(BeNil())

response, err := srClient.GetRoute(context.TODO(), &sr.GetRouteRequest{

FromGeoPointId: int64(fromGeoPointID),

ToGeoPointId: int64(toGeoPointID),

Quantity: 1,

Volume: 1,

Weight: 1,

})

Expect(err).To(Succeed())

Expect(response).NotTo(BeNil())

Expect(response.RouteCost).NotTo(BeNil())

Expect(response.RouteCost.RouteUid).To(HaveSuffix(expectedUID))

Expect(response.RouteCost.GetCost()).To(BeNumerically(">", expectedCostGreaterThan))

Entry("from(geo=3)->to(geo=2)", 3, 2, "-3-2", float64(10)),

)

ORM for go

https://github.com/Masterminds/squirrel Never used it as we always write SQL queries manually. But looks okay for ORM (well, actually a query-builder).

How to make grpc call from shell

1 https://github.com/grpc/grpc/blob/master/doc/command_line_tool.md

grpc_cli call localhost:7020 ChatAPI.GetChats "external_user:{id:'30594028',type:1}, limit:10, offset:0, order:ORDER_DESC, requested_by_external_user:{id:'30594028',type:1},with_unread_count:true"

1	grpc_cli call localhost:7020 ChatAPI.GetChats "external_user:{id:'30594028',type:1}, limit:10, offset:0, order:ORDER_DESC, requested_by_external_user:{id:'30594028',type:1},with_unread_count:true"

2 https://github.com/fullstorydev/grpcurl

grpcurl -plaintext -emit-defaults -d '{"lozon_id": 15515160432000}' -H 'User-Name: grpcurl' localhost:7020 points/FindPointByLozonID

1	grpcurl -plaintext -emit-defaults -d '{"lozon_id": 15515160432000}' -H 'User-Name: grpcurl' localhost:7020 points/FindPointByLozonID

How to analyze the performance of your go application in production

You should definitely use chi’s middleware for running pprof and stuff in your admin panel. That’s the repo — https://github.com/go-chi/chi That’s the profiler — https://github.com/go-chi/chi/blob/master/middleware/profiler.go

Using GOPROXY with go mod

GOPROXY=https://<some_url> go mod download

1	GOPROXY=https://<some_url> go mod download

Nice list of image resizer libs in go

With speedtests and other nice things. https://github.com/fawick/speedtest-resize I tried these two: https://github.com/disintegration/imaging https://github.com/bamiaux/rez They are quite the same talking about file sizes and imaging is muuch easier to use.

Mocking for testing go code

If you’re testing go code and have a huge API you have to mock, you have two options: make your dummy struct with embedded interface and implement only methods you need, or use your own interface that has only methods you need (and change your code to use that). For instance, I had amazon’s s3 …

BDD Framework For Golang

There is a good one: https://github.com/onsi/ginkgo It prefers to use http://onsi.github.io/gomega/ as a matcher.

Golang, PostgreSQL and array_agg

If you have SQL like this: