Author Archives: bullgare
Force ipv4 for golang http client
Sometimes you want to prevent your http client from using ipv6/tcp6. That’s how you do it.
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dialer := &net.Dialer{ Timeout: dialTimeout, KeepAlive: keepAliveTimeout, } transport := &http.Transport{ Proxy: http.ProxyFromEnvironment, ForceAttemptHTTP2: false, DialContext: func(ctx context.Context, network string, addr string) (net.Conn, error) { ipv4, err := resolveIPv4(addr) if err != nil { return nil, err } return dialer.DialContext(ctx, network, ipv4) }, } httpClient := &http.Client{ Transport: transport, Timeout: args.HTTPTimeout, } // resolveIPv4 resolves an address to IPv4 address. func resolveIPv4(addr string) (string, error) { url := strings.Split(addr, ":") m := new(dns.Msg) m.SetQuestion(dns.Fqdn(url[0]), dns.TypeA) m.RecursionDesired = true config, _ := dns.ClientConfigFromFile("/etc/resolv.conf") c := new(dns.Client) r, _, err := c.Exchange(m, net.JoinHostPort(config.Servers[0], config.Port)) if err != nil { return "", err } for _, ans := range r.Answer { if a, ok := ans.(*dns.A); ok { url[0] = a.A.String() } } return strings.Join(url, ":"), nil } |
Mocking for unit-tests and e2e-tests in golang
Some patterns to test your golang app. Mocking an interface
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mockS3 := &mocks.S3API{} mockResultFn := func(input *s3.ListObjectsInput) *s3.ListObjectsOutput { output := &s3.ListObjectsOutput{} output.SetCommonPrefixes([]*s3.CommonPrefix{ &s3.CommonPrefix{ Prefix: aws.String("2017-01-01"), }, }) return output } // NB: .Return(...) must return the same signature as the method being mocked. // In this case it's (*s3.ListObjectsOutput, error). mockS3.On("ListObjects", mock.MatchedBy(func(input *s3.ListObjectsInput) bool { return input.Delimiter != nil && *input.Delimiter == "/" && input.Prefix == nil })).Return(mockResultFn, nil) listingInput := &s3.ListObjectsInput{ Bucket: aws.String("foo"), Delimiter: aws.String("/"), } listingOutput, err := mockS3.ListObjects(listingInput) if err != nil { panic(err) } for _, x := range listingOutput.CommonPrefixes { fmt.Printf("common prefix: %+v\n", *x) } |
https://github.com/vektra/mockery Mocking SQL database
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// a successful case func TestShouldUpdateStats(t *testing.T) { db, mock, err := sqlmock.New() if err != nil { t.Fatalf("an error '%s' was not expected when opening a stub database connection", err) } defer db.Close() mock.ExpectBegin() mock.ExpectExec("UPDATE products").WillReturnResult(sqlmock.NewResult(1, 1)) mock.ExpectExec("INSERT INTO product_viewers").WithArgs(2, 3).WillReturnResult(sqlmock.NewResult(1, 1)) mock.ExpectCommit() // now we execute our method if err = recordStats(db, 2, 3); err != nil { t.Errorf("error was not expected while updating stats: %s", err) } // we make sure that all expectations were met if err := mock.ExpectationsWereMet(); err != nil { t.Errorf("there were unfulfilled expectations: %s", err) } } |
https://github.com/DATA-DOG/go-sqlmock Mocking HTTP server for unit-tests
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handler := func(w http.ResponseWriter, r *http.Request) { io.WriteString(w, "<html><body>Hello World!</body></html>") } req := httptest.NewRequest("GET", "http://example.com/foo", nil) w := httptest.NewRecorder() handler(w, req) resp := w.Result() body, _ := ioutil.ReadAll(resp.Body) fmt.Println(resp.StatusCode) fmt.Println(resp.Header.Get("Content-Type")) fmt.Println(string(body)) |
https://golang.org/pkg/net/http/httptest/ Stubbing HTTP server for e2e-tests
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{ "host": "example.com", "method": "GET|POST|PUT|PATCH|... (Mandatory)", "path": "/your/path/:variable (Mandatory)", "queryStringParameters": { "name": ["value"], "name": ["value", "value"] }, "headers": { "name": ["value"] }, "cookies": { "name": "value" }, "body": "Expected Body" } |
https://github.com/jmartin82/mmock Mocking for e2e-tests with dockertest
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var db *sql.DB func TestMain(m *testing.M) { // uses a sensible default on windows (tcp/http) and linux/osx (socket) pool, err := dockertest.NewPool("") if err != nil { log.Fatalf("Could not connect to docker: %s", err) } // pulls an image, creates a container based on it and runs it resource, err := pool.Run("mysql", "5.7", []string{"MYSQL_ROOT_PASSWORD=secret"}) if err != nil { log.Fatalf("Could not start resource: %s", err) } // exponential backoff-retry, because the application in the container might not be ready to accept connections yet if err := pool.Retry(func() error { var err error db, err = sql.Open("mysql", fmt.Sprintf("root:secret@(localhost:%s)/mysql", resource.GetPort("3306/tcp"))) if err != nil { return err } return db.Ping() }); err != nil { log.Fatalf("Could not connect to docker: %s", err) } code := m.Run() // You can't defer this because os.Exit doesn't care for defer if err := pool.Purge(resource); err != nil { log.Fatalf("Could not purge resource: %s", err) } os.Exit(code) } func TestSomething(t *testing.T) { // db.Query() } |
https://github.com/ory/dockertest
Install go2 beta on MacOS
A quick guide on installing golang v2 development revision. It works for my MacOS Big Sur (with an Intel processor).
Using DataDog on your CentOs
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DD_AGENT_MAJOR_VERSION=7 DD_API_KEY=<your-key> DD_SITE="datadoghq.eu" bash -c "$(curl -L https://s3.amazonaws.com/dd-agent/scripts/install_script.sh)" sudo nano /etc/datadog-agent/datadog.yaml # uncomment logs_enabled: true sudo systemctl restart datadog-agent sudo mkdir /etc/datadog-agent/conf.d/go.d sudo nano /etc/datadog-agent/conf.d/go.d/conf.yaml # and add contents from the url below |
https://app.datadoghq.eu/logs/onboarding/server https://docs.datadoghq.com/agent/faq/error-restarting-agent-already-listening-on-a-configured-port/ Or, if you want a dockerized version of DataDog agent, and you want to listen to docker logs, you can do this:
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docker run -d --name datadog-agent \ -e DD_API_KEY=<DATADOG_API_KEY> \ -e DD_LOGS_ENABLED=true \ -e DD_LOGS_CONFIG_CONTAINER_COLLECT_ALL=true \ -e DD_CONTAINER_EXCLUDE_LOGS="name:datadog-agent" \ -e DD_SITE="datadoghq.eu" \ -v /var/run/docker.sock:/var/run/docker.sock:ro \ -v /proc/:/host/proc/:ro \ -v /opt/datadog-agent/run:/opt/datadog-agent/run:rw \ -v /sys/fs/cgroup/:/host/sys/fs/cgroup:ro \ datadog/agent:latest |
More info here — https://docs.datadoghq.com/agent/docker/log/?tab=containerinstallation Then you will see your logs here — https://app.datadoghq.eu/logs
Install go with gvm on MacOS Big Sur
I used to use gvm for this — https://github.com/moovweb/gvm. But initial installation of go from scratch does not work for Big Sur as 1.4 does not have a binary for this OS (this command fails — gvm install go1.4 -B). To use gvm, you can do this: 0. Install gvm — bash <
Use brew cask to install software on MacOS
That’s the way to automate your favorite apps installed on a new machine with one command and a config file. https://github.com/Homebrew/homebrew-cask. You can either install apps manually with a command like brew cask install goland or install all your apps by provided config. One downside is that it has a limited list of apps supported …
Mac fan control
It is interesting to check mac’s CPU/GPU temperature and manage fan speed. You can do it with https://crystalidea.com/macs-fan-control/download
Add all lines from a .env file to environment
zsh:
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zsh ./configs/dev/dev.env|sed 's/#1.*$//g'|grep '^[^#]'|grep -v '^$'|sed 's/^/export /g' |
bash:
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bash ./configs/dev/dev.env|sed 's/#1.*$//g'|grep '^[^#]'|grep -v '^$'|sed 's/^/export /g' |
to output to stdout
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cat ./configs/dev/dev.env|sed 's/#1.*$//g'|grep '^[^#]'|grep -v '^$'|sed 's/^/export /g' |
prepend running a command (did not try it, but something similar):
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env $(cat ./configs/dev/dev.env|sed 's/#.*$//g'|grep '^[^#]'|grep -v '^$'|xargs) |
Complete list of swagger options to protobuf file
Here is an example with many options that help generate proper swagger out of protofile. Original URL — https://raw.githubusercontent.com/grpc-ecosystem/grpc-gateway/master/examples/internal/proto/examplepb/a_bit_of_everything.proto.
Refactor your code and know it’s completely backward compatible
The idea is to run 2 versions of code on production: 1 (control group) — is your old implementation which will be returned to the end user 2 (the experiment) — is a new implementation which results will be checked against the control group and logged It will be run asynchronously and only for a …