Web Application with Gin & Docker-client

• A web application with golang.
• Fetchs running containers info through docker daemon.
• Keeps the information at cache instead of fetching through docker socket for each requesti

Usage

GO

go build main.go
./main

Links

• API: http://localhost:8080/containers

DOCKER

docker-compose up --build

Links

• Prometheus: http://localhost:9099
• Jaeger: http://localhost:16686
• Exporter: http://localhost:2222/metrics
• API: http://localhost:8080/containers

Options

Environment Variable	Default
APP_PORT	8080
LOG_LEVEL	INFO
LOG_FILE	logfile
CACHE_DEFAULT_EXPIRATION_TIME	10
CACHE_CLEANUP_INTERVAL_TIME	10
PROMETHEUS_EXPORTER_ENABLED	false
PROMETHEUS_EXPORTER_PORT	2222 (Update prometheus config)
JAEGER_EXPORTER_ENABLED	false
JAEGER_URL	localhost:14268
DOCKER_HOST

Usecases

• List All Containers: Listing whole containers with a small amount of metadata

curl --location --request GET 'http://localhost:8080/containers/'

• Get Container By ID: Get details for the specified container

curl --location --request GET 'http://localhost:8080/containers/:containerId'

• Run container: Run a container as a daemon (for instance nginx)

curl --location --request POST 'http://localhost:8080/containers' \
--header 'Content-Type: application/json' \
--data-raw '{
    "name": "test-uzumlukek-test",
    "image": "uzumlukek/local-firestore:testing",
    "exposePort": "3000",
    "publishPort": "3000"
}'

• Delete Container By ID: Delete the specified container

curl --location --request DELETE 'http://localhost:8080/containers/:containerId'

Resources

Docker-client

• https://docs.docker.com/engine/api/sdk/examples/
• https://pkg.go.dev/github.com/docker/docker/client#APIClient
• https://medium.com/trendyol-tech/golang-docker-client-ile-container-i%CC%87%C5%9Flemleri-6417884f4dbb

Gin - Web Service

• https://go.dev/doc/tutorial/web-service-gin

Caching

• https://github.com/patrickmn/go-cache

Automapper - DTO & Model

• https://github.com/stroiman/go-automapper

Logging

• https://pkg.go.dev/go.uber.org/zap

Tracing - Opentelemetry & Gin & Jaeger Exporter

• https://opentelemetry.uptrace.dev/instrumentations/go-gin.html#installation
• https://github.com/open-telemetry/opentelemetry-go-contrib/tree/main/instrumentation/github.com/gin-gonic/gin/otelgin
• https://pkg.go.dev/go.opentelemetry.io/otel/exporters
• https://pkg.go.dev/go.opentelemetry.io/otel/exporters/jaeger
• https://github.com/open-telemetry/opentelemetry-go/blob/main/example/jaeger/main.go
• https://github.com/open-telemetry/opentelemetry-go/blob/main/example/prometheus/main.go

Manual Trace Instrumentation

tr := otel.Tracer("gin-gonic")
_, span := tr.Start(c.Request.Context(), "controller")
span.SetAttributes(attribute.Key("limit").String(limit))
span.AddEvent("Container Controller")
defer span.End()

Manual Metric Instrumentation

meter := global.Meter("custom")

observerLock := new(sync.RWMutex)
observerValueToReport := new(float64)
observerAttrsToReport := []attribute.KeyValue{attribute.String("app", "docker-client")}

gaugeObserver, err := meter.AsyncFloat64().Gauge("uptime")
if err != nil {
    log.Panicf("failed to initialize instrument: %v", err)
}
_ = meter.RegisterCallback([]instrument.Asynchronous{gaugeObserver}, func(ctx context.Context) {
    (*observerLock).RLock()
    value := *observerValueToReport
    attrs := observerAttrsToReport
    (*observerLock).RUnlock()
    gaugeObserver.Observe(ctx, value, attrs...)
})

go func() {
    for {
        *observerValueToReport = *observerValueToReport + 1.0
        time.Sleep(time.Second)
    }
}()

Pre-commit

• https://pre-commit.com/
• https://github.com/dnephin/pre-commit-golang

Testing

• https://github.com/golang/mock
• https://github.com/gin-gonic/gin#testing

mockgen -source=service_layer/containerServiceInterface.go -destination=mock/mock_container_service.go -package=mock

Regex

• https://yourbasic.org/golang/regexp-cheat-sheet/