Merge pull request #83 from lukaszbudnik/ping-reachability-analyzer

implemented ping and reachability analyzer functionality

.gitignore

@@ -1,2 +1,3 @@
 debug.test
+cover.out
 yosoy

Dockerfile

@@ -2,8 +2,12 @@ FROM golang:1.21-alpine as builder
 
 LABEL maintainer="Łukasz Budnik [email protected]"
 
+# install prerequisites
+RUN apk update && apk add git
+
 # build yosoy
 ADD . /go/yosoy
+RUN go env -w GOPROXY=direct
 RUN cd /go/yosoy && go build
 
 FROM alpine:3.18

README.md

@@ -1,15 +1,18 @@
 # yosoy ![Go](https://github.com/lukaszbudnik/yosoy/workflows/Go/badge.svg) ![Docker](https://github.com/lukaszbudnik/yosoy/workflows/Docker%20Image%20CI/badge.svg)
 
-yosoy is a HTTP service for stubbing and prototyping distributed applications. It is a service which will introduce itself to the caller and print some useful information about its environment. "Yo soy" in español means "I am".
+yosoy is an HTTP service for stubbing and prototyping distributed applications. It is a service that introduces itself to the caller and prints useful information about its runtime environment. 
 
-yosoy is extremely useful when creating a distributed application stub and you need to see more meaningful responses than a default nginx welcome page.
+yosoy is extremely useful when creating a stub for a distributed application, as it provides more meaningful responses than, for example, a default nginx welcome page. Further, yosoy incorporates a built-in reachability analyzer to facilitate troubleshooting connectivity issues in distributed systems. A dedicated reachability analyzer endpoint validates network connectivity between yosoy and remote endpoints.
 
 Typical use cases include:
 
-- testing HTTP routing & ingress
-- testing HTTP load balancing
-- testing HTTP caching
-- stubbing and prototyping distributed applications
+- Testing HTTP routing and ingress
+- Testing HTTP load balancing
+- Testing HTTP caching
+- Executing reachability analysis
+- Stubbing and prototyping distributed applications
+
+"Yo soy" means "I am" in Spanish.
 
 ## API
 
@@ -31,27 +34,24 @@ yosoy responds to all requests with a JSON containing the information about:
   - Env variables if `YOSOY_SHOW_ENVS` is set to `true`, `yes`, `on`, or `1`
   - Files' contents if `YOSOY_SHOW_FILES` is set to a comma-separated list of (valid) files
 
-Checkout out [Sample JSON response](#sample-json-response) below to see how useful yosoy is when troubleshooting/stubbing/prototyping distributed applications.
+Check [Sample JSON response](#sample-json-response) to see how you can use yosoy for stubbing/prototyping/troubleshooting distributed applications.
+
+Check [ping/reachability analyzer](#pingreachability-analyzer) to see how you can use yosoy for troubleshooting network connectivity.
 
 ## Docker image
 
-The docker image is available on docker hub:
+The docker image is available on docker hub and ghcr.io:
 
 ```sh
 docker pull lukasz/yosoy
-```
-
-and ghcr.io:
-
-```sh
 docker pull ghcr.io/lukaszbudnik/yosoy
 ```
 
 It exposes HTTP service on port 80.
 
 ## Kubernetes example
 
-There is a sample Kubernetes deployment file in the `test` folder. It uses both `YOSOY_SHOW_ENVS` and `YOSOY_SHOW_FILES`. The deployment uses Kubernetes Downward API to expose labels and annotations as volume files which are then returned by yosoy.
+There is a sample Kubernetes deployment file in the `test` folder. It uses both `YOSOY_SHOW_ENVS` and `YOSOY_SHOW_FILES` features. The deployment uses Kubernetes Downward API to expose labels and annotations as volume files which are then returned by yosoy.
 
 Deploy it to minikube and execute curl to the service a couple of times:
 
@@ -131,3 +131,42 @@ A sample yosoy JSON response to a request made from a single page application (S
   }
 }
 ```
+
+## ping/reachability analyzer
+
+yosoy includes a simple ping/reachability analyzer. You can use this functionality when prototyping distributed systems to validate whether a given component can reach a specific endpoint. yosoy exposes a dedicated `/_/yosoy/ping` endpoint which accepts the following 3 query parameters:
+
+* `h` - required - hostname of the endpoint
+* `p` - required - port of the endpoint
+* `n` - optional - network, all valid Go networks are supported (including the most popular ones like `tcp`, `udp`, IPv4, IPV6, etc.). If `n` parameter is not provided, it defaults to `tcp`. Go will throw an error if `n` parameter will be set to unknown network.
+
+For example, to test if yosoy can connect to `google.com` on port `443` using default `tcp` network use the following command:
+
+```bash
+curl "$URL/_/yosoy/ping?h=google.com&p=443"
+```
+
+To see an unsuccessful response you may use localhost with some random port number:
+
+```bash
+curl "$URL/_/yosoy/ping?h=127.0.0.1&p=12345"
+```
+
+## Building and testing locally
+
+Here are some commands to get you started.
+
+Run yosoy directly on port 80.
+
+```bash
+go test -coverprofile cover.out
+go tool cover -html=cover.out
+go run server.go
+```
+
+Building local Docker container and run it on port 8080:
+
+```bash
+docker build -t yosoy-local:latest .
+docker run --rm --name yosoy-local -p 8080:80 yosoy-local:latest
+```

go.mod

@@ -1,9 +1,16 @@
 module github.com/lukaszbudnik/yosoy
 
-go 1.16
+go 1.21
 
 require (
 	github.com/gorilla/handlers v1.5.2
 	github.com/gorilla/mux v1.8.1
 	github.com/stretchr/testify v1.8.4
 )
+
+require (
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/felixge/httpsnoop v1.0.3 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

go.sum

@@ -1,4 +1,3 @@
-github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
 github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
 github.com/felixge/httpsnoop v1.0.3 h1:s/nj+GCswXYzN5v2DpNMuMQYe+0DDwt5WVCU6CWBdXk=
@@ -9,15 +8,9 @@ github.com/gorilla/mux v1.8.1 h1:TuBL49tXwgrFYWhqrNgrUNEY92u81SPhu7sTdzQEiWY=
 github.com/gorilla/mux v1.8.1/go.mod h1:AKf9I4AEqPTmMytcMc0KkNouC66V3BtZ4qD5fmWSiMQ=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
-github.com/stretchr/objx v0.4.0/go.mod h1:YvHI0jy2hoMjB+UWwv71VJQ9isScKT/TqJzVSSt89Yw=
-github.com/stretchr/objx v0.5.0/go.mod h1:Yh+to48EsGEfYuaHDzXPcE3xhTkx73EhmCGUpEOglKo=
-github.com/stretchr/testify v1.7.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
-github.com/stretchr/testify v1.8.0/go.mod h1:yNjHg4UonilssWZ8iaSj1OCr/vHnekPRkoO+kdMU+MU=
 github.com/stretchr/testify v1.8.4 h1:CcVxjf3Q8PM0mHUKJCdn+eZZtm5yQwehR5yeSVQQcUk=
 github.com/stretchr/testify v1.8.4/go.mod h1:sz/lmYIOXD/1dqDmKjjqLyZ2RngseejIcXlSw2iwfAo=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405 h1:yhCVgyC4o1eVCa2tZl7eS0r+SDo693bJlVdllGtEeKM=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
-gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
 gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
 gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

server.go

@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/json"
 	"log"
+	"net"
 	"net/http"
 	"os"
 	"strings"
@@ -26,6 +27,14 @@ type response struct {
 	Files        map[string]string   `json:"files,omitempty"`
 }
 
+type errorResponse struct {
+	Error string `json:"error"`
+}
+
+type successResponse struct {
+	Message string `json:"message"`
+}
+
 var counter = 0
 var hostname = os.Getenv("HOSTNAME")
 
@@ -85,6 +94,55 @@ func handler(w http.ResponseWriter, req *http.Request) {
 	json.NewEncoder(w).Encode(response)
 }
 
+func ping(w http.ResponseWriter, req *http.Request) {
+	// get h, p, t parameters from query string
+	hostname := req.URL.Query().Get("h")
+	port := req.URL.Query().Get("p")
+	network := req.URL.Query().Get("n")
+
+	// return HTTP BadRequest when hostname is empty
+	if hostname == "" {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Header().Add("Content-Type", "application/json; charset=utf-8")
+		json.NewEncoder(w).Encode(&errorResponse{"hostname is empty"})
+		return
+	}
+	// return HTTP BadRequest when port is empty
+	if port == "" {
+		w.WriteHeader(http.StatusBadRequest)
+		w.Header().Add("Content-Type", "application/json; charset=utf-8")
+		json.NewEncoder(w).Encode(&errorResponse{"port is empty"})
+		return
+	}
+	// if network is empty set default to tcp
+	if network == "" {
+		network = "tcp"
+	}
+	// ping the hostname and port by opening a socket
+	err := pingHost(hostname, port, network)
+	if err != nil {
+		w.WriteHeader(http.StatusInternalServerError)
+		w.Header().Add("Content-Type", "application/json; charset=utf-8")
+		json.NewEncoder(w).Encode(&errorResponse{err.Error()})
+		return
+	}
+	// return HTTP OK
+	w.WriteHeader(http.StatusOK)
+	w.Header().Add("Content-Type", "application/json; charset=utf-8")
+	json.NewEncoder(w).Encode(&successResponse{"ping succeeded"})
+}
+
+func pingHost(hostname, port, network string) error {
+	// open a socket to hostname and port
+	conn, err := net.Dial(network, hostname+":"+port)
+	if err != nil {
+		return err
+	}
+	// close the socket
+	conn.Close()
+	return nil
+}
+
 func remoteAddrWithoutPort(req *http.Request) string {
 	remoteAddr := req.RemoteAddr
 	if index := strings.LastIndex(remoteAddr, ":"); index > 0 {
@@ -99,6 +157,7 @@ func main() {
 	r := mux.NewRouter()
 
 	r.Handle("/favicon.ico", r.NotFoundHandler)
+	r.HandleFunc("/_/yosoy/ping", ping).Methods(http.MethodGet)
 	r.PathPrefix("/").HandlerFunc(preflight).Methods(http.MethodOptions)
 	r.PathPrefix("/").HandlerFunc(handler).Methods(http.MethodGet, http.MethodPut, http.MethodPatch, http.MethodPost, http.MethodDelete, http.MethodConnect, http.MethodHead, http.MethodTrace)