Add sample Sinatra app and Golang binary sidecar

To be referenced in an upcoming Cloud Foundry blog post.

Inspired by some test apps in the capi-bara-tests acceptance test suite:
cloudfoundry/capi-bara-tests@7a0c511

[#165355813](https://www.pivotaltracker.com/story/show/165355813)

Authored-by: Tim Downey <[email protected]>

Author: tcdowney

README.md

@@ -1,3 +1,14 @@
 # capi-sidecar-samples
 
 Sample apps demonstrating how to use [sidecar processes](http://v3-apidocs.cloudfoundry.org/version/release-candidate/#sidecars) in Cloud Foundry.
+
+## Apps
+This repository currently contains the following sample apps and sidecars.
+
+You can quickly deploy both apps by targeting your Cloud Foundry api using the `cf cli` and running the `push_sample_app_with_sidecar.sh` script.
+
+### config-server-sidecar
+A simple Golang binary that emulates a "configuration server" for the parent app to call out to.
+
+### sidecar-dependent-app
+A simple Sinatra app that calls out to the `config-server-sidecar` binary and echoes back its response.

config-server-sidecar/.gitignore

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+config-server

config-server-sidecar/README.md

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+# Sample "Config Server" Sidecar Process
+
+This is a simple Golang "config server" designed to be used along with the sample `sidecar-dependent-app`.
+It listens on `localhost:$CONFIG_SERVER_PORT/config/` and returns some hard coded "configuration" for the parent app to consume.
+
+
+## Building the binary
+```
+GOOS=linux GOARCH=amd64 go build -o config-server .
+```
+
+## Running the config server
+```
+CONFIG_SERVER_PORT=8082 ./config-server
+```

config-server-sidecar/config_server.go

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+package main
+
+import (
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"os"
+)
+
+func main() {
+	// Emulate an external configuration service
+	http.HandleFunc("/config/", config)
+	fmt.Println("listening...")
+	err := http.ListenAndServe(":"+os.Getenv("CONFIG_SERVER_PORT"), nil)
+	if err != nil {
+		panic(err)
+	}
+}
+
+type Config struct {
+	Scope    string
+	Password string
+}
+
+func config(res http.ResponseWriter, req *http.Request) {
+	config := Config{"some-service.admin", "not-a-real-p4$$w0rd"}
+
+	js, err := json.Marshal(config)
+	if err != nil {
+		panic(err)
+	}
+
+	fmt.Println("Received a request for config.")
+	fmt.Fprintln(res, string(js))
+}

config-server-sidecar/manifest.yml

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+---
+applications:
+- env:
+    GOPACKAGENAME: config-server

push_sample_app_with_sidecar.sh

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+#!/usr/bin/env bash
+
+SAMPLE_APP_PATH="sidecar-dependent-app"
+CONFIG_SERVER_SIDECAR_PATH="config-server-sidecar"
+
+function clean() {
+    rm "${SAMPLE_APP_PATH}/config-server"
+    rm "${CONFIG_SERVER_SIDECAR_PATH}/config-server"
+}
+
+function build_config_server() {
+    pushd ${CONFIG_SERVER_SIDECAR_PATH} > /dev/null
+        GOOS=linux GOARCH=amd64 go build -o config-server .
+    popd > /dev/null
+    cp "${CONFIG_SERVER_SIDECAR_PATH}/config-server" ${SAMPLE_APP_PATH}
+}
+
+function push_app_with_sidecars() {
+    pushd ${SAMPLE_APP_PATH} > /dev/null
+      cf v3-create-app sidecar-dependent-app
+      cf v3-apply-manifest -f manifest.yml
+      cf v3-push sidecar-dependent-app
+    popd > /dev/null
+}
+
+function main() {
+    clean
+    build_config_server
+    push_app_with_sidecars
+}
+
+main

sidecar-dependent-app/.gitignore

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+config-server

sidecar-dependent-app/Gemfile

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+source "http://rubygems.org"
+
+gem "sinatra"
+gem "json"
+gem "typhoeus"
+
+group :test, :development do
+  gem "rspec"
+  gem "rack-test"
+end

sidecar-dependent-app/Gemfile.lock

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+GEM
+  remote: http://rubygems.org/
+  specs:
+    diff-lcs (1.3)
+    ethon (0.12.0)
+      ffi (>= 1.3.0)
+    ffi (1.10.0)
+    json (2.1.0)
+    mustermann (1.0.3)
+    rack (2.0.6)
+    rack-protection (2.0.4)
+      rack
+    rack-test (0.8.3)
+      rack (>= 1.0, < 3)
+    rspec (3.7.0)
+      rspec-core (~> 3.7.0)
+      rspec-expectations (~> 3.7.0)
+      rspec-mocks (~> 3.7.0)
+    rspec-core (3.7.1)
+      rspec-support (~> 3.7.0)
+    rspec-expectations (3.7.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.7.0)
+    rspec-mocks (3.7.0)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.7.0)
+    rspec-support (3.7.1)
+    sinatra (2.0.4)
+      mustermann (~> 1.0)
+      rack (~> 2.0)
+      rack-protection (= 2.0.4)
+      tilt (~> 2.0)
+    tilt (2.0.9)
+    typhoeus (1.3.1)
+      ethon (>= 0.9.0)
+
+PLATFORMS
+  ruby
+
+DEPENDENCIES
+  json
+  rack-test
+  rspec
+  sinatra
+  typhoeus
+
+BUNDLED WITH
+   1.17.3

sidecar-dependent-app/Procfile

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+web: bundle exec rackup config.ru -p $PORT