Convert Traffic Ops into a Service Oriented architecture(SOA) product

CHANGELOG.md

@@ -16,6 +16,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Replaces all Traffic Portal Tenant select boxes with a novel tree select box [#6427](https://github.com/apache/trafficcontrol/issues/6427).
 - Traffic Monitor: Add support for `access.log` to TM.
 - Added functionality for login to provide a Bearer token and for that token to be later used for authorization.
+- [Traffic Ops] Added support for backend configurations so that Traffic Ops can act as a reverse proxy for these services [#6754](https://github.com/apache/trafficcontrol/pull/6754).
 - Added functionality for CDN locks, so that they can be shared amongst a list of specified usernames. 
 - [Traffic Ops | Traffic Go Clients | T3C] Add additional timestamp fields to server for queuing and dequeueing config and revalidate updates.
 - Added layered profile feature to 4.0 for `GET` /servers/, `POST` /servers/, `PUT` /servers/{id} and `DELETE` /servers/{id}.

docs/source/admin/traffic_ops.rst

@@ -19,7 +19,7 @@
 ***********
 Traffic Ops
 ***********
-Traffic Ops is quite possible the single most complex and most important Traffic Control component. It has many different configuration options that affect a wide range of other components and their interactions.
+Traffic Ops is quite possibly the single most complex and most important Traffic Control component. It has many different configuration options that affect a wide range of other components and their interactions.
 
 .. _to-install:
 
@@ -257,7 +257,7 @@ While this section contains instructions for running Traffic Ops manually, the o
 
 traffic_ops_golang
 ------------------
-``traffic_ops_golang [--version] [--plugins] [--api-routes] --cfg CONFIG_PATH --dbcfg DB_CONFIG_PATH [--riakcfg RIAK_CONFIG_PATH]``
+``traffic_ops_golang [--version] [--plugins] [--api-routes] --cfg CONFIG_PATH --dbcfg DB_CONFIG_PATH [--riakcfg RIAK_CONFIG_PATH] [--backendcfg BACKEND_CONFIG_PATH]``
 
 .. option:: --cfg CONFIG_PATH
 
@@ -282,6 +282,10 @@ traffic_ops_golang
 
 	.. impl-detail:: The name of this flag is derived from the current database used in the implementation of Traffic Vault - `Riak KV <https://riak.com/products/riak-kv/index.html>`_.
 
+.. option:: --backendcfg BACKEND_CONFIG_PATH
+
+	This optional command line flag specifies the absolute or relative path to a configuration file used by Traffic Ops to act as a reverse proxy and forward requests on the specified paths to the corresponding hosts - `backends.conf`_
+
 .. option:: --version
 
 	Print version information and exit.
@@ -586,6 +590,32 @@ This file sets authentication options for connections to Riak when used as the T
 
 .. impl-detail:: The name of this file is derived from the current database used in the implementation of Traffic Vault - `Riak KV <https://riak.com/products/riak-kv/index.html>`_.
 
+backends.conf
+"""""""""""""
+This file deals with the configuration parameters of running Traffic Ops as a reverse proxy for certain endpoints that need to be served externally by other backend services. It is a JSON-format set of options and their respective values. `traffic_ops_golang`_ will use whatever file is specified (if any) by its :option:`--backendcfg` option. The keys of the file are described below.
+
+:routes: This is an array of options to configure Traffic Ops to forward requests of specified types to the appropriate backends.
+
+	:path:              The regex matching the endpoint that will be served by the backend, for example, :regexp:`^/api/4.0/foo?$`.
+	:method:            The HTTP method for the above mentioned path, for example, ``GET`` or ``PUT``.
+	:routeId:           The integral identifier for the new route being added.
+	:hosts:             An array of the host object, which specifies the protocol, hostname and port where the request (if matched) needs to be forwarded to.
+
+		:protocol:     The protocol/scheme to be followed while forwarding the requests to the backend service.
+		:hostname:     The hostname of the server where the backend service is running.
+		:port:         The port (integer) on the backend server where the service is running.
+
+	:insecure:          A boolean specifying whether or not TO should verify the backend server's certificate chain and host name. This is not recommended for production use. This is an optional parameter, defaulting to ``false`` when not present.
+	:permissions:       An array of permissions (strings) specifying the permissions required by the user to use this API route.
+	:opts:              A collection of key value pairs to control how the requests should be forwarded/ handled, for example, ``"alg": "roundrobin"``. Currently, only ``roundrobin`` is supported (which is also the default if nothing is specified) by Traffic Ops.
+
+Example backends.conf
+'''''''''''''''''''''
+.. include:: ../../../traffic_ops/app/conf/backends.conf
+	:code: json
+	:tab-width: 4
+
+
 Installing the SSL Certificate
 ------------------------------
 By default, Traffic Ops runs as an SSL web server (that is, over HTTPS), and a certificate needs to be installed.

traffic_ops/app/conf/backends.conf

@@ -0,0 +1,52 @@
+{
+  "routes": [
+    {
+      "path": "^/api/4.0/foo?$",
+      "method": "GET",
+      "hosts": [
+        {
+          "protocol": "https",
+          "hostname": "localhost",
+          "port": 8444
+        },
+        {
+          "protocol": "https",
+          "hostname": "localhost",
+          "port": 8445
+        }
+      ],
+      "insecure": true,
+      "permissions": [
+        "CDN:READ"
+      ],
+      "routeId": 123456,
+      "opts": {
+        "alg": "roundrobin"
+      }
+    },
+    {
+      "path": "^/api/4.0/foos?$",
+      "method": "GET",
+      "hosts": [
+        {
+          "protocol": "https",
+          "hostname": "localhost",
+          "port": 8444
+        },
+        {
+          "protocol": "https",
+          "hostname": "localhost",
+          "port": 8445
+        }
+      ],
+      "insecure": true,
+      "permissions": [
+        "CDN:READ"
+      ],
+      "routeId": 123457,
+      "opts": {
+        "alg": "roundrobin"
+      }
+    }
+  ]
+}

traffic_ops/app/conf/production/backends.conf

@@ -0,0 +1,3 @@
+{
+	"routes": [],
+}

traffic_ops/etc/init.d/traffic_ops

@@ -50,7 +50,7 @@ start ()
 	stop
 	echo -e "Starting Traffic Ops\n"
 	ulimit -n 200000 || echo "Setting ulimit max files failed for traffic_ops_golang"
-	cd $TO_DIR && $TO_DIR/bin/traffic_ops_golang -cfg $TO_DIR/conf/cdn.conf -dbcfg $TO_DIR/conf/production/database.conf -riakcfg $TO_DIR/conf/production/riak.conf &
+	cd $TO_DIR && $TO_DIR/bin/traffic_ops_golang -cfg $TO_DIR/conf/cdn.conf -dbcfg $TO_DIR/conf/production/database.conf -riakcfg $TO_DIR/conf/production/riak.conf -backendcfg $TO_DIR/conf/production/backends.conf &
 }
 
 stop ()

traffic_ops/traffic_ops_golang/config/config.go

@@ -36,6 +36,35 @@ import (
 	"github.com/apache/trafficcontrol/lib/go-util"
 )
 
+// Options is a structure used to hold the route configuration options that can be supplied for the backend routes.
+type Options struct {
+	Algorithm string `json:"alg"`
+}
+
+// Host is a structure that holds the host info for the backend route.
+type Host struct {
+	Protocol string `json:"protocol"`
+	Hostname string `json:"hostname"`
+	Port     int    `json:"port"`
+}
+
+// BackendRoute holds all the information about a configured route, for which Traffic Ops serves as a reverse proxy.
+type BackendRoute struct {
+	Path        string   `json:"path"`
+	Method      string   `json:"method"`
+	Hosts       []Host   `json:"hosts"`
+	Opts        Options  `json:"opts"`
+	ID          int      `json:"routeId"`
+	Insecure    bool     `json:"insecure"`
+	Permissions []string `json:"permissions"`
+	Index       int
+}
+
+// BackendConfig is a structure that holds the configuration supplied to Traffic Ops, which makes it act as a reverse proxy to the specified routes.
+type BackendConfig struct {
+	Routes []BackendRoute `json:"routes"`
+}
+
 // Config reflects the structure of the cdn.conf file
 type Config struct {
 	URL                         *url.URL `json:"-"`
@@ -286,6 +315,31 @@ func (c Config) EventLog() log.LogLocation {
 const BlockStartup = true
 const AllowStartup = false
 
+func LoadBackendConfig(backendConfigPath string) (BackendConfig, error) {
+	confBytes, err := ioutil.ReadFile(backendConfigPath)
+	if err != nil {
+		return BackendConfig{}, fmt.Errorf("reading backend conf '%s': %v", backendConfigPath, err)
+	}
+
+	cfg := BackendConfig{}
+	err = json.Unmarshal(confBytes, &cfg)
+	if err != nil {
+		return BackendConfig{}, fmt.Errorf("unmarshalling '%s': %v", backendConfigPath, err)
+	}
+	for _, r := range cfg.Routes {
+		if r.Opts.Algorithm != "" && r.Opts.Algorithm != "roundrobin" {
+			return cfg, errors.New("algorithm can only be roundrobin or blank")
+		}
+		for _, h := range r.Hosts {
+			rawURL := h.Protocol + "://" + h.Hostname + ":" + strconv.Itoa(h.Port)
+			if _, err = url.ParseRequestURI(rawURL); err != nil {
+				return cfg, fmt.Errorf("couldn't convert host info into a valid URI: %v", err)
+			}
+		}
+	}
+	return cfg, nil
+}
+
 func LoadCdnConfig(cdnConfPath string) (Config, error) {
 	// load json from cdn.conf
 	confBytes, err := ioutil.ReadFile(cdnConfPath)

traffic_ops/traffic_ops_golang/routing/middleware/wrappers.go

@@ -212,7 +212,7 @@ func WrapAccessLog(secret string, h http.Handler) http.HandlerFunc {
 					imsType = IMSMISS
 				}
 			}
-			log.EventfRaw(`%s - %s [%s] "%v %v?%v %s" %v %v %v "%v" %v %s`, r.RemoteAddr, user, time.Now().Format(AccessLogTimeFormat), r.Method, r.URL.Path, r.URL.RawQuery, r.Proto, iw.Code, iw.ByteCount, int(time.Now().Sub(start)/time.Millisecond), r.UserAgent(), r.Header.Get(RouteID), imsType)
+			log.EventfRaw(`%s - %s [%s] "%v %v?%v %s" %v %v %v "%v" %v %s`, r.RemoteAddr, user, time.Now().Format(AccessLogTimeFormat), r.Method, r.URL.Path, r.URL.RawQuery, r.Proto, iw.Code, iw.ByteCount, int(time.Now().Sub(start)/time.Millisecond), r.UserAgent(), r.Context().Value(RouteID), imsType)
 		}()
 		h.ServeHTTP(iw, r)
 	}
@@ -276,6 +276,14 @@ func NotImplementedHandler() http.Handler {
 	})
 }
 
+func BackendErrorHandler(code int, userErr error, sysErr error) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.Header().Set(rfc.ContentType, rfc.ApplicationJSON)
+		w.WriteHeader(code)
+		api.HandleErr(w, r, nil, code, userErr, sysErr)
+	})
+}
+
 // DisabledRouteHandler returns a http.Handler which returns a HTTP 5xx code to the client, and an error message indicating the route is currently disabled.
 // This is used for routes which have been disabled via configuration. See config.ConfigTrafficOpsGolang.RoutingBlacklist.DisabledRoutes.
 func DisabledRouteHandler() http.Handler {