API endpoint and associated RPC changes to resolve VMs IP's (#188)

* API endpoint and associated RPC changes to resolve VMs IP's

* Fix "Missing expected argument '<name>'" error when doing "tart set"

* Implement TestIPEndpoint() and IP() method in controller HTTP client

internal/controller/api_vms_ip.go

@@ -0,0 +1,69 @@
+package controller
+
+import (
+	"context"
+	"github.com/cirruslabs/orchard/internal/responder"
+	v1 "github.com/cirruslabs/orchard/pkg/resource/v1"
+	"github.com/cirruslabs/orchard/rpc"
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"net/http"
+	"strconv"
+	"time"
+)
+
+func (controller *Controller) ip(ctx *gin.Context) responder.Responder {
+	if responder := controller.authorize(ctx, v1.ServiceAccountRoleComputeWrite); responder != nil {
+		return responder
+	}
+
+	// Retrieve and parse path and query parameters
+	name := ctx.Param("name")
+
+	waitRaw := ctx.Query("wait")
+	wait, err := strconv.ParseUint(waitRaw, 10, 16)
+	if err != nil {
+		return responder.Code(http.StatusBadRequest)
+	}
+	waitContext, waitContextCancel := context.WithTimeout(ctx, time.Duration(wait)*time.Second)
+	defer waitContextCancel()
+
+	// Look-up the VM
+	vm, responderImpl := controller.waitForVM(waitContext, name)
+	if responderImpl != nil {
+		return responderImpl
+	}
+
+	// Send an IP resolution request and wait for the result
+	session := uuid.New().String()
+	boomerangConnCh, cancel := controller.ipRendezvous.Request(ctx, session)
+	defer cancel()
+
+	err = controller.workerNotifier.Notify(ctx, vm.Worker, &rpc.WatchInstruction{
+		Action: &rpc.WatchInstruction_ResolveIpAction{
+			ResolveIpAction: &rpc.WatchInstruction_ResolveIP{
+				Session: session,
+				VmUid:   vm.UID,
+			},
+		},
+	})
+	if err != nil {
+		controller.logger.Warnf("failed to request VM's IP from the worker %s: %v",
+			vm.Worker, err)
+
+		return responder.Code(http.StatusServiceUnavailable)
+	}
+
+	select {
+	case ip := <-boomerangConnCh:
+		result := struct {
+			IP string `json:"ip"`
+		}{
+			IP: ip,
+		}
+
+		return responder.JSON(http.StatusOK, &result)
+	case <-ctx.Done():
+		return responder.Error(ctx.Err())
+	}
+}