From d78abcf58453a045c30c88fb3417f7befc243a34 Mon Sep 17 00:00:00 2001
From: Ken Hibino <ken.hibino7@gmail.com>
Date: Wed, 30 Dec 2020 08:58:50 -0800
Subject: [PATCH] Add API endpoint for listing running servers

---
 conversion_helpers.go | 54 +++++++++++++++++++++++++++++++++++++++++++
 main.go               |  3 +++
 server_handlers.go    | 34 +++++++++++++++++++++++++++
 3 files changed, 91 insertions(+)
 create mode 100644 server_handlers.go

diff --git a/conversion_helpers.go b/conversion_helpers.go
index 313d3be..96c82aa 100644
--- a/conversion_helpers.go
+++ b/conversion_helpers.go
@@ -285,3 +285,57 @@ func toSchedulerEnqueueEvents(in []*asynq.SchedulerEnqueueEvent) []*SchedulerEnq
 	}
 	return out
 }
+
+type ServerInfo struct {
+	ID             string         `json:"id"`
+	Host           string         `json:"host"`
+	PID            int            `json:"pid"`
+	Concurrency    int            `json:"concurrency"`
+	Queues         map[string]int `json:"queue_priorities"`
+	StrictPriority bool           `json:"strict_priority_enabled"`
+	Started        string         `json:"start_time"`
+	Status         string         `json:"status"`
+	ActiveWorkers  []*WorkerInfo  `json:"active_workers"`
+}
+
+func toServerInfo(info *asynq.ServerInfo) *ServerInfo {
+	return &ServerInfo{
+		ID:             info.ID,
+		Host:           info.Host,
+		PID:            info.PID,
+		Concurrency:    info.Concurrency,
+		Queues:         info.Queues,
+		StrictPriority: info.StrictPriority,
+		Started:        info.Started.Format(time.RFC3339),
+		Status:         info.Status,
+		ActiveWorkers:  toWorkerInfoList(info.ActiveWorkers),
+	}
+}
+
+func toServerInfoList(in []*asynq.ServerInfo) []*ServerInfo {
+	out := make([]*ServerInfo, len(in))
+	for i, s := range in {
+		out[i] = toServerInfo(s)
+	}
+	return out
+}
+
+type WorkerInfo struct {
+	Task    *ActiveTask `json:"task"`
+	Started string      `json:"start_time"`
+}
+
+func toWorkerInfo(info *asynq.WorkerInfo) *WorkerInfo {
+	return &WorkerInfo{
+		Task:    toActiveTask(info.Task),
+		Started: info.Started.Format(time.RFC3339),
+	}
+}
+
+func toWorkerInfoList(in []*asynq.WorkerInfo) []*WorkerInfo {
+	out := make([]*WorkerInfo, len(in))
+	for i, w := range in {
+		out[i] = toWorkerInfo(w)
+	}
+	return out
+}
diff --git a/main.go b/main.go
index 09aaaeb..a192d1a 100644
--- a/main.go
+++ b/main.go
@@ -112,6 +112,9 @@ func main() {
 	api.HandleFunc("/queues/{qname}/dead_tasks:run_all", newRunAllDeadTasksHandlerFunc(inspector)).Methods("POST")
 	api.HandleFunc("/queues/{qname}/dead_tasks:batch_run", newBatchRunTasksHandlerFunc(inspector)).Methods("POST")
 
+	// Servers endpoints.
+	api.HandleFunc("/servers", newListServersHandlerFunc(inspector)).Methods("GET")
+
 	// Scheduler Entry endpoints.
 	api.HandleFunc("/scheduler_entries", newListSchedulerEntriesHandlerFunc(inspector)).Methods("GET")
 	api.HandleFunc("/scheduler_entries/{entry_id}/enqueue_events", newListSchedulerEnqueueEventsHandlerFunc(inspector)).Methods("GET")
diff --git a/server_handlers.go b/server_handlers.go
new file mode 100644
index 0000000..921202c
--- /dev/null
+++ b/server_handlers.go
@@ -0,0 +1,34 @@
+package main
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/hibiken/asynq"
+)
+
+// ****************************************************************************
+// This file defines:
+//   - http.Handler(s) for server related endpoints
+// ****************************************************************************
+
+type ListServersResponse struct {
+	Servers []*ServerInfo `json:"servers"`
+}
+
+func newListServersHandlerFunc(inspector *asynq.Inspector) http.HandlerFunc {
+	return func(w http.ResponseWriter, r *http.Request) {
+		srvs, err := inspector.Servers()
+		if err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+		resp := ListServersResponse{
+			Servers: toServerInfoList(srvs),
+		}
+		if err := json.NewEncoder(w).Encode(resp); err != nil {
+			http.Error(w, err.Error(), http.StatusInternalServerError)
+			return
+		}
+	}
+}