[ci skip] Update readme

README.md

@@ -1,6 +1,31 @@
 # Asynq [![Build Status](https://travis-ci.com/hibiken/asynq.svg?token=paqzfpSkF4p23s5Ux39b&branch=master)](https://travis-ci.com/hibiken/asynq)
 
-Asynq is a simple asynchronous task queue library in Go.
+Simple, efficent asynchronous task processing library in Go.
+
+## Table of Contents
+
+- [Overview](#overview)
+- [Requirements](#requirements)
+- [Installation](#installation)
+- [Getting Started](#getting-started)
+- [License](#license)
+
+## Overview
+
+Asynq provides a simple interface to asynchronous task processing.
+
+Asynq also ships with a CLI to monitor the queues and take manual actions if needed.
+
+Asynq provides:
+
+- Clear separation of task producer and consumer
+- Ability to schedule task processing in the future
+- Automatic retry of failed tasks with exponential backoff
+- Ability to configure max retry count per task
+- Ability to configure max number of worker goroutines to process tasks
+- Unix signal handling to safely shutdown background processing
+- Enhanced reliability TODO(hibiken): link to wiki page describing this.
+- CLI to query and mutate queues state for mointoring and administrative purposes
 
 ## Requirements
 
@@ -10,7 +35,7 @@ Asynq is a simple asynchronous task queue library in Go.
 ## Installation
 
 ```
-go get -u github.com/hibiken/asynq
+go get github.com/hibiken/asynq
 ```
 
 ## Getting Started
@@ -29,14 +54,14 @@ func main() {
         Addr: "localhost:6379",
     })
 
-    t1 := &asynq.Task{
+    t1 := asynq.Task{
         Type: "send_welcome_email",
         Payload: map[string]interface{}{
           "recipient_id": 1234,
         },
     }
 
-    t2 := &asynq.Task{
+    t2 := asynq.Task{
         Type: "send_reminder_email",
         Payload: map[string]interface{}{
           "recipient_id": 1234,
@@ -44,10 +69,13 @@ func main() {
     }
 
     // process the task immediately.
-    client.Process(t1, time.Now())
+    err := client.Process(&t1, time.Now())
 
     // process the task 24 hours later.
-    client.Process(t2, time.Now().Add(24 * time.Hour))
+    err = client.Process(&t2, time.Now().Add(24 * time.Hour))
+
+    // specify the max number of retry (default: 25)
+    err = client.Process(&t1, time.Now(), asynq.MaxRetry(1))
 }
 ```
 
@@ -59,24 +87,56 @@ func main() {
         Addr: "localhost:6379",
     })
 
-    bg.Run(asynq.HandlerFunc(handler))
+    // Blocks until signal TERM or INT is received.
+    // For graceful shutdown, send signal TSTP to stop processing more tasks
+    // before sending TERM or INT signal.
+    bg.Run(handler)
 }
+```
 
-// if handler returns an error or panics, the task will be retried after some delay.
+The argument to `(*asynq.Background).Run` is an interface `asynq.Handler` which has one method `ProcessTask`.
+
+```go
+// ProcessTask should return nil if the processing of a task
+// is successful.
+//
+// If ProcessTask return a non-nil error or panics, the task
+// will be retried.
+type Handler interface {
+    ProcessTask(*Task) error
+}
+```
+
+The simplest way to implement a handler is to define a function with the same signature and use `asynq.HandlerFunc` adapter type when passing it to `Run`.
+
+```go
 func handler(t *asynq.Task) error {
     switch t.Type {
-        case "send_welcome_email":
-            id, err := t.Payload.GetInt("recipient_id")
-            if err != nil{
-                return err
-            }
-            fmt.Printf("Send Welcome Email to %d\n", id)
+    case "send_welcome_email":
+        id, err := t.Payload.GetInt("recipient_id")
+        if err != nil {
+            return err
+        }
+        fmt.Printf("Send Welcome Email to %d\n", id)
 
-        // ... handle other task types.
+    // ... handle other types ...
 
-        default:
-            return fmt.Errorf("unexpected task type: %s", t.Type)
+    default:
+        return fmt.Errorf("unexpected task type: %s", t.Type)
     }
     return nil
 }
+
+func main() {
+    bg := asynq.NewBackground(10, &asynq.RedisOpt{
+        Addr: "localhost:6379",
+    })
+
+    // Use asynq.HandlerFunc adapter for a handler function
+    bg.Run(asynq.HandlerFunc(handler))
+}
 ```
+
+## License
+
+Asynq is released under the MIT license. See [LICENSE](https://github.com/hibiken/asynq/blob/master/LICENSE).