refactor keep-alive; update guide

guide/src/SUMMARY.md

@@ -3,9 +3,9 @@
 [Quickstart](./qs_1.md)
 - [Getting Started](./qs_2.md)
 - [Application](./qs_3.md)
+- [Server](./qs_3_5.md)
 - [Handler](./qs_4.md)
 - [Errors](./qs_4_5.md)
-- [State](./qs_6.md)
 - [URL Dispatch](./qs_5.md)
 - [Request & Response](./qs_7.md)
 - [WebSockets](./qs_9.md)

guide/src/qs_3.md

@@ -56,3 +56,46 @@ fn main() {
 ```
 
 All `/app1` requests route to first application, `/app2` to second and then all other to third.
+
+## State
+
+Application state is shared with all routes and resources within same application.
+State could be accessed with `HttpRequest::state()` method as a read-only item
+but interior mutability pattern with `RefCell` could be used to archive state mutability.
+State could be accessed with `HttpContext::state()` in case of http actor. 
+State also available to route matching predicates and middlewares.
+
+Let's write simple application that uses shared state. We are going to store requests count
+in the state: 
+ 
+```rust
+# extern crate actix;
+# extern crate actix_web;
+# 
+use actix_web::*;
+use std::cell::Cell;
+
+// This struct represents state
+struct AppState {
+    counter: Cell<usize>,
+}
+
+fn index(req: HttpRequest<AppState>) -> String {
+    let count = req.state().counter.get() + 1; // <- get count
+    req.state().counter.set(count);            // <- store new count in state
+
+    format!("Request number: {}", count)       // <- response with count
+}
+
+fn main() {
+    Application::with_state(AppState{counter: Cell::new(0)})
+        .resource("/", |r| r.method(Method::GET).f(index))
+        .finish();
+}
+```
+
+Note on application state, http server accepts application factory rather than application
+instance. Http server construct application instance for each thread, so application state
+must be constructed multiple times. If you want to share state between different thread
+shared object should be used, like `Arc`. Application state does not need to be `Send` and `Sync`
+but application factory must be `Send` + `Sync`.

guide/src/qs_6.md

@@ -1,37 +0,0 @@
-# Application state
-
-Application state is shared with all routes and resources within same application.
-State could be accessed with `HttpRequest::state()` method as a read-only item
-but interior mutability pattern with `RefCell` could be used to archive state mutability.
-State could be accessed with `HttpContext::state()` in case of http actor. 
-State also available to route matching predicates. State is not available
-to application middlewares, middlewares receives `HttpRequest<()>` object.
-
-Let's write simple application that uses shared state. We are going to store requests count
-in the state: 
- 
-```rust
-# extern crate actix;
-# extern crate actix_web;
-# 
-use actix_web::*;
-use std::cell::Cell;
-
-// This struct represents state
-struct AppState {
-    counter: Cell<usize>,
-}
-
-fn index(req: HttpRequest<AppState>) -> String {
-    let count = req.state().counter.get() + 1; // <- get count
-    req.state().counter.set(count);            // <- store new count in state
-
-    format!("Request number: {}", count)       // <- response with count
-}
-
-fn main() {
-    Application::with_state(AppState{counter: Cell::new(0)})
-        .resource("/", |r| r.method(Method::GET).f(index))
-        .finish();
-}
-```