add some comments to design sticky session

src/backend/mod.rs

@@ -28,12 +28,15 @@ use x509_parser::prelude::*;
 #[derive(Builder)]
 pub struct Backend {
   #[builder(setter(into))]
+  /// backend application name, e.g., app1
   pub app_name: String,
   #[builder(setter(custom))]
+  /// server name, e.g., example.com, in String ascii lower case
   pub server_name: String,
+  /// struct of reverse proxy serving incoming request
   pub reverse_proxy: ReverseProxy,
 
-  // tls settings
+  /// tls settings
   #[builder(setter(custom), default)]
   pub tls_cert_path: Option<PathBuf>,
   #[builder(setter(custom), default)]

src/backend/upstream.rs

@@ -17,6 +17,7 @@ pub struct ReverseProxy {
 }
 
 impl ReverseProxy {
+  /// Get an appropriate upstream destination for given path string.
   pub fn get<'a>(&self, path_str: impl Into<Cow<'a, str>>) -> Option<&UpstreamGroup> {
     // trie使ってlongest prefix match させてもいいけどルート記述は少ないと思われるので、
     // コスト的にこの程度で十分
@@ -52,9 +53,14 @@ impl ReverseProxy {
 
 #[allow(dead_code)]
 #[derive(Debug, Clone)]
+/// Load Balancing Option
 pub enum LoadBalance {
+  /// Simple round robin without session persistance
   RoundRobin,
+  /// Randomly chose one upstream server
   Random,
+  /// Round robin with session persistance using cookie
+  StickyRoundRobin,
 }
 impl Default for LoadBalance {
   fn default() -> Self {
@@ -63,22 +69,32 @@ impl Default for LoadBalance {
 }
 
 #[derive(Debug, Clone)]
+/// Upstream struct just containing uri without path
 pub struct Upstream {
-  pub uri: hyper::Uri, // base uri without specific path
+  /// Base uri without specific path
+  pub uri: hyper::Uri,
 }
 
 #[derive(Debug, Clone, Builder)]
+/// Struct serving multiple upstream servers for, e.g., load balancing.
 pub struct UpstreamGroup {
+  /// Upstream server(s)
   pub upstream: Vec<Upstream>,
   #[builder(setter(custom), default)]
+  /// Path like "/path" in [[PathNameBytesExp]] associated with the upstream server(s)
   pub path: PathNameBytesExp,
   #[builder(setter(custom), default)]
+  /// Path in [[PathNameBytesExp]] that will be used to replace the "path" part of incoming url
   pub replace_path: Option<PathNameBytesExp>,
+
   #[builder(default)]
+  /// Load balancing option
   pub lb: LoadBalance,
   #[builder(default)]
-  pub cnt: UpstreamCount, // counter for load balancing
+  /// Counter for load balancing
+  pub cnt: UpstreamCount,
   #[builder(setter(custom), default)]
+  /// Activated upstream options defined in [[UpstreamOption]]
   pub opts: HashSet<UpstreamOption>,
 }
 impl UpstreamGroupBuilder {
@@ -116,6 +132,7 @@ impl UpstreamGroupBuilder {
 pub struct UpstreamCount(Arc<AtomicUsize>);
 
 impl UpstreamGroup {
+  /// Get an enabled option of load balancing [[LoadBalance]]
   pub fn get(&self) -> Option<&Upstream> {
     match self.lb {
       LoadBalance::RoundRobin => {
@@ -127,13 +144,16 @@ impl UpstreamGroup {
         let max = self.upstream.len() - 1;
         self.upstream.get(rng.gen_range(0..max))
       }
+      LoadBalance::StickyRoundRobin => todo!(), // TODO: TODO:
     }
   }
 
+  /// Get a current count of upstream served
   fn current_cnt(&self) -> usize {
     self.cnt.0.load(Ordering::Relaxed)
   }
 
+  /// Increment count of upstream served
   fn increment_cnt(&self) -> usize {
     if self.current_cnt() < self.upstream.len() - 1 {
       self.cnt.0.fetch_add(1, Ordering::Relaxed)

src/handler/handler_main.rs

@@ -266,6 +266,8 @@ where
     };
 
     // Fix unique upstream destination since there could be multiple ones.
+    // TODO: StickyならCookieをここでgetに与える必要
+    // TODO: Stickyで、Cookieが与えられなかったらset-cookie向けにcookieを返す必要。upstreamオブジェクトに含めるのも手。
     let upstream_chosen = upstream_group.get().ok_or_else(|| anyhow!("Failed to get upstream"))?;
 
     // apply upstream-specific headers given in upstream_option

src/utils/bytes_name.rs

@@ -1,5 +1,5 @@
 /// Server name (hostname or ip address) representation in bytes-based struct
-/// For searching hashmap or key list by exact or longest-prefix matching
+/// for searching hashmap or key list by exact or longest-prefix matching
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Default)]
 pub struct ServerNameBytesExp(pub Vec<u8>); // lowercase ascii bytes
 impl From<&[u8]> for ServerNameBytesExp {
@@ -8,8 +8,8 @@ impl From<&[u8]> for ServerNameBytesExp {
   }
 }
 
-/// Server name (hostname or ip address) representation in bytes-based struct
-/// For searching hashmap or key list by exact or longest-prefix matching
+/// Path name, like "/path/ok", represented in bytes-based struct
+/// for searching hashmap or key list by exact or longest-prefix matching
 #[derive(Clone, Debug, PartialEq, Eq, Hash, Default)]
 pub struct PathNameBytesExp(pub Vec<u8>); // lowercase ascii bytes
 impl PathNameBytesExp {