rewrite CommandServer with MIO

The multi-threaded, event-based architecture was too complicated and
prevented introducing protobuf channels.
The new CommandServer functions on the same principle as the proxy
logic of Sōzu: listen to events with Mio in an event loop, dispatch
the events accordingly by creating WorkerSessions, ClientSessions.
This new CommandServer allows to create Tasks, that can scatter
requests to all workers, gather their responses as the event loop goes,
and invoke the task finish() when all responses are gathered.

A worker whose unix socket is disconnected will be killed,
and automatically restarted if configurated to. Conversely, if the
main process dies, the orphaned workers will perform a hard stop.

Sōzu channels used everywhere for communication with workers and
clients.

Automatic counting and respawning of workers, at each tick

implement soft stop and hard stop

improve CLI:
- disable logging in CLI when displaying JSON
- sort list of workers when displaying status

error handling with thiserror

remove obsolete documentation on managing workers
remove unused dependencies: smol, futures, futures-lite, anyhow

Co-Authored-By: Emmanuel BOSQUET <[email protected]>

bin/Cargo.toml

@@ -14,22 +14,12 @@ authors = [
   "Florentin Dubois <[email protected]>",
 ]
 categories = ["network-programming"]
-edition="2021"
+edition = "2021"
 rust-version = "1.70.0"
-include = [
-  "README.md",
-  "Cargo.toml",
-  "src/**/*",
-]
+include = ["README.md", "Cargo.toml", "src/**/*"]
 
 [dependencies]
-anyhow = "^1.0.79"
-async-dup = "^1.2.4"
-async-io = "^1.13.0"
 clap = { version = "^4.4.18", features = ["derive"] }
-futures = "^0.3.30"
-futures-lite = "^1.13.0"
-hex = "^0.4.3"
 jemallocator = { version = "^0.5.4", optional = true }
 libc = "^0.2.152"
 log = "^0.4.20"
@@ -40,13 +30,12 @@ paw = "^1.0.0"
 serde = { version = "^1.0.195", features = ["derive"] }
 serde_json = "^1.0.111"
 time = "^0.3.29"
-regex = "^1.10.3"
-smol = "^1.3.0"
 tempfile = "^3.9.0"
 termion = "^3.0.0"
-
 sozu-command-lib = { path = "../command", version = "^0.15.19" }
 sozu-lib = { path = "../lib", version = "^0.15.19" }
+thiserror = "^1.0.49"
+
 
 [target.'cfg(target_os="linux")'.dependencies]
 num_cpus = "^1.16.0"

bin/src/cli.rs

@@ -109,7 +109,10 @@ pub enum SubCmd {
         #[clap(long = "hard", help = "do not wait for connections to finish")]
         hard: bool,
     },
-    #[clap(name = "upgrade", about = "upgrade the proxy")]
+    #[clap(
+        name = "upgrade",
+        about = "upgrade the main process OR a specific worker. Specify a longer timeout."
+    )]
     Upgrade {
         #[clap(long = "worker", help = "upgrade a specific worker")]
         worker: Option<u32>,