examples: Add distributed key value store (#1281)

* examples: Add distributed key value store

This commit adds a basic distributed key value store supporting GET and
PUT commands using Kademlia and mDNS.

* examples/distributed-key-value-store: Fix typo

Author: mxinden

examples/distributed-key-value-store.rs

@@ -0,0 +1,209 @@
+// Copyright 20l9 Parity Technologies (UK) Ltd.
+//
+// Permission is hereby granted, free of charge, to any person obtaining a
+// copy of this software and associated documentation files (the "Software"),
+// to deal in the Software without restriction, including without limitation
+// the rights to use, copy, modify, merge, publish, distribute, sublicense,
+// and/or sell copies of the Software, and to permit persons to whom the
+// Software is furnished to do so, subject to the following conditions:
+//
+// The above copyright notice and this permission notice shall be included in
+// all copies or substantial portions of the Software.
+//
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
+// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+// FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+//! A basic key value store demonstrating libp2p and the mDNS and Kademlia protocols.
+//!
+//! 1. Using two terminal windows, start two instances. If you local network
+//!    allows mDNS, they will automatically connect.
+//!
+//! 2. Type `PUT my-key my-value` in terminal one and hit return.
+//!
+//! 3. Type `GET my-key` in terminal two and hit return.
+//!
+//! 4. Close with Ctrl-c.
+
+use futures::prelude::*;
+use libp2p::kad::record::store::MemoryStore;
+use libp2p::kad::{record::Key, Kademlia, KademliaEvent, PutRecordOk, Quorum, Record};
+use libp2p::{
+    build_development_transport, identity,
+    mdns::{Mdns, MdnsEvent},
+    swarm::NetworkBehaviourEventProcess,
+    tokio_codec::{FramedRead, LinesCodec},
+    tokio_io::{AsyncRead, AsyncWrite},
+    NetworkBehaviour, PeerId, Swarm,
+};
+
+fn main() {
+    env_logger::init();
+
+    // Create a random key for ourselves.
+    let local_key = identity::Keypair::generate_ed25519();
+    let local_peer_id = PeerId::from(local_key.public());
+
+    // Set up a an encrypted DNS-enabled TCP Transport over the Mplex protocol.
+    let transport = build_development_transport(local_key);
+
+    // We create a custom network behaviour that combines Kademlia and mDNS.
+    #[derive(NetworkBehaviour)]
+    struct MyBehaviour<TSubstream: AsyncRead + AsyncWrite> {
+        kademlia: Kademlia<TSubstream, MemoryStore>,
+        mdns: Mdns<TSubstream>,
+    }
+
+    impl<TSubstream: AsyncRead + AsyncWrite> NetworkBehaviourEventProcess<MdnsEvent>
+        for MyBehaviour<TSubstream>
+    {
+        // Called when `mdns` produces an event.
+        fn inject_event(&mut self, event: MdnsEvent) {
+            if let MdnsEvent::Discovered(list) = event {
+                for (peer_id, multiaddr) in list {
+                    self.kademlia.add_address(&peer_id, multiaddr);
+                }
+            }
+        }
+    }
+
+    impl<TSubstream: AsyncRead + AsyncWrite> NetworkBehaviourEventProcess<KademliaEvent>
+        for MyBehaviour<TSubstream>
+    {
+        // Called when `kademlia` produces an event.
+        fn inject_event(&mut self, message: KademliaEvent) {
+            match message {
+                KademliaEvent::GetRecordResult(Ok(result)) => {
+                    for Record { key, value, .. } in result.records {
+                        println!(
+                            "Got record {:?} {:?}",
+                            std::str::from_utf8(key.as_ref()).unwrap(),
+                            std::str::from_utf8(&value).unwrap(),
+                        );
+                    }
+                }
+                KademliaEvent::GetRecordResult(Err(err)) => {
+                    eprintln!("Failed to get record: {:?}", err);
+                }
+                KademliaEvent::PutRecordResult(Ok(PutRecordOk { key })) => {
+                    println!(
+                        "Successfully put record {:?}",
+                        std::str::from_utf8(key.as_ref()).unwrap()
+                    );
+                }
+                KademliaEvent::PutRecordResult(Err(err)) => {
+                    eprintln!("Failed to put record: {:?}", err);
+                }
+                _ => {}
+            }
+        }
+    }
+
+    // Create a swarm to manage peers and events.
+    let mut swarm = {
+        // Create a Kademlia behaviour.
+        let store = MemoryStore::new(local_peer_id.clone());
+        let kademlia = Kademlia::new(local_peer_id.clone(), store);
+
+        let behaviour = MyBehaviour {
+            kademlia,
+            mdns: Mdns::new().expect("Failed to create mDNS service"),
+        };
+
+        Swarm::new(transport, behaviour, local_peer_id)
+    };
+
+    // Read full lines from stdin.
+    let stdin = tokio_stdin_stdout::stdin(0);
+    let mut framed_stdin = FramedRead::new(stdin, LinesCodec::new());
+
+    // Listen on all interfaces and whatever port the OS assigns.
+    Swarm::listen_on(&mut swarm, "/ip4/0.0.0.0/tcp/0".parse().unwrap()).unwrap();
+
+    // Kick it off.
+    let mut listening = false;
+    tokio::run(futures::future::poll_fn(move || {
+        loop {
+            match framed_stdin.poll().expect("Error while polling stdin") {
+                Async::Ready(Some(line)) => {
+                    handle_input_line(&mut swarm.kademlia, line);
+                }
+                Async::Ready(None) => panic!("Stdin closed"),
+                Async::NotReady => break,
+            };
+        }
+
+        loop {
+            match swarm.poll().expect("Error while polling swarm") {
+                Async::Ready(Some(_)) => {}
+                Async::Ready(None) | Async::NotReady => {
+                    if !listening {
+                        if let Some(a) = Swarm::listeners(&swarm).next() {
+                            println!("Listening on {:?}", a);
+                            listening = true;
+                        }
+                    }
+                    break;
+                }
+            }
+        }
+
+        Ok(Async::NotReady)
+    }));
+}
+
+fn handle_input_line<TSubstream: AsyncRead + AsyncWrite>(
+    kademlia: &mut Kademlia<TSubstream, MemoryStore>,
+    line: String,
+) {
+    let mut args = line.split(" ");
+
+    match args.next() {
+        Some("GET") => {
+            let key = {
+                match args.next() {
+                    Some(key) => Key::new(&key),
+                    None => {
+                        eprintln!("Expected key");
+                        return;
+                    }
+                }
+            };
+            kademlia.get_record(&key, Quorum::One);
+        }
+        Some("PUT") => {
+            let key = {
+                match args.next() {
+                    Some(key) => Key::new(&key),
+                    None => {
+                        eprintln!("Expected key");
+                        return;
+                    }
+                }
+            };
+            let value = {
+                match args.next() {
+                    Some(value) => value.as_bytes().to_vec(),
+                    None => {
+                        eprintln!("Expected value");
+                        return;
+                    }
+                }
+            };
+            let record = Record {
+                key,
+                value,
+                publisher: None,
+                expires: None,
+            };
+            kademlia.put_record(record, Quorum::One);
+        }
+        _ => {
+            eprintln!("expected GET or PUT");
+        }
+    }
+}