fix(iroh-relay): bring back unique node counts (#3197)

## Description

This got lost in #3093 and
wasn't covered in #3194

## Breaking Changes

<!-- Optional, if there are any breaking changes document them,
including how to migrate older code. -->

## Notes & open questions

<!-- Any notes, remarks or open questions you have to make about the PR.
-->

## Change checklist
<!-- Remove any that are not relevant. -->
- [ ] Self-review.
- [ ] Documentation updates following the [style
guide](https://rust-lang.github.io/rfcs/1574-more-api-documentation-conventions.html#appendix-a-full-conventions-text),
if relevant.
- [ ] Tests if relevant.
- [ ] All breaking changes documented.
- [ ] List all breaking changes in the above "Breaking Changes" section.
- [ ] Open an issue or PR on any number0 repos that are affected by this
breaking change. Give guidance on how the updates should be handled or
do the actual updates themselves. The major ones are:
    - [ ] [`quic-rpc`](https://github.com/n0-computer/quic-rpc)
    - [ ] [`iroh-gossip`](https://github.com/n0-computer/iroh-gossip)
    - [ ] [`iroh-blobs`](https://github.com/n0-computer/iroh-blobs)
    - [ ] [`dumbpipe`](https://github.com/n0-computer/dumbpipe)
    - [ ] [`sendme`](https://github.com/n0-computer/sendme)

---------

Co-authored-by: Floris Bruynooghe <[email protected]>

Author: Arqu

Cargo.lock

@@ -85,6 +85,7 @@ reloadable-state = { version = "0.1", optional = true }
 rustls-cert-reloadable-resolver = { version = "0.7.1", optional = true }
 rustls-cert-file-reader = { version = "0.4.1", optional = true }
 rustls-pemfile = { version = "2.1", optional = true }
+time = { version = "0.3.37", optional = true }
 tokio-rustls-acme = { version = "0.6", optional = true }
 tokio-tungstenite = { version = "0.24", default-features = false, optional = true } # keep version in sync with what tokio-tungstenite-wasm depends on
 toml = { version = "0.8", optional = true }
@@ -143,6 +144,7 @@ server = [
     "dep:rustls-cert-file-reader",
     "dep:rustls-cert-reloadable-resolver",
     "dep:rustls-pemfile",
+    "dep:time",
     "dep:tokio-rustls-acme",
     "dep:tokio-tungstenite",
     "dep:toml",

iroh-relay/Cargo.toml

@@ -1,13 +1,17 @@
 //! The server-side representation of an ongoing client relaying connection.
 
-use std::{future::Future, num::NonZeroU32, pin::Pin, sync::Arc, task::Poll, time::Duration};
+use std::{
+    collections::HashSet, future::Future, num::NonZeroU32, pin::Pin, sync::Arc, task::Poll,
+    time::Duration,
+};
 
 use anyhow::{bail, Context, Result};
 use bytes::Bytes;
 use iroh_base::NodeId;
 use iroh_metrics::{inc, inc_by};
 use n0_future::{FutureExt, Sink, SinkExt, Stream, StreamExt};
 use rand::Rng;
+use time::{Date, OffsetDateTime};
 use tokio::{
     sync::mpsc::{self, error::TrySendError},
     time::MissedTickBehavior,
@@ -105,6 +109,7 @@ impl Client {
             node_id,
             connection_id,
             clients: clients.clone(),
+            client_counter: ClientCounter::default(),
             ping_tracker: PingTracker::default(),
         };
 
@@ -205,6 +210,8 @@ struct Actor {
     connection_id: u64,
     /// Reference to the other connected clients.
     clients: Clients,
+    /// Statistics about the connected clients
+    client_counter: ClientCounter,
     ping_tracker: PingTracker,
 }
 
@@ -214,6 +221,9 @@ impl Actor {
         // connection is accepted long before this in the HTTP server, but it is clearer to
         // handle the metric here.
         inc!(Metrics, accepts);
+        if self.client_counter.update(self.node_id) {
+            inc!(Metrics, unique_client_keys);
+        }
         match self.run_inner(done).await {
             Err(e) => {
                 warn!("actor errored {e:#?}, exiting");
@@ -557,6 +567,38 @@ impl Sink<Frame> for RateLimitedRelayedStream {
     }
 }
 
+/// Tracks how many unique nodes have been seen during the last day.
+#[derive(Debug)]
+struct ClientCounter {
+    clients: HashSet<NodeId>,
+    last_clear_date: Date,
+}
+
+impl Default for ClientCounter {
+    fn default() -> Self {
+        Self {
+            clients: HashSet::new(),
+            last_clear_date: OffsetDateTime::now_utc().date(),
+        }
+    }
+}
+
+impl ClientCounter {
+    fn check_and_clear(&mut self) {
+        let today = OffsetDateTime::now_utc().date();
+        if today != self.last_clear_date {
+            self.clients.clear();
+            self.last_clear_date = today;
+        }
+    }
+
+    /// Marks this node as seen, returns whether it is new today or not.
+    fn update(&mut self, client: NodeId) -> bool {
+        self.check_and_clear();
+        self.clients.insert(client)
+    }
+}
+
 #[cfg(test)]
 mod tests {
     use bytes::Bytes;
@@ -595,6 +637,7 @@ mod tests {
             connection_id: 0,
             node_id,
             clients: clients.clone(),
+            client_counter: ClientCounter::default(),
             ping_tracker: PingTracker::default(),
         };