Proxy metrics (#3290)

Implement proxy metrics collection.
Only collect metric for outbound traffic.

Add proxy CLI parameters:
- metric-collection-endpoint
- metric-collection-interval.

Add test_proxy_metric_collection test.

Move shared consumption metrics code to libs/consumption_metrics.
Refactor the code.

libs/consumption_metrics/Cargo.toml

@@ -0,0 +1,16 @@
+[package]
+name = "consumption_metrics"
+version = "0.1.0"
+edition = "2021"
+license = "Apache-2.0"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+anyhow = "1.0.68"
+chrono = { version = "0.4", default-features = false, features = ["clock", "serde"] }
+rand = "0.8.3"
+serde = "1.0.152"
+serde_with = "2.1.0"
+utils = { version = "0.1.0", path = "../utils" }
+workspace_hack = { version = "0.1.0", path = "../../workspace_hack" }

libs/consumption_metrics/src/lib.rs

@@ -0,0 +1,50 @@
+//!
+//! Shared code for consumption metics collection
+//!
+use chrono::{DateTime, Utc};
+use rand::Rng;
+use serde::Serialize;
+
+#[derive(Serialize, Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
+#[serde(tag = "type")]
+pub enum EventType {
+    #[serde(rename = "absolute")]
+    Absolute { time: DateTime<Utc> },
+    #[serde(rename = "incremental")]
+    Incremental {
+        start_time: DateTime<Utc>,
+        stop_time: DateTime<Utc>,
+    },
+}
+
+#[derive(Serialize, Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
+pub struct Event<Extra> {
+    #[serde(flatten)]
+    #[serde(rename = "type")]
+    pub kind: EventType,
+
+    pub metric: &'static str,
+    pub idempotency_key: String,
+    pub value: u64,
+
+    #[serde(flatten)]
+    pub extra: Extra,
+}
+
+pub fn idempotency_key(node_id: String) -> String {
+    format!(
+        "{}-{}-{:04}",
+        Utc::now(),
+        node_id,
+        rand::thread_rng().gen_range(0..=9999)
+    )
+}
+
+pub const CHUNK_SIZE: usize = 1000;
+
+// Just a wrapper around a slice of events
+// to serialize it as `{"events" : [ ] }
+#[derive(serde::Serialize)]
+pub struct EventChunk<'a, T> {
+    pub events: &'a [T],
+}