Continuous memory profiling (#4572)

## Motivation

For debugging production memory issues, ideally we'll have continuous
memory profiling always on.

## Proposal

This exposes a couple endpoints:
* One that generates a pprof and returns it once the endpoint is queried
* One that generates a flamegraph and returns it once the endpoint is
queried

The former will be used by Alloy on the deployment side, to generate
profiles every 30 seconds or so. It shows no visible performance
regression.

## Test Plan

Deployed a network with this and the `linera-infra` changes, saw the
memory flamegraphs on Pyroscope, and managed to curl the flamegraph
endpoint and get a memory profile svg returned to me.

![Screenshot 2025-09-06 at
02.27.50.png](https://app.graphite.dev/user-attachments/assets/f5c2407e-af25-4b8c-b43a-9e56258a9373.png)

## Release Plan

- Nothing to do / These changes follow the usual release cycle.

Author: ndr-ds

Cargo.lock

@@ -136,6 +136,7 @@ indexed_db_futures = "0.4.1"
 insta = "1.36.1"
 is-terminal = "0.4.12"
 itertools = "0.14.0"
+jemalloc_pprof = "0.8.1"
 js-sys = "0.3.70"
 k256 = { version = "0.13.4", default-features = false, features = [
     "ecdsa",

Cargo.toml

@@ -25,7 +25,7 @@ ARG binaries=
 ARG copy=${binaries:+_copy}
 ARG build_flag=--release
 ARG build_folder=release
-ARG build_features=scylladb,metrics
+ARG build_features=scylladb,metrics,memory-profiling
 ARG rustflags="-C force-frame-pointers=yes"
 
 FROM rust:1.74-slim-bookworm AS builder
@@ -39,7 +39,8 @@ ARG rustflags
 RUN apt-get update && apt-get install -y \
     pkg-config \
     protobuf-compiler \
-    clang
+    clang \
+    make
 
 COPY examples examples
 COPY linera-base linera-base

docker/Dockerfile

@@ -42,7 +42,7 @@ use linera_execution::{
     Committee, ExecutionError, Operation,
 };
 #[cfg(feature = "metrics")]
-use linera_metrics::prometheus_server;
+use linera_metrics::monitoring_server;
 use linera_storage::{Clock as _, Storage};
 use serde::{Deserialize, Serialize};
 use tokio::sync::{oneshot, Notify};
@@ -662,7 +662,7 @@ where
         let index_handler = axum::routing::get(graphiql).post(Self::index_handler);
 
         #[cfg(feature = "metrics")]
-        prometheus_server::start_metrics(self.metrics_address(), cancellation_token.clone());
+        monitoring_server::start_metrics(self.metrics_address(), cancellation_token.clone());
 
         let app = Router::new()
             .route("/", index_handler)