From b30ff6affc7a9c84a6748a8f431f8c7066accfa7 Mon Sep 17 00:00:00 2001
From: Paul Hauner <paul@paulhauner.com>
Date: Tue, 2 Mar 2021 22:35:47 +0000
Subject: [PATCH] Expose the startup timestamp to Prometheus (#2233)

## Issue Addressed

Resolves #1788

## Proposed Changes

As per #1788, expose the time at which the process started via the `process_start_time_seconds` Prometheus metric. This will help users track uptime.

## Additional Info

NA

Co-authored-by: Michael Sproul <michael@sigmaprime.io>
---
 Cargo.lock                |  2 ++
 lighthouse/Cargo.toml     |  2 ++
 lighthouse/src/main.rs    |  5 +++++
 lighthouse/src/metrics.rs | 22 ++++++++++++++++++++++
 4 files changed, 31 insertions(+)
 create mode 100644 lighthouse/src/metrics.rs

diff --git a/Cargo.lock b/Cargo.lock
index 84096da4c..7f0362d94 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3721,6 +3721,8 @@ dependencies = [
  "environment",
  "eth2_network_config",
  "futures 0.3.13",
+ "lazy_static",
+ "lighthouse_metrics",
  "lighthouse_version",
  "logging",
  "remote_signer",
diff --git a/lighthouse/Cargo.toml b/lighthouse/Cargo.toml
index 185002e8b..2a4efae62 100644
--- a/lighthouse/Cargo.toml
+++ b/lighthouse/Cargo.toml
@@ -41,6 +41,8 @@ directory = { path = "../common/directory" }
 lighthouse_version = { path = "../common/lighthouse_version" }
 account_utils = { path = "../common/account_utils" }
 remote_signer = { "path" = "../remote_signer" }
+lighthouse_metrics = { path = "../common/lighthouse_metrics" }
+lazy_static = "1.4.0"
 
 [dev-dependencies]
 tempfile = "3.1.0"
diff --git a/lighthouse/src/main.rs b/lighthouse/src/main.rs
index 53f3f2c10..c282c687d 100644
--- a/lighthouse/src/main.rs
+++ b/lighthouse/src/main.rs
@@ -1,3 +1,5 @@
+mod metrics;
+
 use beacon_node::{get_eth2_network_config, ProductionBeaconNode};
 use clap::{App, Arg, ArgMatches};
 use env_logger::{Builder, Env};
@@ -219,6 +221,9 @@ fn run<E: EthSpec>(
 
     let log = environment.core_context().log().clone();
 
+    // Allow Prometheus to export the time at which the process was started.
+    metrics::expose_process_start_time(&log);
+
     if matches.is_present("spec") {
         warn!(
             log,
diff --git a/lighthouse/src/metrics.rs b/lighthouse/src/metrics.rs
new file mode 100644
index 000000000..ac880602f
--- /dev/null
+++ b/lighthouse/src/metrics.rs
@@ -0,0 +1,22 @@
+use lazy_static::lazy_static;
+pub use lighthouse_metrics::*;
+use slog::{error, Logger};
+use std::time::{SystemTime, UNIX_EPOCH};
+
+lazy_static! {
+    pub static ref PROCESS_START_TIME_SECONDS: Result<IntGauge> = try_create_int_gauge(
+        "process_start_time_seconds",
+        "The unix timestamp at which the process was started"
+    );
+}
+
+pub fn expose_process_start_time(log: &Logger) {
+    match SystemTime::now().duration_since(UNIX_EPOCH) {
+        Ok(duration) => set_gauge(&PROCESS_START_TIME_SECONDS, duration.as_secs() as i64),
+        Err(e) => error!(
+            log,
+            "Failed to read system time";
+            "error" => %e
+        ),
+    }
+}