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introduce LaunchTimestamp to identify process restarts

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This patch adds a LaunchTimestamp type to the `metrics` crate,
along with a `libmetric_` Prometheus metric.

The initial user is pageserver.
In addition to exposing the Prometheus metric, it also reproduces
the launch timestamp as a header in the API responses.

The motivation for this is that we plan to scrape the pageserver's
/v1/tenant/:tenant_id/timeline/:timeline_id/layer
HTTP endpoint over time. It will soon expose access metrics (#3496)
which reset upon process restart. We will use the pageserver's launch
ID to identify a restart between two scrape points.

However, there are other potential uses. For example, we could use
the Prometheus metric to annotate Grafana plots whenever the launch
timestamp changes.
This commit is contained in:
Christian Schwarz
2023-02-03 18:12:17 +01:00
committed by Christian Schwarz
parent be81db21b9
commit 87cd2bae77
8 changed files with 112 additions and 7 deletions
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pageserver/src/bin/pageserver.rs
+19 -5
View File
@@ -7,6 +7,7 @@ use std::{env, ops::ControlFlow, path::Path, str::FromStr};
use anyhow::{anyhow, Context};
use clap::{Arg, ArgAction, Command};
use fail::FailScenario;
use metrics::launch_timestamp::{set_launch_timestamp_metric, LaunchTimestamp};
use remote_storage::GenericRemoteStorage;
use tracing::*;
@@ -52,6 +53,8 @@ fn version() -> String {
}
fn main() -> anyhow::Result<()> {
let launch_ts = Box::leak(Box::new(LaunchTimestamp::generate()));
let arg_matches = cli().get_matches();
if arg_matches.get_flag("enabled-features") {
@@ -108,7 +111,7 @@ fn main() -> anyhow::Result<()> {
virtual_file::init(conf.max_file_descriptors);
page_cache::init(conf.page_cache_size);
start_pageserver(conf).context("Failed to start pageserver")?;
start_pageserver(launch_ts, conf).context("Failed to start pageserver")?;
scenario.teardown();
Ok(())
@@ -203,13 +206,24 @@ fn initialize_config(
})
}
fn start_pageserver(conf: &'static PageServerConf) -> anyhow::Result<()> {
fn start_pageserver(
launch_ts: &'static LaunchTimestamp,
conf: &'static PageServerConf,
) -> anyhow::Result<()> {
// Initialize logging
logging::init(conf.log_format)?;
// Print version to the log, and expose it as a prometheus metric too.
info!("version: {}", version());
// Print version and launch timestamp to the log,
// and expose them as prometheus metrics.
// A changed version string indicates changed software.
// A changed launch timestamp indicates a pageserver restart.
info!(
"version: {} launch_timestamp: {}",
version(),
launch_ts.to_string()
);
set_build_info_metric(GIT_VERSION);
set_launch_timestamp_metric(launch_ts);
// If any failpoints were set from FAILPOINTS environment variable,
// print them to the log for debugging purposes
@@ -307,7 +321,7 @@ fn start_pageserver(conf: &'static PageServerConf) -> anyhow::Result<()> {
{
let _rt_guard = MGMT_REQUEST_RUNTIME.enter();
let router = http::make_router(conf, auth.clone(), remote_storage)?
let router = http::make_router(conf, launch_ts, auth.clone(), remote_storage)?
.build()
.map_err(|err| anyhow!(err))?;
let service = utils::http::RouterService::new(router).unwrap();