From c377b136aaf55ad13f28a34410ca79c35bbfb2f3 Mon Sep 17 00:00:00 2001
From: Greg Heartsfield <scsibug@imap.cc>
Date: Wed, 1 Feb 2023 18:09:30 -0600
Subject: [PATCH] improvement: prometheus metric for db connections (sqlite)

---
 src/repo/sqlite.rs | 6 +++++-
 src/server.rs      | 7 +++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/repo/sqlite.rs b/src/repo/sqlite.rs
index e756af6..d016e71 100644
--- a/src/repo/sqlite.rs
+++ b/src/repo/sqlite.rs
@@ -351,6 +351,10 @@ impl NostrRepo for SqliteRepo {
             let mut filter_count = 0;
             // remove duplicates from the filter list.
             if let Ok(mut conn) = self.read_pool.get() {
+                {
+                    let pool_state = self.read_pool.state();
+                    metrics.db_connections.set((pool_state.connections - pool_state.idle_connections).into());
+                }
                 for filter in sub.filters.iter() {
                     let filter_start = Instant::now();
                     filter_count += 1;
@@ -367,7 +371,7 @@ impl NostrRepo for SqliteRepo {
                     let mut last_successful_send = Instant::now();
                     // execute the query.
                     // make the actual SQL query (with parameters inserted) available
-                    conn.trace(Some(|x| {debug!("SQL trace: {:?}", x)}));
+                    conn.trace(Some(|x| {trace!("SQL trace: {:?}", x)}));
                     let mut stmt = conn.prepare_cached(&q)?;
                     let mut event_rows = stmt.query(rusqlite::params_from_iter(p))?;
 
diff --git a/src/server.rs b/src/server.rs
index ef0029d..d956459 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -14,6 +14,7 @@ use crate::nip05;
 use crate::notice::Notice;
 use crate::subscription::Subscription;
 use prometheus::IntCounterVec;
+use prometheus::IntGauge;
 use prometheus::{Encoder, Histogram, IntCounter, HistogramOpts, Opts, Registry, TextEncoder};
 use futures::SinkExt;
 use futures::StreamExt;
@@ -248,6 +249,9 @@ fn create_metrics() -> (Registry, NostrMetrics) {
         "nostr_connections_total",
         "New connections",
     )).unwrap();
+    let db_connections = IntGauge::with_opts(Opts::new(
+        "nostr_db_connections", "Active database connections"
+    )).unwrap();
     let query_aborts = IntCounterVec::new(
         Opts::new("nostr_query_abort_total", "Aborted queries"),
         vec!["reason"].as_slice(),
@@ -273,6 +277,7 @@ fn create_metrics() -> (Registry, NostrMetrics) {
     registry.register(Box::new(write_events.clone())).unwrap();
     registry.register(Box::new(sent_events.clone())).unwrap();
     registry.register(Box::new(connections.clone())).unwrap();
+    registry.register(Box::new(db_connections.clone())).unwrap();
     registry.register(Box::new(query_aborts.clone())).unwrap();
     registry.register(Box::new(cmd_req.clone())).unwrap();
     registry.register(Box::new(cmd_event.clone())).unwrap();
@@ -284,6 +289,7 @@ fn create_metrics() -> (Registry, NostrMetrics) {
         write_events,
         sent_events,
         connections,
+        db_connections,
 	disconnects,
         query_aborts,
 	cmd_req,
@@ -837,6 +843,7 @@ async fn nostr_server(
 pub struct NostrMetrics {
     pub query_sub: Histogram, // response time of successful subscriptions
     pub query_db: Histogram, // individual database query execution time
+    pub db_connections: IntGauge, // database connections in use
     pub write_events: Histogram, // response time of event writes
     pub sent_events: IntCounterVec, // count of events sent to clients
     pub connections: IntCounter, // count of websocket connections