Improve Prometheus stats + Add Grafana dashboard (#785)

We were missing some labels on metrics generated by the Prometheus exporter so I fixed that. There are still some gaps that I want to address with respect to the metrics we track but this seems like a good start.

I also created a Grafana Dashboard and exported it to JSON. It is designed with the same metric names the Prometheus exporter uses.

README.md

@@ -268,6 +268,8 @@ psql -h 127.0.0.1 -p 6432 -d pgbouncer -c 'SHOW DATABASES'
 
 Additionally, Prometheus statistics are available at `/metrics` via HTTP.
 
+We also have a [basic Grafana dashboard](https://github.com/postgresml/pgcat/blob/main/grafana_dashboard.json) based on Prometheus metrics that you can import into Grafana and build on it or use it for monitoring.
+
 ### Live configuration reloading
 
 The config can be reloaded by sending a `kill -s SIGHUP` to the process or by querying `RELOAD` to the admin database. All settings except the `host` and `port` can be reloaded without restarting the pooler, including sharding and replicas configurations.

src/prometheus.rs

@@ -12,19 +12,30 @@ use std::collections::HashMap;
 use std::fmt;
 use std::net::SocketAddr;
 use std::sync::atomic::Ordering;
-use std::sync::Arc;
 use tokio::net::TcpListener;
 
 use crate::config::Address;
 use crate::pool::{get_all_pools, PoolIdentifier};
+use crate::stats::get_server_stats;
 use crate::stats::pool::PoolStats;
-use crate::stats::{get_server_stats, ServerStats};
 
 struct MetricHelpType {
     help: &'static str,
     ty: &'static str,
 }
 
+struct ServerPrometheusStats {
+    bytes_received: u64,
+    bytes_sent: u64,
+    transaction_count: u64,
+    query_count: u64,
+    error_count: u64,
+    active_count: u64,
+    idle_count: u64,
+    login_count: u64,
+    tested_count: u64,
+}
+
 // reference for metric types: https://prometheus.io/docs/concepts/metric_types/
 // counters only increase
 // gauges can arbitrarily increase or decrease
@@ -127,22 +138,46 @@ static METRIC_HELP_AND_TYPES_LOOKUP: phf::Map<&'static str, MetricHelpType> = ph
     },
     "servers_bytes_received" => MetricHelpType {
         help: "Volume in bytes of network traffic received by server",
-        ty: "gauge",
+        ty: "counter",
     },
     "servers_bytes_sent" => MetricHelpType {
         help: "Volume in bytes of network traffic sent by server",
-        ty: "gauge",
+        ty: "counter",
     },
     "servers_transaction_count" => MetricHelpType {
         help: "Number of transactions executed by server",
-        ty: "gauge",
+        ty: "counter",
     },
     "servers_query_count" => MetricHelpType {
         help: "Number of queries executed by server",
-        ty: "gauge",
+        ty: "counter",
     },
     "servers_error_count" => MetricHelpType {
         help: "Number of errors",
+        ty: "counter",
+    },
+    "servers_idle_count" => MetricHelpType {
+        help: "Number of server connection in idle state",
+        ty: "gauge",
+    },
+    "servers_active_count" => MetricHelpType {
+        help: "Number of server connection in active state",
+        ty: "gauge",
+    },
+    "servers_tested_count" => MetricHelpType {
+        help: "Number of server connection in tested state",
+        ty: "gauge",
+    },
+    "servers_login_count" => MetricHelpType {
+        help: "Number of server connection in login state",
+        ty: "gauge",
+    },
+    "servers_is_banned" => MetricHelpType {
+        help: "0 if server is not banned, 1 if server is banned",
+        ty: "gauge",
+    },
+    "servers_is_paused" => MetricHelpType {
+        help: "0 if server is not paused, 1 if server is paused",
         ty: "gauge",
     },
     "databases_pool_size" => MetricHelpType {
@@ -210,7 +245,9 @@ impl<Value: fmt::Display> PrometheusMetric<Value> {
         labels.insert("shard", address.shard.to_string());
         labels.insert("role", address.role.to_string());
         labels.insert("pool", address.pool_name.clone());
+        labels.insert("index", address.address_index.to_string());
         labels.insert("database", address.database.to_string());
+        labels.insert("user", address.username.clone());
 
         Self::from_name(&format!("databases_{}", name), value, labels)
     }
@@ -225,8 +262,9 @@ impl<Value: fmt::Display> PrometheusMetric<Value> {
         labels.insert("shard", address.shard.to_string());
         labels.insert("role", address.role.to_string());
         labels.insert("pool", address.pool_name.clone());
+        labels.insert("index", address.address_index.to_string());
         labels.insert("database", address.database.to_string());
-
+        labels.insert("user", address.username.clone());
         Self::from_name(&format!("servers_{}", name), value, labels)
     }
 
@@ -236,7 +274,9 @@ impl<Value: fmt::Display> PrometheusMetric<Value> {
         labels.insert("shard", address.shard.to_string());
         labels.insert("pool", address.pool_name.clone());
         labels.insert("role", address.role.to_string());
+        labels.insert("index", address.address_index.to_string());
         labels.insert("database", address.database.to_string());
+        labels.insert("user", address.username.clone());
 
         Self::from_name(&format!("stats_{}", name), value, labels)
     }
@@ -338,34 +378,51 @@ fn push_database_stats(lines: &mut Vec<String>) {
 // Adds relevant metrics shown in a SHOW SERVERS admin command.
 fn push_server_stats(lines: &mut Vec<String>) {
     let server_stats = get_server_stats();
-    let mut server_stats_by_addresses = HashMap::<String, Arc<ServerStats>>::new();
+    let mut prom_stats = HashMap::<String, ServerPrometheusStats>::new();
     for (_, stats) in server_stats {
-        server_stats_by_addresses.insert(stats.address_name(), stats);
+        let entry = prom_stats
+            .entry(stats.address_name())
+            .or_insert(ServerPrometheusStats {
+                bytes_received: 0,
+                bytes_sent: 0,
+                transaction_count: 0,
+                query_count: 0,
+                error_count: 0,
+                active_count: 0,
+                idle_count: 0,
+                login_count: 0,
+                tested_count: 0,
+            });
+        entry.bytes_received += stats.bytes_received.load(Ordering::Relaxed);
+        entry.bytes_sent += stats.bytes_sent.load(Ordering::Relaxed);
+        entry.transaction_count += stats.transaction_count.load(Ordering::Relaxed);
+        entry.query_count += stats.query_count.load(Ordering::Relaxed);
+        entry.error_count += stats.error_count.load(Ordering::Relaxed);
+        match stats.state.load(Ordering::Relaxed) {
+            crate::stats::ServerState::Login => entry.login_count += 1,
+            crate::stats::ServerState::Active => entry.active_count += 1,
+            crate::stats::ServerState::Tested => entry.tested_count += 1,
+            crate::stats::ServerState::Idle => entry.idle_count += 1,
+        }
     }
 
     for (_, pool) in get_all_pools() {
         for shard in 0..pool.shards() {
             for server in 0..pool.servers(shard) {
                 let address = pool.address(shard, server);
-                if let Some(server_info) = server_stats_by_addresses.get(&address.name()) {
+                if let Some(server_info) = prom_stats.get(&address.name()) {
                     let metrics = [
-                        (
+                        ("bytes_received", server_info.bytes_received),
-                            "bytes_received",
+                        ("bytes_sent", server_info.bytes_sent),
-                            server_info.bytes_received.load(Ordering::Relaxed),
+                        ("transaction_count", server_info.transaction_count),
-                        ),
+                        ("query_count", server_info.query_count),
-                        ("bytes_sent", server_info.bytes_sent.load(Ordering::Relaxed)),
+                        ("error_count", server_info.error_count),
-                        (
+                        ("idle_count", server_info.idle_count),
-                            "transaction_count",
+                        ("active_count", server_info.active_count),
-                            server_info.transaction_count.load(Ordering::Relaxed),
+                        ("login_count", server_info.login_count),
-                        ),
+                        ("tested_count", server_info.tested_count),
-                        (
+                        ("is_banned", if pool.is_banned(address) { 1 } else { 0 }),
-                            "query_count",
+                        ("is_paused", if pool.paused() { 1 } else { 0 }),
-                            server_info.query_count.load(Ordering::Relaxed),
-                        ),
-                        (
-                            "error_count",
-                            server_info.error_count.load(Ordering::Relaxed),
-                        ),
                     ];
                     for (key, value) in metrics {
                         if let Some(prometheus_metric) =