Integrate HikariCP db cxn pool and metrics

deps.edn

@@ -7,6 +7,7 @@
 
   org.xerial/sqlite-jdbc {:mvn/version "3.40.0.0"}
   com.github.seancorfield/next.jdbc {:mvn/version "1.3.847"}
+  com.zaxxer/HikariCP {:mvn/version "5.0.1"}
 
   fr.acinq.secp256k1/secp256k1-kmp {:mvn/version "0.7.0"}
   fr.acinq.secp256k1/secp256k1-kmp-jni-jvm {:mvn/version "0.7.0"}
@@ -20,7 +21,7 @@
 
   metrics-clojure/metrics-clojure {:mvn/version "2.10.0"}
   metrics-clojure-jvm/metrics-clojure-jvm {:mvn/version "2.10.0"}
-  io.dropwizard.metrics/metrics-json {:mvn/version "4.2.14"}
+  io.dropwizard.metrics/metrics-json {:mvn/version "4.2.15"}
 
   org.clojure/tools.logging {:mvn/version "1.2.4"}
   ch.qos.logback/logback-classic {:mvn/version "1.4.5"}}

src/me/untethr/nostr/app.clj

@@ -20,7 +20,8 @@
     [org.httpkit.server :as hk]
     [ring.middleware.params]
     [reitit.ring :as ring])
-  (:import (java.nio.charset StandardCharsets)
+  (:import (com.codahale.metrics MetricRegistry)
+           (java.nio.charset StandardCharsets)
            (java.util UUID)
            (java.io File)
            (javax.sql DataSource)
@@ -582,8 +583,7 @@
 (defn go!
   "Start the server and sleep forever, blocking the main process thread."
   [^Conf conf nip05-json nip11-json]
-  (let [^DataSource db (store/init! (:sqlite-file conf))
-        ;; This is our subscription registry, stored in an atom for concurrent
+  (let [;; This is our subscription registry, stored in an atom for concurrent
         ;; access. All updates to this atom will be implementd in the subscribe
         ;; namespace.
         subs-atom (atom (subscribe/create-empty-subs))
@@ -599,12 +599,21 @@
         ;; any corresponding ongoing fulfillment for that id; or if the websocket
         ;; is closed, we kill any associated fulfillments).
         fulfill-atom (atom (fulfill/create-empty-registry))
+        ;; We have a cyclic dependency between our db/datasource and metric
+        ;; registry. (Mainly we want the metric registry to be able to query
+        ;; the db for max-rowid. But we also want our datasource to be able
+        ;; to report metrics.) So we use a holder volatile so the metrics
+        ;; registry can use it after it's been instantiated.
+        db-holder (volatile! nil)
         ;; We report various server metrics and expose them via http for
         ;; observability (we use https://metrics.dropwizard.io/ for this):
         metrics (metrics/create-metrics
-                  #(store/max-event-rowid db)
+                  #(if @db-holder
+                     (store/max-event-rowid @db-holder) -1)
                   #(subscribe/num-subscriptions subs-atom)
-                  #(subscribe/num-firehose-filters subs-atom))]
+                  #(subscribe/num-firehose-filters subs-atom))
+        ^DataSource db (store/init! (:sqlite-file conf) ^MetricRegistry (:codahale-registry metrics))
+        _ (vreset! db-holder db)]
     ;; Run our ring-compatible httpkit server on the configured port. :max-ws
     ;; here is the max websocket message size.
     (hk/run-server

src/me/untethr/nostr/store.clj

@@ -4,13 +4,63 @@
             [clojure.tools.logging :as log]
             [next.jdbc :as jdbc]
             [next.jdbc.result-set :as rs])
-  (:import (javax.sql DataSource)
+  (:import (com.codahale.metrics MetricRegistry)
+           (com.zaxxer.hikari HikariConfig HikariDataSource)
+           (com.zaxxer.hikari.metrics.dropwizard CodahaleMetricsTrackerFactory)
+           (javax.sql DataSource)
            (org.sqlite SQLiteException)))
 
-(def get-datasource*
+(defn- create-hikari-datasource
+  ^HikariDataSource [jdbc-url]
+  (HikariDataSource.
+    (doto (HikariConfig.)
+      (.setJdbcUrl jdbc-url)
+      ;; note: jdbc.next with-transaction disables and re-enables auto-commit
+      ;; before/after running the transaction.
+      (.setAutoCommit true)
+      ;; how long for a connection request to wait before throwing a SQLException
+      ;; from DataSource/getConnection (See also maximumPoolSize below)
+      (.setConnectionTimeout (* 15 1000)) ;; 15s.
+      ;; Setting 0 here means we never remove idle connections from the pool.
+      (.setIdleTimeout 0)
+      ;; See docs @ https://github.com/brettwooldridge/HikariCP
+      (.setKeepaliveTime (* 5 60 1000)) ;; 5 minutes.
+      ;; And at some point read,
+      ;;  https://github.com/brettwooldridge/HikariCP/wiki/About-Pool-Sizing
+      (.setMaximumPoolSize 10)
+      ;; note: we leave .setMinimumIdle alone per docs recommendation.
+      ;; Setting 0 here means no maximum lifetime to a connection in the pool.
+      (.setMaxLifetime 0)
+      ;; note: we will leave .setValidationTimeout as default. it must be
+      ;; less than conn timeout. when HikariCP takes a connection from pool
+      ;; this is how long it's allowed to validate it before returning it
+      ;; from getConnection.
+      ;; Trying 15s for now for leakDetectionThreshold.
+      (.setLeakDetectionThreshold (* 15 1000))
+      )))
+
+(defn- create-connection-pool
+  "Create a connection pool. Our configuration here has all of our connections
+   living forever in a fixed-sized pool. While the pool may or may not give us
+   enormous benefit over a file-sys based db like sqlite, it's integration with
+   metrics gives us a ton of observability with what's happening with the db."
+  (^DataSource [jdbc-url]
+   (create-connection-pool jdbc-url nil))
+  (^DataSource [jdbc-url ^MetricRegistry metric-registry]
+   (let [the-pool (create-hikari-datasource jdbc-url)]
+     (when (some? metric-registry)
+       (.setMetricsTrackerFactory the-pool
+         (CodahaleMetricsTrackerFactory. metric-registry)))
+     the-pool)))
+
+(def get-unpooled-datasource*
   (memoize
     #(jdbc/get-datasource (str "jdbc:sqlite:" %))))
 
+(def get-datasource*
+  (memoize
+    #(create-connection-pool (str "jdbc:sqlite:" %1) %2)))
+
 (defn- comment-line?
   [line]
   (str/starts-with? line "--"))
@@ -27,6 +77,7 @@
           acc)))))
 
 (defn apply-schema! [db]
+  {:pre [(some? db)]}
   (doseq [statement (parse-schema)]
     (try
       (jdbc/execute-one! db [statement])
@@ -38,12 +89,12 @@
           (throw e))))))
 
 (defn init!
-  ^DataSource [path]
-  (doto (get-datasource* path)
+  ^DataSource [path ^MetricRegistry metric-registry]
+  (doto (get-datasource* path metric-registry)
     apply-schema!))
 
 (comment
-  (init! "./n.db"))
+  (init! "./n.db" nil))
 
 ;; --