✨ Make the pool initialization process and defaults reusable

And add the ability to skip pool initialization if no enough data is
provided. Mainly for initialize pools based on configuration for not
essential/dynamic services.

backend/src/app/db.clj

@@ -55,54 +55,66 @@
 (s/def ::migrations map?)
 (s/def ::name keyword?)
 (s/def ::password ::us/string)
-(s/def ::read-only ::us/boolean)
 (s/def ::uri ::us/not-empty-string)
 (s/def ::username ::us/string)
 (s/def ::validation-timeout ::us/integer)
+(s/def ::read-only? ::us/boolean)
 
-(defmethod ig/pre-init-spec ::pool [_]
-  (s/keys :req-un [::uri ::name
+(s/def ::pool-options
+  (s/keys :opt-un [::uri ::name
                    ::min-size
                    ::max-size
                    ::connection-timeout
-                   ::validation-timeout]
-          :opt-un [::migrations
+                   ::validation-timeout
+                   ::migrations
                    ::username
                    ::password
                    ::mtx/metrics
-                   ::read-only]))
+                   ::read-only?]))
+
+(def defaults
+  {:name :main
+   :min-size 0
+   :max-size 30
+   :connection-timeout 10000
+   :validation-timeout 10000
+   :idle-timeout 120000 ; 2min
+   :max-lifetime 1800000 ; 30m
+   :read-only? false})
 
 (defmethod ig/prep-key ::pool
   [_ cfg]
-  (merge {:name :main
-          :min-size 0
-          :max-size 30
-          :connection-timeout 10000
-          :validation-timeout 10000
-          :idle-timeout 120000 ; 2min
-          :max-lifetime 1800000 ; 30m
-          :read-only false}
-         (d/without-nils cfg)))
+  (merge defaults (d/without-nils cfg)))
+
+;; Don't validate here, just validate that a map is received.
+(defmethod ig/pre-init-spec ::pool [_] ::pool-options)
 
 (defmethod ig/init-key ::pool
-  [_ {:keys [migrations name read-only] :as cfg}]
-  (l/info :hint "initialize connection pool"
-          :name (d/name name)
-          :uri (:uri cfg)
-          :read-only read-only
-          :with-credentials (and (contains? cfg :username)
-                                 (contains? cfg :password))
-          :min-size (:min-size cfg)
-          :max-size (:max-size cfg))
+  [_ {:keys [migrations read-only? uri] :as cfg}]
+  (if uri
+    (let [pool (create-pool cfg)]
+      (l/info :hint "initialize connection pool"
+              :name (d/name (:name cfg))
+              :uri uri
+              :read-only read-only?
+              :with-credentials (and (contains? cfg :username)
+                                     (contains? cfg :password))
+              :min-size (:min-size cfg)
+              :max-size (:max-size cfg))
+      (when-not read-only?
+        (some->> (seq migrations) (apply-migrations! pool)))
+      pool)
 
-  (let [pool (create-pool cfg)]
-    (when-not read-only
-      (some->> (seq migrations) (apply-migrations! pool)))
-    pool))
+    (do
+      (l/warn :hint "unable to initialize pool, missing url"
+              :name (d/name (:name cfg))
+              :read-only read-only?)
+      nil)))
 
 (defmethod ig/halt-key! ::pool
   [_ pool]
-  (.close ^HikariDataSource pool))
+  (when pool
+    (.close ^HikariDataSource pool)))
 
 (defn- apply-migrations!
   [pool migrations]
@@ -126,7 +138,7 @@
       (.setJdbcUrl           (str "jdbc:" uri))
       (.setPoolName          (d/name (:name cfg)))
       (.setAutoCommit true)
-      (.setReadOnly          (:read-only cfg))
+      (.setReadOnly          (:read-only? cfg))
       (.setConnectionTimeout (:connection-timeout cfg))
       (.setValidationTimeout (:validation-timeout cfg))
       (.setIdleTimeout       (:idle-timeout cfg))