#420: adding possibility to fine tune connection pool and their behavior on DB and sending DB metrics to Prometheus

Author: lsulak

server/src/main/resources/reference.conf

@@ -8,8 +8,16 @@
     user=atum_user
     password=changeme
     passwordSecretId="serviceUserSecretKey"
-    # maximum number of connections that HikariCP will keep in the pool, including both idle and in-use connections
-    maxPoolSize=10
+    # Pool settings
+    minimumIdle=4  # Min number of idle connections Hikari maintains in the pool. default = maxPoolSize
+    maxPoolSize=10  # Max number of connections that HikariCP will keep in the pool, including both idle and in-use ones
+    # Connection lifecycle settings
+    idleTimeout=180000  # How long a connection can sit idle in the pool before being removed.
+    keepaliveTime=60000 # How often Hikari sends a keep-alive query to verify the connection is still valid while it's idle in the pool.
+    maxLifetime=600000  # Refresh connections regularly
+    # Misc settings
+    leakDetectionThreshold=60000 # this is disabled by default
+    prometheusMetricsEnabled=true
   }
   aws {
     region = "af-south-1"

server/src/main/scala/za/co/absa/atum/server/api/database/TransactorProvider.scala

@@ -17,7 +17,9 @@
 package za.co.absa.atum.server.api.database
 
 import com.zaxxer.hikari.HikariConfig
+import com.zaxxer.hikari.metrics.prometheus.PrometheusMetricsTrackerFactory
 import doobie.hikari.HikariTransactor
+import io.prometheus.client.CollectorRegistry
 import za.co.absa.atum.server.config.PostgresConfig
 import zio.Runtime.defaultBlockingExecutor
 import zio._
@@ -40,8 +42,24 @@ object TransactorProvider {
         val config = new HikariConfig()
         config.setDataSourceClassName(postgresConfig.dataSourceClass)
         config.setDataSourceProperties(dataSourceProperties)
-        config.setMaximumPoolSize(postgresConfig.maxPoolSize)
+
+        // Pool settings, especially sizing
         config.setPoolName("DoobiePostgresHikariPool")
+        config.setMinimumIdle(postgresConfig.minimumIdle)
+        config.setMaximumPoolSize(postgresConfig.maxPoolSize)
+
+        // Connection lifecycle settings
+        config.setIdleTimeout(postgresConfig.idleTimeout)
+        config.setKeepaliveTime(postgresConfig.keepaliveTime)
+        config.setMaxLifetime(postgresConfig.maxLifetime)
+
+        // Misc DB settings
+        config.setLeakDetectionThreshold(postgresConfig.leakDetectionThreshold)
+
+        // Prometheus metrics integration
+        if (postgresConfig.prometheusMetricsEnabled)
+          config.setMetricsTrackerFactory(new PrometheusMetricsTrackerFactory(CollectorRegistry.defaultRegistry))
+
         config
       }
 

server/src/main/scala/za/co/absa/atum/server/config/PostgresConfig.scala

@@ -26,8 +26,14 @@ case class PostgresConfig(
   databaseName: String,
   user: String,
   password: String,
+  passwordSecretId: String,
+  minimumIdle: Int,
   maxPoolSize: Int,
-  passwordSecretId: String
+  idleTimeout: Int,
+  keepaliveTime: Int,
+  maxLifetime: Int,
+  leakDetectionThreshold: Int,
+  prometheusMetricsEnabled: Boolean
 )
 
 object PostgresConfig {