chore: postres driver allow setting the max number of connection from a parameter (#2246)

* postres driver: allow setting the max number of connections from a parameter

apps/wakunode2/app.nim

@@ -491,6 +491,7 @@ proc setupProtocols(node: WakuNode,
     let archiveDriverRes = ArchiveDriver.new(conf.storeMessageDbUrl,
                                              conf.storeMessageDbVacuum,
                                              conf.storeMessageDbMigration,
+                                             conf.storeMaxNumDbConnections,
                                              onErrAction)
     if archiveDriverRes.isErr():
       return err("failed to setup archive driver: " & archiveDriverRes.error)

apps/wakunode2/external_config.nim

@@ -273,6 +273,11 @@ type
         defaultValue: true,
         name: "store-message-db-migration" }: bool
 
+      storeMaxNumDbConnections* {.
+        desc: "Maximum number of simultaneous Postgres connections.",
+        defaultValue: 50,
+        name: "store-max-num-db-connections" }: int
+
       ## Filter config
 
       filter* {.

waku/waku_archive/driver/builder.nim

@@ -28,12 +28,14 @@ proc new*(T: type ArchiveDriver,
           url: string,
           vacuum: bool,
           migrate: bool,
+          maxNumConn: int,
           onErrAction: OnErrHandler):
           Result[T, string] =
   ## url - string that defines the database
   ## vacuum - if true, a cleanup operation will be applied to the database
   ## migrate - if true, the database schema will be updated
-  ## onErrAction - called if, e.g., the connection with db got lost forever
+  ## maxNumConn - defines the maximum number of connections to handle simultaneously (Postgres)
+  ## onErrAction - called if, e.g., the connection with db got lost
 
   let dbUrlValidationRes = dburl.validateDbUrl(url)
   if dbUrlValidationRes.isErr():
@@ -81,7 +83,9 @@ proc new*(T: type ArchiveDriver,
 
   of "postgres":
     when defined(postgres):
-      let res = PostgresDriver.new(dbUrl = url, onErrAction = onErrAction)
+      let res = PostgresDriver.new(dbUrl = url,
+                                   maxConnections = maxNumConn,
+                                   onErrAction = onErrAction)
       if res.isErr():
         return err("failed to init postgres archive driver: " & res.error)
 

waku/waku_archive/driver/postgres_driver/postgres_driver.nim

@@ -84,18 +84,21 @@ const SelectWithCursorAscStmtDef =
           storedAt <= $6
     ORDER BY storedAt ASC LIMIT $7;"""
 
-const MaxNumConns = 50 #TODO: we may need to set that from app args (maybe?)
+const DefaultMaxNumConns = 50
 
 proc new*(T: type PostgresDriver,
           dbUrl: string,
-          maxConnections: int = MaxNumConns,
+          maxConnections = DefaultMaxNumConns,
           onErrAction: OnErrHandler = nil):
           ArchiveDriverResult[T] =
 
-  let readConnPool = PgAsyncPool.new(dbUrl, maxConnections).valueOr:
+  ## Very simplistic split of max connections
+  let maxNumConnOnEachPool = int(maxConnections / 2)
+
+  let readConnPool = PgAsyncPool.new(dbUrl, maxNumConnOnEachPool).valueOr:
     return err("error creating read conn pool PgAsyncPool")
 
-  let writeConnPool = PgAsyncPool.new(dbUrl, maxConnections).valueOr:
+  let writeConnPool = PgAsyncPool.new(dbUrl, maxNumConnOnEachPool).valueOr:
     return err("error creating write conn pool PgAsyncPool")
 
   if not isNil(onErrAction):