add lock

5 files changed, 16 insertions, 1 deletions

diff --git a/.gitignore b/.gitignore
index 296fc8c..fcbfd70 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,2 +1,3 @@
 .direnv
 _build
+gatling
diff --git a/docker-compose.yml b/docker-compose.yml
index eb90487..3304f71 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -34,6 +34,7 @@ services:
           memory: "110MB"
 
   db:
+    command: postgres -c 'max_connections=30'
     image: postgres:latest
     environment:
       - POSTGRES_PASSWORD=123
diff --git a/lib/handler.ml b/lib/handler.ml
index 121a0c5..4babe6e 100644
--- a/lib/handler.ml
+++ b/lib/handler.ml
@@ -8,6 +8,10 @@ let valid_debit value limit balance =
 let create_transaction client_id (db_pool : Query.pool) (request : Request.t) =
   Caqti_eio.Pool.use
     (fun conn ->
+      let module C = (val conn : Rapper_helper.CONNECTION) in
+      C.with_transaction
+      @@ fun () ->
+      let _ = Query.lock client_id conn in
       let client_opt =
         Option.join @@ Result.to_option @@ Query.find_client client_id conn
       in
diff --git a/lib/query.ml b/lib/query.ml
index 1fdc2c3..2dab927 100644
--- a/lib/query.ml
+++ b/lib/query.ml
@@ -58,6 +58,14 @@ module Q = struct
         |sql}
         record_out]
   ;;
+
+  let lock =
+    [%rapper
+      execute
+        {sql|
+          SELECT pg_advisory_xact_lock(%int{client_id})
+        |sql}]
+  ;;
 end
 
 let ( let* ) = Result.bind
@@ -80,3 +88,4 @@ let execute_transaction ~client_id ~(op : Operation.transaction_op) conn =
 let find_client id conn = Q.client ~id conn
 let balance client_id conn = Q.balance ~client_id conn
 let transactions client_id conn = Q.transactions ~client_id conn
+let lock client_id conn = Q.lock ~client_id conn
diff --git a/nginx.conf b/nginx.conf
index 42d8b20..c005fad 100644
--- a/nginx.conf
+++ b/nginx.conf
@@ -1,5 +1,5 @@
 events {
-    worker_connections 2000;
+    worker_connections 256;
 }
 
 http {