feat: introduce pool acquisition timeout (fixes #2348)

The configuration option db-pool-acquisition-timeout
specifies the time in seconds to wait for the pool to
free up a connection slot. Otherwise, a 504 error is
returned. By default, there is no timeout.

test/io/configs/expected/aliases.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public"
 db-max-rows = 1000
 db-plan-enabled = false
 db-pool = 10
+db-pool-acquisition-timeout = ""
 db-pre-request = "check_alias"
 db-prepared-statements = true
 db-root-spec = "open_alias"

test/io/configs/expected/boolean-numeric.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public"
 db-max-rows = ""
 db-plan-enabled = false
 db-pool = 10
+db-pool-acquisition-timeout = ""
 db-pre-request = ""
 db-prepared-statements = false
 db-root-spec = ""

test/io/configs/expected/boolean-string.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public"
 db-max-rows = ""
 db-plan-enabled = false
 db-pool = 10
+db-pool-acquisition-timeout = ""
 db-pre-request = ""
 db-prepared-statements = false
 db-root-spec = ""

test/io/configs/expected/defaults.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public"
 db-max-rows = ""
 db-plan-enabled = false
 db-pool = 10
+db-pool-acquisition-timeout = ""
 db-pre-request = ""
 db-prepared-statements = true
 db-root-spec = ""

test/io/configs/expected/no-defaults-with-db-other-authenticator.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public,extensions,other"
 db-max-rows = 100
 db-plan-enabled = true
 db-pool = 1
+db-pool-acquisition-timeout = 10
 db-pre-request = "test.other_custom_headers"
 db-prepared-statements = false
 db-root-spec = "other_root"

test/io/configs/expected/no-defaults-with-db.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public,extensions,private"
 db-max-rows = 1000
 db-plan-enabled = true
 db-pool = 1
+db-pool-acquisition-timeout = 10
 db-pre-request = "test.custom_headers"
 db-prepared-statements = false
 db-root-spec = "root"

test/io/configs/expected/no-defaults.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public,test"
 db-max-rows = 1000
 db-plan-enabled = true
 db-pool = 1
+db-pool-acquisition-timeout = 10
 db-pre-request = "please_run_fast"
 db-prepared-statements = false
 db-root-spec = "openapi_v3"

test/io/configs/expected/types.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public"
 db-max-rows = ""
 db-plan-enabled = false
 db-pool = 10
+db-pool-acquisition-timeout = ""
 db-pre-request = ""
 db-prepared-statements = true
 db-root-spec = ""

test/io/configs/no-defaults-env.yaml

@@ -7,6 +7,7 @@ PGRST_DB_EXTRA_SEARCH_PATH: public, test
 PGRST_DB_MAX_ROWS: 1000
 PGRST_DB_PLAN_ENABLED: true
 PGRST_DB_POOL: 1
+PGRST_DB_POOL_ACQUISITION_TIMEOUT: 10
 PGRST_DB_PREPARED_STATEMENTS: false
 PGRST_DB_PRE_REQUEST: please_run_fast
 PGRST_DB_ROOT_SPEC: openapi_v3

test/io/configs/no-defaults.config

@@ -5,6 +5,7 @@ db-extra-search-path = "public, test"
 db-max-rows = 1000
 db-plan-enabled = true
 db-pool = 1
+db-pool-acquisition-timeout = 10
 db-pre-request = "please_run_fast"
 db-prepared-statements = false
 db-root-spec = "openapi_v3"

test/io/test_io.py

@@ -548,6 +548,22 @@ def test_pool_size(defaultenv, metapostgrest):
         assert delta > 1 and delta < 1.5
 
 
+def test_pool_acquisition_timeout(defaultenv, metapostgrest):
+    "Verify that PGRST_DB_POOL_ACQUISITON_TIMEOUT times out when the pool is empty"
+
+    env = {
+        **defaultenv,
+        "PGRST_DB_POOL": "1",
+        "PGRST_DB_POOL_ACQUISITION_TIMEOUT": "1",  # 1 second
+    }
+
+    with run(env=env, no_pool_connection_available=True) as postgrest:
+        response = postgrest.session.get("/projects")
+        assert response.status_code == 504
+        data = response.json()
+        assert data["message"] == "Timed out acquiring connection from connection pool."
+
+
 def test_change_statement_timeout_held_connection(defaultenv, metapostgrest):
     "Statement timeout changes take effect immediately, even with a request outliving the reconfiguration"
 

test/spec/SpecHelper.hs

@@ -79,6 +79,7 @@ baseCfg = let secret = Just $ encodeUtf8 "reallyreallyreallyreallyverysafe" in
   , configDbMaxRows             = Nothing
   , configDbPlanEnabled         = False
   , configDbPoolSize            = 10
+  , configDbPoolAcquisitionTimeout = Nothing
   , configDbPreRequest          = Just $ QualifiedIdentifier "test" "switch_role"
   , configDbPreparedStatements  = True
   , configDbRootSpec            = Nothing