[uss_qualifier] Reduce number of UTMClientSessions generated by DSSInstanceResource and add timeout_seconds config option

monitoring/monitorlib/infrastructure.py

@@ -84,6 +84,10 @@ class UTMClientSession(requests.Session):
     If the URL starts with '/', then automatically prefix the URL with the
     `prefix_url` specified on construction (this is usually the base URL of the
     DSS).
+
+    When possible, a UTMClientSession should be reused rather than creating a
+    new one because an excessive number of UTMClientSessions can exhaust the
+    number of connections allowed by the system (see #1407).
     """
 
     def __init__(

monitoring/uss_qualifier/resources/astm/f3411/dss.py

@@ -5,6 +5,7 @@
 from implicitdict import ImplicitDict
 
 from monitoring.monitorlib import infrastructure
+from monitoring.monitorlib.infrastructure import UTMClientSession
 from monitoring.monitorlib.rid import RIDVersion
 from monitoring.uss_qualifier.reports.report import ParticipantID
 from monitoring.uss_qualifier.resources.communications import AuthAdapterResource
@@ -40,12 +41,12 @@ def __init__(
         participant_id: ParticipantID,
         base_url: str,
         rid_version: RIDVersion,
-        auth_adapter: infrastructure.AuthAdapter,
+        client: UTMClientSession,
     ):
         self.participant_id = participant_id
         self.base_url = base_url
         self.rid_version = rid_version
-        self.client = infrastructure.UTMClientSession(base_url, auth_adapter)
+        self.client = client
 
     def is_same_as(self, other: DSSInstance) -> bool:
         return (
@@ -81,7 +82,9 @@ def __init__(
             specification.participant_id,
             specification.base_url,
             specification.rid_version,
-            auth_adapter.adapter,
+            infrastructure.UTMClientSession(
+                specification.base_url, auth_adapter.adapter
+            ),
         )
 
     @classmethod

monitoring/uss_qualifier/resources/astm/f3548/v21/dss.py

@@ -41,10 +41,10 @@
 )
 from uas_standards.astm.f3548.v21.constants import Scope
 
-from monitoring.monitorlib import infrastructure
 from monitoring.monitorlib.fetch import Query, QueryError, QueryType, query_and_describe
 from monitoring.monitorlib.fetch import scd as fetch
 from monitoring.monitorlib.fetch.scd import FetchedSubscription, FetchedSubscriptions
+from monitoring.monitorlib.infrastructure import UTMClientSession
 from monitoring.monitorlib.inspection import calling_function_name, fullname
 from monitoring.monitorlib.mutate import scd as mutate
 from monitoring.monitorlib.mutate.scd import MutatedSubscription
@@ -65,6 +65,9 @@ class DSSInstanceSpecification(ImplicitDict):
     supports_ovn_request: Optional[bool]
     """Whether this DSS instance supports the optional extension not part of the original F3548 standard API allowing a USS to request a specific OVN when creating or updating an operational intent."""
 
+    timeout_seconds: Optional[float]
+    """If specified, number of seconds to allow before timing out requests to this DSS instance."""
+
     def __init__(self, *args, **kwargs):
         super().__init__(**kwargs)
         try:
@@ -77,21 +80,21 @@ class DSSInstance:
     participant_id: str
     user_participant_ids: list[str]
     base_url: str
-    client: infrastructure.UTMClientSession
+    client: UTMClientSession
     _scopes_authorized: set[str]
 
     def __init__(
         self,
         participant_id: str,
         user_participant_ids: list[str],
         base_url: str,
-        auth_adapter: infrastructure.AuthAdapter,
+        client: UTMClientSession,
         scopes_authorized: list[str],
     ):
         self.participant_id = participant_id
         self.user_participant_ids = user_participant_ids
         self.base_url = base_url
-        self.client = infrastructure.UTMClientSession(base_url, auth_adapter)
+        self.client = client
         self._scopes_authorized = set(
             s.value if isinstance(s, Enum) else s for s in scopes_authorized
         )
@@ -126,7 +129,11 @@ def with_different_auth(
             participant_id=self.participant_id,
             user_participant_ids=self.user_participant_ids,
             base_url=self.base_url,
-            auth_adapter=auth_adapter.adapter,
+            client=UTMClientSession(
+                self.base_url,
+                auth_adapter=auth_adapter.adapter,
+                timeout_seconds=self.client.timeout_seconds,
+            ),
             scopes_authorized=list(scopes_required),
         )
 
@@ -694,6 +701,7 @@ def delete_subscription(self, sub_id: str, sub_version: str) -> MutatedSubscript
 class DSSInstanceResource(Resource[DSSInstanceSpecification]):
     _specification: DSSInstanceSpecification
     _auth_adapter: AuthAdapterResource
+    _client: UTMClientSession
 
     def __init__(
         self,
@@ -704,6 +712,14 @@ def __init__(
         super().__init__(specification, resource_origin)
         self._specification = specification
         self._auth_adapter = auth_adapter
+        timeout_seconds = (
+            specification.timeout_seconds
+            if "timeout_seconds" in specification
+            else None
+        )
+        self._client = UTMClientSession(
+            self._specification.base_url, auth_adapter.adapter, timeout_seconds
+        )
 
     def can_use_scope(self, scope: str) -> bool:
         return scope in self._auth_adapter.scopes
@@ -777,7 +793,7 @@ def get_instance(self, scopes_required: dict[str, str]) -> DSSInstance:
                 else []
             ),
             self._specification.base_url,
-            self._auth_adapter.adapter,
+            self._client,
             list(scopes_required),
         )
 

schemas/monitoring/uss_qualifier/resources/astm/f3548/v21/dss/DSSInstanceSpecification.json

@@ -22,6 +22,13 @@
         "null"
       ]
     },
+    "timeout_seconds": {
+      "description": "If specified, number of seconds to allow before timing out requests to this DSS instance.",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
     "user_participant_ids": {
       "description": "IDs of any participants using this DSS instance, apart from the USS responsible for this DSS instance.",
       "items": {