feat (diracx): add a randomized connection pooling

docs/source/conf.py

@@ -306,6 +306,7 @@ def setup(app):
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3/", None),
     "matplotlib": ("https://matplotlib.org/", None),
+    "requests": ("https://requests.readthedocs.io/en/latest/", None),
 }
 
 # check for :param / :return in html, points to faulty syntax, missing empty lines, etc.

src/DIRAC/FrameworkSystem/Utilities/diracx.py

@@ -1,11 +1,16 @@
+import random
 import requests
 
 from cachetools import TTLCache, LRUCache, cached
 from cachetools.keys import hashkey
 from pathlib import Path
+from requests.adapters import HTTPAdapter
 from tempfile import NamedTemporaryFile
 from typing import Any
 from collections.abc import Generator
+from urllib3 import PoolManager
+from urllib3.connectionpool import HTTPConnectionPool, HTTPSConnectionPool
+
 from DIRAC import gConfig
 from DIRAC.ConfigurationSystem.Client.Helpers import Registry
 from contextlib import contextmanager
@@ -26,7 +31,74 @@
 DEFAULT_TOKEN_CACHE_TTL = 5 * 60
 DEFAULT_TOKEN_CACHE_SIZE = 1024
 
-legacy_exchange_session = requests.Session()
+# Number of pools to use for a given host.
+# It should be in the order of host behind the alias
+SESSION_NUM_POOLS = 20
+# Number of connection per Pool
+SESSION_CONNECTION_POOL_MAX_SIZE = 10
+
+
+class RandomizedPoolManager(PoolManager):
+    """
+    A PoolManager subclass that creates multiple connection pools per host.
+    Each connection request randomly picks one of the available pools.
+    """
+
+    def __init__(self, num_pools=3, **kwargs):
+        self.num_pools = num_pools
+        super().__init__(**kwargs)
+
+    def connection_from_host(self, host, port=None, scheme="http", pool_kwargs=None):
+        # Pick a random index to diversify the pool key.
+
+        rand_index = random.randint(0, self.num_pools - 1)
+        pool_key = (f"{host}-{rand_index}", port, scheme)
+        if pool_key in self.pools:
+            return self.pools[pool_key]
+
+        # Create a new pool if none exists for this key.
+        if scheme == "http":
+            self.pools[pool_key] = HTTPConnectionPool(host, port, **self.connection_pool_kw)
+        elif scheme == "https":
+            self.pools[pool_key] = HTTPSConnectionPool(host, port, **self.connection_pool_kw)
+        else:
+            raise ValueError(f"Unsupported scheme: {scheme}")
+
+        return self.pools[pool_key]
+
+
+class RandomizedHTTPAdapter(HTTPAdapter):
+    """
+    An HTTPAdapter that uses the RandomizedPoolManager.
+    """
+
+    def __init__(self, num_pools=3, maxsize=10, **kwargs):
+        self.num_pools = num_pools
+        self.custom_maxsize = maxsize
+        super().__init__(**kwargs)
+
+    def init_poolmanager(self, connections, maxsize, block=False, **pool_kwargs):
+        """
+        Initialize the pool manager with our custom RandomizedPoolManager.
+        """
+        # This ends up being passed to the HTTP(s)ConnectionPool constructors
+        pool_kwargs.update(
+            {
+                "maxsize": self.custom_maxsize,
+                "block": block,
+            }
+        )
+        self.poolmanager = RandomizedPoolManager(**pool_kwargs)
+
+
+# Create a requests session.
+diracx_session = requests.Session()
+# Create an instance of the custom adapter.
+diracx_pool_adapter = RandomizedHTTPAdapter(num_pools=SESSION_NUM_POOLS, maxsize=SESSION_CONNECTION_POOL_MAX_SIZE)
+
+# Mount the adapter to handle both HTTP and HTTPS.
+diracx_session.mount("http://", diracx_pool_adapter)
+diracx_session.mount("https://", diracx_pool_adapter)
 
 
 def get_token(
@@ -45,7 +117,7 @@ def get_token(
     vo = Registry.getVOForGroup(group)
     scopes = [f"vo:{vo}", f"group:{group}"] + [f"property:{prop}" for prop in dirac_properties]
 
-    r = legacy_exchange_session.get(
+    r = diracx_session.get(
         f"{diracxUrl}/api/auth/legacy-exchange",
         params={
             "preferred_username": username,