SQLite cache: Use requests_cache.CachedSession for better concurrency

Users on Apple M2 Max reported DB lock errors:

[grafana_wtf.core]
  INFO: Fetching dashboards in parallel with 5 concurrent requests

[requests_cache.backends.sqlite]
  WARNING: Database is locked in thread 6272069632; retrying (1/3)

Also segmentation faults, and leaks:

  UserWarning: resource_tracker: There appear to be 1 leaked semaphore
  objects to clean up at shutdown

CHANGES.rst

@@ -12,6 +12,8 @@ in progress
 - Add subcommand ``explore permissions``. Thanks, @meyerder.
 - Added support for Python 3.12
 - Removed support for Python 3.7
+- SQLite cache: Use ``requests_cache.CachedSession`` for better concurrency
+  behaviour. Thanks, @JensRichnow and @JWCook.
 
 2024-03-07 0.18.0
 =================

grafana_wtf/__init__.py

@@ -2,3 +2,6 @@
 
 __appname__ = "grafana-wtf"
 __version__ = "0.18.0"
+
+# Amalgamate `requests` to `niquests`.
+import grafana_wtf.compat

grafana_wtf/compat.py

@@ -0,0 +1,12 @@
+from sys import modules
+
+import niquests
+import urllib3
+
+# Amalgamate the module namespace to make all modules aiming
+# to use `requests`, in fact use `niquests` instead.
+modules["requests"] = niquests
+modules["requests.adapters"] = niquests.adapters
+modules["requests.sessions"] = niquests.sessions
+modules["requests.exceptions"] = niquests.exceptions
+modules["requests.packages.urllib3"] = urllib3

grafana_wtf/core.py

@@ -16,6 +16,7 @@
 from grafana_client.api import GrafanaApi
 from grafana_client.client import GrafanaClientError, GrafanaUnauthorizedError
 from munch import Munch, munchify
+from requests_cache import CachedSession
 from tqdm import tqdm
 from tqdm.contrib.logging import tqdm_logging_redirect
 from urllib3.exceptions import InsecureRequestWarning
@@ -34,6 +35,8 @@
 
 
 class GrafanaEngine:
+    session = niquests.Session()
+
     def __init__(self, grafana_url, grafana_token):
         self.grafana_url = grafana_url
         self.grafana_token = grafana_token
@@ -56,9 +59,11 @@ def enable_cache(self, expire_after=60, drop_cache=False):
             log.info(f"Response cache will expire immediately (expire_after=0)")
         else:
             log.info(f"Response cache will expire after {expire_after} seconds")
-        requests_cache.install_cache(cache_name=__appname__, expire_after=expire_after, use_cache_dir=True)
-        cache_database_file = requests_cache.get_cache().db_path
-        log.info(f"Response cache database location is {cache_database_file}")
+
+        self.session = CachedSession(cache_name=__appname__, expire_after=expire_after, use_cache_dir=True)
+
+        cache = self.session.cache
+        log.info(f"Response cache database location is: {cache.db_path}")
         if drop_cache:
             log.info("Dropping response cache")
             self.clear_cache()
@@ -72,8 +77,8 @@ def clear_cache(self):
     def enable_concurrency(self, concurrency):
         self.concurrency = concurrency
 
-    @staticmethod
-    def grafana_client_factory(grafana_url, grafana_token=None):
+    @classmethod
+    def grafana_client_factory(cls, grafana_url, grafana_token=None):
         url = urlparse(grafana_url)
 
         # Grafana API Key auth
@@ -97,6 +102,9 @@ def grafana_client_factory(grafana_url, grafana_token=None):
             url_path_prefix=url.path.lstrip("/"),
             verify=verify,
         )
+        if cls.session:
+            cls.session.headers["User-Agent"] = grafana.client.user_agent
+            grafana.client.s = cls.session
 
         return grafana