From 042eedfa2b56caef0d4873583e768ca3664a881f Mon Sep 17 00:00:00 2001
From: Erik Johnston <erik@matrix.org>
Date: Wed, 21 Feb 2018 20:49:55 +0000
Subject: [PATCH] Add hacky cache factor override system

---
 synapse/app/synctl.py              |  4 ++++
 synapse/storage/state.py           |  4 ++--
 synapse/util/caches/__init__.py    | 10 ++++++++++
 synapse/util/caches/descriptors.py |  4 ++--
 4 files changed, 18 insertions(+), 4 deletions(-)

diff --git a/synapse/app/synctl.py b/synapse/app/synctl.py
index 712dfa870..56ae08612 100755
--- a/synapse/app/synctl.py
+++ b/synapse/app/synctl.py
@@ -171,6 +171,10 @@ def main():
     if cache_factor:
         os.environ["SYNAPSE_CACHE_FACTOR"] = str(cache_factor)
 
+    cache_factors = config.get("synctl_cache_factors", {})
+    for cache_name, factor in cache_factors.iteritems():
+        os.environ["SYNAPSE_CACHE_FACTOR_" + cache_name.upper()] = str(factor)
+
     worker_configfiles = []
     if options.worker:
         start_stop_synapse = False
diff --git a/synapse/storage/state.py b/synapse/storage/state.py
index bdee14a8e..c11bc5217 100644
--- a/synapse/storage/state.py
+++ b/synapse/storage/state.py
@@ -23,7 +23,7 @@ from twisted.internet import defer
 
 from synapse.storage.background_updates import BackgroundUpdateStore
 from synapse.storage.engines import PostgresEngine
-from synapse.util.caches import intern_string, CACHE_SIZE_FACTOR
+from synapse.util.caches import intern_string, get_cache_factor_for
 from synapse.util.caches.descriptors import cached, cachedList
 from synapse.util.caches.dictionary_cache import DictionaryCache
 from synapse.util.stringutils import to_ascii
@@ -57,7 +57,7 @@ class StateGroupWorkerStore(SQLBaseStore):
         super(StateGroupWorkerStore, self).__init__(db_conn, hs)
 
         self._state_group_cache = DictionaryCache(
-            "*stateGroupCache*", 100000 * CACHE_SIZE_FACTOR
+            "*stateGroupCache*", 500000 * get_cache_factor_for("stateGroupCache")
         )
 
     @cached(max_entries=100000, iterable=True)
diff --git a/synapse/util/caches/__init__.py b/synapse/util/caches/__init__.py
index 183faf75a..900575eb3 100644
--- a/synapse/util/caches/__init__.py
+++ b/synapse/util/caches/__init__.py
@@ -22,6 +22,16 @@ import six
 
 CACHE_SIZE_FACTOR = float(os.environ.get("SYNAPSE_CACHE_FACTOR", 0.5))
 
+
+def get_cache_factor_for(cache_name):
+    env_var = "SYNAPSE_CACHE_FACTOR_" + cache_name.upper()
+    factor = os.environ.get(env_var)
+    if factor:
+        return float(factor)
+
+    return CACHE_SIZE_FACTOR
+
+
 caches_by_name = {}
 collectors_by_name = {}
 
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index fc1874b65..65a1042de 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -17,7 +17,7 @@ import logging
 
 from synapse.util.async import ObservableDeferred
 from synapse.util import unwrapFirstError, logcontext
-from synapse.util.caches import CACHE_SIZE_FACTOR
+from synapse.util.caches import get_cache_factor_for
 from synapse.util.caches.lrucache import LruCache
 from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
 from synapse.util.stringutils import to_ascii
@@ -313,7 +313,7 @@ class CacheDescriptor(_CacheDescriptorBase):
             orig, num_args=num_args, inlineCallbacks=inlineCallbacks,
             cache_context=cache_context)
 
-        max_entries = int(max_entries * CACHE_SIZE_FACTOR)
+        max_entries = int(max_entries * get_cache_factor_for(orig.__name__))
 
         self.max_entries = max_entries
         self.tree = tree