Merge branch 'erikj/reduce_size_of_cache' into erikj/merge_cache_prs

changelog.d/9881.feature

@@ -0,0 +1 @@
+Add experimental option to track memory usage of the caches.

mypy.ini

@@ -172,3 +172,6 @@ ignore_missing_imports = True
 
 [mypy-txacme.*]
 ignore_missing_imports = True
+
+[mypy-pympler.*]
+ignore_missing_imports = True

synapse/app/generic_worker.py

@@ -454,6 +454,7 @@ def start(config_options):
         config.server.update_user_directory = False
 
     synapse.events.USE_FROZEN_DICTS = config.use_frozen_dicts
+    synapse.util.caches.lrucache.TRACK_MEMORY_USAGE = config.caches.track_memory_usage
 
     hs = GenericWorkerServer(
         config.server_name,

synapse/app/homeserver.py

@@ -341,6 +341,7 @@ def setup(config_options):
         sys.exit(0)
 
     events.USE_FROZEN_DICTS = config.use_frozen_dicts
+    synapse.util.caches.lrucache.TRACK_MEMORY_USAGE = config.caches.track_memory_usage
 
     hs = SynapseHomeServer(
         config.server_name,

synapse/config/cache.py

@@ -17,6 +17,8 @@ import re
 import threading
 from typing import Callable, Dict
 
+from synapse.python_dependencies import DependencyException, check_requirements
+
 from ._base import Config, ConfigError
 
 # The prefix for all cache factor-related environment variables
@@ -189,6 +191,15 @@ class CacheConfig(Config):
                 )
             self.cache_factors[cache] = factor
 
+        self.track_memory_usage = cache_config.get("track_memory_usage", False)
+        if self.track_memory_usage:
+            try:
+                check_requirements("cache_memory")
+            except DependencyException as e:
+                raise ConfigError(
+                    e.message  # noqa: B306, DependencyException.message is a property
+                )
+
         # Resize all caches (if necessary) with the new factors we've loaded
         self.resize_all_caches()
 

synapse/python_dependencies.py

@@ -121,6 +121,7 @@ CONDITIONAL_REQUIREMENTS = {
     # hiredis is not a *strict* dependency, but it makes things much faster.
     # (if it is not installed, we fall back to slow code.)
     "redis": ["txredisapi>=1.4.7", "hiredis"],
+    "cache_memory": ["pympler"],
 }
 
 ALL_OPTIONAL_REQUIREMENTS = set()  # type: Set[str]

synapse/util/caches/__init__.py

@@ -24,6 +24,11 @@ from synapse.config.cache import add_resizable_cache
 
 logger = logging.getLogger(__name__)
 
+
+# Whether to track estimated memory usage of the LruCaches.
+TRACK_MEMORY_USAGE = False
+
+
 caches_by_name = {}  # type: Dict[str, Sized]
 collectors_by_name = {}  # type: Dict[str, CacheMetric]
 
@@ -32,6 +37,11 @@ cache_hits = Gauge("synapse_util_caches_cache:hits", "", ["name"])
 cache_evicted = Gauge("synapse_util_caches_cache:evicted_size", "", ["name"])
 cache_total = Gauge("synapse_util_caches_cache:total", "", ["name"])
 cache_max_size = Gauge("synapse_util_caches_cache_max_size", "", ["name"])
+cache_memory_usage = Gauge(
+    "synapse_util_caches_cache_memory_usage",
+    "Estimated size in bytes of the caches",
+    ["name"],
+)
 
 response_cache_size = Gauge("synapse_util_caches_response_cache:size", "", ["name"])
 response_cache_hits = Gauge("synapse_util_caches_response_cache:hits", "", ["name"])
@@ -52,6 +62,7 @@ class CacheMetric:
     hits = attr.ib(default=0)
     misses = attr.ib(default=0)
     evicted_size = attr.ib(default=0)
+    memory_usage = attr.ib(default=None)
 
     def inc_hits(self):
         self.hits += 1
@@ -62,6 +73,19 @@ class CacheMetric:
     def inc_evictions(self, size=1):
         self.evicted_size += size
 
+    def inc_memory_usage(self, memory: int):
+        if self.memory_usage is None:
+            self.memory_usage = 0
+
+        self.memory_usage += memory
+
+    def dec_memory_usage(self, memory: int):
+        self.memory_usage -= memory
+
+    def clear_memory_usage(self):
+        if self.memory_usage is not None:
+            self.memory_usage = 0
+
     def describe(self):
         return []
 
@@ -81,6 +105,8 @@ class CacheMetric:
                 cache_total.labels(self._cache_name).set(self.hits + self.misses)
                 if getattr(self._cache, "max_size", None):
                     cache_max_size.labels(self._cache_name).set(self._cache.max_size)
+                if self.memory_usage is not None:
+                    cache_memory_usage.labels(self._cache_name).set(self.memory_usage)
             if self._collect_callback:
                 self._collect_callback()
         except Exception as e:

synapse/util/caches/lrucache.py

@@ -17,8 +17,10 @@ from functools import wraps
 from typing import (
     Any,
     Callable,
+    Collection,
     Generic,
     Iterable,
+    List,
     Optional,
     Type,
     TypeVar,
@@ -30,9 +32,35 @@ from typing import (
 from typing_extensions import Literal
 
 from synapse.config import cache as cache_config
-from synapse.util.caches import CacheMetric, register_cache
+from synapse.util.caches import TRACK_MEMORY_USAGE, CacheMetric, register_cache
 from synapse.util.caches.treecache import TreeCache
 
+try:
+    from pympler.asizeof import Asizer
+
+    def _get_size_of(val: Any, *, recurse=True) -> int:
+        """Get an estimate of the size in bytes of the object.
+
+        Args:
+            val: The object to size.
+            recurse: If true will include referenced values in the size,
+                otherwise only sizes the given object.
+        """
+        # Ignore singleton values when calculating memory usage.
+        if val in ((), None, ""):
+            return 0
+
+        sizer = Asizer()
+        sizer.exclude_refs((), None, "")
+        return sizer.asizeof(val, limit=100 if recurse else 0)
+
+
+except ImportError:
+
+    def _get_size_of(val: Any, *, recurse=True) -> int:
+        return 0
+
+
 # Function type: the type used for invalidation callbacks
 FT = TypeVar("FT", bound=Callable[..., Any])
 
@@ -54,16 +82,67 @@ def enumerate_leaves(node, depth):
 
 
 class _Node:
-    __slots__ = ["prev_node", "next_node", "key", "value", "callbacks"]
+    __slots__ = ["prev_node", "next_node", "key", "value", "callbacks", "memory"]
 
     def __init__(
-        self, prev_node, next_node, key, value, callbacks: Optional[set] = None
+        self,
+        prev_node,
+        next_node,
+        key,
+        value,
+        callbacks: Collection[Callable[[], None]] = (),
     ):
         self.prev_node = prev_node
         self.next_node = next_node
         self.key = key
         self.value = value
-        self.callbacks = callbacks or set()
+        self.memory = 0
+
+        # Set of callbacks to run when the node gets deleted. We store as a list
+        # rather than a set to keep memory usage down (and since we expect few
+        # entries per node the performance of checking for duplication in a list
+        # vs using a set is negligible).
+        #
+        # Note that we store this as an optional list to keep the memory
+        # footprint down. Empty lists are 56 bytes (and empty sets are 216 bytes).
+        self.callbacks = None  # type: Optional[List[Callable[[], None]]]
+
+        self.add_callbacks(callbacks)
+
+        if TRACK_MEMORY_USAGE:
+            self.memory = (
+                _get_size_of(key)
+                + _get_size_of(value)
+                + _get_size_of(self.callbacks, recurse=False)
+                + _get_size_of(self, recurse=False)
+            )
+            self.memory += _get_size_of(self.memory, recurse=False)
+
+    def add_callbacks(self, callbacks: Collection[Callable[[], None]]) -> None:
+        """Add to stored list of callbacks, removing duplicates."""
+
+        if not callbacks:
+            return
+
+        if not self.callbacks:
+            self.callbacks = []
+
+        for callback in callbacks:
+            if callback not in self.callbacks:
+                self.callbacks.append(callback)
+
+    def run_and_clear_callbacks(self) -> None:
+        """Run all callbacks and clear the stored set of callbacks. Used when
+        the node is being deleted.
+        """
+
+        if not self.callbacks:
+            return
+
+        for callback in self.callbacks:
+            callback()
+
+        self.callbacks = None
 
 
 class LruCache(Generic[KT, VT]):
@@ -177,10 +256,10 @@ class LruCache(Generic[KT, VT]):
 
         self.len = synchronized(cache_len)
 
-        def add_node(key, value, callbacks: Optional[set] = None):
+        def add_node(key, value, callbacks: Collection[Callable[[], None]] = ()):
             prev_node = list_root
             next_node = prev_node.next_node
-            node = _Node(prev_node, next_node, key, value, callbacks or set())
+            node = _Node(prev_node, next_node, key, value, callbacks)
             prev_node.next_node = node
             next_node.prev_node = node
             cache[key] = node
@@ -188,6 +267,9 @@ class LruCache(Generic[KT, VT]):
             if size_callback:
                 cached_cache_len[0] += size_callback(node.value)
 
+            if TRACK_MEMORY_USAGE and metrics:
+                metrics.inc_memory_usage(node.memory)
+
         def move_node_to_front(node):
             prev_node = node.prev_node
             next_node = node.next_node
@@ -211,16 +293,18 @@ class LruCache(Generic[KT, VT]):
                 deleted_len = size_callback(node.value)
                 cached_cache_len[0] -= deleted_len
 
-            for cb in node.callbacks:
-                cb()
-            node.callbacks.clear()
+            node.run_and_clear_callbacks()
+
+            if TRACK_MEMORY_USAGE and metrics:
+                metrics.dec_memory_usage(node.memory)
+
             return deleted_len
 
         @overload
         def cache_get(
             key: KT,
             default: Literal[None] = None,
-            callbacks: Iterable[Callable[[], None]] = ...,
+            callbacks: Collection[Callable[[], None]] = ...,
             update_metrics: bool = ...,
         ) -> Optional[VT]:
             ...
@@ -229,7 +313,7 @@ class LruCache(Generic[KT, VT]):
         def cache_get(
             key: KT,
             default: T,
-            callbacks: Iterable[Callable[[], None]] = ...,
+            callbacks: Collection[Callable[[], None]] = ...,
             update_metrics: bool = ...,
         ) -> Union[T, VT]:
             ...
@@ -238,13 +322,13 @@ class LruCache(Generic[KT, VT]):
         def cache_get(
             key: KT,
             default: Optional[T] = None,
-            callbacks: Iterable[Callable[[], None]] = (),
+            callbacks: Collection[Callable[[], None]] = (),
             update_metrics: bool = True,
         ):
             node = cache.get(key, None)
             if node is not None:
                 move_node_to_front(node)
-                node.callbacks.update(callbacks)
+                node.add_callbacks(callbacks)
                 if update_metrics and metrics:
                     metrics.inc_hits()
                 return node.value
@@ -260,10 +344,8 @@ class LruCache(Generic[KT, VT]):
                 # We sometimes store large objects, e.g. dicts, which cause
                 # the inequality check to take a long time. So let's only do
                 # the check if we have some callbacks to call.
-                if node.callbacks and value != node.value:
-                    for cb in node.callbacks:
-                        cb()
-                    node.callbacks.clear()
+                if value != node.value:
+                    node.run_and_clear_callbacks()
 
                 # We don't bother to protect this by value != node.value as
                 # generally size_callback will be cheap compared with equality
@@ -273,7 +355,7 @@ class LruCache(Generic[KT, VT]):
                     cached_cache_len[0] -= size_callback(node.value)
                     cached_cache_len[0] += size_callback(value)
 
-                node.callbacks.update(callbacks)
+                node.add_callbacks(callbacks)
 
                 move_node_to_front(node)
                 node.value = value
@@ -326,12 +408,14 @@ class LruCache(Generic[KT, VT]):
             list_root.next_node = list_root
             list_root.prev_node = list_root
             for node in cache.values():
-                for cb in node.callbacks:
-                    cb()
+                node.run_and_clear_callbacks()
             cache.clear()
             if size_callback:
                 cached_cache_len[0] = 0
 
+            if TRACK_MEMORY_USAGE and metrics:
+                metrics.clear_memory_usage()
+
         @synchronized
         def cache_contains(key: KT) -> bool:
             return key in cache