diff --git a/synapse/util/async.py b/synapse/util/async.py
index 35380bf8ed..1453faf0ef 100644
--- a/synapse/util/async.py
+++ b/synapse/util/async.py
@@ -89,6 +89,11 @@ class ObservableDeferred(object):
deferred.addCallbacks(callback, errback)
def observe(self):
+ """Observe the underlying deferred.
+
+ Can return either a deferred if the underlying deferred is still pending
+ (or has failed), or the actual value. Callers may need to use maybeDeferred.
+ """
if not self._result:
d = defer.Deferred()
@@ -101,7 +106,7 @@ class ObservableDeferred(object):
return d
else:
success, res = self._result
- return defer.succeed(res) if success else defer.fail(res)
+ return res if success else defer.fail(res)
def observers(self):
return self._observers
diff --git a/synapse/util/caches/descriptors.py b/synapse/util/caches/descriptors.py
index 19595df422..9d0d0be1f9 100644
--- a/synapse/util/caches/descriptors.py
+++ b/synapse/util/caches/descriptors.py
@@ -15,12 +15,9 @@
import logging
from synapse.util.async import ObservableDeferred
-from synapse.util import unwrapFirstError
+from synapse.util import unwrapFirstError, logcontext
from synapse.util.caches.lrucache import LruCache
from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
-from synapse.util.logcontext import (
- PreserveLoggingContext, preserve_context_over_deferred, preserve_context_over_fn
-)
from . import DEBUG_CACHES, register_cache
@@ -227,8 +224,20 @@ class _CacheDescriptorBase(object):
)
self.num_args = num_args
+
+ # list of the names of the args used as the cache key
self.arg_names = all_args[1:num_args + 1]
+ # self.arg_defaults is a map of arg name to its default value for each
+ # argument that has a default value
+ if arg_spec.defaults:
+ self.arg_defaults = dict(zip(
+ all_args[-len(arg_spec.defaults):],
+ arg_spec.defaults
+ ))
+ else:
+ self.arg_defaults = {}
+
if "cache_context" in self.arg_names:
raise Exception(
"cache_context arg cannot be included among the cache keys"
@@ -292,18 +301,31 @@ class CacheDescriptor(_CacheDescriptorBase):
iterable=self.iterable,
)
+ def get_cache_key(args, kwargs):
+ """Given some args/kwargs return a generator that resolves into
+ the cache_key.
+
+ We loop through each arg name, looking up if its in the `kwargs`,
+ otherwise using the next argument in `args`. If there are no more
+ args then we try looking the arg name up in the defaults
+ """
+ pos = 0
+ for nm in self.arg_names:
+ if nm in kwargs:
+ yield kwargs[nm]
+ elif pos < len(args):
+ yield args[pos]
+ pos += 1
+ else:
+ yield self.arg_defaults[nm]
+
@functools.wraps(self.orig)
def wrapped(*args, **kwargs):
# If we're passed a cache_context then we'll want to call its invalidate()
# whenever we are invalidated
invalidate_callback = kwargs.pop("on_invalidate", None)
- # Add temp cache_context so inspect.getcallargs doesn't explode
- if self.add_cache_context:
- kwargs["cache_context"] = None
-
- arg_dict = inspect.getcallargs(self.orig, obj, *args, **kwargs)
- cache_key = tuple(arg_dict[arg_nm] for arg_nm in self.arg_names)
+ cache_key = tuple(get_cache_key(args, kwargs))
# Add our own `cache_context` to argument list if the wrapped function
# has asked for one
@@ -328,11 +350,9 @@ class CacheDescriptor(_CacheDescriptorBase):
defer.returnValue(cached_result)
observer.addCallback(check_result)
- return preserve_context_over_deferred(observer)
except KeyError:
ret = defer.maybeDeferred(
- preserve_context_over_fn,
- self.function_to_call,
+ logcontext.preserve_fn(self.function_to_call),
obj, *args, **kwargs
)
@@ -342,10 +362,14 @@ class CacheDescriptor(_CacheDescriptorBase):
ret.addErrback(onErr)
- ret = ObservableDeferred(ret, consumeErrors=True)
- cache.set(cache_key, ret, callback=invalidate_callback)
+ result_d = ObservableDeferred(ret, consumeErrors=True)
+ cache.set(cache_key, result_d, callback=invalidate_callback)
+ observer = result_d.observe()
- return preserve_context_over_deferred(ret.observe())
+ if isinstance(observer, defer.Deferred):
+ return logcontext.make_deferred_yieldable(observer)
+ else:
+ return observer
wrapped.invalidate = cache.invalidate
wrapped.invalidate_all = cache.invalidate_all
@@ -362,7 +386,11 @@ class CacheListDescriptor(_CacheDescriptorBase):
"""Wraps an existing cache to support bulk fetching of keys.
Given a list of keys it looks in the cache to find any hits, then passes
- the list of missing keys to the wrapped fucntion.
+ the list of missing keys to the wrapped function.
+
+ Once wrapped, the function returns either a Deferred which resolves to
+ the list of results, or (if all results were cached), just the list of
+ results.
"""
def __init__(self, orig, cached_method_name, list_name, num_args=None,
@@ -433,8 +461,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
args_to_call[self.list_name] = missing
ret_d = defer.maybeDeferred(
- preserve_context_over_fn,
- self.function_to_call,
+ logcontext.preserve_fn(self.function_to_call),
**args_to_call
)
@@ -443,8 +470,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
# We need to create deferreds for each arg in the list so that
# we can insert the new deferred into the cache.
for arg in missing:
- with PreserveLoggingContext():
- observer = ret_d.observe()
+ observer = ret_d.observe()
observer.addCallback(lambda r, arg: r.get(arg, None), arg)
observer = ObservableDeferred(observer)
@@ -471,7 +497,7 @@ class CacheListDescriptor(_CacheDescriptorBase):
results.update(res)
return results
- return preserve_context_over_deferred(defer.gatherResults(
+ return logcontext.make_deferred_yieldable(defer.gatherResults(
cached_defers.values(),
consumeErrors=True,
).addCallback(update_results_dict).addErrback(
diff --git a/synapse/util/logcontext.py b/synapse/util/logcontext.py
index ff67b1d794..990216145e 100644
--- a/synapse/util/logcontext.py
+++ b/synapse/util/logcontext.py
@@ -310,6 +310,10 @@ def preserve_context_over_fn(fn, *args, **kwargs):
def preserve_context_over_deferred(deferred, context=None):
"""Given a deferred wrap it such that any callbacks added later to it will
be invoked with the current context.
+
+ Deprecated: this almost certainly doesn't do want you want, ie make
+ the deferred follow the synapse logcontext rules: try
+ ``make_deferred_yieldable`` instead.
"""
if context is None:
context = LoggingContext.current_context()
@@ -330,12 +334,8 @@ def preserve_fn(f):
LoggingContext.set_current_context(LoggingContext.sentinel)
return result
- # XXX: why is this here rather than inside g? surely we want to preserve
- # the context from the time the function was called, not when it was
- # wrapped?
- current = LoggingContext.current_context()
-
def g(*args, **kwargs):
+ current = LoggingContext.current_context()
res = f(*args, **kwargs)
if isinstance(res, defer.Deferred) and not res.called:
# The function will have reset the context before returning, so
@@ -359,6 +359,25 @@ def preserve_fn(f):
return g
+@defer.inlineCallbacks
+def make_deferred_yieldable(deferred):
+ """Given a deferred, make it follow the Synapse logcontext rules:
+
+ If the deferred has completed (or is not actually a Deferred), essentially
+ does nothing (just returns another completed deferred with the
+ result/failure).
+
+ If the deferred has not yet completed, resets the logcontext before
+ returning a deferred. Then, when the deferred completes, restores the
+ current logcontext before running callbacks/errbacks.
+
+ (This is more-or-less the opposite operation to preserve_fn.)
+ """
+ with PreserveLoggingContext():
+ r = yield deferred
+ defer.returnValue(r)
+
+
# modules to ignore in `logcontext_tracer`
_to_ignore = [
"synapse.util.logcontext",
|
