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Reduce cache size by not storing deferreds #2158

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merged 2 commits into from
Apr 25, 2017
Merged

Reduce cache size by not storing deferreds #2158

merged 2 commits into from
Apr 25, 2017

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erikjohnston
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Currently the cache descriptors store deferreds rather than raw values, this is a simple way of triggering only one database hit and sharing the result if two callers attempt to get the same value.

However, there are a few caches that simply store a mapping from string to string (or int). These caches can have a large number of entries, under the assumption that each entry is small. However, the size of a
deferred (specifically the size of ObservableDeferred) is significantly larger than that of the raw value, 2kb vs 32b.

This PR therefore changes the cache descriptors to store the raw values rather than the deferreds.

As a side effect cached storage function now either return a deferred or the actual value, as the cached list decriptor already does. This is fine as we always end up just yield'ing on the returned value eventually, which handles that case correctly.

@erikjohnston
Reduce cache size by not storing deferreds
119cb9b 
Currently the cache descriptors store deferreds rather than raw values,
this is a simple way of triggering only one database hit and sharing the
result if two callers attempt to get the same value.

However, there are a few caches that simply store a mapping from string
to string (or int). These caches can have a large number of entries,
under the assumption that each entry is small. However, the size of a
deferred (specifically the size of ObservableDeferred) is signigicantly
larger than that of the raw value, 2kb vs 32b.

This PR therefore changes the cache descriptors to store the raw values
rather than the deferreds.

As a side effect cached storage function now either return a deferred or
the actual value, as the cached list decriptor already does. This is
fine as we always end up just yield'ing on the returned value
eventually, which handles that case correctly.
NegativeMjark
NegativeMjark reviewed Apr 25, 2017
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synapse/util/caches/descriptors.py
@@ -335,20 +346,10 @@ def wrapped(*args, **kwargs):
try:
cached_result_d = cache.get(cache_key, callback=invalidate_callback)

observer = cached_result_d.observe()
if DEBUG_CACHES:
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aw, I liked the read-through cache it was useful for debugging.
If you really want to remove it from here you should probably remove the DEBUG_CACHES variable entirely.

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Removed

NegativeMjark
NegativeMjark approved these changes Apr 25, 2017
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LGTM?

@erikjohnston erikjohnston merged commit b4da08c into develop Apr 25, 2017
psaavedra added a commit to psaavedra/synapse that referenced this pull request May 19, 2017
@psaavedra
Merge tag 'v0.21.0' into v0.21.0_no_federate_by_default
badd30b 
Changes in synapse v0.21.0 (2017-05-18)
=======================================

No changes since v0.21.0-rc3

Changes in synapse v0.21.0-rc3 (2017-05-17)
===========================================

Features:

* Add per user rate-limiting overrides (PR matrix-org#2208)
* Add config option to limit maximum number of events requested by ``/sync``
  and ``/messages`` (PR matrix-org#2221) Thanks to @psaavedra!

Changes:

* Various small performance fixes (PR matrix-org#2201, matrix-org#2202, matrix-org#2224, matrix-org#2226, matrix-org#2227, matrix-org#2228,
  matrix-org#2229)
* Update username availability checker API (PR matrix-org#2209, matrix-org#2213)
* When purging, don't de-delta state groups we're about to delete (PR matrix-org#2214)
* Documentation to check synapse version (PR matrix-org#2215) Thanks to @hamber-dick!
* Add an index to event_search to speed up purge history API (PR matrix-org#2218)

Bug fixes:

* Fix API to allow clients to upload one-time-keys with new sigs (PR matrix-org#2206)

Changes in synapse v0.21.0-rc2 (2017-05-08)
===========================================

Changes:

* Always mark remotes as up if we receive a signed request from them (PR matrix-org#2190)

Bug fixes:

* Fix bug where users got pushed for rooms they had muted (PR matrix-org#2200)

Changes in synapse v0.21.0-rc1 (2017-05-08)
===========================================

Features:

* Add username availability checker API (PR matrix-org#2183)
* Add read marker API (PR matrix-org#2120)

Changes:

* Enable guest access for the 3pl/3pid APIs (PR matrix-org#1986)
* Add setting to support TURN for guests (PR matrix-org#2011)
* Various performance improvements (PR matrix-org#2075, matrix-org#2076, matrix-org#2080, matrix-org#2083, matrix-org#2108,
  matrix-org#2158, matrix-org#2176, matrix-org#2185)
* Make synctl a bit more user friendly (PR matrix-org#2078, matrix-org#2127) Thanks @APwhitehat!
* Replace HTTP replication with TCP replication (PR matrix-org#2082, matrix-org#2097, matrix-org#2098,
  matrix-org#2099, matrix-org#2103, matrix-org#2014, matrix-org#2016, matrix-org#2115, matrix-org#2116, matrix-org#2117)
* Support authenticated SMTP (PR matrix-org#2102) Thanks @DanielDent!
* Add a counter metric for successfully-sent transactions (PR matrix-org#2121)
* Propagate errors sensibly from proxied IS requests (PR matrix-org#2147)
* Add more granular event send metrics (PR matrix-org#2178)

Bug fixes:

* Fix nuke-room script to work with current schema (PR matrix-org#1927) Thanks
  @zuckschwerdt!
* Fix db port script to not assume postgres tables are in the public schema
  (PR matrix-org#2024) Thanks @jerrykan!
* Fix getting latest device IP for user with no devices (PR matrix-org#2118)
* Fix rejection of invites to unreachable servers (PR matrix-org#2145)
* Fix code for reporting old verify keys in synapse (PR matrix-org#2156)
* Fix invite state to always include all events (PR matrix-org#2163)
* Fix bug where synapse would always fetch state for any missing event (PR matrix-org#2170)
* Fix a leak with timed out HTTP connections (PR matrix-org#2180)
* Fix bug where we didn't time out HTTP requests to ASes  (PR matrix-org#2192)

Docs:

* Clarify doc for SQLite to PostgreSQL port (PR matrix-org#1961) Thanks @benhylau!
* Fix typo in synctl help (PR matrix-org#2107) Thanks @HarHarLinks!
* ``web_client_location`` documentation fix (PR matrix-org#2131) Thanks @matthewjwolff!
* Update README.rst with FreeBSD changes (PR matrix-org#2132) Thanks @feld!
* Clarify setting up metrics (PR matrix-org#2149) Thanks @encks!
@erikjohnston erikjohnston deleted the erikj/reduce_cache_size branch October 26, 2017 11:00
richvdh added a commit that referenced this pull request May 18, 2018
@richvdh
Fix error in handling receipts
8b1c856 
Fixes an error which has been happening ever since #2158 (v0.21.0-rc1):

> TypeError: argument of type 'ObservableDeferred' is not iterable

fixes #3234
This was referenced May 18, 2018
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