From 707d5e4e48e839dabd34e4b67426fe8382a2c978 Mon Sep 17 00:00:00 2001 From: Erik Johnston Date: Tue, 28 Sep 2021 10:37:58 +0100 Subject: Encode JSON responses on a thread in C, mk2 (#10905) Currently we use `JsonEncoder.iterencode` to write JSON responses, which ensures that we don't block the main reactor thread when encoding huge objects. The downside to this is that `iterencode` falls back to using a pure Python encoder that is *much* less efficient and can easily burn a lot of CPU for huge responses. To fix this, while still ensuring we don't block the reactor loop, we encode the JSON on a threadpool using the standard `JsonEncoder.encode` functions, which is backed by a C library. Doing so, however, requires `respond_with_json` to have access to the reactor, which it previously didn't. There are two ways of doing this: 1. threading through the reactor object, which is a bit fiddly as e.g. `DirectServeJsonResource` doesn't currently take a reactor, but is exposed to modules and so is a PITA to change; or 2. expose the reactor in `SynapseRequest`, which requires updating a bunch of servlet types. I went with the latter as that is just a mechanical change, and I think makes sense as a request already has a reactor associated with it (via its http channel). --- changelog.d/10905.feature | 1 + 1 file changed, 1 insertion(+) create mode 100644 changelog.d/10905.feature (limited to 'changelog.d/10905.feature') diff --git a/changelog.d/10905.feature b/changelog.d/10905.feature new file mode 100644 index 0000000000..07e7b2c6a7 --- /dev/null +++ b/changelog.d/10905.feature @@ -0,0 +1 @@ +Speed up responding with large JSON objects to requests. -- cgit 1.5.1