Detect accidentally dropped errors in tests #243
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Manifold has a debug mechanism which instruments deferreds so that a warning is logged when they are in an error state with no error handler attached at garbage collection time. Such errors are referred to as "dropped errors" and the instrumented deferreds are called "leak-aware". The dropped error logging feature is enabled by default but for performance reasons, only every 1024th deferred is made leak-aware (see `manifold.deferred/deferred`). However, deferreds constructed via `manifold.deferred/error-deferred` are always leak-aware. This patch introduces a new option `manifold.debug/*leak-aware-deferred-rate*` which allows changing the rate of leak-aware deferreds being instantiated, with default still being 1024. When this option is set to to 1 (= every deferred will be leak-aware), dropped errors can be detected more reliably e.g. during testing. To that end, the patch also includes a test util for instrumenting all tests in a namespace so that they fail when a dropped error was detected. All test namespaces are now instrumented like this (except for `:benchmark` and `:stress` tests), which already uncovered a few latent dropped errors. These will be fixed in separate patches.
Dunno, I just mimicked the neighboring prior art for I suggest I close this PR here and create a fresh one based on the branch that lives in this repo now (GH doesn't allow changing the source branch on an existing PR ...) so that we can review & merge all fixes into that one. Otherwise we'd have to merge the currently failing build which seems undesirable. WDYT? |
Just went ahead and did it (see #245) so that I can start opening those follow-up patch PRs. Hope that's OK! |
I've never understood why so many Clojure examples use alter-var-root for constants... |
Manifold has a debug mechanism which instruments deferreds so that a warning is logged when they are in an error state with no error handler attached at garbage collection time. Such errors are referred to as "dropped errors" and the instrumented deferreds are called "leak-aware".
The dropped error logging feature is enabled by default but for performance reasons, only every 1024th deferred is made leak-aware (see
manifold.deferred/deferred). However, deferreds constructed viamanifold.deferred/error-deferredare always leak-aware.This patch introduces a new option
manifold.debug/*leak-aware-deferred-rate*which allows changing the rate of leak-aware deferreds being instantiated, with default still being 1024. When this option is set to to 1 (= every deferred will be leak-aware), dropped errors can be detected more reliably e.g. during testing.To that end, the patch also includes a test util for instrumenting all tests in a namespace so that they fail when a dropped error was detected. All test namespaces are now instrumented like this (except for
:benchmarkand:stresstests), which already uncovered a few latent dropped errors. These will be fixed in separate patches.This was prompted by investigating the causes of clj-commons/aleph#766. One of these was found to originate in Manifold itself which will be addressed in a follow-up PR.