1231802 - Build an event recorder into Gecko

Status: RESOLVED INCOMPLETE

(Core :: General, defect)

Description

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Sometimes it's hard to reproduce a problem that detected in monkey/fuzz testing.
It may require a very specific timing or gesture, so one maybe need to retry many times to reproduce the problem.
This also makes it hard to report or share the problem to other people, because sometimes a stack trace is not enough.

If we have a mechanism to let developers simply replay what the specific execution do, then it will be easier to debug.

Comment 1

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: build-an-event-recorder-into-gecko-WIP.patch

TODO:
1. remove external JSON code
2. record event timing
3. record message
4. find out which API need to be mocked

Comment 2

[Boris Zbarsky [:bzbarsky]]

Note bug 1207696.

Comment 3

[Thinker Li [:sinker]]

Comment on attachment 8697377 [details] [diff] [review]
build-an-event-recorder-into-gecko-WIP.patch

Review of attachment 8697377 [details] [diff] [review]:
-----------------------------------------------------------------

Just a question!

::: dom/events/_jsonc/json.h
@@ +7,5 @@
> + *
> + * This library is free software; you can redistribute it and/or modify
> + * it under the terms of the MIT license. See COPYING for details.
> + *
> + */

Is there any reason that you don't use json parser and generator already in our code base?

Comment 4

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

(In reply to Thinker Li [:sinker] from comment #3)
> Comment on attachment 8697377 [details] [diff] [review]
> 
> Is there any reason that you don't use json parser and generator already in
> our code base?

As far as I know, the only JSON parser in the code base is JSONParser, which
needs a JSContext. When I ported it to B2G it always crashes while starting
b2g, so I temporary replaced that part to an external library.

It should use pickling traits in IPCMessageUtils.h for a more compact serialization.

Comment 5

[Nicholas Nethercote [inactive]]

mfbt/JSONWriter.h is a JSON pretty-printer that's designed to minimize the amount of memory used while printing.

Comment 6

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0001-build-an-event-recorder-into-gecko.patch

Comment 7

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0002-add-devtools-bridge.patch

Comment 8

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0003-enable-debug-only-prefs.patch

Comment 9

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Added a devtools actor (still WIP): eventPlayerActor.

The actor supports 3 commands: start, stop, play.

command example:

{
  "to": "server2.conn0.child1/eventPlayerActor26",
  "type": "start"
}

{
  "to": "server2.conn0.child1/eventPlayerActor26",
  "type": "stop"
}

{
  "to": "server2.conn0.child1/eventPlayerActor26",
  "type": "play",
  "events": {}
}

Comment 10

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0001-build-an-event-recorder-into-gecko.patch

Removed external JSON library.

Comment 11

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0002-add-xpcom-service.patch

Comment 12

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0003-add-actor-to-devtools.patch

Comment 13

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0004-enable-debug-only-prefs.patch

this patch is optional.

Comment 14

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0001-build-an-event-recorder-into-gecko.patch

Add some mouse events.
Reduce event replay speed.

Comment 15

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0002-add-xpcom-service.patch

Comment 16

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0003-add-actor-to-devtools.patch

Comment 17

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0004-enable-debug-only-prefs.patch

This patch is optional.

Comment 18

[Wei-Cheng Pan [:wcpan] [:wcp] [:legnaleurc] (left Mozilla)]

Attachment: 0001-build-an-event-recorder-into-gecko.patch

add some common events

Comment 19

[BugBot [:suhaib / :marco/ :calixte]]

The bug assignee didn't login in Bugzilla in the last 7 months, so the assignee is being reset.

Comment 20

[Andrew McCreight [:mccr8]]

rr sort of works for these things, assuming you are okay with being Linux-only. There's also WebReplay as mentioned. I think we can close this for now, as it seems to be some experiment that didn't pan out.