580850 - Add E10S message manager to Services.jsm

Status: RESOLVED WORKSFORME

(Core :: General, defect)

Description

[Justin Dolske [:Dolske]]

Attachment: Patch v.1

Self explanatory.

I'm kind of tempted to want |Services.mm| to just return the appropriate thing for the context it's called from (since, afaik, the chrome process will never want a nsIContentFrameMessageManager, and viceversa for the content process). But I suppose that's a little too magical, and I could see people getting confused by |Services.mm.foo()| working in one place but not another.

We can always switch in the (near) future, since the change from mmChrome/mmContent to mm is just a mechanic code change...

Comment 1

[:Gavin Sharp [email: [e-mail]]]

Given that the same service seems to implement both interfaces, is there any reason not to make this a single property QIed to both (as we do for e.g. the prefservice)? Does the QI fail depending on the context or something?

Comment 2

[Justin Dolske [:Dolske]]

I didn't try, the concern in comment 0 (re "Services.mm.foo()") struck me first.

Smaug, any opinion here? I'm increasingly tempted to just make Services.mm work for both content/chrome.

Comment 3

[Olli Pettay [:smaug][[e-mail]]]

QIing depends on whether the message manager is chrome message manager
or content message manager.
http://bonsai-hg.konigsberg.mozilla.org/bonsai/cvsblame.cgi?file=/content/base/src/nsFrameMessageManager.cpp&rev=c6673716fd47&tree=mozilla-central&mark=77-78#69

I'm not familiar with Services.jsm, but I assume it is a helper for js to
get some services. I don't understand how mmContent would work, though. 
There is no global message manager in content process.

Comment 4

[Olli Pettay [:smaug][[e-mail]]]

Or you can create the global message manager in content process, but
it wouldn't have any child message managers, so sending messages would be no-op.

Comment 5

[Justin Dolske [:Dolske]]

(clearing assignment of bugs I'm no long planning to work on)

Comment 6

[Anthony Lieuallen]

So this bug is over four years old, but I desperately want this.  I'm trying to follow the docs [1] which says that "... the only way to implement per-child process code is to use a frame script which imports a custom javascript module (JSM)."  But in the JSM I don't have a handle to a message manager, so I don't have access to all the parent-process-only features under e10s.  If I could just grab a property from Services I would be so happy.

[1] https://developer.mozilla.org/en-US/Firefox/Multiprocess_Firefox/The_message_manager#Loading_scripts_per_child_process

Comment 7

[Josh Matthews [:jdm]]

You don't need a property on Services for that; you can obtain the exact same one yourself by using getService("@mozilla.org/globalmessagemanager;1") and QIing to either nsIChromeFrameMessageManager or nsIContentFrameMessageManager as necessary.

Comment 8

[Josh Matthews [:jdm]]

er, Cc["@mozilla.org/globalmessagemanager;1"].getService(Ci.nsIChromeFrameMessageManager), that is. I don't write privileged JS often enough, obviously.

Comment 9

[Anthony Lieuallen]

If I put this code in my frame script:

  var c = Cc['@mozilla.org/globalmessagemanager;1'];
  var s = c.getService(Ci.nsIContentFrameMessageManager);

Then the second line gives:

  JavaScript error: chrome://x/content/x.js, line 299:     NS_ERROR_XPC_GS_RETURNED_FAILURE: Component returned failure code: 0x80570016 (NS_ERROR_XPC_GS_RETURNED_FAILURE) [nsIJSCID.getService]

Same if I switch content to nsIChromeFrameMessageManager.  Plus of course, neither of those interfaces have the sendSyncMessage() method I'm looking to call, even if I could get such an object.

I've tried and tried ( http://stackoverflow.com/questions/28115739 ) to find the magic incantation that gives me the message manager I need in order to sendSyncMessage() from child to parent.  But nothing seems to work.

Comment 10

[Anthony Lieuallen]

Ah, Stack Overflow finally comes to the rescue.  I think my original point stands, though.  There's so many different kinds of message manager objects (parent, child, global, system, mobile) it's really hard to know what to use when.  If there was some sort of helper that abstracted away the logical actions (send an X, listen for a Y, etc.) I would have had a significantly easier time of this.

Comment 11

[:Gijs (out for now; he/him)]

Fixed by bug 1068087, I believe.

Comment 12

[Anthony Lieuallen]

No, I'm concerned about the entire constellation of communication scopes.  Chrome child to chrome parent.  Same when one side is a frame script, same when one side is in a JSM, same when one side is a JS component, same for all combinations.  All of those again for parent to child.

I actually don't care about content at all.  Just the difficulty I had in making my extensions not break under e10s separation.

Comment 13

[:Gijs (out for now; he/him)]

(In reply to Anthony Lieuallen from comment #12)
> No, I'm concerned about the entire constellation of communication scopes. 
> Chrome child to chrome parent. 

Services.cpmm is the child process message manager, so that should work to send messages to the parent process, and listen for messages from the parent process. In the parent, you could use Services.ppmm to do the same, AIUI. It doesn't matter whether you call those from frame scripts or JSMs or components - as long as you're in the right process, they will work.

Also note that as of bug 1133594 you can now load a script once into the child process rather than just loading the same frame script for every process tab.

Comment 14

[Anthony Lieuallen]

> Services.cpmm is the child process message manager, so that should work to send messages to the parent process, and listen for messages from the parent process. In the parent, you could use Services.ppmm to do the same, AIUI.

Is this in the docs?

Comment 15

[:Gijs (out for now; he/him)]

(In reply to Anthony Lieuallen from comment #14)
> > Services.cpmm is the child process message manager, so that should work to send messages to the parent process, and listen for messages from the parent process. In the parent, you could use Services.ppmm to do the same, AIUI.
> 
> Is this in the docs?

https://developer.mozilla.org/en-US/Firefox/Multiprocess_Firefox/The_message_manager#Process_Message_Managers implies this, yes, though IMO we could do with improvements. Certainly the per-process (rather than per-frame) script loading that I mentioned didn't seem to be documented last I checked.

The problem is there are a lot of scenarios to cover. I wonder if someone (Mike?) has ideas about how to improve docs to be easier to follow here, and/or what e10s efforts there are for this.

Comment 16

[Mike Conley (:mconley) (:⚙️)]

I think wbamberg might be the one to ask about this - he's been leading the charge on our multi-process documentation. He might have some ideas on how to make this clearer.

Comment 17

[:Gijs (out for now; he/him)]

(let's take the documentation worries to bug 962705)

Comment 18

[:Gijs (out for now; he/him)]

Thanks Mike!