Making communicating with chrome from in-content pages easy

As Firefox increasingly switches to support running in multiple processes we’ve been finding common problems. Where we can we are designing nice APIs to make solving them easy. One problem is that we often want to run in-content pages like about:newtab and about:home in the child process without privileges making it safer and less likely to bring down Firefox in the event of a crash. These pages still need to get information from and pass information to the main process though, so we have had to come up with ways to handle that. Often we use custom code in a frame script acting as a middle-man, using things like DOM events to listen for requests from the in-content page and then messaging to the main process.

We recently added a new API to make this problem easier to solve. Instead of needing code in a frame script the RemotePageManager module allows special pages direct access to a message manager to communicate with the main process. This can be useful for any page running in the content area, regardless of whether it needs to be run at low privileges or in the content process since it takes care of listening for documents and hooking up the message listeners for you.

There is a low-level API available but the higher-level API is probably more useful in most cases. If your code wants to interact with a page like about:myaddon just do this from the main process:

Components.utils.import("resource://gre/modules/RemotePageManager.jsm");
let manager = new RemotePages("about:myaddon");

The manager object is now something resembling a regular process message manager. It has sendAsyncMessage and addMessageListener methods but unlike the regular e10s message managers it only communicates with about:myaddon pages. Unlike the regular message managers there is no option to send synchronous messages or pass cross-process wrapped objects.

When about:myaddon is loaded it has sendAsyncMessage and addMessageListener functions defined in its global scope for regular JavaScript to call. Anything that can be structured-cloned can be passed between the processes

The module documentation has more in-depth examples showing message passing between the page and the main process.

The RemotePageManager module is available in nightlies now and you can see it in action with the simple change I landed to switch about:plugins to run in the content process. For the moment the APIs only support exact URL matching but it would be possible to add support for regular expressions in the future if that turns out to be useful.

hgchanges is back up

The offending changeset that broke hgchanges yesterday turns out to be a merge from an ancient branch to current tip. That makes the diff insanely huge which is why things like hgweb were tripping over it. Kwierso point out that just ignoring those changesets would solve the problem. It’s not ideal but since in this case they aren’t useful changesets I’ve gone ahead and done that and so hgchanges is now updating again.

hgchanges is down for now

My handy tool for tracking changes to directories in the mozilla mercurial repositories is going to be broken for a little while. Unfortunately a particular changeset seems to be breaking things in ways I don’t have the time to fix right now. Specifically trying to download the raw patch for the changeset is causing hgweb to timeout. Short of finding time to debug and fix the problem my only solution is to wait until that patch is old enough that it no longer attempts to index it. That could take a week or so.

Obviously I’ll happily accept patches to fix this problem sooner.

Welcome the new Toolkit peers

I have been a little lax in my duty of keeping the list of peers for Toolkit up to date and there have been a few notable exceptions. Thankfully we’re good about disregarding rules when it makes sense to and so many people who should be peers have already been doing reviews. Of course that’s no use to new contributors trying to figure out who should review what so I am grateful to someone who prodded me into updating the list.

As I was doing so I came to the conclusion that there is a lot of overlap between Firefox code and Toolkit code. Lots of patches touch both at the same time and it often doesn’t make a lot of sense to require different reviewers there. I also couldn’t think of a reason why someone would be a trusted reviewer of Firefox code and yet not be trusted to review Toolkit code. Looking at the differences in the lists of peers confirmed that all those missing really should be Toolkit peers too.

So going forwards I have decided that Firefox peers will automatically be considered to be Toolkit peers. That means I can announce a whole bunch of new people who are now Toolkit peers, please congratulate them in the usual way, by flooding their review queue:

  • Ehsan Akhgari
  • Mike de Boer
  • Mike Conley
  • Georg Fritzsche
  • Mark Hammond
  • Felipe Gomes
  • Gijs Kruitbosch
  • Florian Quèze
  • Tim Taubert

You might ask if the reverse should hold true, should all Toolkit peers be Firefox peers? i.e. should we just merge the lists. I leave that to the Firefox owner to decide but I will say that there are a few pieces of Toolkit that are very much not front-end and so in some cases I could see a reviewer for that area not needing to be listed in the Firefox list, not because they wouldn’t be trusted to turn down the patches they couldn’t review but just because there would be almost no patches in their area in Firefox. Maybe that case is so rare that it isn’t worth the hassle of two lists though.

The bizarre world of the expectant father

I don’t often blog about non-work related stuff. Actually scratch that, I don’t often blog. But I can’t help but talk about how life becomes very strange when you’re expecting. None of this is new but it is new to me so therefore you must read it again and in some cases relive it.

Random strangers are suddenly your closest friend

I don’t know how my wife copes with it at least I don’t have to wear a stamp on my forehead proclaiming me to be an expectant father. Even so the fact does occasionally slip out while I’m talking to people I don’t know. All of a sudden I’m expected to offer up details on how far along we are, how my wife is feeling, if we know the sex, what names have we picked and damnit I just want to order some new checks please I don’t need to hear about how great the schools are around here.

They’re also all experts

So far I’ve been told in no uncertain terms that the city I live in is great for kids and terrible for kids. Natural birth is way better but epidurals are the way to go. Working from home is going to be great when the baby is here but also terrible. I don’t know what it is but when it comes to raising a child people suddenly start talking like they’re an authority rather than giving you suggestions like for other subjects.

They all think that you must be excited

Of course we must. I mean we’re only a few weeks from a large change in the status quo that by all accounts nothing can prepare you for so excitement is the natural reaction right? Generally I tell people that I’m actually petrified and everyone laughs like they think I am joking.

Which is strange because they apparently also think that your life is about to become terrible

  • What’s that? You’re feeling a little tired? Haha just wait until your baby is here!
  • You went to the cinema? Better do as much of that while you still can!
  • Laundry day? When your baby is here it will be laundry hour, amirite!

Need I go on?

But naturally we’ll want a second

Without a doubt the most bizarre thing to me is how common it is for everyone from friends and family to the supermarket trolley boy to ask when we’re planning to have our second. Hold your horses there buddy the first one isn’t even cooked yet, plenty of time to be thinking about dessert later.

Welcome to the new Toolkit peers – Paolo, Matt, Jared and Irving

Slightly belated in some cases but I’d like to formally welcome four new toolkit peers. Paolo Amadini, Matthew Noorenberghe, Jared Wein and Irving Reid have all shown themselves to be well capable of reviewing patches in any of the toolkit code. Paolo, Matt and Jared actually got added a few months ago but apparently I failed to make an announcement at the time. Irving was added just last week. Please congratulate them all and don’t go too hard on their review queues!

Also if you think there are others who should be peers of Toolkit (or current peers that are no longer relevant) then please let me know.

An update for hgchanges

Nearly a year ago I showed off the first version of my webapp for displaying recent changes in mercurial repositories. I’ve heard directly from a number of people that use it but it’s had a few problems that I’ve spent some of my spare time trying to solve. I’m now pleased to say that a new version is up and running. I’m not sure it’s accurate to call this a rewrite since it was entirely incremental but when I look back over of the code changes there really isn’t much that wasn’t touched in some way or other. So what’s new? For you, a person using the site absolutely nothing! So what on earth have I been doing rewriting the code?

Hopefully I’ve been making the thing a whole lot more stable. Eagle eyed users may have noticed that periodically the site would stop updating, sometimes for days at a time. The site is split into two pieces. One is a django website to display the changes. The other is the important bit that reads the change data out of mercurial and puts it into a database that the website can use. I do this caching because it would be too expensive to work it out on the fly. The problem is that the process of reading the data out of mercurial meant keeping a local version of every repository on the server (some 5GB for the four currently tracked) and reading the changes using mercurial’s python API was slow and used a lot of memory. The shared hosting environment that I run this out of kept killing the process when it used too many resources. Normally it could recover but occasionally it would need a manual kick. Worse there is some mercurial bug where sometimes pulling a repository will end up with an inconsistent database. It’s rare so many people don’t see it but when you’re pulling repositories every ten minutes it starts happing every couple of weeks, again requiring manual work to fix the problem.

I did dabble with getting this into shape so I could run it on a mozilla server. PAAS seemed like the obvious option but after a lot of work it turned out that the database size restrictions there made this impossible. Since then I’ve seem so many horror stories about PAAS falling over that I think I’m glad I never got there. I also tried getting a dedicated server from Mozilla to run this on but they were quite rightly wary when I mentioned that the process used a bunch of memory and wanted harder figures before committing, unfortunately I never found out a way to give those figures.

The final solution has been ripping out the mercurial API dependency. Now rather than needing local mercurial repositories the import process instead talks to them over the web. The default mercurial web APIs aren’t great but luckily all of the repositories I care about have pushlog installed which has a good JSON API for retrieving recently pushed changesets. So now the process is to pull the recent pushlog, get the patches for every changeset and parse them to work out which files have changed. By not having to load the mercurial structures there is far less memory used and since the process now has to delay as it downloads each patch file it keeps the CPU usage low.

I’ve also made the database itself a lot more efficient. Previously I recorded every changeset for every repository, but many repositories have the same changeset in them. So by noting that the database gets a little more complicated but uses much less space and since you only have to parse the changeset once the import process becomes faster. It took me a while to get the website performing as fast as before with these changes but I think it’s there now (barring some strange slowness in Django that I can’t identify). I’ve also turned on some quite aggressive caching both on the client and server side, if someone has visited the same page as you’re trying to access recently then it should load super fast.

So, the new version is up and running at the same location as the old. Chances are you’re using it already so if you’re noticing any unexpected slowness or something not looking right please let me know.

Developer Tools meet-up in Portland

Two weeks ago the developer tools teams and a few others met in the Portland office for a very successful week of discussions and hacking. The first day was about setting the stage for the week and working out what everyone was going to work on. Dave Camp kicked us off with a review of the last six months in developer tools and talked about what is going to be important for us to focus on in 2014. We then had a little more in-depth information from each of the teams. After lunch a set of lightning talks went over some projects and ideas that people had been working on recently.

After that everyone got started prototyping new ideas, hacking on features and fixing bugs. The amount of work that happens at these meet-ups is always mind-blowing and this week was no exception, even one of our contributors got in on the action. Here is a list of the things that the team demoed on Friday:

This only covers the work demoed on Friday, a whole lot more went on during the week as a big reason for doing these meet-ups is so that groups can split off to have important discussions. We had Darrin Henein on hand to help out with UX designs for some of the tools and Kyle Huey joined us for a couple of days to help work out the final kinks in the plan for debugging workers. Lot’s of work went on to iron out some of the kinks in the new add-on SDK widgets for Australis, there were discussions about memory and performance tools as well as some talk about how to simplify child processes for Firefox OS and electrolysis.

Of course there was also ample time in the evenings for the teams to socialise. One of the downsides of being a globally distributed team is that getting to know one another and building close working relationships can be difficult over electronic forms of communication so we find that it’s very important to all come together in one place to meet face to face. We’re all looking forward to doing it again in about six months time.

An editable box model view in the devtools

This week the whole devtools group has been sequestered in Mozilla’s Portland office having one of our regular meet-ups. As always it’s been a fantastically productive week with lots of demos to show for it. I’ll be writing a longer write-up later but I wanted to post about what I played with over the week.

My wife does the odd bit of web development on the side. For a long time she was a loyal Firebug user and a while ago I asked her what she thought of Firefox’s built in devtools. She quickly pointed out a couple of features that Firebug had that Firefox did not. As I was leaving for this week I mentioned I’d be with the devtools group and she asked whether her features had been fixed yet. It turns out that colour swatches had been but the box model still wasn’t editable. So I figured I could earn myself some brownie points by hacking on that this week.

The goal here is to be able to inspect an element on the page, pull up the box model and be able to quickly play with the margins, borders and padding to tweak the positioning until it looks right. Then armed with the right values you can go update your stylesheets. It saves a lot of trial and error with positioning.

It turned out to be relatively simple to implement a pretty full version. The feature allows you to click one of the box model values and type whatever value you like, in any CSS unit you prefer. If the size had been set in the stylesheet in some specific unit then that is what appears in the input box for you to change. Better yet as you type numbers the element updates in the page on the fly and you can use the arrow keys to increase/decrease the value until you’re happy. It’s a really natural way to play with the element’s position.

The changes made appear on the element so you can find them in the rule view pretty easily. This patch is based on an updated version of the box model view which is why it looks so different to existing Firefox, all my work does is make the numbers editable.

I actually completed this so quickly that I decided to take this one step further. One thing missing from the box model display is information about border colours. So I added some colour swatches for each border and made them editable with the regular devtools colour picker.

Both of these patches are pretty much complete but they’ll have to wait for the new box model highlighter to be complete before they can be reviewed and land.

Sycamore Canyon, July 27th

We went for a hike through Sycamore Canyon this afternoon getting some amazing overlooks of the Pacific coast as well as seeing some very alien landscape. This canyon was one of those hit by the wildfire recently and while the firefighters clearly worked hard to keep the campsite untouched as soon as you walk out onto the trails the impact is clear. The area looks almost desolate with blackened trees littering the hills. It’s so quiet up there too, it seems that few people want to explore while the canyon is in this state but I found it quite interesting to see just how different everything is right now. It’s not all bad news, there are lots of signs of regrowth, prickly pears with green buds, agave with green shoots and many trees are showing new green leaves. I think the most spectacular thing was how a lot of the damage was clearly only skin deep. Lots of the trees there are black on the outside yes, but where the bark has started to peel away the branches are a bright red underneath, as if untouched by the heat and flames. It makes for quite a spectacular contrast. We’re planning on going back there a lot to see how everything changes.

This trail was just under 4 miles though we extended it by having to park down the road because the campsite was full. It’s mostly a loop with a spur off to follow the ridge to overlook the coast. It is amazing to be up so high and see down the coast. Today the skies were clear and the ocean was a beautiful blue making for some truly epic views. Check out the photos I took on the map below.