Name of cache busting parameter

[millette]

Hello, I'm new to MathJax, but checked older (and closed issues) and I don't think this was brought up yet.

Long story short, I'm using CouchDB to serve the MathJax files for a CouchApp (instead of nginx or another http server). The rev parameter that's added to the automatically loaded JS files is interfering with CouchDB's semantics.

Searching this source code, I see rev is only used in a couple of places, and only for cache busting. Correct me if I'm wrong.

May I suggest changing rev to ver? From what I understand, if shouldn't change anything in MathJax, but it would stop interfering with CouchDB. If you feel using another hardcoded parameter name could lead the further problems down the line, we could make it an option.

For now, I'm using this workaround:

window.MathJax = {
  AuthorInit: function () {
    // couchdb really doesn't like the ?rev argument
    // appended by the MathJax loader;
    // taking care of that here (side effects, perhaps?)
    window.MathJax.cdnVersion = ''
  }
}

I'm ready to write a quick patch for the 1st option if this solution is accepted (s/rev/ver/). I can also try to make it an option if that's preferable.

Thoughts?

[pkra]

Could you provide some background on why this is causing problems with CouchDB?

[millette]

According to the Officlal CouchDB Docs:

Query Parameters:

rev (string)

Document’s revision. Optional

rev is used to fetch CouchDB internal revisions for an attachment, and the name of this query parameter can't be changed (without recompiling erlang, I guess). I also inquired on #couchdb (Freenode) and got the same reply.

[millette]

In effect, the JavaScript files autoloaded by MathJax aren't found (404) when attached to a CouchDB document since the specified rev doesn't exist according to it. Using ver or any other parameter name would probably work, only rev conflicts.

[dpvc]

I don't have any problem with changing rev to ver; it is only used to break caches, as you point out. @pkra, what do you think?

I was going to suggest essentially the patch that you are already using (I didn't see it in the email version sent to me when you initially posted, so I assume you edited it afterward).

Alternatively, you could use

var MathJax = {
  AuthorInit: function () {
    MathJax.Ajax.fileRev = function (file) {
      var ver = MathJax.cdnFileVersions[file] || MathJax.cdnVersion || '';
      if (ver) ver = "?ver="+ver;
      return ver;
    }
  }
}

which does the change you are asking for.

[millette]

Ah, replacing the fileRev(), less magic than my workaround, thanks.

CouchDB might not be the most popular web server, it's probably less work to change the parameter name than to add a description of the workaround to a FAQ on in the README.

The patch would be trivial but let me know if you want me to provide it.

With the possibility of changing fileRev(), I hereby retract my suggestion to make the "rev" parameter changeable thru an option :-) A new hardcoded value will do just fine.

[dpvc]

It is probably easier for us to do it, as contributed changes require an SLA, which is too much of a hassle for this one-word change.

[millette]

I wouldn't want copyright to swap 2 letters :-)

[dpvc]

Right. But administrators like to have all the forms. Thanks for your contribution!

[pkra]

@pkra, what do you think?

I don't mind either way. @zorkow?

[dpvc]

The issue1570 branch of my fork of MathJax includes the change.

[dpvc]

==> Merged

[millette]

Thanks!

[zorkow]

I'm fine with that.

[smonsarr]

We just got bitten by this.
In our content provider ?V=xxx means select a specific "view", all resources loaded with ?V=2.7.9 are met with 404.

Have changed this to :
if (V) {V = "?mjv!"+V}

This has the benefit of not being a standard query parameter, and therefore a lot less likely to interfere with other systems while fulfilling the required effect of making the URL to MathJax resources reflect the current version.