online Scala interpreter from browser?

On Tuesday 16 December 2008 08:09, Jon Steelman wrote:
> Hi there,
> Is there a Scala interpreter online usable from a browser? I didn't
> run across one when searching.
>
> If there isn't, I suggest that Scala-lang.org add one. Ruby has a
> number of them. It is convenient and enticing for a newbie to be able
> to give Scala a quick whirl. Also, it is nice if you are working
> through the Scala book and aren't near your own computer but have
> access to a browser somewhere and want to run/play with the examples.

A couple points / questions:

1) How do they handle badly-behaved code fragments (infinite loops,
calls to the equivalent of java.lang.System.exit(), etc.)?

2) The #haskell IRC channel has lambdabot and one of the Clojure
aficionados is working on a counterpart for #clojure.

2a) Does Scala have an IRC channel?
2b) If not, should it?
2c) If it does, would a ScalaBot be a good idea?

> Thanks,
> Jon

Randall Schulz

On Tue, Dec 16, 2008 at 4:29 PM, Randall R Schulz wrote:
> 2a) Does Scala have an IRC channel?

It does: #scala on freenode. All welcome ...

> 2b) If not, should it?

See above ...

> 2c) If it does, would a ScalaBot be a good idea?

Talk to Ricky Clarkson aka mapreduce ...

Cheers,

Miles

On Tue, Dec 16, 2008 at 11:29 AM, Randall R Schulz <rschulz@sonic.net> wrote:

On Tuesday 16 December 2008 08:09, Jon Steelman wrote:
> Hi there,
> Is there a Scala interpreter online usable from a browser? I didn't
> run across one when searching.
>
> If there isn't, I suggest that Scala-lang.org add one. Ruby has a
> number of them. It is convenient and enticing for a newbie to be able
> to give Scala a quick whirl. Also, it is nice if you are working
> through the Scala book and aren't near your own computer but have
> access to a browser somewhere and want to run/play with the examples.

How do they handle badly-behaved code fragments (infinite loops,
calls to the equivalent of java.lang.System.exit(), etc.)?

Not sure. If its a problem, they've likely come up with a solution.

For this situation how challenging/easy would it be in Scala to catch runaway execution?

Thanks,
Jon

On Tuesday 16 December 2008 08:42, Jon Steelman wrote:
> On Tue, Dec 16, 2008 at 11:29 AM, Randall R Schulz
wrote:
> > ...
> >
> > How do they handle badly-behaved code fragments (infinite loops,
> > calls to the equivalent of java.lang.System.exit(), etc.)?
>
> Not sure. If its a problem, they've likely come up with a solution.
>
> For this situation how challenging/easy would it be in Scala to catch
> runaway execution?

Presumably most of the nasty stuff can be handled by sandboxing the bot
appropriately. As to excessive (or unbounded) CPU consumption, I'm not
sure if there's a simple solution (in pure Java) or if you have to
explicitly monitor a thread started for the purpose of executing a
remote execution request. And the last time I checked, there was no
pure Java way to find out about a thread's CPU consumption, only clock
time (which is obviously not a per-thread thing).

> Thanks,
> Jon

Randall Schulz

On Tue, Dec 16, 2008 at 11:09 AM, Jon Steelman <jon.steelman@gmail.com> wrote:

Hi there,
Is there a Scala interpreter online usable from a browser? I didn't run across one when searching.

If there isn't, I suggest that Scala-lang.org add one. Ruby has a number of them. It is convenient and enticing for a newbie to be able to give Scala a quick whirl. Also, it is nice if you are working through the Scala book and aren't near your own computer but have access to a browser somewhere and want to run/play with the examples.

This is actually hardish to do with the way the interpreter currently works. It requires access to the file system, which is unhappy as applets run sandboxed.

There are definitely ways around this (e.g. you could compile on the server and load from the browser), but it requires a non-trivial amount of work.

The other problem of course is that the scala standard library jars are really very large.

On Tue, Dec 16, 2008 at 11:50 AM, Randall R Schulz <rschulz@sonic.net> wrote:

On Tue, Dec 16, 2008 at 11:50 AM, David MacIver <david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 11:09 AM, Jon Steelman <jon.steelman@gmail.com> wrote:

Hi there,
Is there a Scala interpreter online usable from a browser? I didn't run across one when searching.

If there isn't, I suggest that Scala-lang.org add one. Ruby has a number of them. It is convenient and enticing for a newbie to be able to give Scala a quick whirl. Also, it is nice if you are working through the Scala book and aren't near your own computer but have access to a browser somewhere and want to run/play with the examples.

This is actually hardish to do with the way the interpreter currently works. It requires access to the file system, which is unhappy as applets run sandboxed.

There are definitely ways around this (e.g. you could compile on the server and load from the browser), but it requires a non-trivial amount of work.

The other problem of course is that the scala standard library jars are really very large.

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Thanks,
Jon

On Tue, Dec 16, 2008 at 11:54 AM, Jon Steelman <jon.steelman@gmail.com> wrote:

On Tue, Dec 16, 2008 at 11:50 AM, David MacIver <david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 11:09 AM, Jon Steelman <jon.steelman@gmail.com> wrote:

Hi there,
Is there a Scala interpreter online usable from a browser? I didn't run across one when searching.

If there isn't, I suggest that Scala-lang.org add one. Ruby has a number of them. It is convenient and enticing for a newbie to be able to give Scala a quick whirl. Also, it is nice if you are working through the Scala book and aren't near your own computer but have access to a browser somewhere and want to run/play with the examples.

This is actually hardish to do with the way the interpreter currently works. It requires access to the file system, which is unhappy as applets run sandboxed.

There are definitely ways around this (e.g. you could compile on the server and load from the browser), but it requires a non-trivial amount of work.

The other problem of course is that the scala standard library jars are really very large.

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Ah. That's not really less problematic though. If anything it's slightly scarier because it gives people remote code execution. :-)

David MacIver wrote:

a1a662200812160858y3b0d5bb7naaf85fac91c7aa41 [at] mail [dot] gmail [dot] com" type="cite">On Tue, Dec 16, 2008 at 11:54 AM, Jon Steelman <jon [dot] steelman [at] gmail [dot] com" rel="nofollow">jon.steelman@gmail.com> wrote:

On Tue, Dec 16, 2008 at 11:50 AM, David MacIver <david [dot] maciver [at] gmail [dot] com" target="_blank" rel="nofollow">david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 11:09 AM, Jon Steelman <jon [dot] steelman [at] gmail [dot] com" target="_blank" rel="nofollow">jon.steelman@gmail.com> wrote:

Hi there,
Is there a Scala interpreter online usable from a browser? I didn't run across one when searching.

If there isn't, I suggest that Scala-lang.org add one. Ruby has a number of them. It is convenient and enticing for a newbie to be able to give Scala a quick whirl. Also, it is nice if you are working through the Scala book and aren't near your own computer but have access to a browser somewhere and want to run/play with the examples.

This is actually hardish to do with the way the interpreter currently works. It requires access to the file system, which is unhappy as applets run sandboxed.

There are definitely ways around this (e.g. you could compile on the server and load from the browser), but it requires a non-trivial amount of work.

The other problem of course is that the scala standard library jars are really very large.

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Ah. That's not really less problematic though. If anything it's slightly scarier because it gives people remote code execution. :-)

Executing the code on the server sounds really scary to me.  What about a Java Web Start interpreter?  I believe that if signed it can access the file system, and it caches applications which should help mitigate the jar file size.  Plus it could have an editor nicer than what would be (readily available on) a web page.

On Tue, Dec 16, 2008 at 12:17 PM, Matt Weaver <mweaver@mailbolt.com> wrote:

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Ah. That's not really less problematic though. If anything it's slightly scarier because it gives people remote code execution. :-)

Executing the code on the server sounds really scary to me. 

Well in theory it's safe to do. The JVM is set up for sandboxing.

In practice I wouldn't want to do it except on a VM running network isolated from the rest of my infrastructure. Something like codepad's setup would be ideal.

You could run the interpreter JVM on an arbitrarily crippled EC2 instance... But that would cost $$$.

--j

On Tue, Dec 16, 2008 at 11:26 AM, David MacIver <david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 12:17 PM, Matt Weaver <mweaver@mailbolt.com> wrote:

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Ah. That's not really less problematic though. If anything it's slightly scarier because it gives people remote code execution. :-)

Executing the code on the server sounds really scary to me. 

Well in theory it's safe to do. The JVM is set up for sandboxing.

In practice I wouldn't want to do it except on a VM running network isolated from the rest of my infrastructure. Something like codepad's setup would be ideal.

On Tue, Dec 16, 2008 at 12:26 PM, David MacIver <david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 12:17 PM, Matt Weaver <mweaver@mailbolt.com> wrote:

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Ah. That's not really less problematic though. If anything it's slightly scarier because it gives people remote code execution. :-)

Executing the code on the server sounds really scary to me. 

Well in theory it's safe to do. The JVM is set up for sandboxing.

In practice I wouldn't want to do it except on a VM running network isolated from the rest of my infrastructure. Something like codepad's setup would be ideal.

To focus this back on the original & non-research topic.... and challenging corner cases not withstanding....

Recommending for newbie consumption that Scala-lang.org offer an online Scala interpreter that can be invoked from *any* web browser (including no Java support) and executes Scala code outside of the end user's machine for a no-fuss, no-download, no-wait, no-barrier-to-try & easy to use way to try out first Scala steps.

Cheers,
Jon

On Tue, Dec 16, 2008 at 4:04 PM, Jon Steelman <jon.steelman@gmail.com> wrote:

On Tue, Dec 16, 2008 at 12:26 PM, David MacIver <david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 12:17 PM, Matt Weaver <mweaver@mailbolt.com> wrote:

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Ah. That's not really less problematic though. If anything it's slightly scarier because it gives people remote code execution. :-)

Executing the code on the server sounds really scary to me. 

Well in theory it's safe to do. The JVM is set up for sandboxing.

In practice I wouldn't want to do it except on a VM running network isolated from the rest of my infrastructure. Something like codepad's setup would be ideal.

To focus this back on the original & non-research topic.... and challenging corner cases not withstanding....

Ok. Let's focus on the nice idea rather than the things that need to be done in order to implement the nice idea.

Um.

What was it you wanted to talk about again?

On Tue, Dec 16, 2008 at 4:11 PM, David MacIver <david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 4:04 PM, Jon Steelman <jon.steelman@gmail.com> wrote:

On Tue, Dec 16, 2008 at 12:26 PM, David MacIver <david.maciver@gmail.com> wrote:

On Tue, Dec 16, 2008 at 12:17 PM, Matt Weaver <mweaver@mailbolt.com> wrote:

I should have been more clear. Not applet based .... the lightest weight & preferred solution would have the Scala sessions hosted remotely so that the browser is nothing more than a window to the interpreter session.

Ah. That's not really less problematic though. If anything it's slightly scarier because it gives people remote code execution. :-)

Executing the code on the server sounds really scary to me. 

Well in theory it's safe to do. The JVM is set up for sandboxing.

In practice I wouldn't want to do it except on a VM running network isolated from the rest of my infrastructure. Something like codepad's setup would be ideal.

To focus this back on the original & non-research topic.... and challenging corner cases not withstanding....

Ok. Let's focus on the nice idea rather than the things that need to be done in order to implement the nice idea.

Um.

What was it you wanted to talk about again?

LOL. Killjoy!  ;-)
Of course I want the interesting, challenging & corner cases to be attended to.... I'm just trying to give voice to what I think would be helpful to the Scala evangalization effort.

Jon

Maybe the page could forward code evaluation requests to a script
running inside a Linux VirtualBox (or vmware etc.) that launches the
JVM as an unprivileged user, gives it a maximum of say 10 seconds to
run, and returns its ouput, or an error if it didn't complete...

On 12/16/08, Jon Steelman wrote:
> On Tue, Dec 16, 2008 at 4:11 PM, David MacIver
> wrote:
>
>> On Tue, Dec 16, 2008 at 4:04 PM, Jon Steelman
>> wrote:
>>
>>> On Tue, Dec 16, 2008 at 12:26 PM, David MacIver
>>> wrote:
>>>
>>>> On Tue, Dec 16, 2008 at 12:17 PM, Matt Weaver
>>>> wrote:
>>>>
>>>>> I should have been more clear. Not applet based .... the lightest
>>>>>> weight & preferred solution would have the Scala sessions hosted
>>>>>> remotely so
>>>>>> that the browser is nothing more than a window to the interpreter
>>>>>> session.
>>>>>>
>>>>>
>>>>> Ah. That's not really less problematic though. If anything it's
>>>>> slightly
>>>>> scarier because it gives people remote code execution. :-)
>>>>>
>>>>> Executing the code on the server sounds really scary to me.
>>>>>
>>>>
>>>> Well in theory it's safe to do. The JVM is set up for sandboxing.
>>>>
>>>> In practice I wouldn't want to do it except on a VM running network
>>>> isolated from the rest of my infrastructure. Something like codepad's
>>>> setup
>>>> would be ideal.
>>>>
>>>
>>> To focus this back on the original & non-research topic.... and
>>> challenging corner cases not withstanding....
>>>
>>
>> Ok. Let's focus on the nice idea rather than the things that need to be
>> done in order to implement the nice idea.
>>
>> Um.
>>
>> What was it you wanted to talk about again?
>>
>
> LOL. Killjoy! ;-)
> Of course I want the interesting, challenging & corner cases to be attended
> to.... I'm just trying to give voice to what I think would be helpful to the
> Scala evangalization effort.
>
> Jon
>

Matt Weaver-3 wrote:
>
> Executing the code on the server sounds really scary to me.  What about
> a Java Web Start interpreter?  I believe that if signed it can access
> the file system, and it caches applications which should help mitigate
> the jar file size.  Plus it could have an editor nicer than what would
> be (readily available on) a web page.
>
+1 for this. There is no reason the terminal/server-session approach
couldn't also be worked on, but setting up a .JNLP file to make the Scala
interpreter run via Java Web Start is something that could be accomplished
very quickly...

On Wed, Dec 17, 2008 at 5:58 PM, Paul J. LaCrosse wrote:
> +1 for this. There is no reason the terminal/server-session approach
> couldn't also be worked on, but setting up a .JNLP file to make the Scala
> interpreter run via Java Web Start is something that could be accomplished
> very quickly...
It won't work, since the interpreter is just the compiler behind a
shallow facade. And the compiler needs access to the actual class
files to read out the custom scala signatures, which is difficult to
do in a Java Web Start scenario.

Johannes

-----------------------------------------------
Johannes Rudolph
http://virtual-void.net

(another try, forgot cc)
With some hacking the Scala Compiler can run as a signed applet (aka full acccess) if you make io wrapper classes that write to memory. You can then control the classfiles the compiler loads when it compiles the source code. You'll also need your own classloader (hench the signed applet) to load the compiled classfile, but you could then load the compiled classfile into it's own protectiondomain with reduced access. The problem with the size of classfiles can be reduced by pruning away unnessecary code with proguard and then lzma pack the resulting classfiles (without proguard lzma brings its down from 9.5mb to 2.9mb). From my experimentation with it, I remember getting security warnings when the compiler ran in a sandbox (maybe reflections).

For what it's worth, you can run the Scala interpreter with the java security manager and the following security policy:

grant {
  permission java.util.PropertyPermission "*", "read,write";
  permission java.io.FilePermission "<<ALL FILES>>", "read";
  permission java.lang.RuntimePermission "createClassLoader";
  permission java.lang.RuntimePermission "setContextClassLoader";
  permission java.lang.RuntimePermission "accessDeclaredMembers";
};

I'm not a Java security expert so I don't know if it's really safe but I figure if you can run it in a lightweight and contrived virtualized environment (e.g. Xen) and limit interpreter sessions to 15 minutes then I think you've got a pretty good solution.

alex

Can Scala-lang.org put one together and make it available? The
brainstorming here has provided some good suggestions on how to
provide a remote online Scala interpreter session through a browser
that is safe & controlled on the server side. Again, this is helpful
for evangelizing Scala.... for newbies, people just wanting to get the
quickest taste of Scala without any effort or barrier to try, and
people on the run using a restricted system.

Thanks,
Jon

If it's done as a Linux virtual computer, I guess that linux installation could be "headless" (no X server)...

I think this discussion is popular because it is an interesting problem.  Personally, I do not think that an in-browser Scala interpreter is going to help evangelize Scala.  It is already very simple to install.  The audience that you are targeting, those too lazy to install Scala, are probably not likely going too choose Scala.  It is the desire of many to make Scala more popular, but I think such efforts could be spent in other places.  Jon, this may be a good project for you to take on, as you have received some very good comments and ideas.

If there is ever a reason to put this together, it would be for a scala interpeter IRC bot.

FYI, I am a novice Scala user with no background in marketing so take my opinions as you please.

Regards,
Bryan