Behaviour of 'source' with URLs and proxy

On 05/10/2011 13:45, Prof Brian Ripley wrote:

On Wed, 5 Oct 2011, Renaud Gaujoux wrote:

From the help page ?file I -- had -- read the following:

"For ?url? the description is a complete URL, including scheme
(such as ?http://?, ?ftp://? or ?file://?). Proxies can be
specified for HTTP and FTP ?url? connections: see ?download.file?."

So you should have known that it was the same as url()!

I agree. I just thought -- incorrectly -- that any attempt to download a file 
from R would eventually call the same C code as download.file. Or maybe

source() does not download and source, but reads the file on the fly?

From the internet.info messages it seems that the proxy is actually used, 
but somehow differently than what download.file does (via wget).

No, somewhat differently than *wget* does.  As that help page says, the 
section on proxies only refers to the internal method.

Is source supposed to work through a proxy?

Yes, and it has been tested to do so.  But not tested on your proxy ....

OK, I agree that my settings look special, but in the end it is supposed to 
be a plain local proxy with no authentication.
The proxy is effectively used by the internal method and, from the messages 
(below), the remote file is opened, http headers are returned, but nothing 
else happens and I have to cancel the command (Ctrl-C).

This is where I would like to have some input, so that I can work out the 
issue.
I tried to go through the C code for internet with no great luck: seems that 
in_R_HTTPRead and RxmlNanoHTTPRead would the place to look at.

Any idea on what would cause these functions to hang (infinite loop, 
communication problem, ...)?
I know, I am too curious.

Thank you

Sys.getenv('http_proxy')

[1] "http://localhost:8080/"

Sys.getenv('no_proxy')

[1] "localhost,127.0.0.0/8,*.local"

options(internet.info=0)
download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt")

trying URL 'http://lib.stat.cmu.edu/datasets/csb/ch3a.txt'
Content type 'text/plain' length 1209 bytes
opened URL
^C
There were 15 warnings (use warnings() to see them)

warnings()

Warning messages:
1: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
 connected to 'localhost' on port 8080.
2: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
 -> (Proxy) GET http://lib.stat.cmu.edu/datasets/csb/ch3a.txt HTTP/1.0
Host: lib.stat.cmu.edu
User-Agent: R (2.13.2 x86_64-pc-linux-gnu x86_64 linux-gnu)

3: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- HTTP/1.1 200 OK
4: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Via: 1.1 SRVWINTMG003, 1.1 SRVWINTMG004
5: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Connection: Keep-Alive
6: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Proxy-Connection: Keep-Alive
7: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Content-Length: 1209
8: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Age: 747
9: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Date: Wed, 05 Oct 2011 11:52:25 GMT
10: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Content-Type: text/plain
11: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- ETag: "5c700f3-4b9-399383c0"
12: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Server: Apache
13: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Accept-Ranges: bytes
14: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
<- Last-Modified: Fri, 29 Jul 1994 14:21:11 GMT
15: In download.file("http://lib.stat.cmu.edu/datasets/csb/ch3a.txt",  ... :
 Code 200, content-type 'text/plain'

-- 
Renaud Gaujoux
Computational Biology - University of Cape Town
South Africa


On 05/10/2011 12:26, Prof Brian Ripley wrote:

On Wed, 5 Oct 2011, Renaud Gaujoux wrote:

Hi,

I am having troubles sourcing a file from our local network from R.
It looks like this file are not properly accessed by 'source', even they 
can be downloaded with download.file. (See below my settings and some 
tests I did). I ended up with a work around, but I would like to 
understand what is going on.

Doesn't source/readLines uses the same mechanism as download.file to 
access URLs?

No. They use url() connections. See ?file.

Thank you.

Renaud

My setting:
- I am using R 2.13.2 on Ubuntu 11.04.
- I am accessing internet through a proxy (set up with cntlm, not sure 
if this is the issue but I don't know how to check without it). This 
means that http_proxy='http://localhost:8080/'.
- We have local CRNA/BioConductor mirrors that can be accessed without 
going through the proxy.
- My .Rprofile sources a file 'setrepos.R' on the local network, that 
sets all relevant repos to our local mirrors.

From the shell:
- I can wget any URL (local or internet) from command line without a 
problem.
- In particular I can wget the file 'setrepos.R' from command line.

Symptoms:
- with options(download.file.method='wget'), I can download any URL 
(local or internet) with download.file
- I _cannot_ source any local or internet URL if http_proxy is set. It 
simply freezes. Using internet.info=0 gives the following messages:
############
Warning messages:
1: In file(file, "r", encoding = encoding) :
using HTTP proxy 'http://localhost:8080/'
2: In file(file, "r", encoding = encoding) :
connected to 'localhost' on port 8080.
3: In file(file, "r", encoding = encoding) :
-> (Proxy) GET http://*OUR_HOST*/~renaud/R/setrepos.R HTTP/1.0
Host: *OUR_HOST*
Pragma: no-cache
User-Agent: R (2.13.2 x86_64-pc-linux-gnu x86_64 linux-gnu)

4: In file(file, "r", encoding = encoding) : <- HTTP/1.1 200 OK
5: In file(file, "r", encoding = encoding) : <- Via: 1.1 SRVWINTMG004
6: In file(file, "r", encoding = encoding) : <- Connection: Keep-Alive
7: In file(file, "r", encoding = encoding) : <- Proxy-Connection: 
Keep-Alive
8: In file(file, "r", encoding = encoding) : <- Content-Length: 1597
9: In file(file, "r", encoding = encoding) :
<- Date: Wed, 05 Oct 2011 06:43:13 GMT
10: In file(file, "r", encoding = encoding) : <- Content-Type: 
text/plain
11: In file(file, "r", encoding = encoding) :
<- ETag: "30b8018-63d-4a627b821c980"
12: In file(file, "r", encoding = encoding) :
<- Server: Apache/2.2.9 (Ubuntu) DAV/2 SVN/1.5.1 PHP/5.2.6-2ubuntu4.6 
with Suhosin-Patch mod_python/3.3.1 Python/2.5.2 mod_ssl/2.2.9 
OpenSSL/0.9.8g mod_perl/2.0.4 Perl/v5.10.0
13: In file(file, "r", encoding = encoding) : <- Accept-Ranges: bytes
14: In file(file, "r", encoding = encoding) :
<- Last-Modified: Mon, 20 Jun 2011 17:03:50 GMT
15: In file(file, "r", encoding = encoding) : Code 200, content-type 
'text/plain'
############

- Setting options(download.file.method='wget') before sourcing does not 
change the behaviour.
- However, I can source any local URL if http_proxy='', without changing 
download.file.method. But then download.file does not work for internet 
URL any more since the proxy settings are wrong. I could set 
http_proxy='', then source, then restore the proxy settings and set 
options(download.file.method='wget'). But this is just a work around and 
I would like to understand what is going on.

Session Info:

R version 2.13.2 (2011-09-30)
Platform: x86_64-pc-linux-gnu (64-bit)

locale:
[1] LC_CTYPE=en_ZA.UTF-8 LC_NUMERIC=C
[3] LC_TIME=en_ZA.UTF-8 LC_COLLATE=en_ZA.UTF-8
[5] LC_MONETARY=C LC_MESSAGES=en_US.UTF-8
[7] LC_PAPER=en_ZA.UTF-8 LC_NAME=C
[9] LC_ADDRESS=C LC_TELEPHONE=C
[11] LC_MEASUREMENT=en_ZA.UTF-8 LC_IDENTIFICATION=C

attached base packages:
[1] stats graphics grDevices utils datasets methods base

other attached packages:
[1] devtools_0.4

loaded via a namespace (and not attached):
[1] RCurl_1.6-10 tools_2.13.2




-- 

Renaud Gaujoux
Computational Biology - University of Cape Town
South Africa




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