Month: July 2012

Categories
Admin Internet Mail Linux

Yahoo! stopped accepting emails – what we can learn about sendmail from this

Flash Update
I noticed yahoo.com, yahoo.ca and yahoo.com.br had stopped accepting emails today.

I wanted to provide insight into this problem that few others would have, namely, when did the problem first occur?

I looked at my stuck messages in queue. I realized that with sendmail, there is no easy way to answer the question: what is the oldest stuck message for domain XYZ in the queue? So I rigged up something, very crude, but typical for a Unix command line-type of guy.

Namely:

$ grep yahoo */qf*|grep for|cut -d\; -f2|sort|head

The answer? My first stuck message comes from 12:43:46 EST today (July 31st). As of this writing, 3:53 PM, the problem still exists, which already makes it a quite long outage even if it is fixed in the next few minutes. Just minutes later, around 4 PM, I noticed a lot of the messages being delivered, so the problem seems to have finally cleared up.

The expression above works if you are root and the current directory is, e.g., /mqueue, under which you have queue directories q0, q1, …, q9, etc corresponding to an MC statement:

define(`QUEUE_DIR',`/mqueue/q*')dnl

The grep above might miss a few messages, but if you have lots of them as I do, it doesn’t really matter as it’s purpose is just to convey the general idea of when the problem started. In my case it can be safely assumed that I am continuously sending emails to yahoo.com, so it is not possible to have a window that isn’t covered of more than ten minutes or so during the day.

Conclusion
We helped document a complete three-hour outage of Yahoo mail. Along the way we learned of a deficiency in sendmail’s mailq command – how limited its reporting options are. We compensated for that by rolling our own series of commands to answer the question of what is the oldest mail of this type in our queues.

Categories
JavaScript Linux Perl

A simple Perl script to build JavaScript folder objects

Part 2
Intro
This is the 2nd part in a two-part blog where I present a simple example of a JavaScript folder browser. In Part 1 I provided all the JavaScript required. By itself it may have seemed an academic exercise, but once you appreciate that it isn’t hard to write a program which creates the JavaScript objects from your server’s directory structure, well, now you have something that’s pretty powerful and useful.

The details
I considered writing this in Python, which seems to be a more current language, but old habits die hard as they say. I just know Perl too well to suffer the pain of learning all those neat tricks all over again in another language. Maybe someday I’ll re-write it in Python.
Notice the recursion through the directories? I first used that 17 years ago! Why throw out good code?

Here is the code, which I named scan.pl:

#!/usr/bin/perl
# DrJ - 7/2012
# scan picture-containing directories using recursion and build javascript objects from them
use Getopt::Std;
getopts('d:j:');
$homedir = $opt_d;
$jsfile = $opt_j;
usage() if ! $opt_d || ! $opt_j;
$DEBUG = 0;
print "Homedir: $homedir, jsfile: $jsfile\n";
open(JS,">$jsfile") || die "Cannot open JavaScript file: $jsfile!!\n";
$date = `date +%D`;
($homedirnoslash) = $homedir =~ /^\/(.+)/; # assumes leading "/"
 
# print opening of function
print JS qq#function init() {
// Generated data from scan.pl - DrJ $date
folder['browse'] = {path:'',depth:0,kids:['$homedirnoslash']};
#;
 
# get things going with our recursive function
traverse($homedir,0);
 
# closing statement
print JS qq(}\n);  # close of init JavaScript function
close(JS);
 
sub traverse {
my ($dir,$depth) = @_;
my @kids = ();
print "Traverse. dir: $dir\n" if $DEBUG;
opendir(DIR, $dir) || die "Cannot open dir $dir!!\n";
foreach (readdir(DIR)) {
  next if $_ eq '.' || $_ eq '..';
  print "Traverse. file: $_\n" if $DEBUG;
  $path = "$dir/$_";
  if (-d $path) {         # a directory
# we want only the last part of the path
    (my $lastpath) = $path =~ /([^\/]+)$/;
    push(@kids,$lastpath);
    traverse($path,$depth + 1); # recurse!
  } elsif ($_=~/$filespec/) {        #
  }
} # end loop over files in this directory
# write out the JS objects
print JS qq(folder["$dir"] = {path:"$dir",depth:$depth,kids:[);
my $i = 0;
# kids are in jumbled order.  Do regular sort on them.
foreach (sort @kids) {
  $comma = $i++ > 0 ? "," : "";
  print JS qq($comma"$_");
}
# end of object. close it out.
print JS qq(]};\n);
} # end sub traverse
#
sub usage {
  print "usage: $0 -d root_directory -j JavaScript_output_file\n";
  exit(1);
}

It’s pretty self-explanatory. Call it like this example:

> ./scan.pl -d /homepic -j init.js

and it produces an init.js file filled with an init() function and all the necessary folder objects, assuming the top-level folder to browse is /homepic.

My init.js looks like this:

function init() {
// Generated data from scan.pl - DrJ 07/27/12
 
folder['browse'] = {path:'',depth:0,kids:['homepic']};
folder["/homepic/pictures_chronological/2011_06"] = {path:"/homepic/pictures_chronological/2011_06",depth:2,kids:[]};
// lots more lines like this omitted
folder["/homepic"] = {path:"/homepic",depth:0,kids:["kodak_pictures","pictures_chronological"]};
}

And I tested it in browse13.html, which looks just like browse12.html, except I got rid of the init() function and added an include line at the top:

<html>
<head>
<script type="text/javascript" src="init.js"></script>
...

I am a little concerned about performance. This clearly isn’t designed to scale to tens of thousands of directories, but will it be sufficiently fast for my purposes? My init.js is 213 lines and about 25 KB in size. browse13.html which calls it loads fast and runs fast. So, yes, success!

Part 1, A Simple Javascript Folder Browser

Conclusion
We have created a fairly powerful and general-purpose folder browser out of fairly simple usage of JavaScript and Perl. It makes an ideal base upon which to build further.

Categories
Apache JavaScript Perl

A Simple Javascript Folder Browser

Part 1

Intro
I haven’t posted much lately. I’ve been tied up creating this folder browser using client-side JavaScript. I probably made every mistake in the book, but I worked through them all and the outcome is pretty cool, if I say so myself! It works in IE, FireFox and even Blackberry!

The details
I broke down the development of this browse app into 12 stages. Given time, I might show the progression of my thinking as each version becomes closer and closer to fulfilling all initial objectives. But who has time? I’ll show the source for browse3.html, warts and all, and then skip many iterations and jump to showing the final source, browse12.html.

Browse3.html
It ain’t pretty. It isn’t even correct. But it “does stuff.” It assumes Apache web server is running and “borrows” the closed and open folder icons from apache’s /icons directory. In my case I have a top-level directory called /homepic with folders under that and sub-folders under those folders that I want the ability to browse and , ultimately, take some action such as displaying all the folder’s images in the image viewer I wrote earlier.

<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
// global object
var folder = new Object;
function displayDate()
{
document.getElementById("demo").innerHTML=Date();
}
function init() {
// big initialization - generated code from perl perusal of directories
// see http://www.quirksmode.org/js/associative.html
//  var folder = new Object;
// we need this empty assignment to extend object with subproperties later on
  folder['homepic'] = '/homepic';
  //folder['/homepic'].path = '/homepic';
  folder.homepic.state = 'closed';
  folder[0] = '/homepic/kodak_pictures';
  folder[1] = '/homepic/pictures_chronological';
  folder['/homepic/kodak_pictures'] = '/homepic/kodak_pictures';
  folder['/homepic/kodak_pictures'].state = 'closed';
  //folder['/homepic/kodak_pictures'].path = '/homepic/kodak_pictures';
  folder['/homepic/pictures_chronological'] = '/homepic/pictures_chronological';
  folder['/homepic/pictures_chronological'].state = 'closed';
  //folder['/homepic/pictures_chronological'].path = '/homepic/pictures_chronological';
  var child = 'homepic';
  var cstate = folder['homepic'].state;
  var cpath = folder[0];
}
function browse(f) {
document.getElementById("demo").innerHTML="folder: "+f+" ";
var icon;
var imgid;
var fname;
if (f == "browse") {
// see http://www.quirksmode.org/dom/intro.html#create
// one-time initialization
  init();
  document.getElementById("browse").innerHTML='';
  icon = document.createElement('IMG');
  icon.src = "/icons/folder.gif";
  icon.id = "icon-/homepic";
  icon.onclick = Function('browse("/homepic")');
  document.getElementById("browse").appendChild(icon);
  var divfolder = document.createElement('DIV');
  divfolder.id = "/homepic";
  document.getElementById("browse").appendChild(divfolder);
  var x = document.createTextNode('homepic');
  document.getElementById('/homepic').appendChild(x);
  //document.getElementById("browse").innerHTML='<img id="homepic" onclick="browse(\'homepic\')" src="/icons/folder.gif">ho
mepic<br>';
} else {
  imgid = 'icon-' + f;
// change img to one of open folder
  document.getElementById(imgid).src = "/icons/folder.open.gif";
  // nope? imgid.src  = "/icons/folder.open.gif";
  for (i=0;i<3;i++) {
    icon = document.createElement('IMG');
    icon.src = "/icons/folder.gif";
    fname = folder[f].children[i];
    //fname = folder['homepic'].children[i];
    icon.id = "icon-" + fname;
    icon.onclick = Function('browse('+fname+')');
    document.getElementById(f).appendChild(icon);
    var divfolder = document.createElement('DIV');
    divfolder.id = fname;
    document.getElementById(f).appendChild(divfolder);
    var x = document.createTextNode(fname);
    document.getElementById(f).appendChild(x);
  } // end loop over children
}
}
// note variable # or arguments are being passed
function  openfolder()
{
var f = arguments[0];
var dir = "/icons/";
var fopen = "folder.open.gif";
var fclosed = "folder.gif";
var folder = document.getElementById(f);
var ftype = folder.src;
// src includes http... Get rid of stuff in front
var patt = /.*(folder.+)/;
var ftypebare = ftype.replace(patt,"$1");
// for debugging
document.getElementById("demo").innerHTML="folder: "+f+" "+ftypebare;
if (ftypebare == fopen) {
// close folder and remove sub-folders
  folder.src = dir+fclosed;
  document.getElementById("homepic/pictures_chronological").innerHTML='';
} else {
// open up folder and reveal sub-folders
  folder.src = dir+fopen;
  for (var i = 0; i < arguments.length; i++) {
    var placeid = arguments[i];
    var srcid = '/' + placeid;
    document.getElementById(placeid).innerHTML='&nbsp;&nbsp;&nbsp;<img id="' + srcid + '" onclick="openfolder(\'pictures_ch
ronological\')" src="/icons/folder.gif"/> pictures_chronological<br>';
  }
}
 
}
</script>
</head>
<body>
 
<h1>Folder Browser</h1>
<p id="demo">Debug Aid.</p>
<p id="browse"><a href="#" onclick='browse("browse")'>Folder Browser</a></p>
 
<img id="homepic" onclick="openfolder('homepic','homepic/pictures_chronological','homepic/canon_pictures')" src="/icons/fol
der.gif"/> homepic<br>
<div id="homepic/pictures_chronological"></div>
<div id="homepic/canon_pictures"></div>
<img id="cfolder2" onclick="openfolder(2)" src="/icons/folder.gif"/><br>
<img id="cfolder3" onclick="openfolder(3)" src="/icons/folder.gif"/><br>
<img id="cfolder4" onclick="openfolder(4)" src="/icons/folder.gif"/><br>
 
</body>
</html>

So you see in browse3 I’m wrestling with how to work with JavaScript Objects (which I didn’t really know existed at that time). I badly wanted to give an associative array properties, as in the initialization line

folder['/homepic/kodak_pictures'].state = 'closed';

but I couldn’t find any examples on the Internet. I eventually learned that wasn’t a correct assignment.

So one of my biggest and most worthwhile lessons was to gain a decent understanding of JavaScript objects, which hold multiple values, and object properties.

I tried to use Firebug for Firefox, with very limited success, but at least I could step through the Javascript code and see which branch in a conditional was being executed compared to what I thought should be executed, which tipped me off to one vexing problem concerning opening and closing folders multiple times. Also just looking up the error in Internet Explorer by double-=clicking the warning sign in the corner was tremendously helpful.

So…skipping for now versions 4 – 11, we arrive at browse12.html:

Browse12.html

<!DOCTYPE html>
<html>
<head>
<script type="text/javascript">
// global object
var folder = new Object;
function displayDate()
{
document.getElementById("demo").innerHTML=Date();
}
function init() {
// big initialization - generated code from perl perusal of directories
// I think my big breakthrough was to learn about Javascript objects and their properties
// from the book Javascript The Definitive Guide, 5th edition by D.Flanagan
// Some additional inspiration came from http://www.quirksmode.org/dom/intro.html#create
// folder is an associative array with properties path, state,depth and kids (which is itself an array)
// first entry is initial top-level to get things started
  folder['browse'] = {path:'',depth:0,kids:['homepic']};
// regular entries:
  folder['/homepic'] = {path:'/homepic',depth:1,kids:['kodak_pictures','pictures_chronological']};
// values for sub-folders
// /homepic/kodak_pictures
  folder['/homepic/kodak_pictures'] = {path:'/homepic/kodak_pictures',depth:2,kids:['2002_05','2002_06']};
// /homepic/pictures_chronological
  folder['/homepic/pictures_chronological'] = {path:'/homepic/pictures_chronological',depth:2,kids:['2011_11','2011_12']};
}
function browse(f) {
document.getElementById("demo").innerHTML="folder: "+f+" ";
var icon;
var imgid;
var fname;
var table;
if (f == "browse") {
// one-time initialization
  init();
}
 
imgid = 'icon-' + f;
if (!folder[f]) {
// folder not defined: must be a terminal folder. Do something here eventually
// but for now do nothing whatsoever
} else {
  if (folder[f].state === undefined || folder[f].state == 'closed') {
  // change img to one of open folder
    if (f == 'browse') {
      document.getElementById(f).innerHTML='';
    } else {
      document.getElementById(imgid).src = "/icons/folder.open.gif";
    }
    var kids = folder[f].kids;
    for(var i=0;  i < kids.length; i++) {
      table = document.createElement("table");
      table.border = 0;
      var row = document.createElement("tr");
      var td1 = document.createElement("td");
      var td2 = document.createElement("td");
      var td3 = document.createElement("td");
      icon = document.createElement("img");
      icon.src = "/icons/folder.gif";
      if (f == "browse") {
        fname = "/" + kids[i];
      } else {
        fname = f + "/" + kids[i];
      }
      icon.id = "icon-" + fname;
      if (folder[fname])
        folder[fname].state = 'closed';
      icon.onclick = Function('browse("'+fname+'")');
      td1.width = 27 + folder[folder].depth*27;
      td1.align = "right";
      td1.appendChild(icon);
      var node = document.createTextNode(kids[i]);
      td3.appendChild(node);
      row.appendChild(td1); row.appendChild(td2); row.appendChild(td3);
      table.appendChild(row);
      document.getElementById(f).appendChild(table);
      var divfolder = document.createElement("div");
      divfolder.id = fname;
      document.getElementById(f).appendChild(divfolder);
      folder[f].state = 'open';
    } // end loop over children
  } else {
  // set folder to closed state
  // this innerHTML nullification is kind of a kludge, but it works
    document.getElementById(f).innerHTML='';
    document.getElementById(imgid).src = "/icons/folder.gif";
    folder[f].state = 'closed';
  } // end conditional over folder state
} // end condition over whether folder is defined or not
} // end function browse
 
</script>
</head>
<body>
 
<h1>Folder Browser</h1>
<p id="demo">Debug Aid.</p>
<p id="browse"><a href="#" onclick='browse("browse")'>Folder Browser</a></p>
</body>
</html>

That’s it! Not bad, huh? I pan to generate the init() function periodically and automatically from a Perl script which peruses my directories.

I could have used Ajax and generated the subfolder information on the fly as it is needed – not that I know how, I just know enough to know it is possible and therefore I could do it – but I thought this method of pre-loading all the information might be a little more efficient. If this were a folder and file browser it would be different, but for now it is just a folder browser.

So the main revelation is that I had to set my associative array members to be objects during initialization, as in

folder['/homepic'] = {path:'/homepic',depth:1,kids:['kodak_pictures','pictures_chronological']};

and one of the object values is itself an anonymous array that holds the sub-folders.

Buying an actual book was probably a good move. I went with JavaScript, The Definitive Guide, 5th edition. Note that this is not the latest edition – the 6th – but this way I could buy the book used for a lot less and not get myself further confused by HTML5, which I am not ready to tackle and which many browsers do not yet fully support. The book is pretty heavy going and the discussion of DOM was particularly difficult and the examples too few and too removed from the real world. But the Core Javascript discussion made a lot of sense to me so was by itself worth the purchase price.

In my next post I’ve posted the Perl script which can generate the folder object initialization.

Part 2, A simple Perl script to build JavaScript folder objects

Conclusion
In this part one of a two-part post I’ve provided the JavaScript that implements a very compact folder browser. It has been tested on both IE and Firefox. The 2nd part of this series will provide the Perl Jvascript code generator for automation of the object creation.

Categories
Admin Network Technologies

The IT Detective Agency: Two of our sites got cut off!

Intro
I sometimes consult for the networking group of a large company. This incident really happened. I don’t know that it could ever happen again to anyone else, but it’s so bizarre that I just had to document it as an example of “you wouldn’t believe it unless you had actually been through it yourself.”

Let’s get into it
This company has lots of small and mid-sized offices connected via MPLS. WAN services are provided by a single telecom throughout the country. I feel obliged to not divulge specifics here. Let’s call the telecom “OE” as in over-extended.

So just before lunch yesterday they tell me that no PCs at one of their sites can access Internet, and this information is coming from a very reliable source. It also comes out that a second site is similarly affected. It kind of sounds like a WAN problem, but no other sites are affected. In the old days you’d almost certainly know to look at the WAN, but these days it’s a little more complicated. Everyone’s PC is in AD and they have the ability to push a GPO to all PCs at a site, so you just never know if the desktop group wasn’t involved in messing them up.

So they tell me they can PING their corporate Intranet server. Fine. But they cannot telnet to port 80. Newsflash. How did they get telnet enabled in Windows 7? I mentally stored this question for my continuing education. Crises are also great learning/teaching moments if you are of that frame-of-mind!

Ping is good. Of course I test the Intranet server myself, iwww.intranet. I can reach port 80 just fine. It happens that the front-end for iwww.intranet is a load balancer. I decide to do a trace using tcpdump. I’m not sure what I’ll find, but taking a trace is sort of a gut reaction in these cases. There’s lots of other traffic so we have to use a filter to see the tree in the forest. They give me the IP of the PC they’re testing from. My expression is something like this:

> tcpdump -i 0.0 host WKSTATION.AD.INTRANE

The 0.0 on this particular device is its way of saying use any and all interfaces.

Here’s what the output looks like:

11:51:03.852511 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de0a5), length 100
11:51:05.855446 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de101), length 100
11:51:06.187940 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de10b), length 100
11:51:08.857957 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de16d), length 100
11:51:09.184072 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de179), length 100
11:51:09.858865 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de198), length 100
11:51:14.855327 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de272), length 100
11:51:15.183349 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3de27f), length 100
11:52:19.898380 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3decab), length 100
11:52:22.901684 IP WKSTATION.AD.INTRANET > iwww.intranet: ESP(spi=0xd7ca145d,seq=0x3ded28), length 100

I had never seen that before. I loop up ESP and see it is related to IP protocol 50 which in turn is used in IPSEC for VPN connections.

What the…?

Yeah. Let’s review. He’s sending TCP packets to port 80 of iwww.intranet and all I’m seeing are these ESP packets, which isn’t even TCP. Of course the load balancer has no idea whatsoever what to do with those packets and simply does not respond to them.

What would you do? I felt the nail in the coffin would be to take a trace on the PC itself – see how the packets are when they’re coming straight out of the PC. But to be honest they never did make that trace. They didn’t have Wireshark installed so it would take awhile.

Meanwhile, the infrastructure folks are talking to each other and someone mentions the OE has a certain project “runVPN” that thay’re rolling out. Now that sounds suspicous. In the imperfect world you have to work with what you have, not what you’d like to have. Based on our experiences and educated hunches, we now feel pretty certain it’s gotta be a WAN problem caused by OE.

Within an hour OE confirms the problem is of their creation, and they have it fixed. They are very unhappy with the tech who caused it.

Conclusion
Sometimes things are what they appear to be. If you notice I didn’t do much to really help with the issue, and that’s all just about anyone can do when so much is outsourced. They did feel that my trace helped to convince the telecom that this really was their issue.

I guess they were encrypting WAN traffic on one end, but forgot to decrypt it on the other end. One of the strangest things to have on a production network.

Turning on telnet in Windows 7
Did I mention that they tested with telnet on Windows 7? They later explained how to enable it. Go to control panel / Programs / Programs and Features / Turn Windows features on. There is an option for Telnet client. Reboot (yes, you really need to reboot for this to take effect) and you’re good to go.