ExtJS Store Shared Between Multiple ComboBox Controls

Environment: ExtJS 4.1.3, auto loaded store, shared by multiple comboboxes

Problem:
Combobox with auto-complete behaves strangely. Sometimes, the list is obviously filtered down by something else.

Cause:
The same data store instance is shared by multiple combobox on the page. "doQuery" function in the combobox will try to reserve the store's filter that is not created by the combobox itself (see ComboBox.js > clearFilter, and doQuery implementation). This design allows the auto-complete filter of different dropdown pickers to interfere with each other.

Solution:
1. create custom control, then override "doQuery" function to call store.clearFilter()
Pros:
- Clean, reusable design
Cons
- Validation still has cross contamination of conflicting filtering
- In cases you want to preserve an existing filter, this solution need more tweaks or configuration input to make it working

2. Declare store of the combobox using the following style: store: {type: 'myStoreAlias'}, instead of store: 'myStoreName'. This way it will ensure each combobox has their own instance of the store, thus not interfering each other's filtering.
Pros:
- No other hidden surprises lurking around
Cons:
- Pretty much have to abandon the store: 'myStoreName' completely, because in a module design, you just don't know which combobox may live in the same page with another one and using the same store
- Network and memory overhead to maintain multiple copies of the same data

Coldfusion Error: "Value can not be converted to requested type."

Symptom: All of a sudden the test cases that worked before, stopped working. Error message is: "Value can not be converted to requested type.". Wasted hours trying to diff and check typos with no avail. Finally, surrender, and Googled the following article published in 2006:

ColdFusion Query Error: Value Can Not Be Converted To Requested Type

http://www.bennadel.com/blog/194-ColdFusion-Query-Error-Value-Can-Not-Be-Converted-To-Requested-Type.htm

So, it is an old problem that never go away. Everything clicks now. Database schema was just updated with a few new columns. "SELECT *" combined with CFQUERYPARAM seems to have some caching issue and everything just messed up from there.

Solution? remove SELECT *, change to use explicit column names. The problem simply goes away for good.

HTML + JavaScript Charting Solutions

• Ext JS, Example (good for intranet application)
• d3.js (extremely popular at this moment)
• Dojo Charting
• YUI Chart
• Google Chart (Big down side, at least at this time, is that Google will receive every single data point you want to plot. Not a good thing for any data that requires privacy!)
• Flotr2
• Flash charts? lots of good choices there, but not accessible on mobile clients, and in danger of being completely out in a few years?

Support JSONP in Coldfusion

Let say you already have a Coldfusion page that serves JSON data to your AJAX web application, now you want to support JSONP from cross domain client call. Here is the code snippet that will do it:

Solr in Coldfusion 9

Some tips for using Coldfusion 9 Solr search:

• Lesson Number 1: Make sure you review ALL the files under your collections \conf folder, many of them need to be commented out or changed from default values. Here is an incomplete list of what I changed:
• Commented out words in protwords.txt
• Deleted content in spellings.txt
• Updated synonyms.txt, deleted the test words, and added new synonyms based on the vocabulary specific to my application's domain
• schema.xml:
• Updated default query operator from AND to OR
• solrconfig.xml
• commented out "solr", "rocks" and other similar configurations
• Enable term highlighting (see http://help.adobe.com/en_US/ColdFusion/9.0/Developing/WSe9cbe5cf462523a0-5bf1c839123792503fa-8000.html \), but it's still not quite there. Still looking for a complte solution for this one.
• In Coldfusion Admin, change Solr buffer limit from default value 40 to 80 (http://bloggeraroundthecorner.blogspot.com/2009/08/tuning-coldfusion-solr-part-1.html)
• Ensure "Coldfusion 9 Solr Service" is started and set to "Automatic" startup type
• To access Solr collection from remote Coldfusion servers, 
• For the remote CF servers: change Solr server name in Coldfsuion Admin, DATA & Service > Solr Server > Solr Host Name
• For the Solr Host: Allow remote server to have access to its Solr instance. Configure Jetty to listen on all incoming IP address. Coldfusion's default configuration is allow only 127.0.0.1, thus disabling remote CF server's access to it's hosted Solr instance. To change this, just open jetty.xml in {coldfusion home}\solr\ect, and comment out the host line which restricts to listen on 127.0.0.1 only (interestingly, I found this solution from this link: http://helpx.adobe.com/coldfusion/kb/coldfusion-9-limit-access-solr.html, which claims Coldfusion's default configuration is to listen on all ip addressed
• Web access to Solr admin: http://{Your CF Server Name}:8983/solr/
• Last and a big one, when you try to update multiple indexes, you will see error like this:

Error_opening_new_searcher_exceeded_limit_of_maxWarmingSearchers4_try_again_later

Stack Trace:
...
org.apache.solr.common.SolrException: Error_opening_new_searcher_exceeded_limit_of_maxWarmingSearchers4_try_again_later

Error_opening_new_searcher_exceeded_limit_of_maxWarmingSearchers4_try_again_later

request: http://localhost:8983/solr/.../update?commit=true&waitFlush=false&waitSearcher=false&wt=javabin&version=1
    at org.apache.solr.client.solrj.impl.CommonsHttpSolrServer.request(CommonsHttpSolrServer.java:424)
    at org.apache.solr.client.solrj.impl.CommonsHttpSolrServer.request(CommonsHttpSolrServer.java:243)
    at org.apache.solr.client.solrj.request.AbstractUpdateRequest.process(AbstractUpdateRequest.java:105)
    at coldfusion.tagext.search.SolrUtils.commitToServer(SolrUtils.java:1024)
    at coldfusion.tagext.search.SolrUtils.addDocument(SolrUtils.java:664)
    at coldfusion.tagext.search.IndexTag.doQueryUpdate(IndexTag.java:929)
    at coldfusion.tagext.search.IndexTag.doStartTag(IndexTag.java:254)
    at coldfusion.runtime.CfJspPage._emptyTcfTag(CfJspPage.java:2722)
…

This error will be consistently showing up in production environment with even very light traffic, and became a big show stopper for the usage of Solr collection provided by Coldfusion (does not seem to be a Solr problem, instead a problem of Coldfusion integration problem). 

Root cause seems to be that Coldfusion commits every index update, and causing excessive Solr searcher warming. Combining with misconfigured default Solr configuration, this problem starts to appear for a collection of only a few hundred entries.

In Coldfusion 10, this problems seems like easier to solve by using the newly introduced "autoCommit" attribute, which should always be "no" (i.e. never use the default value). Then I guess configuring the "autoCommit" in solr config file will solve the above problem in Coldfusion 10.

However, production environment that is already in CF 9 is stuck. My solution for it is a combination attack:

• Manually throttle cfindex update by adding a sleep after every update
• Wrap try catch block around the cfindex update, then add a longer sleep time in the catch block, and add retry logic to try update again after the sleep
• Database flag of index entries, this flag will be set only after index is updated successfully. A scheduled CF task will scan this flag to identify missed updates (due to the above error), and try to update index again

The above approach so far allows me to update thousands of indexes without any problem.

Downloadify Stopped Working in Google Chrome

Downloadify uses Flash's download functionality to enable client side download. It saves server side roundtrip.  There is also nice user extensions using Downloadify to export ExtJS grid on the client side. HTML 5 does have some limited support of client side download, but it suffers inconsistent support between browsers.

Ok, after all the justification for using it, Downloadify stopped working for Google Chrome recently. And here are the observations:

• Environment: Windows, Google Chrome is up-to-date
• Download still works in IE and Firefox;
• Download only works in Chrome if I'm testing using Intranet URL. But it does not work if the URL looks like Internet address (i.e. http://localhost works, but http://10.10.10.1 won't work);
• IE, Firefox are on Flash 11.3, and Chrome is running Flash 11.4

Solution:
Not really a solution. It's more like a workaround.

1. In Chrome address bar type: "about:plugins"
2. Click on "Details" button to expand into more detailed view
3. Find "Flash" section, and disable the Flash player 11.4 (something called "PepperFlash"\"pepflashplayer.dll")
4. Make sure there is another Flash player listed here, which should be Adobe's distribution

Root Cause?
I can only guess. Still not sure why and how to fix it properly.
Turns out Google Chrome has it's own Flash distribution. (Only guessing) It seems to be different from Adobe's official one, and somehow has higher default security settings.

itemId and id in ExtJS

The story: 
Here is a lesson for not reading document thoroughly. My very first ExtJS project goes smoothly until one day I created multiple tabs, and then closed some of them. All of sudden the layout completely messed up. In the debug console, there is null reference error. Call stack is deep in the ExtJS library.

Fast forward, after several hours of digging around, I found out I was using "id" config for several ExtJS controls. Then, close tab action will cause all the controls on the other tabs with the same "id" got deleted from DOM.

Solution:
Use "itemId" instead of "id" config for controls.

Comparison to ASP.NET
Came from ASP.NET world, I guess that is why I was using "id" config without any second thought. Below is a comparison of similar concepts in ASP.NET

ExtJS	ASP.NET	_
itemId	ID	(Recommended) HTML element's ID is automatically generated to ensure uniqueness, usually by concatenating ID of the container hierarchy. Programmer only need to ensure ID is unique within it's container.
id	ClientID	(Not recommended) Rendered HTML element will use this property as their ID. It's programmer's responsibility to ensure it is unique across the whole page (think when you starting to have multiple instances of the same control on a page).

(To check out more ExtJS related posts from me, click here: http://developertips.blogspot.com/search/label/ExtJS)

SQL Performance Sample Queries

ASP.NET Exception: "Session state has created a session id, but cannot save it ..."

Symptom:

• Only happens for new session
• Exception Message:
  A first chance exception of type 'System.Web.HttpException' occurred in System.Web.dll Additional information: Session state has created a session id, but cannot save it because the response was already flushed by the application.

•  Stack Trace: 

[HttpException (0x80004005): Session state has created a session id, but cannot save it because the response was already flushed by the application.]   System.Web.SessionState.SessionIDManager.SaveSessionID(HttpContext context, String id, Boolean& redirected, Boolean& cookieAdded) +3691007   System.Web.SessionState.SessionStateModule.DelayedGetSessionId() +199   System.Web.SessionState.SessionStateModule.ReleaseStateGetSessionID() +25   System.Web.SessionState.SessionStateModule.OnReleaseState(Object source, EventArgs eventArgs) +874   System.Web.SyncEventExecutionStep.System.Web.HttpApplication.IExecutionStep.Execute() +80   System.Web.HttpApplication.ExecuteStep(IExecutionStep step, Boolean& completedSynchronously) +270 

Cause:

• I was able to narrow down the cause of this problem to setting page's Buffer="false"
• Reasoning would be that without buffering, all content are pushed to client immediately, and somehow, ASP.NET decided to set cookie at a very late stage where it can no longer write to HTTP header to set SessionID cookie

Solution:
Set Buffer to true is not a solution for me, because I will need to flush content to deliver real-time progress information.
Based on some understanding, a solution quickly came up with some Google search. Simply add the following line to Global.asax.cs > Session_Start, the problem is resolved.
string sessionID = Session.SessionID;

Faster Flex Builder Compile Time

To increase Flex Builder compile time during development, the following tweak helped my Flex 3 builder to go from 30 seconds to just a few seconds for a medium sized project.
Open project property, under Flex Compiler -> Additional compiler arguments, add " -incremental -keep-generated-actionscript"

It definitely helps me go from compile once every hour, to every few minutes. Such that I can get immediate feedback through compiler errors or warnings.

file 'lib' not found

When installing Ruby on Rails using command: gem install rails
Got this error message: file 'lib' not found
Seems like it's fixed by running gem instal rdoc followed by gem install rails again.

Cross Site XMLHttpRequest

• IE8 and above:
  • use XDomainRequest instead
  • Can only cross from HTTP to HTTP or HTTPS to HTTPS (i.e. if web page is served from HTTP, then cannot cross-site access HTTPS. Or web page served over SSL cannot cross site access HTTP content. Will get "Access Denied" error.)
• Cross site request server must send this response header:  Access-Control-Allow-Orig *

Useful Sysinternals Utilities

As a software engineer (not system administrator), I found the following tools from Sysinternal to be useful.

• Autoruns: mainly used to turn off unnecessary executables during boot and login to speed up system boot performance
• Portmon: used to monitor serial port traffic (similar to wireshark for network traffic)
• Process Explorer: used mainly to find file locks, so that I know which process to kill to be able to free up the lock.
• Process Monitor
• PsExec: remote execute console application. Examples:

• psexec \\vm-001 ipconfig /all
• psexec \\vm-001 cmd
• This command copies the program test.exe to the remote system and executes it interactively: psexec \\vm-001 -c test.exe

• PsKill: kill local or remote processes. Mainly used in server software for house keeping (for example: kill stuck Office Automation process)
• PsService
• ZoomIt: usefuly for presentation. Zoom in screen, draw lines on the screen.

Disable Touchpad on Dell Laptop

Problem
Ever frustrated with Touchpad being overly sensitive?

I frequently got random mouse movements and clicks while using Laptop's keyboard. They are caused by the Touchpad being overly sensitive. It is especially a problem when I am using remote desktop working on another computer. I guess the Touchpad sensitivity settings does not work on remote desktop client?

And this is a major frustration, because when I finish typing a line of code, they frequently show up on the wrong line, and did not show up anywhere at all, because the random mouse clicks has took their focus away.

Research
Today, finally it struck me that I should disable this thing. And turns out the latest DELL tool has some nice options available. For one thing, I can permanently enable/disable "Pointing Stick", "Pointing Stick Buttons", "Touchpad", and "Touchpad Buttons". But, there is also a very nice feature called: "Disable Touchpad/Point Stick when external USB mouse is present". This is really a very user friendly feature that I never thought of searching for before.

Conclusion
I put a check next to the option:  "Disable Touchpad/Point Stick when external USB mouse is present", and got a wireless mouse. Problem solved. Happily typing code again.

Google Code Search will be shutdown January 15, 2012

http://techcrunch.com/2011/10/14/google-axes-more-services-jaiku-code-search-more/?utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+Techcrunch+%28TechCrunch%29
It was a very useful tool for me.

Portable Mouse with a Hook or Loop

Goal: to allow portable mouse to be even more portable

Going to meeting with a laptop, a pen and notebook (made with paper) and a mouse can be a handful (not to mention when you have a cup of coffee). What if we have a hook or ring on the mouse so that it can dangle on a finger (or belt?).
 
Potential Solutions
- retractable ring
- foldable ring
- hook

Need to pay attention of location of ring or hook so that they don't interfere with normal mouse use.

Adobe Flash Builder 4 and Coldfusion Builder crash during startup

Symptom: all of sudden, my Flash Builder 4 and Coldfusion Builder can not be started. They will crash during start. They are running on Eclipse 3.4.2, and 3.5.2 respectively.

Diagnostic: Coldfusion builder simply show me an error dialog without any useful information. It just generically states something like: Visual C++ request application to exit in abnormal way.
Of course, I tried to reset Eclipse and clear it's workspace to no avail.
However, luckily, Flash Builder 4 throws an exception. And I got a chance to start Visual Studio 2010 debugger session on it. Once in Visual Studio debugger, I saw exception type "bad_day_of_month" from boost library. Then I turn to "Stack Trace" tab, and saw callstack: Kernel32->atmlib.dll->UpdateNotifications.dll. A little Google on this end turned up a thread talking about similar problem from other Adobe users. So, I read the thread, it starts to mention how the "UpdateNotification" library will look at Windows Scheduled Tasks for Adobe updater. Then it occurs to me what might be, and later proven to actually be the root cause.

Cause: A few days earlier, in an effort to speed up my computer, I ran "AutoRuns" utility from "System Internals", and disabled a bunch of "Scheduled Tasks". Among them was a task named "AdobeAAMUpdater-1.0......".

Fix: using "AutoRuns" utilities, I turned the "AdobeAAMUpdater-1.0....." scheduled task back on. Then Flash Builder 4 and Coldfusion Builder are all back to normal.

SQL Maintenance Plan Failed

Environment: SQL 2005
Symptom: Scheduled SQL maintenance plan to do partial backup failed. Got two message logged in SQL Server log:
Error: 3041, Severity: 16, State: 1
BACKUP failed to complete the command BACKUP DATABASE master WITH DIFFERENTIAL. Check the backup application log for detailed messages.
Cause: Master database does not support partial backup. So, if the task is for "Differential" backup, "master" database should not be included.
Solution: Open the plan details, in the "Database(s)" section make sure database that needs to be backup are explicitly selected, instead of having "All databases" checked.

Coldfusion Webservice Input Name Changed to in0

Symptom: Coldfusion webservices sometimes complain about input parameter "In0"

Environment: Coldfusion 9 on Windows

Solution: Login to Coldfuion 9 Administrator portal, Go to Server Settings > Caching, click on "Clear Template Cache Now" and "Clear Component Cache Now". This seems to trigger to re-compile of webservices WSDL thus fixed the problem.


However:

1. I don't know what is the root cause of this problem. Google turn-up some similar complains, but could not find any official answers on this
2. The solution which required human interaction does not help in production environment
3. The solution does not solve the problem permanently, sooner or later I'll hit the same error, and has to go back to the server and clear cache again

CFQUERYPARAM: LIST and SEPARATOR attributes

Adobe online document only listed these two attributes without much explanation. I found the following link with very thorough explanation of the effects and usage of these two attributes:
http://www.pukkared.com/2011/01/using-cfqueryparam-list-attribute-when-using-in-operator/