Another Dead Mac Disk. Backup Woes

The disk in an iMac died. Disk replacement was a little easier than in the one earlier this year.

After the replacement, tried Time Machine with an external USB-3 Toshiba drive. Worked fine twice, then the next morning it showed backup errors. The system.log listed file type modification errors. After a Disk Repair, backup functioned OK. Maybe the external drive goes to sleep over night?

Being in backup mode, tried the Control Panel "Backup & Restore" on a Windows computer. Ended in backup errors

c:\windows\system32\config\systemprofile\syncup 0x80070002 The sytem cannot find the file specified

Fix mentioned on http://en.community.dell.com/support-forums/software-os/f/3526/p/19431232/20030578.aspx: Open the Windows navigator. In the left panel, it lists the Windows 7 "Libraries" for Documents, Music, Pictures, Videos. Each one contains a user specific folder like "My Documents", a shared folder and a "Sync Up" entry. Delete the Sync Up entry, and backup works fine.

Nook Simple Touch Hung on Update

Found my Nook Simple Touch hung this morning in an update. Unclear when this started, some time over night. The Nook was plugged into the charger all the time.

After about 10 minutes I decided that the "Please don't turn off your NOOK!" is nonsense, because nothing was happening. Note that the progress bar at the bottom was not animated and appeared somewhat mispainted.

After holding the power button at the back of the device pressed for at least 20 seconds, the device power cycled and went through a bootup cycle which almost immadiately entered the "Installing..." display again. But this time, the progress bar at the bottom was animated, slowly filling from the left. Then it switched to another startup screen, the progress too about 2 minutes.

Finally the usual screen saver appeared. I could unlock the device, and the main screen displayed a notification icon regarding a software update. The time of the update is the time of the power cycle.

Apple iMac Harddrive Replacement

Needed to replace the Harddrive on an Apple iMac. This is a white plastic Intel iMac. After removing all screws from the bottom (where the memory modules are also installed), the back of the case can be pulled off, starting at the bottom, with a 'crack'. There's a lot of aluminium-backed tape inside, and after removing the LCD panel the hard drive becomes accessible.

The original drive was 160GB. A 250GB replacement was found for around $60 (3.5", SATA).

Then it came to re-installing the operating system from DVDs, where I ran into two surprises:

1. No disk found.
   With Linux, installing an OS from DVDs is fairly straight forward. You are guided through partitioning the hard drive etc. With OS X, I was expecting it to be even easier, but wrong: The installation asks you to select a hard drive for the installation without offering anything. Solution: Close the installer, select Tools/Disk Utility from the menu to format and partition the drive. When installing again, you can now select the drive.
2. Can't eject the disk??
   When prompted to insert the second installation DVD, I could not figure out how to eject the first one. Nothing worked. Finally I learned that the drive was empty ... I had not fully re-assembled the case because I first wanted to check if everything "worked". When the iMac ejects a DVD, it's usually kept half-way in the drive because of the felt lining of the DVD slot. This time, the iMac had ejected the first OS installation DVD, it had rolled of the table and vanished under some cubboard. From the outside, I could not tell if there's a DVD in the drive or not. Since I didn't remember ejecting the DVD nor saw one in the usual half-out-of-the-drive position, I had assumed that it's still "in"....

JDBC 'commit' even for SELECT

You probably knew this, but a 'commit' can even be necessary for SELECT calls that don't change any data.

After calling JDBC Connection.setAutoCommit(true)), every JDBC call, be it SELECT, INSERT, UPDATE, DELETE starts a transaction that needs to be ended with a commit (or rollback).

This might be obvious for a sequence of INSERT or UPDATE calls that change data, and you want a final commit() to perform an atomic update.

With a SELECT, the update is necessary to avoid the following situation:

1. Calling SELECT to fetch something. That starts a Transaction!
2. Now somebody else changes the data.
3. You call SELECT again to get the 'latest', but since you're still in the original Transaction, you get the same old data as in step 1.

If you have other code that changes the data and happens to call commit() before you reach step 3, all will look OK, but to be sure that you end the original reading transaction and always get the 'latest' data in a later read, it has to be done like this:

1. SELECT, commit()
2. Now the data might change.
3. If you later need to fetch the 'latest', again SELECT and commit()

Oracle JDBC Version Woes

Ran into a strange Oracle error today in a Tomcat program.

The code ran fine in two other Tomcat instances, but failed in a third one.

The error happened to be

ORA-03115: unsupported network datatype or representation

which basically means: There is a version mismatch between the database and the JDBC library.

Reason

That Tomcat instance had a copy of ojdbc14.jar in its lib/ subdirectory that was used instead of the ojdbc14.jar included in the application's *.war file.

Unfortunately it is hard to tell the version of an ojdbc14.jar from the outside.

Possible Solutions

1. Unzip the ojdbc14.jar and check its manifest file.
2. Get the version programmatically

The latter can for example be displayed on some 'internal' web page of your application:

Connection connection = ...;

DatabaseMetaData md = connection.getMetaData();

out.append(...md.getDriverName() + " " + md.getDriverVersion() ...);

That way it is possible at runtime to check which version you are actually using.

Moral

Don't put *.jar files in the Tomcat lib/ directory. Include them in the *.war file.

Yes, this way you might load multiple copies, one for each *.war, but that beats later wating time to debug an app that suddenly stops working because some Tomcat instance has the wrong *.jar in its lib/ directory.

Mercurial seems to hang in SourceForge connection because of host key change

Had a problem where mercurial seemed to hang forever in a SourceForge transaction.

It was run from within Eclipse via MercurialEclipse, and there was no indication as to

what's happening nor any way to stop it other than to kill Eclipse.

This was under Windows with hg calling putty, which in turn was configured to use an ssh key pair registered with SourceForge that had worked OK some time ago.

When executing hg from the command line, it would also hang, but I could stop it with Control-C, and then it would show the following message:

hg clone ssh://name@....hg.sourceforge.net/hgroot/....

interrupted!

remote: The server's host key is not cached in the registry. You

remote: have no guarantee that the server is the computer you

remote: think it is.

remote: The server's rsa2 key fingerprint is:

remote: ssh-rsa 2048 86:7b:1b:12:85:35:8a:b7:98:b6:d2:97:5e:96:58:1d

remote: If you trust this host, enter "y" to add the key to

remote: PuTTY's cache and carry on connecting.

remote: If you want to carry on connecting just once, without

remote: adding the key to the cache, enter "n".

remote: If you do not trust this host, press Return to abandon the

remote: connection.

remote: Store key in cache? (y/n) ^C

Again this was under Windows. On a real operating system the host key change prompt might have appeared before the Ctrl-C and thus be more obvious.

Anyway, the fix:

Run

putty -i path\to\the\key.ppk

once which will show the same host key change prompt and this time you can accept it.

From then on, hg works OK again.

Associative JavaScript Arrays by Numeric 'ID'

I needed to keep browser-side information about certain objects by numeric ID.

When using an associative JavaScript array like this:

var gadgets;

gadgets[4711].name = 'Fred';

gadgets[4711].color = 'red';

you will find that it creates an array with (mostly empty) elements gadgets[0] to gadgets[4711].

On the other hand, when initializing the array like this:

gadgets['4711'].name = 'Fred';

it creates a single element in an associative container. Once created, you can access such elements with either gadgets[4711] or gatgets['4711']!

Belkin Play B600 Duplicate IP Address Problem

I have a cable modem internet connection that's shared by several computers at home via a Belkin wireless router. A Windows Vista PC is actually wired to the router, the other computers are on a WLAN.

The router is at http://192.168.2.1/. The wired PC is usually at 192.168.2.2. Other wireless devices get addresses like 192.168.2.3, 192.168.2.9 etc., meaning: Everything is on the same subnet, contrary to my previous wireless router that used different subnets for the wired and wireless devices.

Sometimes the wired PC reports a duplicate IP address error. The "easiest" fix seems to be:

1. Power the PC down
2. Power-cycle the wireless router
3. Start the PC back up

"Portable" Eclipse Projects

When you create a new Eclipse 'Plug-in' project, its initial configuration will lock to your current JRE and compiler settings.

When you then share that project with other people, they will see compiler errors because you may have used Java 1.6_19 on Linux while they use Java 1.6_20 on Windows.

To make your project more portable, do this:

1. In the Package Explorer, right-click on your Plug-in Project and select "Properties"
2. Under "Java Build Path", select tab "Libraries", item "JRE System Library", button "Edit". It should default to a specific "Execution environment" like "JavaSE1-6 (MacOS X 1.6.0 System). Change that to "Workspace default JRE", meaning: Use whatever the developer has configured in her workspace.
3. Under "Java Compiler", by default "Enable project specific settings" will be checked. Uncheck that, meaning: Use the compiler settings that the developer has selected in her workspace.
4. When you now switch to the Navigator view, you should find that the ".settings" directory that previously contained project-specific compiler settings is now empty. You can delete it.

After these steps, developers on other operating systems with slightly different java versions will have fever problems when they try to use your Plug-in source. Your MANIFEST.MF can still require a certain execution environment, so you are not loosing much control.

Hudson ignored CVS updates

In a setup where Hudson polls CVS for updates I ended up in a situation where newly added directories were ignored, and thus Hudson did not trigger a re-build of the product.

The Hudson "CVS Polling Log" looked like this:

[workspace] $ cvs -q -z0 -n update -PdC -D "Wednesday, March 2, 2011 3:51:38 PM UTC"
cvs update: New directory `.....' -- ignored

The fix was to delete everything inside the "workspace" directory. On the next Hudson run, it performed a complete cvs checkout and that included all changes.

Java Audio, FreeTTS "LINE UNAVAILABLE" Error

A program based on FreeTTS, the free text-to-speech engine for Java, was getting occasional errors

"LINE UNAVAILABLE: Format is ..."

The reason was later found in the KDE desktop: Its configuration panel has options to keep the audio device open for some time after playing beeps or other desktop sounds. The default seemed to be rather high at 60 seconds. But even after changing that to only 2 seconds, the FreeTTS library still needs to compete with some occasional other users of the audio devices.

Turns out there is no Java Exception or other mechanism to detect this error that occurs inside the FreeTTS library. All you get is the message on System.out, so there is no good way to react programatically.

Workaround: Configure the FreeTTS audio player to attempt accessing the audio device more than once until it succeeds. In this example, a short delay of 0.1 seconds is used to not miss an opportunity to grab the audio device; we keep trying for 30 seconds:

System.setProperty("com.sun.speech.freetts.audio.AudioPlayer.openFailDelayMs", "100");
System.setProperty("com.sun.speech.freetts.audio.AudioPlayer.totalOpenFailDelayMs", "30000");

If the audio device is permanently used by another program, there is of course no way to get access. Under Linux, this command will display the ID of the process that is currently holding the audio device, so you can then try to get rid of the offending program:

  /sbin/fuser /dev/dsp

Eclipse Build Path Problem After Mac OS X Java Update

In early January 2011, I received a Mac OS X Software Update that included Java changes.

This was on a Mac that had been upgraded to Snow Leopard, so older Java setups were still present, but this update must have removed older JVMs and JDKs.

As a result, Eclipse builds would fail with this error:

The container 'JRE System Library [J2SE-1.5]' references non existing library '/System/Library/Frameworks/JavaVM.framework/Versions/1.6.0/Classes/laf.jar'

In general, the OS X Java setup changed from using

/System/Library/Frameworks/Java.VM.framework/Versions/...

to using a path like

/System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home

After going to Eclipse/Preferences/Java/Installed JREs and "Add..."ing a new JVM that uses the above path with ".../JavaVirtualMachines/..." all is fine again. You might have to look for the full path to that .../Home in a terminal window and copy/paste it into the Eclipse preference dialog, because the "Browse" button in the dialog might only show the 1.6.0.jdk as a package, not as a subdirectory into which you can drill down.

Next issue: You might not have a src.jar in that JDK to be able to view the Java sources, so you cannot view the source code for String, Map, ... and the other standard Java classes. That's because the default JDK is really more like a JRE.

After downloading the Java Development package from the Apple Developer Connection, something like javadeveloper_10.6_10m3261.dmg, you get a new JDK in

/Library/Java/JavaVirtualMachines/1.6.0_22-b04-307.jdk

and that one has a Content/Home/src.jar.

Note that the JDK that you install yourself, the one that includes the sources, is under /Library/Java/... while the Java stuff that comes with the OS is under /System/Library/Java/...

Eclipse should automatically detect the src.jar in the JDK that you install.

Note on finding the Java Development package as of August 2011:

• http://developer.apple.com/
• Member Center
• Dev Centers: Mac
• Resources
• Mac OS X Developer Downloads
• Java
• Java for Mac OS X ... Developer ...

Eclipse Draw2D and GEF Sources, Online Help

When installing the Eclipse IDE for RCP development, it includes the Draw2D and GEF binaries, but not the sources. At least not in the Mac OS X version for Eclipse 3.5 and 3.6(.1).

How to get them: Also download the "Modeling" version of the IDE, and copy the following plugins from that into your RCP IDE's plugins directory:

• org.eclipse.draw2d.doc.*.jar
• org.eclipse.draw2d.source_*.jar
• org.eclipse.gef.doc.*.jar

Yes, this contradicts everything you ever learned about P2, but it seemed the simplest way to get the sources & help.

Arduino Links

• http://www.arduino.cc/ - Main Page
• http://adafruit.com/, http://www.sparkfun.com - Good kits
• http://tronixstuff.wordpress.com/ - Tons of ideas
• http://www.freeduino.org/ - Info
• http://joelspadin.blogspot.com/2009/12/morse-code-arduino-sketch.html
• http://web.media.mit.edu/~leah/LilyPad/index.html
• http://www.ladyada.net
• http://ruggedcircuits.com/html/circuit_gallery.html

WII Coding

• http://wiibrew.org/wiki/Homebrew_setup - GNU C compiler suite for WII programming. Requires pre-4.3 menu system. Some variety of apps already available.

FreeMind

.. from http://freemind.sourceforge.net/wiki/index.php/Main_Page now has interesting extensions:

• Converter to meeting notes: http://code.google.com/p/mm2notes/
• Java lib to write own tools: http://jcommons.sourceforge.net/references/maputils.html

Netflix error in Safari: errorcode 2105

Netflix player stopped working from one day to the next with "ErrorCode 2105".

There was a link to nonsense about checking for fonts.

What helped:

1. Close Safari
2. Delete the file /Library/Internet Plug-Ins/Silverlight.plugin
3. Start Safari, access Netflix, try to play movie, install the now missing Silverlight again
4. Safari's Help/Installed Plugins shows Silverlight Plug-In version 4.0.50826.0

Top 10 Computer Languages

According to http://www.tiobe.com/index.php/content/paperinfo/tpci/index.html, it's

• Java on top - Couldn't agree more
• C before C++ - I'd still prefer C++ over C if used 'carefully', whatever that means
• C# gains, but is behind
• PHP, python above Perl - Hmm. For quick hacks, I do like perl

Systems that sound interesting, but looking at them I get a "well, maybe not":

• go, Limbo: Inspired by Plan 9, built-in communication channels
• Erlang

No longer seem to matter:

• Prolog way down on list
• Smalltalk off top-50

LEGO Mindstorms RCX 2.0

Still have LEGO Mindstorms RCX 2.0 from ca. 2003. The original software that came with it does not run under Vista. It does run under Windows XP, but caused 2 problems:

1. Will quit with an out-of-memory error when a current version of Quicktime is installed. Installing the older version of QT from the LEGO CD works, but will break online movie sites that require a more recent QT.
2. The "Robotics Invention System" software will auto-start when Windows starts up. Remove the corresponding entry from the registry via regedit.exe in HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Run

LEJOS, http://lejos.sourceforge.net, might be a better choice for the actual program, but the graphical LEGO program is neat for children.

Comcast Arris Cable/Phone Modem Signal Levels

After intermittent phone problems via our Arris Touchstone digital phone and cable modem, a Comcast technician adjusted the signal levels and checked connectors outside of the house. Now that everything is good again, they look like this:

Go to http://192.168.100.1 to view the RF status.

• Downstream should be around 0 dBmV (currently it's -1 dBmV)
• Upstream should be around 45 dBmV

A few weeks later, there were still too many times when the modem seemed to restart/reboot on its own or otherwise loose connections (most LEDs on its front off). It was replaced with a Thompson RCA DHG536 modem that uses the same http://192.168.100.1 to view its status.