Gnarcade:

Gnarcade from Mike Benson on Vimeo.

A videogame invasion has hit Mt Hood and High Cascade! Check out Scott Stevens, Micah Hollinger, Chris Beresford, Tim Eddy, Ben Bogart, and Casey Wrightsman as they live life like it’s one big game.

From: Amazon EC2 Notification
Subject: Notice: Degraded Amazon EC2 Instance

Hello,

We have noticed that one or more of your instances are running on a host degraded due to hardware failure.

i-xxxxxx

The host needs to undergo maintenance and will be taken down at 12:00 GMT on 2010-06-23. Your instances will be terminated at this point.

The risk of your instances failing is increased at this point. We cannot determine the health of any applications running on the instances. We recommend that you launch replacement instances and start migrating to them.

Feel free to terminate the instances with the ec2-terminate-instance API when you are done with them.

Sincerely,

The Amazon EC2 Team

Sounded like they would terminate the instance because of hardware failure, and that would be very bad – this is a high volume eCommerce site. I looked around to see what was the best way to “clone” the instance and relaunch it, and it turned out to be really simple.

When I setup EC2 stuff I always use an EBS volume for the important data like the /home, the MySQL storage, most of the configurations in /etc like Apache vhost configs. I also use an Elastic IP address so I can switch it to another instance easily, and it won’t require modifying DNS records at all. So all I had to do was:

• get all your AWS access keys, certs, and user id, onto the instance
• create a folder for the AMI bundling work
• bundle the root volume on the dying instance

$ sudo mkdir /mnt/ami && sudo ec2-bundle-vol -d /mnt/ami -k pk-CKXXXXXXXXXXXX.pem -u 12345678 -c cert-CKXXXXXXXXXXXXXXX.pem

• upload the bundle to S3 and register the AMI

$ ec2-upload-bundle -b somesite-post-degraded -m /mnt/ami/image.manifest.xml -a XXXXXXXXXX -s XXXXXXXXXXXXX/00XX
$ ec2-register somesite-post-degraded/image.manifest.xml

• launch a new instance with the AMI
• unattach the EBS volume from the old instance
• attach the EBS volume to new instance
• re-assign elastic IP to new instance

You can do a lot of these tasks from the AWS Management Console. All of that took about 2 hours, most of the time was spent waiting for the AMI to bundle and upload as it was pretty large.

Everything worked perfectly after the migration, when I set up the EC2 infrastructure I had planned for things like these and in theory migration should go without any glitch, but I never actually had a need to migrate an instance. It’s good to know that everything actually worked as designed.

- (void)viewWillAppear:(BOOL)animated {
	[super viewWillAppear:animated];

	self.navigationController.navigationBar.barStyle = UIBarStyleBlack;
	self.navigationController.navigationBar.translucent = YES;
}

#pragma mark -
#pragma mark UISplitViewControllerDelegate methods

- (void)splitViewController:(UISplitViewController *)svc willHideViewController:(UIViewController *)aViewController withBarButtonItem:(UIBarButtonItem *)barButtonItem forPopoverController:(UIPopoverController *)pc {
	self.navigationController.navigationBar.translucent = NO; //if I don't do this we get extra space in popover
	barButtonItem.title = @"Some Title";

	// Keep references to the popover controller and the popover button, and tell the detail view controller to show the button.
	self.popoverController = pc;
	self.rootPopoverButtonItem = barButtonItem;
	UIViewController <SubstitutableDetailViewController> *detailViewController = [splitViewController.viewControllers objectAtIndex:1];
	[detailViewController showRootPopoverButtonItem:rootPopoverButtonItem];
}

- (void)splitViewController:(UISplitViewController *)svc willShowViewController:(UIViewController *)aViewController invalidatingBarButtonItem:(UIBarButtonItem *)barButtonItem {
	//setting it back to black translucent
	self.navigationController.navigationBar.barStyle = UIBarStyleBlack;
	self.navigationController.navigationBar.translucent = YES;

	// Nil out references to the popover controller and the popover button, and tell the detail view controller to hide the button.
	UIViewController <SubstitutableDetailViewController> *detailViewController = [splitViewController.viewControllers objectAtIndex:1];
	[detailViewController invalidateRootPopoverButtonItem:rootPopoverButtonItem];
	self.popoverController = nil;
	self.rootPopoverButtonItem = nil;
}

- (void)apiCall {
	NSString *urlString = [[NSString alloc] initWithFormat:@"%@/some_models/some_action.json", apiEndpoint];
	NSURL *url = [[NSURL alloc] initWithString:urlString];
	NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
	[request setHTTPMethod:@"GET"];
	[NSURLConnection connectionWithRequest:request delegate:self];
	[url release];
	[urlString release];
}

This fires off the API call asynchronously, and then you implement some delegate methods like this:

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
	responseData = [[NSMutableData alloc] initWithCapacity:[response expectedContentLength]+100];
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
	[responseData appendData:data];
}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
	NSString *jsonString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
	[self dictionaryToCoreData:[jsonString JSONValue]]; //this parses the JSON data and persists into Core Data
	[jsonString release];
	[responseData release];
}

This approach works fine, but when you run it on the real devices, you might notice that the table view locks up when you go between the navigation flow. Basically the table view ignores user inputs until everything above is finished. This is because everything is performed on the main thread and it locks up the UI. The asynchronous NSURLConnection method used above doesn’t like to be used in a background thread, and there is really no reason to do things asynchronously if you’re working in the background, conveniently, there is a +sendSynchronousRequest method that waits until we get the response and data in NSURLConnection. To perform the above API call in a background thread, the code is actually much simpler:

- (void)apiCall {
	[self performSelectorInBackground:@selector(backgroundApiCall) withObject:nil];
}

- (void)backgorundApiCall {
	@synchronized(self) {
		NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; // Top-level pool

		NSString *urlString = [[NSString alloc] initWithFormat:@"%@/some_models/some_action.json", apiEndpoint];
		NSURL *url = [[NSURL alloc] initWithString:urlString];
		NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
		[request setHTTPMethod:@"GET"];

		NSURLResponse *resp;
		NSError *error;
		NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&resp error:&error];
		// you should probably do some error handling here
		NSString *jsonString = [[NSString alloc] initWithData:responseData encoding:NSUTF8StringEncoding];
		[self dictionaryToCoreData:[jsonString JSONValue]];
		[jsonString release];
		[url release];
		[urlString release];
		[pool release];
	}
}

Now, when the table view is first loaded, it displays the stale data in Core Data, the API call is fired off in the background, and when we get data back from the call the table view is updated with the new data. Stale data is better than locked up UI.

Notice the very first time you run the app the table view will be empty until the background thread finishes, if this bothers you, you can preload the database with sample data. In our app we can’t really do this as the data is unique to the user, but it might make sense for you to ship your apps with pre-loaded data.

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** +[Reachability<0xf37d0> init]: cannot init a class object.'

You can fix it by commenting out the [super init] line in + (Reachability*) reachabilityForLocalWiFi in Reachability.m:

+ (Reachability*) reachabilityForLocalWiFi;
{
	//[super init];
	struct sockaddr_in localWifiAddress;
	bzero(&localWifiAddress, sizeof(localWifiAddress));
	localWifiAddress.sin_len = sizeof(localWifiAddress);
	localWifiAddress.sin_family = AF_INET;
	// IN_LINKLOCALNETNUM is defined in <netinet/in.h> as 169.254.0.0
	localWifiAddress.sin_addr.s_addr = htonl(IN_LINKLOCALNETNUM);
	Reachability* retVal = [self reachabilityWithAddress: &localWifiAddress];
	if(retVal!= NULL)
	{
		retVal->localWiFiRef = YES;
	}
	return retVal;
}

If this blog were hosted at geocities it would look like this or like this (I like the animated gif of Gates).

Currently, Apple’s stock is at an all time high. A share today is worth over 40 times its value seven years ago. So, how much would you have today if you purchased stock instead of an Apple product? See for yourself in the table below.

via Kyle Conroy’s Personal Blog and Portfolio – Should I have bought that Apple Product?.