Wednesday, August 21, 2013

Submitting iOS App in Application Loader with Firewall Restrictions

If you submit an iOS ipa file via Apple's Application Loader and see the activity gets stuck at the TCP/UDP connectivity testing step. It may be because your current network is blocked by firewall. An easy solution but may be hard to find is to change the Delivery mechanism option in the Application Loader's Preferences. 

Uncheck 'Signiant' and 'Aspera' will force the loader to use DAV SSL port 443. It worked for me.

Monday, May 6, 2013

Use HTTP Options to query whether a RESTful resource can be created

My colleagues and I ran into a problem about how to check whether a RESTful resource can be created before sending the HTTP POST to create the resource.  The use case is that there is a business requirement setting a limit on how many resources can be stored for a user.

For example, a bank may limit the number of accounts a customer can open. It would be a bad user experience if we allow a user to type information about a new account and hit submit to see an error that the maximum number of accounts has been reached.

Request: HTTP POST /customers/xxx/accounts
Response: HTTP 400 Bad Request with 'Maximum number of accounts has been reached' error message. 

We decided to make a request to check whether a new account resource can be crated before we ask users to enter information. We explored a couple of options. One is to define a new endpoint to query whether a new resource can be created.

Request: HTTP GET /customers/xxx/accounts/can_create
Response: 200 OK or 400 Bad Request 

However, this seems to introduce another verb to the resource. One of my colleagues referred me to HTTP Options and it works perfectly for this use case.

HTTP Options checks whether what HTTP verbs we can operate over the resource URI.  It is specified in the 'Allow' response header.  So if we see that we can POST to the resource, it means that we can create the resource.

Request: HTTP OPTIONS /customers/xxx/accounts
Response: 200 OK
                 Allow: HEAD,GET,POST,PUT,DELETE,OPTIONS
Using HTTP Options allows us to query possible actions we can do with resources without requiring a new end point or payload.  I wish it was mentioned more often in other RESTful resources.

Thursday, March 28, 2013

Use curl to check website gzip encoding support

If you want to check whether a website has gzip encoding support, you can use curl with Accept-Encoding: gzip.deflate http header. Use size_download to check the size like this.
$ curl --silent -H "Accept-Encoding: gzip,deflate" --write-out "size_download=%{size_download}\n" --output /dev/null size_download=50613
And compare without the Accept-Encoding:
$ curl --silent --write-out "size_download=%{size_download}\n" --output /dev/null size_download=245298
If you see the same result with and without Accept-Encoding, the web server does not support gzip.