运行时控制台中的核心数据信息和错误

Question

I have met the following messages in the console at runtime, and i have no idea why. I have searched everywhere and nobody seems to meet this:

INFO: fetch-response is unable to open the file /Users/userName/Library/Application Support/iPhone Simulator/7.0.3/Applications/964A590B-7131-4BAE-958B-1783BEC193EF/Library/Caches/userName.AppName/fsCachedData/2F1A8708-35A9-491E-9C21-154BA428CA10. Errno: 2

ERROR: failed to mmap cache data from FS: /Users/userName/Library/Application Support/iPhone Simulator/7.0.3/Applications/964A590B-7131-4BAE-958B-1783BEC193EF/Library/Caches/userName.AppName/fsCachedData/83A968D1-0A2B-4D20-97D5-487A876649DC, errno:22

It does not seem to affect the execution though, but I suppose it is not a good sign. I am using Core Data with a timer which frequently updates the database from a server. These messages appear synchronously with the updates, but not systematically. Only one at the time, the "INFO" or the "ERROR". Reset Content and Settings in the Simulator did not solve the problem.

Does anyone have any idea about the meaning of these messages?

Answer 1

I experienced this when running on my device with an app I am building. It has worked perfect for weeks and then all of a sudden this error. I figured out that it is due to a lack of memory available on the device. I use a little app call "System Status" that allows you to view the memory stats and release any old unused memory. I only get this error in Xcode when I have less than 5% available memory on my device. Therefore it cannot load the cache file the app is request, hence the error. Either close all your multitasking apps and restart your device or get the app and free you memory.

Answer 2

After some testing/debugging (sorry for the delay), I have at least a temporary solution.

Because of the multi-threaded saving process of Core Data, I found it a little tricky to identify the exact error location, but it definitely appears that the error occurs when Core Data is trying to save one of the context in the stack (probably the last "root" one).

As each save take a few seconds (without freezing the UI :p) , I figured the error could be generated by a " save overlap ".

So even if I do not have enough to be sure, reducing the save frequency effectively solved my problem: no message anymore in the output.

Now there still is a hitch, and any expert answer would be much appreciated!

Answer 3

Uninstalling the app from the device and installing it again removes this error message.

Note that that doesn't fix the problem if you can see this log from earlier versions of your app that is already on your users' devices. It's generally okay to uninstall-install, though, if you're only seeing this during the development phase.

Answer 4

For me this happened when my phone ran out of batteries and died as a result. Deleting the app, then restarting my phone, then rebuilding/installing solved the problem.

Answer 5

I ran into this error because my app was stuck in an infinite loop, doing network requests multiple times a second, causing the file to be overwritten before it could be read.

In the situation described in the original post, this might very well be the case.