If an error cannot be reproduced

When an error occurs over the past few days, when an app calls an HTML webpage, the first attempt is always a white page and the second attempt is successful. It's just a URL. Why is an error in APP calling? The manager called me and asked me if I had to worry about it. The subconscious is that the app call is faulty.

Does the problem have to be solved, and complaints are useless. Today, the manager called again, but provided a very important clue, that is, after killing the process and then entering it, it must be a white page, just for the second time. I used this clue to find the app developer, print the log step by step, and finally click the URL. I was still lazy at the time, because this URL is okay in the browser test, I am lazy to say, stick it to the browser and try? The result is actually a white page. I went back to my computer and pasted the URL under Firefox. For the first time, it was a white page with no content. I turned it off and went in again. I finally caught the error and located it, this row of error is found:

The first access to a message does not exist, and the second access to this information will be normal.

If you encounter such a problem next time, follow these clues.