Question

From: Wang, Jerry

Sent: Friday, 19 June, 2015 4:31 PM

Subject: RE: [Follow up] Why the synchronous request did not BLOCK the UI

Hi all,

這個issue很有意思，昨天和德國同事開會時，他們問我們為什么我們code里寫的odata request是同步的，但是并沒有block 住UI。當時我沒答上來，因為確實我看起來也是沒block UI。
今天我做了研究，通過圖表和視頻 理直氣壯地告訴他們：代碼沒問題，是我們眼睛犯錯了。視頻在下面的share folder里。研究思路在下面的郵件里。

Please read more detail from Jerry’s mail.

Jerry’s analysis process

手動在后臺reques響應里加上一個延時，來模擬后臺耗時很長的scenario.

Then I test in UI with this modified Odata implementation. Now as expected it took around 13 seconds to get the returned image url.
During this timeframe, UI is completely freezed: end user does not have any chances to click anything in UI.

Synchronous mode

Afterwards the synchronous behavior is quite obvious now. I click one item in navigation list to trigger the synchronous request for Image url retrieval. And after that, I cannot do any operation on UI - it is completely freezed.

Please refer to attached video “synchronous.wmv”.

Asynchronous mode

Then I change the manual latency to 20 seconds and retest the UI.

Now every time I click one opportunity in the navigation list, still one http request for image logo is sent out. Compared with synchronous mode, this time the UI is not blocked - I can continue to work on UI without waiting for the response.

This asynchronous behavior could also easily be found in the timechart in Chrome network:

Conclusion

code is correct, our eye is wrong.

要獲取更多Jerry的原創文章，請關注公眾號"汪子熙":

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