A hydrology article I wrote before, the thoughts caused by uploading 300 pictures at once,
became a hot search on 12.02. The number of followers increased from 8 to more than 400, which was really scary. Thank you all for your support and the android lady for her beautiful eyeshadows.
It’s not my intention to be on trending searches and gain fans. CSDN is just to record daily technical work (I blogged before, but most of my energy was spent on dressing up and maintaining the website, so I just used CSDN to save trouble). It's okay to occasionally say a few risqué words in the article, but you won't use some sensational titles or make some sidelines in order to get trending searches. The nonsense stops here and the real movie begins.
1. Browser concurrency limit
1.1 Browser
As mentioned before, in the case of http1.1, the browser has a default concurrency limit. Default is a group of 6
picture links
1.1.1 What is stalled?
1.1.2 Why does the browser have this limitation?
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The Facade mode mentioned here is a brief reflection on the middle layer . There are some mentions in this article.
1.2 Digression-Crawler
Browsers will limit the number of connections. But crawler scripts don't . Even for http1.1 URLs, crawler requests can reach any number of requests per second.
Therefore, when writing crawler code, you need to pay attention not to have too many loops per second. For others and for yourself.
2. http1.1
2.1 View http1.1
If you check whether the website uses http1.1 or http2. In fact, it is very simple. You only need to open the relevant configuration in the network of f12.
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You can see that http2 looks like this:
http1.1 looks like this:
2.2 http1.1 and https
If http1.1 has a browser concurrency limit, then https doesn’t have one either?
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3. http2
3.1 http2 and browser concurrency limits
So why does http2 have no concurrency limit? Image source
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3.2 What is multiplexing
As mentioned above, http2 only has no browser concurrency limit because it can multiplex TCP. So what if you know it's a multiplex?
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You can see that if tcp is reused, then the connectID is the same . Let’s take a practical look:
① The connectID of http1.1 is different
② The connectID of http2 is the same for a period of time
3.3 Turn on http2
How to convert from http1.1 to http2. You can see how to upgrade your website to http/2 . This article is very good, but it may be more complicated. It is both an nginx version and an openssl version. I recommend a little tip: directly modify the nginx configuration and try restarting nginx .
If you are lucky enough. You can see it's the same as mine. It just changed to http2. The previous 6 concurrencies also disappeared.
3.4 http1.1 fun article
Although most mainstream websites are http2. But Baidu is indeed http1.1.
Why is Baidu still using http1.1 protocol instead of http2?
4. Service Worker
4.1 Questions about network pinion
I accidentally saw on a previous project that one request was sent twice. And one has gears and one doesn't. But by looking at the logs, a request was indeed sent. Why is this?
After searching for information, I found that someone said this is
the source of the servicewroker picture .
After checking, there is indeed one written ** from ServiceWorker **. One of them was not written
4.2 Introduction to ServiceWorker
For a preliminary introduction to ServiceWorker, you can briefly read Service Worker: Introduction and Service Worker - this should be a quite comprehensive arrangement.
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4.3 ServiceWorker and http1.1
service worker does not have to be http2, 1 is also acceptable
4.4 ServiceWorker和https
Service workers can only be hosted by HTTPS
4.6 Why are there two requests?
As mentioned before, start ServiceWorker. You will see 2 requests through the network, one with the pinion and one without it.
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4.5 ServiceWorker和angular
4.5.1 Must be accessed through https
ServiceWorker must be accessed through https, as mentioned above
4.5.2 Some browsers do not support
Some browsers do not support ServiceWorker
4.5.3 How to configure
4.5.4 Practical work
4.5.5 What is being cached
4.5.6 How to close
If you don't want to use ServiceWorker, how do you turn it off?
You can see that there is no small gear anymore.
Generally, the project is turned on by default. It is faster after opening than closing. Take the thinking caused by uploading 300 pictures at one time as an example:
after closing, 1 is 25kb, 300 is about 7500 kb = 7.32M; it takes about 10s.
After opening, the same 300 pictures take about 8.73s
4.7 Doubts about ServiceWorker and http2
The attentive may notice,. Service worker made two requests, http2 dropped to 1, connection id changed to 0.
Why? We clearly have http2 enabled. Why is it automatically downgraded to http1.1? Even if it becomes http1.1, why is connectID 0?
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