LVE EP limit and HTTP2?
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  1. Ryan
  2. Tuesday, 16 October 2018
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Just looking for some insight into how EP limits work with HTTP2. If I understand correctly, in HTTP1, browsers typically obeyed the 6-8 requests per domain at 1 time. So if 6 visitors visited a site at the same time, there would never be more than 48 simultaneous requests to the server. So an EP limit of 50 makes sense.

With HTTP2, I know it works a bit differently. A website request only opens up 1 "connection", but can request up to 100 resources at a time. So what is counted towards the EP limit? Is it the 1 connection, or does each resource count? If it's each resource, and the EP limit is 50, then it seems like a web page with more than 50 resources on the same domain could be having EP faults quite often.
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  1. 19.10.2018 11:10:36
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It is actually connections to backend (PHP handler) that are counted against EP limit, so it doesn't matter how many TCP connections are used for that.
  1. 19.10.2018 21:10:48
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Ryan Accepted Answer
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Interesting, thanks for the clarification. The docs talk about "apache slots" which is very misleading then, right? Because static assets are still served through apache. It may also makes it confusing for those who don't use apache.

Out of curiosity, would it be theoretically possible (or should I say realistic) to create a DDoS attack by requesting large static assets from a server?
  1. 22.10.2018 08:10:46
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Out of curiosity, would it be theoretically possible (or should I say realistic) to create a DDoS attack by requesting large static assets from a server?

Yes, this is possible with apache web server and LVE can't help in such cases.
  1. 22.10.2018 14:10:51
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Ryan Accepted Answer
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Thanks. One last question hopefully:

Suppose I set the EP limit extremely high, but kept all other LVE at default settings. Would this pose any risk to the server, or would the other LVE limits kick in and protect the server from being taken down by 1 account?
  1. 24.10.2018 12:10:53
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Other limits will still be active and will effectively limit resources consumed by any customer they are applied to.
  1. 24.10.2018 13:10:04
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Ryan Accepted Answer
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I understand that. I guess what I'm asking is: do EP limits protect against a situation that the other limits can't protect against? In particular, a situation that could cause an issue for the whole server.
  1. 26.10.2018 19:10:53
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Ryan,

NPROC is the closest equivalent, but it might not be helpful here as well... We've seen similar behavior (high EP count) with HTTP/2 and websites serving images from MySQL DB via PHP. If this is the case, you may need to set up MySQL Governor limits instead - do not hesitate to reach out to our support if you are not sure how to choose the right values.
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