[count-inc] Add decrement logic to the incoming function #843
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| @@ -1,29 +1,68 @@ | |||
| local loader = require 'apicast.configuration_loader.remote_v1' | |||
| local _M = require 'apicast.configuration_loader.remote_v1' | |||
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This commit is not related to the rest of the PR, so it should be in a different one.
| assert.returns_error('limits exceeded', rate_limit_policy:access(context)) | ||
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| assert.equal('2', redis:get('11110_fixed_window_test3')) | ||
| assert.equal('1', redis:get('11110_fixed_window_test3')) |
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I don't fully understand the purpose of this change.
Before, we increased the number of hits even when going over limits. Now we force the value to be at most equal to the limit. Why do we need to do this?
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Before, we increased the number of hits even when going over limits.
First, we should not increase the number of hits when going over limits, because we should count the number the client calls the API backend.
The previous behavior is the below:
Case 1:
fixed_window_limiters : [
{ "key" : { "name" : "a"}, "count" : 1, "window" : 10 },
{ "key" : { "name" : "b"}, "count" : 2, "window" : 10 }
]After 2 API requests,
the number of hits 'a' is '1',
the number of hits 'b' is '1'.
-> correct
Case 2:
fixed_window_limiters : [
{ "key" : { "name" : "a"}, "count" : 2, "window" : 10 },
{ "key" : { "name" : "b"}, "count" : 1, "window" : 10 }
]After 2 API requests,
the number of hits 'a' is '1',
the number of hits 'b' is '2'.
-> wrong
y-tabata
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| end | ||
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| if count > limit then | ||
| count, err = dict:incr(key, -1) |
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I believe this should be done by the .uncommit that is being called by resty.limit.traffic.
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@mikz you mean .uncommit needs to be called here with the condition of i == n, right?
https://github.com/openresty/lua-resty-limit-traffic/blob/master/lib/resty/limit/traffic.lua#L27-L29
However resty.limit.conn includes this.
So we should choose which file we edit, resty.limit.traffic and resty.limit.conn, or resty.limit.count-inc.
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@y-tabata I think we don't need to change any resty.limit library. We have to use it correctly.
resty.limit.traffic calls :incoming(key, false) until the last limiter which is called as :incoming(key, true). If any of those return an error, it is fine to just exit. Nothing was committed to the database.
When all of them succeed, it tries to call again :incoming(key, true), but in this case, if any of them fails then call :uncommit(key) for all limiters that it already called :incoming.
So I'd suspect our limiters are not rolled back because they are not wrapped in one resty.limit.traffic.
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resty.limit.traffic calls :incoming(key, false) until the last limiter which is called as :incoming(key, true). If any of those return an error, it is fine to just exit. Nothing was committed to the database.
Using the current count-inc, I think that when the last limiter, which is called as :incoming(key, true), only returns nil and "rejected", the last one is committed to the database.
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Ok. I got it now. Implemented a fix to the upstream library: openresty/lua-resty-limit-traffic@c53f224 (openresty/lua-resty-limit-traffic#34)
I think we can just copy that here.
mikz
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It is just cosmetically different from
openresty/lua-resty-limit-traffic#34 which is not merged anyway, so 👍 .
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Closes #830.