Add code_server cache to prevent code:get_object_code abuse #1640
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In the case of high connection churn, code:get_object_code is called multiple times to find the Module:additional_authn_params method for the direct connection type. In the case of a missing module, the code_server process can be overrun with messages while checking the code path. This change caches the result so that future calls to a missing or bad module are not as time consuming Fixes VESC-888
michaelklishin
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Jul 12, 2018
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I've been running an Erlang pseudo STOMP client that churns through connections at 500-1000 connections/second for about 20 minutes now and the Erlang process count on the node with this change and rabbitmq/rabbitmq-stomp#125 has been stable in the 420-570 process range.
A few questions I had when starting the review:
- Does this cache any client-specific information? The answer is no, only
undeferrors are cached to avoid repeatedcode_serverhits (it's the classic Single Overloaded Process per Node kind of issue) - Does it cache client credentials? No (see above)
- Do we expect the cache to really kick in often and consume a lot of memory? No (see above + rabbitmq/rabbitmq-stomp#125)
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Thanks for the review, and it's very interesting and helpful to know what you were thinking before starting it. |
michaelklishin
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In the case of high connection churn,
code:get_object_codeis called multiple times to find theModule:additional_authn_paramsmethod for the direct connection type. In the case of a missing module (see rabbitmq/rabbitmq-stomp#125), thecode_serverprocess can be overrun with messages while checking the code path. This change caches the result so that future calls to a missing or bad module are not as time consumingFixes VESC-888