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The npm and Composer handlers rewrite every metadata document they serve so that download URLs point at the proxy: decode the whole document into generic maps, change the URLs, encode it again, and for Composer expand the minified format first. That ran on every request, cached metadata included. With metadata caching on and upstream out of the picture, a cached request still cost 7 ms for @babel/core, 17 ms for symfony/console and 155 ms and 134 MB of allocations for typescript, and an 8 vCPU VM serving cached npm packuments to 20 clients ran the proxy at 450% CPU for about 1,100 requests a second. Rewritten documents are now kept in memory, keyed by the ecosystem, proxy URL, package and a SHA-256 of the raw document, so new bytes from upstream are rewritten again and nothing is served stale. Requests that arrive while a document is being rewritten wait for that rewrite rather than running their own; a waiter leaves when its client does, and the rewrite still completes and is cached. The denylist is fixed at startup, so it needs no place in the key. Cooldown filtering depends on the current time, so with cooldown on the cache is bypassed. metadata_rewrite_cache_size bounds the cache (default "256MB", least recently used out first, "0" to rewrite on every request). NewProxy callers keep the old behaviour unless they set it. Whole cached requests, measured locally: @babel/core 7.1 ms -> 0.38 ms, 54,489 -> 119 allocations typescript 155 ms -> 10.5 ms, 1.37M -> 133 allocations symfony/console 17.4 ms -> 0.48 ms, 165,909 -> 123 allocations What remains is reading the raw document from storage and hashing it.
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CI passed on all jobs; closing as planned. The change is going upstream. |
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Draft PR inside the fork, only to run CI on this branch before proposing it upstream. Fork main is behind upstream, so the commit list is long; CI tests the branch merged onto it. Will be closed once CI finishes.