Thank you for the explanation. On Thu, Aug 3, 2023 at 4:56 PM Daniel Stenberg <dan...@haxx.se> wrote:
> On Thu, 3 Aug 2023, Babacar Ndiaye via curl-library wrote: > > > "Typically this means asking for both IPv4 and IPv6 addresses and there > may > > be a whole set of those returned to libcurl. That set of addresses is > then > > tried until one works, or it returns failure." > > > > Does this mean the cache will on remember one single address (the first > one > > that worked)? > > No. The next time the address is used from the cache, the addresses are > tested > in the exact same order as it did the last time: in the order they were > returned by the name resolver function. > > Trying the working version first (and the failing ones last) is certainly > an > optmization waiting to be done. > > > 2. Say we cache an entry and the name gets re-pointed to a new IP > (service > > moved to a new IP). Is your expectation that we'd get a code 7 (couldnt > > connect to server) next time we try to reuse the IP? > > The expectation is primarily to only cache addresses for a period of time > during which it is likely to still work. That's why the the default DNS > cache > timeout is set to only 60 seconds. > > If the host name changes address while the cache still holds the old set, > there are several different potential outcomes when that is used. > Including: > > 1. another service might use that address (and port) now, and if that is > an > unauthenticated protocol you might connect and issue requests to the wrong > host. It might even succeed but give you unexpected data. > > 2. the service might use TLS and then you get a cert error > > 3. nothing might be answering on that IP/port so you get a connect failure > > 4. now something might swallow every packet on that IP so you get a > connect > timeout > > ... > > -- > > / daniel.haxx.se > | Commercial curl support up to 24x7 is available! > | Private help, bug fixes, support, ports, new features > | https://curl.se/support.html >
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