[sled-agent] avoid using hardcoded port number to reach MGS #6430
Conversation
this is one (and the easiest) of three cases i noted in #6363 where we find a service by looking up a SRV record, ignoring the port in that record, keeping IPs from that SRV lookup, and then finally pairing those addresses with a service's hardcoded port. in this case, we were looking up the SRV record for Dendrite, then using the MGS port instead. this this technically works, because the two *will* be running together, but we can just get the right port from the get-go by looking for MGS's SRV record instead. so, do that. this file also mentions MGS_PORT in `init_switch_config`, at which point it's more necessary: in that case, we're configuring *our* switch zone. so we *know* the address we want to reach - it's our own sled - and we just need to add the port of the service we want.
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We should make sure that these DNS records exist on all the usual production and pre-production systems (dogfood, rack3, customer systems). I might be confusing the MGS case with the MGD case but at least in the MGD case there was a long period where only new systems had the DNS records. There's some more detail in #6077 and some issues linked to that one. I think by now we've successfully executed a blueprint on all of these systems and so there should be consistent DNS records everywhere but may be worth double checking? |
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yes, definitely worth double-checking. iiuc at this point there's no reason this should be in R10, so i think we can be even more confident this won't have an issue when it goes out. but i also hadn't realized that the fact these records exist early enough would be relatively recent, so i'd like to understand better before merging. |
this is one (and the easiest) of three cases i noted in #6363 where we find a service by looking up a SRV record, ignoring the port in that record, keeping IPs from that SRV lookup, and then finally pairing those addresses with a service's hardcoded port.
in this case, we were looking up the SRV record for Dendrite, then using the MGS port instead. this this technically works, because the two will be running together, but we can just get the right port from the get-go by looking for MGS's SRV record instead. so, do that.
this file also mentions MGS_PORT in
init_switch_config, at which point it's more necessary: in that case, we're configuring our switch zone. so we know the address we want to reach - it's our own sled - and we just need to add the port of the service we want.