Sometimes timings.phases.dns is not lookup duration

[motiveko]

I use got http client and I use option {dnsCache: true}.

In http-timer packages, theres's two code to calculate dns duration.

1. on socket's lookup event listener
   

   http-timer/source/index.ts

   Lines 93 to 98 in 62f6b38

    const lookupListener = (): void => { 
    	timings.lookup = Date.now(); 
    	timings.phases.dns = timings.lookup - timings.socket!; 
    }; 
     
    socket.prependOnceListener('lookup', lookupListener); 

2. deferToConnect()'s connect callback function
   

   http-timer/source/index.ts

   Lines 102 to 110 in 62f6b38

    timings.connect = Date.now(); 
     
    if (timings.lookup === undefined) { 
    	socket.removeListener('lookup', lookupListener); 
    	timings.lookup = timings.connect; 
    	timings.phases.dns = timings.lookup - timings.socket!; 
    } 
     
    timings.phases.tcp = timings.connect - timings.lookup; 

When use got with dnsCache, once hostname resolved, then until ttl, no lookup event emitted on the socket, so lookup time should be 0.

But above the code 2, dns never be 0 but tcp(connection time) will be 0.

When Server got a lot of traffic and got's socket connection delayed, value of tcp will not increased ( this always be 0 ), but value of dns increased.

I think this is causing confusion and needs to be fixed

[Martin Kolárik]

This is also a problem when the request is made directly to an IP. There's obviously no DNS resolution in that case, but the timings report it.