> On 28 Nov 2020, at 8:14 pm, b.ca...@pobox.com <b.cand...@pobox.com> wrote:
>
> Do you see a forward or reverse DNS lookup being made?
>
> Can you provide a standalone program which demonstrates this behaviour?
>
> I am wondering if either (a) something is logging when the connection is
> terminated, or (b) a new connection is automatically being made and put into
> a pool.
Sure, please find my code here:
https://gist.github.com/amitsaha/3963207e77f7537a5dcc3b3afa8e57ee
My experiment scenario:
1. Modify /etc/hosts to have this entry:
# 216.239.38.21 godoc.org #one of the actual IP addresses
<your local ip> godoc.org
2. Run godoc locally as: sudo ~/go/bin/godoc -http=<your local ip>:80
3. Build and run the above program:
$ go build -o application
$ ./application http://godoc.org
DNS Start Info: {Host:godoc.org}
DNS Done Info: {Addrs:[{IP:192.168.1.109 Zone:} {IP:2001:4860:4802:38::15
Zone:} {IP:2001:4860:4802:36::15 Zone:} {IP:2001:4860:4802:32::15 Zone:}
{IP:2001:4860:4802:34::15 Zone:}] Err:<nil> Coalesced:false}
Got Conn: {Conn:0xc000186000 Reused:false WasIdle:false IdleTime:0s}
Put Idle Conn Error: <nil>
Resp protocol: "HTTP/1.1"
Sleeping now
--------
Got Conn: {Conn:0xc000186000 Reused:true WasIdle:true IdleTime:2.00444722s}
Put Idle Conn Error: <nil>
Resp protocol: "HTTP/1.1"
Sleeping now
--------
…
In a new terminal:
1. Update /etc/hosts to have:
216.239.38.21 godoc.org
#192.168.1.109 godoc.org
2. Kill the godoc server
Then in the terminal you had the application running, you should see:
Got Conn: {Conn:0xc000186000 Reused:true WasIdle:true IdleTime:2.001646523s}
Put Idle Conn Error: <nil>
Resp protocol: "HTTP/1.1"
Sleeping now
————
# This is where the switch to the new IP happens
DNS Start Info: {Host:godoc.org}
DNS Done Info: {Addrs:[{IP:216.239.38.21 Zone:} {IP:2001:4860:4802:32::15
Zone:} {IP:2001:4860:4802:36::15 Zone:} {IP:2001:4860:4802:38::15 Zone:}
{IP:2001:4860:4802:34::15 Zone:}] Err:<nil> Coalesced:false}
Got Conn: {Conn:0xc0000b40b8 Reused:false WasIdle:false IdleTime:0s}
Put Idle Conn Error: <nil>
Resp protocol: "HTTP/1.1"
Sleeping now
--------
Got Conn: {Conn:0xc0000b40b8 Reused:true WasIdle:true IdleTime:2.002040265s}
Put Idle Conn Error: <nil>
Resp protocol: "HTTP/1.1"
Sleeping now
….
My go version:
$ go version
go version go1.15 darwin/amd64
Thank you,
Amit
>
> On Saturday, 28 November 2020 at 01:27:32 UTC amits...@gmail.com wrote:
> Hi, it seems that the http client automatically performs a DNS lookup when an
> existing connection is terminated by the server. I simulated it via changing
> the IP address in /etc/hosts.
>
> Can someone point me to the code where this logic is checked?
>
> I am looking at https://golang.org/src/net/http/transport.go but haven’t
> found something yet - quite a beginner here.
>
> Thanks,
> Amit.
>
>
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