Reliable HTTP 429 error for two concurrent transfers

[vokac]

By running "simultaneously" two transfers from same client we reliable get HTTP 429 for one of these transfers (sometimes for the first one and sometimes for the second one), e.g.

#!/bin/sh
curl --verbose --silent --cert /tmp/x509up_u$(id -u) --key /tmp/x509up_u$(id -u) --cacert /tmp/x509up_u$(id -u) --capath /etc/grid-security/certificates -L https://se1.farm.particle.cz/atlas/atlasscratchdisk/SAM/t1 > /dev/null 2> t1.out &
curl --verbose --silent --cert /tmp/x509up_u$(id -u) --key /tmp/x509up_u$(id -u) --cacert /tmp/x509up_u$(id -u) --capath /etc/grid-security/certificates -L https://se1.farm.particle.cz/atlas/atlasscratchdisk/SAM/t2 > /dev/null 2> t2.out &
wait

one transfer runs OK

* Connected to se1.farm.particle.cz (2001:718:401:6025:2::1000) port 443 (#0)
...
> GET /atlas/atlasscratchdisk/SAM/t1 HTTP/1.1
> Host: se1.farm.particle.cz
> User-Agent: curl/7.76.1
> Accept: */*
...
< HTTP/1.1 302 Found
< Date: Sun, 24 May 2026 10:10:12 GMT
< Server: dCache/11.2.4
< Location: https://ds42.farm.particle.cz:20853/atlas/atlasscratchdisk/SAM/t1?dcache-http-uuid=3955de2e-73db-4839-8d9b-1db70580bcb5&dcache-http-ref=https%3A%2F%2Fse1.farm.particle.cz%3A443
< Content-Length: 0
... 
* Connected to ds42.farm.particle.cz (2001:718:401:6025:2::42) port 20853 (#1)
...
> GET /atlas/atlasscratchdisk/SAM/t1?dcache-http-uuid=3955de2e-73db-4839-8d9b-1db70580bcb5&dcache-http-ref=https%3A%2F%2Fse1.farm.particle.cz%3A443 HTTP/1.1
> Host: ds42.farm.particle.cz:20853
> User-Agent: curl/7.76.1
> Accept: */*
...
< HTTP/1.1 200 OK
< Accept-Ranges: bytes
< Content-Length: 692252
< Content-Disposition: attachment;filename=t1
< Content-Location: https://se1.farm.particle.cz/atlas/atlasscratchdisk/SAM/t1
< Server: dCache/11.2.4

while second fails with HTTP 429

* Connected to se1.farm.particle.cz (2001:718:401:6025:2::1000) port 443 (#0)
...
> GET /atlas/atlasscratchdisk/SAM/t2 HTTP/1.1
> Host: se1.farm.particle.cz
> User-Agent: curl/7.76.1
> Accept: */*
...
< HTTP/1.1 429 Too Many Requests
< Date: Sun, 24 May 2026 10:10:12 GMT
< Server: dCache/11.2.4
< Content-Length: 39
...