Hostname was NOT found in DNS cache - php

Question

One of my projects has intermittent connection problems to gateway.watsonplatform.net. It had been working fine, nothing has changed, but now, 80% of the time, it cannot find hostname in DNS Cache.
I've tried to set CURLOPT_RESOLVE option but it just prepends a line to the output about adding hostname into the cache, but then it's still not found.
I'm trying to run the project locally and I figured out it is network-specific. It works on one access point fine, on the other, it has connection issues.
And another strange hint: curl command in shell works.
There is the output:
Added gateway.watsonplatform.net:80:158.85.132.88 to DNS cache
Hostname was NOT found in DNS cache
Could not resolve host: gateway.watsonplatform.net
UPDATE:
The port should be 443, not 80. After this change, it works. After deleting whole this assignment, it still works. Now, I cannot reproduce the problem.

Answer 1

I had the same problem when I implement one project with IBM Watson inside one Customer. And in this case: You need to release the URL inside your Proxy network.
The reason for cURL and Nodejs calls works is because the server is calling through Firewall, and not passing for your proxy network.
Make sure if the url works when you set the proxy inside your Server: Connect advanced inside your SO (Options internet).

Answer 2

as a little ugly hack to get it working, you could add a hosts file alias, perhaps reinforced with a hourly cronjob to update the real IP - at the cost of the script failing for up to 1 hour every time they actually change IP? (i actually did this a couple of years back when i was facing a similar problem, i don't think i still have the source code though, ill check)
edit: i don't have the original cronjob, but it looked something like this:
<?php
declare(strict_types = 1);
$hosts = '/etc/hosts';
assert ( is_file ( $hosts ) && is_readable ( $hosts ) && is_writable ( $hosts ), 'need access to ' . $hosts );
$host = 'google.com';
$ip = getIP ( $host );
$str = file_get_contents ( $hosts );
$start = strpos ( $str, '#<wtf_cronjob>' );
$end = strpos ( $str, '#</wtf_cronjob>' );
assert ( false !== $start && false !== $end, 'invalid syntax for hosts file!' );
$end += strlen ( '#</wtf_cronjob>' );
$newstr = substr ( $str, 0, $start ) . '#<wtf_cronjob>' . "\n" . $ip . ' ' . $host . ' ' . "\n" . '#</wtf_cronjob>' . substr ( $str, $end );
file_put_contents ( $hosts, $newstr );
function getIP(string $host, string $dns = '8.8.8.8'): string {
exec ( 'host ' . escapeshellarg ( $host ) . ' ' . escapeshellarg ( $dns ) . ' 2>&1', $lines, $ret );
if ($ret !== 0) {
ob_start ();
var_dump ( $lines, $ret );
$debugstr = ob_get_clean ();
throw new \RuntimeException ( 'host failed. debuginfo: ' . $debugstr );
}
foreach ( $lines as $line ) {
if (false === stripos ( $line, 'has address ' )) {
continue;
}
// found it
$ret = trim ( substr ( $line, stripos ( $line, 'has address ' ) + strlen ( 'has address ' ) ) );
if (! filter_var ( $ret, FILTER_VALIDATE_IP )) {
throw new \RuntimeException ( 'the extracted ip address is invalid! (wrong syntax for host?)' );
}
return $ret;
}
throw new \RuntimeException ( 'could not find ip address!' );
}
with the following new lines in the hosts file:
#<wtf_cronjob>
216.58.209.142 google.com
#</wtf_cronjob>

Answer 3

I've tried to assign manually how the domain should be resolved. Since this step, the request is working and after deleting this assignment, it still works.