Why cURL requests to Telegram Bot API suddenly became very slow?

Question

I have several Telegram bots working nice for years; I used 2 ways to send requests to Bot API:

The first is:

file_get_contents($url);

The second is:

$ch = curl_init($url);
curl_setopt_array($ch, [
    CURLOPT_RETURNTRANSFER => true,
    CURLOPT_CONNECTTIMEOUT => 10,
    CURLOPT_TIMEOUT => 60
]);
curl_exec($ch);

Some days ago I noticed that:

1. file_get_contents() stopped working completely returning failed to open stream: Connection timed out every time, but it works nice with requests to other websites;
2. cURL keeps working, but very slow: after I send a message to the bot, I wait 5-8 seconds to receive the answer; when I changed CURLOPT_CONNECTTIMEOUT to 1 the waiting period reduced to 1 second or so.

file_get_contents() has started working as before with this context:

file_get_contents($url, false, stream_context_create([
    'socket' => [
        'bindto' => '0:0'
    ]
]));

The last_error_message is always Read timeout expired. Server reboot does not help. Direct requests to Bot API from a browser works perfectly.

What is happening and how to fix it?

Answer 1

Its probably because Curl tries to Reverse DNS and since it fails it just waiting for the timeout, you can fix it like this:

curl_setopt($ch, CURLOPT_IPRESOLVE, CURL_IPRESOLVE_V4 )