How can I send some http request from postgresql function or trigger

There is an extension to do this, use with caution.

pgsql-http

Any "untrusted" language with HTTP support can do this:

• PL/Pythonu
• PL/perlu
• PL/javau
• ...

but you shouldn't really do it. See Does PLV8 support making http calls to other servers? and why you shouldn't send email from a trigger function.

You could try writing the trigger in PL/Python and use urllib2 to POST.