Logstash http output user password

@Badger @ptambam
I managed to create an authorization with @badger's different answer
here

My config is now

output
{
http
{
format=>"json"
http_method=>"post"
url=>"https://zenossprod.lsk12.com/zport/dmd/evconsole_router"
cacert => "/opt/cert/cert.crt"
headers => {
"Authorization" => "Basic RUxLOldlbGNvbWUxMjMgaHR0cHMbWQvZXZjb25zb2xlX3JvdXRlcg=="
}
}
stdout { codec => rubydebug }
}

But I'm still getting the certificate error,
message=>"PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target",

I also tried with pem and cer type certificates. None of it works,

Please help me resolve it.