Issues with the SWIS API

This used to work fine , but now on a browser it shows a certificate warning and then shows a page cannot be displayed.
On continuous refreshes of the browser , After 5 minutes, prompts for the username and password and starts showing results. 

Having no issues with website. Just this SWIS response are delayed for some reason.

Here is a curl output

curl -k -v -u testuser:testuser https://<SOLARWINDS_SERVER_IP>:17778/Solarwinds/InformationService/v3/json/Query?query=SELECT%20TOP%201%20NodeID,%20Caption%20FROM%20Orion.Nodes

* TCP_NODELAY set
* Connected to <SOLARWINDS_SERVER_IP> port 17778 (#0)
* schannel: SSL/TLS connection with <SOLARWINDS_SERVER_IP> port 17778 (step 1/3)
* schannel: disabled server certificate revocation checks
* schannel: verifyhost setting prevents Schannel from comparing the supplied target name with the subject names in server certificates.
* schannel: sending initial handshake data: sending 178 bytes...
* schannel: sent initial handshake data: sent 178 bytes
* schannel: SSL/TLS connection with <SOLARWINDS_SERVER_IP> port 17778 (step 2/3)
* schannel: failed to receive handshake, need more data
* schannel: SSL/TLS connection with <SOLARWINDS_SERVER_IP> port 17778 (step 2/3)
* schannel: encrypted data got 913
* schannel: encrypted data buffer: offset 913 length 4096
* schannel: sending next handshake data: sending 358 bytes...
* schannel: SSL/TLS connection with <SOLARWINDS_SERVER_IP> port 17778 (step 2/3)
* schannel: encrypted data got 91
* schannel: encrypted data buffer: offset 91 length 4096
* schannel: SSL/TLS handshake complete
* schannel: SSL/TLS connection with <SOLARWINDS_SERVER_IP> port 17778 (step 3/3)
* schannel: stored credential handle in session cache
* Server auth using Basic with user 'testuser'
> GET /Solarwinds/InformationService/v3/json/Query?query=SELECT%20TOP%201%20NodeID,%20Caption%20FROM%20Orion.Nodes HTTP/1.1
> Host: <SOLARWINDS_SERVER_IP>:17778
> Authorization: Basic dGVzdHVzZXI6dGVzdHVzZXI=
> User-Agent: curl/7.55.1
> Accept: */*
>
* schannel: client wants to read 102400 bytes
* schannel: encdata_buffer resized 103424
* schannel: encrypted data buffer: offset 0 length 103424
* schannel: Curl_read_plain returned CURLE_RECV_ERROR
* schannel: encrypted data buffer: offset 0 length 103424
* schannel: encrypted data buffer: offset 0 length 103424
* schannel: decrypted data buffer: offset 0 length 4096
* schannel: schannel_recv cleanup
* Closing connection 0
* schannel: shutting down SSL/TLS connection with <SOLARWINDS_SERVER_IP> port 17778
* Send failure: Connection was reset
* schannel: failed to send close msg: Failed sending data to the peer (bytes written: -1)
* schannel: clear security context handle
curl: (56) Send failure: Connection was reset

I'd follow the troubleshooting recommendations from this thread: https://thwack.solarwinds.com/t5/Discussions/Connection-to-REST-port-getting-reset/m-p/75708 

• See if a firewall is interfering with the communication.
• Check the SWIS logs at C:\ProgramData\SolarWinds\InformationService\v3.0\Orion.InformationService.log for interesting errors.
• Check the Windows Event Log.

• I dont see an issue with the firewall .These queries have same resonse when run on the solarwinds server itself. 
• Didnt find anything related to these queries. In fact sent the dagnostics to Solarwinds support and they werent able to see anything interesting in it
• Have been checking the Event logs. Not able to identify anything specific to this issue.

I did a netstat -an | findstr "17778" and got 1106 rows of ESTABLISHED connections.

We have only around 90 Solarwinds agents pointing to this server 

There is related discussion for this particular case on a separate thread at https://thwack.solarwinds.com/t5/Discussions/slow-response-from-SWIS-API/m-p/590329.  It seems like testing the network connection with tools like NetPath, Traceroute NG, or Wireshark might be the next step.

I also see more than 1000 connections on port 17778 established at a given point of time. Not sure if that might be causing the issues.

I do have Wireshark. Is there anything specific that i need to check or verify ?

I'm not a Wireshark expert, sadly.  You'll want to set up a capture with filters so that you're only looking at traffic between your client machine and your Orion server over port 17778.

https://www.wireshark.org/docs/wsug_html_chunked/ChCapCaptureFilterSection.html

Because the traffic is encrypted, you won't be able to look at the contents.  There are methods for TLS decryption if you know the encryption secrets, but I suspect that's not necessary.

https://wiki.wireshark.org/TLS

I think you just want to run the packet capture, look at the results, and look for errors or any legs of transmission that have high latency.