hi all, some help is needed here :)
we have a testnet node running behind nginx+openresty and whenever we try to reach for example eth_estimateGas (which is properly whitelisted in nginx) I got a 400 bad request and I can see this in nginx log:

2019/10/11 21:04:46 [error] 5683#5683: *7 [lua] jsonrpc-access.lua:48: invalid JSON request, client: 172.22.1.169, server: 172.1.21.72, request: "POST / HTTP/1.1", host: "172.1.21.72"

Error message seems to be pretty clear, but if I hit 4444 directly, I got the following:

{"jsonrpc":"2.0","id":1,"error":{"code":-32603,"message":"Internal server error"}}

So, in one case I got a 400 which points me to a malformed JSON file but in the other I got a 500. Is this expected/known?
How can I resolve that? Do you think it's recommended to completely remove nginx+openresty from the equation so we can hit rsk directly?

any help and/or comments are welcome.
thanks in advance.

curl -v -X POST -H "Content-Type: application/json" --data '{"jsonrpc":"2.0","method":"eth_estimateGas","params":[{'chainId': 31, 'from': '0xF9a841d0C7801df36c2487AF89066ad52DEa582c', 'nonce': 0, 'data': '0xDATA HERE', 'to': b''}],"id":1}' http://172.1.21.72

{"jsonrpc":"2.0","id":1,"result":"0x54d8"}

when going through nginx+openresty does not work. hitting directly 4444 works

OK, I understand that the JSON request is not the issue. Are you filtering any methonds in lua?

server_name *****;
    location / {
        # First attempt to serve request as file, then
        # as directory, then fall back to displaying a 404.
        #try_files $uri $uri/ =404;
        #set $jsonrpc_whitelist 'web3_clientVersion,eth_getTransactionByHash,eth_getTransactionReceipt,eth_sendRawTransaction';
            if ($request_method != OPTIONS ) {
              access_by_lua_file '/usr/local/openresty/nginx/jsonrpc-access.lua';
              }

        proxy_pass http://127.0.0.1:4444;
    }