OK - response body contains a result or an error;
     the error may appear only if something happened within Tarantool,
     for instance: 'method not found'.

INTERNAL SERVER ERROR - may appear in many cases,
                        most of them is 'out of memory' error;

NOT ALLOWED - in reponse to anything but  a POST request.

BAD REQUEST - JSON parse error, empty request body, etc.

BAD GATEWAY - lost connection to Tarantool server(s);
              Since both (i.e. json -> tp and tp -> json) parsers work asynchronouly,
              this error may appear if 'params' or 'method' do not exists in tbe structure
              of incoming JSON, please see the protocol description for more details.
              
              Note: this behavior will change in  the future.

[ { "method": STR, "params":[arg0 ... argN], "id": UINT }, ...N ]

"method"

  A String containing the name of the method to be invoked (i.e. Tarantool "call")

"params"

  Here is a Structured array. Each element is a argument of Tarantool "call".
  

"id"

  An identifier established by the Client MUST contain an unsigned Number not
  greater than unsigned int.
  
  MAY be 0.

These are required fields.

[ { "result": JSON_RESULT_OBJECT, "id":UINT, "error": { "message": STR, "code": INT } }, ...N ]

"result"

  Tarantool executing result as json object/array etc.
  
  MAY be null or undefined.

"id"

  Request id is returned back.
  
  MAY be null or undefined.


"error"

  Here is a Structured object which contains internal error message.
  This field exists only if internal error occured, for instance:
  "too large request", "input json parse error", etc.

  If this field exists input message _probably_ did not pass to Tarantool backend.

  See "message"/"code" field for details.

  Syntax:
  
  --> data sent to Server
  <-- data sent to Client
  
  rpc call 1:
  --> { "method": "echo", "params": [42, 23], "id": 1 }
  <-- { "result": [42, 23], "id": 1 }
  
  rpc call 2: 
  --> { "method": "echo", "params": [ [ {"hello": "world"} ], "!" ], "id": 2 }
  <-- { "result": [ [ {"hello": "world"} ], "!" ], "id": 2 }
  
  rpc call of non-existent method:
  --> { "method": "echo_2", "id": 1 } 
  <-- { "error": {"code": -32601, "message": "Method not found"}, "id": 1 }
  
  rpc call with invalid JSON:
  --> { "method": "echo", "params": [1, 2, 3, __wrong__ ] }
  <-- { "error": { "code": -32700, "message": "Parse error" } }
  
  rpc call Batch:
  --> [
        { "method": "echo", "params": [42, 23], "id": 1 },
        { "method": "echo", "params": [ [ {"hello": "world"} ], "!" ], "id": 2 }
  ]
  <-- [
        { "result": [42, 23], "id": 1 },
        { "result": [ [ {"hello": "world"} ], "!" ], "id": 2 }
  ]
  
  rpc call Batch of non-existent method:
   --> [
        { "method": "echo_2", "params": [42, 23], "id": 1 },
        { "method": "echo", "params": [ [ {"hello": "world"} ], "!" ], "id": 2 }
  ]
  <-- [
        { "error": {"code": -32601, "message": "Method not found"}, "id": 1 },
        { "result": [ [ {"hello": "world"} ], "!" ], "id": 2 }
  ]
  
  rpc call Batch with invalid JSON:
  --> [
        { "method": "echo", "params": [42, 23, __wrong__], "id": 1 },
        { "method": "echo", "params": [ [ {"hello": "world"} ], "!" ], "id": 2 }
  ]
  <-- { "error": { "code": -32700, "message": "Parse error" } }

$ git clone https://github.com/tarantool/nginx_upstream_module.git nginx_upstream_module
$ cd nginx_upstream_module
$ git submodule update --init --recursive
$ git clone https://github.com/nginx/nginx.git nginx
$ make build-all # build-all-debug i.e. debug version

libyajl >= 2.0(https://lloyd.github.io/yajl/)
libmsgpuck >= 1.0 (https://github.com/rtsisyk/msgpuck)

$ ./configure --add-module=REPO_ROOT && make