如何使用 C# 查询 Tableaus GraphQL

Question

(Question also asked here .)

I am attempting to connect to and query Tableau via GraphQL using C#. I have been trying for a while now, and keep hitting a wall when sending the query.

I am creating a httpWebRequest to send the query using the following method.

The variables passed in are:

string Url = MyTableauServer/api/metadata/graphql

string Method = "POST"

string payload = """query TestName1   {  databaseServersConnection(first: 10)     {    totalCount,    pageInfo{endCursor,hasNextPage,}    nodes      {      connectionType,      __typename,      hostName,      name,      port,      isEmbedded,      tables        {        id,        schema,        name,        columns          {          id,          name          }        }      }    }  }"""

The AuthToken is obtained by querying the REST API. The authenticated user has permissions to be able to perform any and all of the required actions.

    public static string SendJsonWebRequest(string Url, string Method, string payload, string AuthToken)

    {

      try

      {

        string response;

        //encode the json payload  

        byte[] buf = Encoding.UTF8.GetBytes(Uri.EscapeDataString(payload));

        //set the system to ignore certificate errors because Tableau server has an invalid cert.  

        System.Net.ServicePointManager.ServerCertificateValidationCallback = ((sender, certificate, chain, sslPolicyErrors) => true);

 

        //Create the web request and add the json payload  

        HttpWebRequest wc = WebRequest.CreateHttp(Url) as HttpWebRequest;

        wc.Method = Method;

        wc.PreAuthenticate = true;

        wc.Headers.Add($"X-Tableau-Auth: {AuthToken}, content-type: application/json, accept: application/json");

        wc.ContentLength = buf.Length;

        wc.GetRequestStream().Write(buf, 0, buf.Length);

 

        try

        {

          //Send the web request and parse the response into a string  

//this is as far as i get

          HttpWebResponse wr = wc.GetResponse() as HttpWebResponse;

          Stream receiveStream = wr.GetResponseStream();

          StreamReader readStream = new StreamReader(receiveStream, Encoding.UTF8);

          response = readStream.ReadToEnd();

          receiveStream.Close();

          readStream.Close();

          wr.Close();

        }

        catch (WebException we)

        {

          //Catch failed request and return the response code  

          if (we.Status == WebExceptionStatus.ProtocolError)

          {

            WebResponse resp = we.Response;

            using (StreamReader sr = new StreamReader(resp.GetResponseStream()))

            {

              response = sr.ReadToEnd();

            }

          }

          else

          {

            response = ((HttpWebResponse)we.Response).StatusCode.ToString();

          }

        }

        return response;

      }

      catch (Exception E)

      {

        logger.Trace($"- ERROR - Error in SendWebRequest. System says: {E.Message}");

        return E.Message;

      }

    }

The most recent error i am getting is "The underlying connection was closed: The connection was closed unexpectedly." being returned at the following line:

HttpWebResponse wr = wc.GetResponse() as HttpWebResponse;

Any ideas or assistance would be greatly appreciated

------------------------------------------------------------

Update:

using Fiddler i get the following response.

{

  "timestamp": 1600939439846,

  "status": 401,

  "error": "Unauthorized",

  "message": "User is not authenticated",

  "path": "/relationship-service-war/graphql"

}

I am authenticated, Authentication token is valid and is passed in the headers.

------------------------------------------------------

Update:

Adding the code for authentication. logged in user is a server admin so no issues with access rights.

    public static string TabLogIn(string User, string Pass, string ContURL = "")
    {
        string response = "";
        try
        {
            using (XmlWriter loginxml = XmlWriter.Create("signin.xml"))
            {
                loginxml.WriteStartDocument();
                loginxml.WriteStartElement("tsRequest");
                loginxml.WriteStartElement("credentials");
                loginxml.WriteAttributeString("name", User);
                loginxml.WriteAttributeString("password", Pass);
                loginxml.WriteStartElement("site");
                loginxml.WriteAttributeString("contentUrl", ContURL);
                loginxml.WriteEndElement();
                loginxml.WriteEndElement();
                loginxml.WriteEndElement();
                loginxml.WriteEndDocument();
            }
            XElement myxml = XElement.Load("signin.xml");
            string myxmlstring = myxml.ToString();

            //send payload to routine to make the web request  
            string URL = $@"{Enums.Server}/api/{Enums.APIVersion34}/auth/signin";


            //Send the above url, the POST method, and the XML Payload string to create the web request  
            var infotl = SendWebRequest(URL, "POST", myxmlstring);

            response = infotl;
            File.Delete("signin.xml");

            return response;
        }
        catch(Exception E)
        {
            logger.Trace($"- ERROR - Error in TabLogIn. System says: {E.Message}");
            return response;
        }
        finally
        {
            if (File.Exists("signin.xml"))
            {
                File.Delete("signin.xml");
            }
        }
    }

    static string SendWebRequest(string Url, string Method, string payload)
    {
        try
        {
            string response;
            //encode the XML payload  
            byte[] buf = Encoding.UTF8.GetBytes(payload);
            //set the system to ignore certificate errors because Tableau server has an invalid cert.  
            System.Net.ServicePointManager.ServerCertificateValidationCallback = ((sender, certificate, chain, sslPolicyErrors) => true);

            //Create the web request and add the XML payload  
            HttpWebRequest wc = WebRequest.Create(Url) as HttpWebRequest;
            wc.Method = Method;
            wc.ContentType = "text/xml";
            wc.ContentLength = buf.Length;
            wc.GetRequestStream().Write(buf, 0, buf.Length);

            try
            {
                //Send the web request and parse the response into a string  
                HttpWebResponse wr = wc.GetResponse() as HttpWebResponse;
                Stream receiveStream = wr.GetResponseStream();
                StreamReader readStream = new StreamReader(receiveStream, Encoding.UTF8);
                response = readStream.ReadToEnd();
                receiveStream.Close();
                readStream.Close();
                wr.Close();
            }
            catch (WebException we)
            {
                //Catch failed request and return the response code  
                response = ((HttpWebResponse)we.Response).StatusCode.ToString();
            }
            return response;
        }
        catch(Exception E)
        {
            logger.Trace($"- ERROR - Error in SendWebRequest. System says: {E.Message}");
            return E.Message;
        }
    }

Answer 1

Double check if you're requesting a token from the correct Tableau Site (if you have multiple sites). Also what permissions does user have and can you share the code where you request the token?