description
NSO Web UI development information.

Web UI Development

Web UI development is thought to be in the hands of the customer's front-end developers. They know best the requirements and how to fulfill those requirements in terms of aesthetics, functionality, and toolchain (frameworks, libraries, external data sources, and services).

NSO comes with a nortbound interface in the shape of a JSON-RPC API. This API is designed with Web UI applications in mind, and it complies with the JSON-RPC 2.0 specification while using HTTP/S as the transport mechanism.

The JSON-RPC API contains a handful of methods with well-defined input method and params, along with the output result.

In addition, the API also implements a Comet model, as long polling, to allow the client to subscribe to different server events and receive event notifications about those events in near real-time.

You can call these from a browser via:

AJAX (e.g., XMLHTTPRequest, jQuery [https://jquery.com/])
Or from the command line (e.g., curl [https://github.com/bagder/curl], httpie [https://github.com/jkbr/httpie])

{% code title="With JQuery" %}

      // with jQuery
      $.ajax({
        type: 'post',
        url: '/jsonrpc',
        contentType: 'application/json',
        data: JSON.stringify({
        jsonrpc: '2.0',
        id: 1,
        method: 'login',
        params: {
          'user': 'joe',
          'passwd': 'SWkkasE32'
        }
        }),
        dataType: 'json'
      })
      .done(function(data) {
        if (data.result)
        alert(data.result);
        else
        alert(data.error.type);
        });

{% endcode %}

{% code title="With Curl" %}

      # with curl
      curl \
      -X POST \
      -H 'Content-Type: application/json' \
      -d '{"jsonrpc": "2.0", "id": 1,
           "method": "login",
           "params": {"user": "joe",
                      "passwd": "SWkkasE32"}}' \
      http://127.0.0.1:8008/jsonrpc

      # with httpie
      http POST http://127.0.0.1:8008/jsonrpc \
      jsonrpc=2.0 id:=1 \
      method=login \
      params:='{"user": "joe", "passwd": "SWkkasE32"}'

{% endcode %}

Example of a Common Flow

You can read in the JSON-RPC API section about all the available methods and their signatures, but here is a working example of how a common flow would look like:

Log in.
Create a new read transaction.
Read a value.
Create a new WebUI (read-write) transaction, in preparation for changing the value.
Change a value.
Commit (save) the changes.
Meanwhile, subscribe to changes and receive a notification.

In the release package, under ${NCS_DIR}/var/ncs/webui/example, you will find the working code to run the example below.

      /*jshint devel:true*/
// !!!
// The following code is purely for example purposes.
// The code has inline comments for a better understanding.
// Your mileage might vary.
// !!!

define([
  'lodash',
  'bluebird',
  './JsonRpc',
  './Comet'
], function(
  _,
  Promise,
  JsonRpc,
  Comet
) {
  'use strict';

  // CHANGE AT LEAST THESE
  // IN ORDER TO MAKE THIS EXAMPLE WORK IN YOUR SETUP
  var jsonrpcUrl = '/jsonrpc', // 'http://localhost:8008/jsonrpc';
      path = '/dhcp:dhcp/max-lease-time',
      value = Math.floor(Math.random() * 800) + 7200;

  var log,
      jsonRpc,
      comet,
      funs = {},
      ths = {
        read: undefined,
        webui: undefined
      };

  // UTILITY
  log = function(msg) {
    document.body.innerHTML =
      '<pre>' +
      msg +
      '</pre>' +
      document.body.innerHTML;
  };

  // SETUP
  jsonRpc = new JsonRpc({
    url: jsonrpcUrl,
    onError: function(method, params, deferred, reply) {
      var error = reply.error,
          msg = [method,
                 params,
                 reply.id,
                 error.code,
                 error.type,
                 error.message
                ];

      if (method === 'comet') {
        return;
      }

      window.alert('JsonRpc error: ' + msg);
    }
  });

  comet = new Comet({
    jsonRpc: jsonRpc,
    onError: function(reply) {
      var error = reply.error,
          msg = [reply.id, error.code, error.type, error.message];

      window.alert('Comet error: ' + msg);
    }
  });

  // CALLS FOR A COMMON SCENARIO
  funs.login = function() {
    log('Logging in as admin:admin...');
    return jsonRpc.call('login', {
      user: 'admin',
      passwd: 'admin'
    }).done(function() {
      log('Logged in.');
    });
  };

  funs.getSystemSetting = function() {
    log('Getting system settings...');
    return jsonRpc.call('get_system_setting').done(function(result) {
      log(JSON.stringify(result, null, 1));
    });
  };

  funs.newReadTrans = function() {
    log('Create a new read-only transaction...');
    return jsonRpc.call('new_read_trans', {
      db: 'running'
    }).done(function(result) {
      ths.read = result.th;
      log('Read-only transaction with th (transaction handle) id: ' +
          result.th + '.');
    });
  };

  funs.newWebuiTrans = function() {
    log('Create a new webui (read-write) transaction...');
    return jsonRpc.call('new_webui_trans', {
      conf_mode: 'private',
      db: 'candidate'
    }).done(function(result) {
      ths.webui = result.th;
      log('webui (read-write) transaction with th (transaction handle) id: ' +
          result.th + '.');
    });
  };

  funs.getValue = function(args /*{th, path}*/) {
    log('Get value for ' + args.path + ' in ' + args.th + ' transaction...');
    if (typeof args.th === 'string') {
      args.th = ths[args.th];
    }
    return jsonRpc.call('get_value', {
      th: args.th,
      path: path
    }).done(function(result) {
      log(path + ' is now set to: ' + result.value + '.');
    });
  };

  funs.setValue = function(args /*{th, path, value}*/) {
    log('Set value for ' + args.path +
        ' to ' + args.value +
        ' in ' + args.th + ' transaction...');
    if (typeof args.th === 'string') {
      args.th = ths[args.th];
    }
    return jsonRpc.call('set_value', {
      th: args.th,
      path: path,
      value: args.value
    }).done(function(result) {
      log(path + ' is now set to: ' + result.value + '.');
    });
  };

  funs.validate = function(args /*{th}*/) {
    log('Validating changes in ' + args.th + ' transaction...');
    if (typeof args.th === 'string') {
      args.th = ths[args.th];
    }
    return jsonRpc.call('validate_commit', {
      th: args.th
    }).done(function() {
      log('Validated.');
    });
  };

  funs.commit = function(args /*{th}*/) {
    log('Commiting changes in ' + args.th + ' transaction...');
    if (typeof args.th === 'string') {
      args.th = ths[args.th];
    }
    return jsonRpc.call('commit', {
      th: args.th
    }).done(function() {
      log('Commited.');
    });
  };

  funs.subscribeChanges = function(args /*{path, handle}*/) {
    log('Subcribing to changes of ' + args.path +
        ' (with handle ' + args.handle + ')...');
    return jsonRpc.call('subscribe_changes', {
      comet_id: comet.id,
      path: args.path,
      handle: args.handle,
    }).done(function(result) {
      log('Subscribed with handle id ' + result.handle + '.');
    });
  };

  // RUN
  Promise.resolve([
    funs.login,
    funs.getSystemSetting,
    funs.newReadTrans,
    function() {
      return funs.getValue({th: 'read', path: path});
    },
    function() {
      var handle = comet.id + '-max-lease-time';
      comet.on(handle, function(msg) {
        log('>>> Notification >>>\n' +
            JSON.stringify(msg, null, 2) +
            '\n<<< Notification <<<');
      });
      return funs.subscribeChanges({th: 'read', path: path, handle: handle});
    },
    funs.newWebuiTrans,
    function() {
      return funs.setValue({th: 'webui', path: path, value: value.toString()});
    },
    function() {
      return funs.getValue({th: 'webui', path: path});
    },
    function() {
      return funs.validate({th: 'webui'});
    },
    function() {
      return funs.commit({th: 'webui'});
    },
    function() {
      return new Promise(function(resolve) {
        log('Waiting 2.5 seconds before one last call to get_value');
        window.setTimeout(function() {
          resolve();
        }, 2500);
      });
    },
    function() {
      return funs.getValue({th: 'read', path: path});
    },
  ]).each(function(fn){
    return fn().then(function() {
      log('--------------------------------------------------');
    });
  });
});


// Local Variables:
// mode: js
// js-indent-level: 2
// End:

Example of a JSON-RPC Client

In the example above describing a common flow, a reference is made to using a JSON-RPC client to make the RPC calls.

An example implementation of a JSON-RPC client, used in the example above:

      /*jshint devel:true*/
// !!!
// The following code is purely for example purposes.
// The code has inline comments for a better understanding.
// Your mileage might vary.
// !!!

define([
  'jquery',
  'lodash'
], function(
  $,
  _
) {
  'use strict';

  var JsonRpc;

  JsonRpc = function(params) {
    $.extend(this, {
      // API

      // Call a JsonRpc method with params
      call: undefined,

      // API (OPTIONAL)

      // Decide what to do when there is no active session
      onNoSession: undefined,
      // Decide what to do when the request errors
      onError: undefined,
      // Set an id to start using in requests
      id: 0,
      // Set another url for the JSON-RPC API
      url: '/jsonrpc',


      // INTERNAL

      makeOnCallDone: undefined,
      makeOnCallFail: undefined
    }, params || {});

    _.bindAll(this, [
      'call',
      'onNoSession',
      'onError',
      'makeOnCallDone',
      'makeOnCallFail'
    ]);
  };

  JsonRpc.prototype = {
    call: function(method, params, timeout) {
      var deferred = $.Deferred();

      // Easier to associate request/response logs
      // when the id is unique to each request
      this.id = this.id + 1;

      $.ajax({
        // HTTP method is always POST for the JSON-RPC API
        type: 'POST',
        // Let's show <method> rather than just "jsonrpc"
        // in the browsers' Developer Tools - Network tab - Name column
        url: this.url + '/' + method,
        // Content-Type is mandatory
        // and is always "application/json" for the JSON-RPC API
        contentType: 'application/json',
        // Optionally set a timeout for the request
        timeout: timeout,
        // Request payload
        data: JSON.stringify({
          jsonrpc: '2.0',
          id: this.id,
          method: method,
          params: params
        }),
        dataType: 'json',
        // Just in case you are doing cross domain requests
        // NOTE: make sure you are setting CORS headers similarly to
        // --
        // Access-Control-Allow-Origin: http://server1.com, http://server2.com
        // Access-Control-Allow-Credentials: true
        // Access-Control-Allow-Headers: Origin, Content-Type, Accept
        // Access-Control-Request-Method: POST
        // --
        // if you want to allow JSON-RPC calls from server1.com and server2.com
        crossDomain: true,
        xhrFields: {
          withCredentials: true
        }
      })
      // When done, or on failure,
      // call a function that has access to both
      // the request and the response information
      .done(this.makeOnCallDone(method, params, deferred))
      .fail(this.makeOnCallFail(method, params, deferred));
      return deferred.promise();
    },

    makeOnCallDone: function(method, params, deferred) {
      var me = this;

      return function(reply/*, status, xhr*/) {
        if (reply.error) {
          return me.onError(method, params, deferred, reply);
        }
        deferred.resolve(reply.result);
      };
    },

    onNoSession: function() {
      // It is common practice that when missing a session identifier
      // or when the session crashes or it times out due to inactivity
      // the user is taken back to the login page
      _.defer(function() {
        window.location.href = 'login.html';
      });
    },

    onError: function(method, params, deferred, reply) {
      if (reply.error.type === 'session.missing_sessionid' ||
          reply.error.type === 'session.invalid_sessionid') {
        this.onNoSession();
      }

      deferred.reject(reply.error);
    },

    makeOnCallFail: function(method, params, deferred) {
      return function(xhr, status, errorMessage) {
        var error;

        error = $.extend(new Error(errorMessage), {
          type: 'ajax.response.error',
          detail: JSON.stringify({method: method, params: params})
        });

        deferred.reject(error);
      };
    }
  };

  return JsonRpc;
});

// Local Variables:
// mode: js
// js-indent-level: 2
// End:

Example of a Comet Client

In the example above describing a common flow, a reference is made to starting a Comet channel and subscribing to changes on a specific path.

An example implementation of a Comet client, used in the example above:

      /*jshint devel:true*/
// !!!
// The following code is purely for example purposes.
// The code has inline comments for a better understanding.
// Your mileage might vary.
// !!!

define([
  'jquery',
  'lodash',
  './JsonRpc'
], function(
  $,
  _,
  JsonRpc
) {
  'use strict';

  var Comet;

  Comet = function(params) {
    $.extend(this, {
      // API

      // Add a callback for a notification handle
      on: undefined,
      // Remove a specific callback or all callbacks for a notification handle
      off: undefined,
      // Stop all comet notifications
      stop: undefined,

      // API (OPTIONAL)

      // Decide what to do when the comet errors
      onError: undefined,
      // Optionally set a different id for this comet channel
      id: 'main-1.' + String(Math.random()).substring(2),
      // Optionally give an existing JsonRpc client
      jsonRpc: new JsonRpc(),
      // Optionally wait 1 second in between polling the comet channel
      sleep: 1 * 1000,

      // INTERNAL

      handlers: [],
      polling: false,
      poll: undefined,
      onPollDone: undefined,
      onPollFail: undefined
    }, params || {});

    _.bindAll(this, [
      'on',
      'off',
      'stop',
      'onError',
      'poll',
      'onPollDone',
      'onPollFail'
    ]);
  };

  Comet.prototype = {
    on: function(handle, callback) {
      if (!callback) {
        throw new Error('Missing a callback for handle ' + handle);
      }

      // Add a handler made of handle id and a callback function
      this.handlers.push({handle: handle, callback: callback});

      // Start polling
      _.defer(this.poll);
    },

    off: function(handle, callback) {
      if (!handle) {
        throw new Error('Missing a handle');
      }

      // Remove all handlers matching the handle,
      // and optionally also the callback function
      _.remove(this.handlers, {handle: handle, callback: callback});

      // If there are no more handlers matching the handle,
      // then unsubscribe from notifications, in order to releave
      // the server and the network from redundancy
      if (!_.find(this.handlers, {handle: handle}).length) {
        this.jsonRpc.call('unsubscribe', {handle: handle});
      }
    },

    stop: function() {
      var me = this,
          deferred = $.Deferred(),
          deferreds = [];

      if (this.polling) {
        // Unsubcribe from all known notifications, in order to releave
        // the server and the network from redundancy
        _.each(this.handlers, function(handler) {
          deferreds.push(me.jsonRpc('unsubscribe', {
            handle: handler.handle
          }));
        });

        $.when.apply($, deferreds).done(function() {
          deferred.resolve();
        }).fail(function(err) {
          deferred.reject(err);
        }).always(function() {
          me.polling = false;
          me.handlers = [];
        });
      } else {
        deferred.resolve();
      }

      return deferred.promise();
    },

    poll: function() {
      var me = this;

      if (this.polling) {
        return;
      }

      this.polling = true;

      this.jsonRpc.call('comet', {
        comet_id: this.id
      }).done(function(notifications) {
        me.onPollDone(notifications);
      }).fail(function(err) {
        me.onPollFail(err);
      }).always(function() {
        me.polling = false;
      });
    },

    onPollDone: function(notifications) {
      var me = this;

      // Polling has stopped meanwhile
      if (!this.polling) {
        return;
      }

      _.each(notifications, function(notification) {
        var handle = notification.handle,
            message = notification.message,
            handlers = _.where(me.handlers, {handle: handle});

        // If we received a notification that we cannot handle,
        // then unsubcribe from it, in order to releave
        // the server and the network from redundancy
        if (!handlers.length) {
          return this.jsonRpc.call('unsubscribe', {handle: handle});
        }

        _.each(handlers, function(handler) {
          _.defer(function() {handler.callback(message);});
        });
      });

      _.defer(this.poll);
    },

    onPollFail: function(error) {
      switch (error.type) {
        case 'comet.duplicated_channel':
        this.onError(error);
        break;

        default:
        this.onError(error);
        _.wait(this.poll, this.sleep);
      }
    },

    onError: function(reply) {
      var error = reply.error,
          msg = [reply.id, error.code, error.type, error.message].join(' ');

      console.error('Comet error: ' + msg);
    }
  };

  return Comet;
});

// Local Variables:
// mode: js
// js-indent-level: 2
// End:

Single Sign-on (SSO)

The Single Sign-On functionality enables users to log in via HTTP-based northbound APIs with a single sign-on authentication scheme, such as SAMLv2. Currently, it is only supported for the JSON-RPC northbound interface.

{% hint style="info" %} For Single Sign-On to work, the Package Authentication needs to be enabled, see Package Authentication). {% endhint %}

When enabled, the endpoint /sso is made public and handles Single Sign-on attempts.

An example configuration for the cisco-nso-saml2-auth Authentication Package is presented below. Note that /ncs-config/aaa/auth-order does not need to be set for Single Sign-On to work!

{% code title="Example: Example ncs.conf to enable SAMLv2 Single Sign-On" %}

<aaa>
  <package-authentication>
    <enabled>true</enabled>
    <packages>
      <package>cisco-nso-saml2-auth</package>
    </packages>
  </package-authentication>
  <single-sign-on>
    <enabled>true</enabled>
  </single-sign-on>
</aaa>

{% endcode %}

A client attempting single sign-on authentication should request the /sso endpoint and then follow the continued authentication operation from there. For example, for cisco-nso-saml2-auth, the client is redirected to an Identity Provider (IdP), which subsequently handles the authentication, and then redirects the client back to the /sso endpoint to validate the authentication and set up the session.

Web Server

An embedded basic web server can be used to deliver static and Common Gateway Interface (CGI) dynamic content to a web client, such as a web browser. See Web Server for more information.

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