portainer/app/docker/components/dashboard-cluster-agent-info/dashboardClusterAgentInfoController.js

angular.module('portainer.docker')
.controller('DashboardClusterAgentInfoController', ['AgentService', 'Notifications',
function (AgentService, Notifications) {
  var ctrl = this;

  this.$onInit = function() {
    AgentService.agents()
    .then(function success(data) {
      ctrl.agentCount = data.length;
    })
    .catch(function error(err) {
      Notifications.error('Failure', err, 'Unable to retrieve agent information');
    });
  };

}]);