when i start kibana by "./kibana", show the exception as below:
{"name":"Kibana","hostname":"meishidev-es-4.office.mos","pid":25210,"level":50,"err":{"message":"unknown error","name":"Error","stack":"Error: unknown error\n at respond (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/src/lib/transport.js:237:15)\n at checkRespForFailure (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/src/lib/transport.js:203:7)\n at HttpConnector. (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/src/lib/connectors/http.js:156:7)\n at IncomingMessage.bound (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/node_modules/lodash-node/modern/internals/baseBind.js:56:17)\n at IncomingMessage.emit (events.js:117:20)\n at _stream_readable.js:944:16\n at process._tickCallback (node.js:442:13)"},"msg":"","time":"2016-01-29T09:37:11.879Z","v":0}
{"name":"Kibana","hostname":"meishidev-es-4.office.mos","pid":25210,"level":60,"err":{"message":"unknown error","name":"Error","stack":"Error: unknown error\n at respond (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/src/lib/transport.js:237:15)\n at checkRespForFailure (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/src/lib/transport.js:203:7)\n at HttpConnector. (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/src/lib/connectors/http.js:156:7)\n at IncomingMessage.bound (/opt/meituan/kibana-4.1.4-linux-x64/src/node_modules/elasticsearch/node_modules/lodash-node/modern/internals/baseBind.js:56:17)\n at IncomingMessage.emit (events.js:117:20)\n at _stream_readable.js:944:16\n at process._tickCallback (node.js:442:13)"},"msg":"","time":"2016-01-29T09:37:11.881Z","v":0}
what's the problem?