Hyperledger composer calling external REST API

I am a developer with hyperledger composer. I try to use Calling an HTTP or REST API from Transaction Processor Functions with method POST and request body but I have error status code 500. I want to use method POST with request body to my server.

My code:

async function testStocks(transaction) {

    const participant = getCurrentParticipant();
    const json = '{"name:tester"}';//my request body

    await request.post({ uri: 'http://www...', json });

    // Update the current participant in the participant registry.
    const participantRegistry = await getParticipantRegistry('org.example.Trader');
    await participantRegistry.update(participant);

}

My error:

{
  "error": {
    "statusCode": 500,
    "name": "Error",
    "message": "Error trying invoke business network. Error: No valid responses from any peers.\nResponse from attempted peer comms was an error: Error: 2 UNKNOWN: error executing chaincode: transaction returned with failure: StatusCodeError: 400 - undefined",
    "stack": "Error: Error trying invoke business network. Error: No valid responses from any peers.\nResponse from attempted peer comms was an error: Error: 2 UNKNOWN: error executing chaincode: transaction returned with failure: StatusCodeError: 400 - undefined\n    at _initializeChannel.then.then.then.then.catch (/home/pc/.nvm/versions/node/v8.10.0/lib/node_modules/composer-rest-server/node_modules/composer-connector-hlfv1/lib/hlfconnection.js:965:34)\n    at <anonymous>"
  }
}