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We have several Kinesis streams set up with event notifications that trigger lambdas.  When the LAMBDA_EXECUTOR is set to 'docker' and we send a large number or records to Kinesis, multiple Lambdas will execute, but currently they are failing to create with error:

```
Exception: Lambda process returned error status code: 1. Output:
time="2019-09-18T17:28:11Z" level=error msg="error getting events from daemon: net/http: request canceled" 
Error response from daemon: driver failed programming external connectivity on endpoint busy_sanderson (a78e45a41d0ce5b0d8bab6ff54344fc34fe2b4969f55bf568e753121abc8759e): Bind for 0.0.0.0:38763 failed: port is already allocated
```

I believe this is due to the new debug_java_port introduced with this PR https://github.com/localstack/localstack/pull/1523

With this change, you are setting the port in the constructor by using a method known to have a race condition (https://github.com/localstack/localstack/blob/master/localstack/utils/common.py#L354)
(https://gist.github.com/gabrielfalcao/20e567e188f588b65ba2)

This should be changed to ensure unique ports are being issued across all lambdas


]}
        self.assertDictEqual(expected_result, result)
    def test_list_non_existant_function_aliases_returns_error(self):
        with self.app.test_request_context():
            result = json.loads(lambda_api.list_aliases(self.FUNCTION_NAME).get_data())
            self.assertEqual(self.RESOURCENOTFOUND_EXCEPTION, result['__type'])
            self.assertEqual(self.RESOURCENOTFOUND_MESSAGE % lambda_api.func_arn(self.FUNCTION_NAME),
                             result['message'])
    def test_get_container_name(self):
        executor = lambda_executors.EXECUTOR_CONTAINERS_REUSE
        name = executor.get_container_name('arn:aws:lambda:us-east-1:00000000:function:my_function_name')
        self.assertEqual(name, 'localstack_lambda_arn_aws_lambda_us-east-1_00000000_function_my_function_name')
    def test_put_concurrency(self):
        with self.app.test_request_context():
            self._create_function(self.FUNCTION_NAME)
            
            
            
            concurrency_data = {'ReservedConcurrentExecutions': 10}
            response = self.client.put('/2017-10-31/functions/{0}/concurrency'.format(self.FUNCTION_NAME),
                                       data=json.dumps(concurrency_data))
            result = json.loads(response.get_data())
            self.assertDictEqual(concurrency_data, result)
    def test_concurrency_get_function(self):
        with self.app.test_request_context():
            self._create_function(self.FUNCTION_NAME)
            
            
            
            concurrency_data = {'ReservedConcurrentExecutions': 10}