functions-host-json-queues.md

{
    "queues": {
      "maxPollingInterval": 2000,
      "visibilityTimeout" : "00:00:30",
      "batchSize": 16,
      "maxDequeueCount": 5,
      "newBatchThreshold": 8
    }
}

Property	Default	Description
maxPollingInterval	60000	The maximum interval in milliseconds between queue polls.
visibilityTimeout	0	The time interval between retries when processing of a message fails.
batchSize	16	The number of queue messages that the Functions runtime retrieves simultaneously and processes in parallel. When the number being processed gets down to the newBatchThreshold, the runtime gets another batch and starts processing those messages. So the maximum number of concurrent messages being processed per function is batchSize plus newBatchThreshold. This limit applies separately to each queue-triggered function. If you want to avoid parallel execution for messages received on one queue, you can set batchSize to 1. However, this setting eliminates concurrency only so long as your function app runs on a single virtual machine (VM). If the function app scales out to multiple VMs, each VM could run one instance of each queue-triggered function. The maximum batchSize is 32.
maxDequeueCount	5	The number of times to try processing a message before moving it to the poison queue.
newBatchThreshold	batchSize/2	Whenever the number of messages being processed concurrently gets down to this number, the runtime retrieves another batch.