HTTP Batching Service

This is a service that batches incoming individual requests before sending them to a backend service for batch processing. The typical usage pattern is to use this service as a reverse proxy.

This service expects the following

• Client to submit POST request with jsonifiable request objects.
• The backend service to expect a list of request objects received from multiple clients.
• The backend service to return a list of jsonifiable response objects. Also the order of this list of response objects must correspond with the order of the request objects.

Example Usage Patterns

Explaining the expected inputs and outputs can best be done using and example.

Suppose you are deploying a service that translates sentences from english to german and requires the following usage pattern:

// Example client request and response

// Request Body
{
    "texts": ["Hello World!", "One two three"]
}

// Response body
{
    "texts": ["Hallo Welt!", "Eins zwei drei"]
}

The service would group multiple request objects into a list and send it to a backend service. It would then expect to receive a corresponding list of response objects from the backend service.

// Example backend request and response

// Request body
[
    {"texts": ["Hello World!", "One two three"]},
    {"texts": ["The quick brown fox jumped over the lazy dog."]}
]

// Response body
[
    {"texts": ["Hallo Welt!", "Eins zwei drei"]},
    {"texts": ["Der schnelle braune Fuchs sprang über den faulen Hund."]}
]

Command Line / Environmental Options

The behavior of the batching service can be defined using command line flags. Alternatively, the BATCHER_CMD_ARGS environmental variable can be used.

• -backend [string] (required)
  The address to the backend batch processing service.

• -bind [string] (default: 0.0.0.0:8000)
  The address to bind this service to.

• -max-batch-size [int] (default: 32)
  The maximum size of each batch.

• -batch-timeout-millis [int] (default: 30)
  The maximum wait time before a batch is sent to backend service.

• -idle-timeout-millis [int] (default: 10000)
  The timeout period for each individual request.

• -max-concurrent-conns [int] (default: 1024)
  The maximum number of clients connected to this service at any given time.

• -version [int] (default: 1024)
  The maximum number of clients connected to this service at any given time.

If the BATCHER_CMD_ARGS environmental variable is set, additional flags will be taken from there. Here's an example of the expected format of BATCHER_CMD_ARGS.

BATCHER_CMD_ARGS='
-backend http://batch-translation-service:5498
-batch-timeout-millis 50
'

Response

Limitations and Caveats

There are a number of things to be mindful of when deploying highly optimized production workflows.

• This service would not rate limit the transactions received or sent to the backend service.
• This service uses JSON payloads which is not optimal for both performance and security.
• This service also does not perform health check on the backend process.