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78 lines
2.0 KiB
Markdown
78 lines
2.0 KiB
Markdown
# Guide on Asynchronous processing
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By default functions are accessed synchronously via the following route:
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```
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$ curl --data "message" http://gateway/function/{function_name}
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```
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As of [PR #131](https://github.com/alexellis/faas/pull/131) asynchronous invocation is available for testing.
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*Logical flow for synchronous functions:*
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## Why use Asynchronous processing?
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* Enable longer time-outs
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* Process work whenever resources are available rather than immediately
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* Consume a large batch of work within a few seconds and let it process at its own pace
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## How does async work?
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Here is a conceptual diagram
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* [queue-worker](https://github.com/open-faas/nats-queue-worker)
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## Deploy the async stack
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The reference implementation for asychronous processing uses NATS Streaming, but you are free to extend OpenFaaS and write your own [queue-worker](https://github.com/open-faas/nats-queue-worker).
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Swarm:
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```
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$ ./deploy_extended.sh
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```
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K8s:
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```
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$ kubectl -f delete ./faas.yml
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$ kubectl -f apply ./faas.async.yml,nats.yml
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```
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## Call a function
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Functions do not need to be modified to work asynchronously, just use this alternate route:
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```
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$ http://gateway/async-function/{function_name}
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```
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If you want the function to call another function or a different endpoint when it is finished then pass the `X-Callback-Url` header. This is optional.
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```
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$ curl http://gateway/async-function/{function_name} --data-binary @sample.json -H "X-Callback-Url: http://gateway/function/send2slack"
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```
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## Extend function timeouts
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Functions have three timeouts configurable by environmental variables expressed in seconds:
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HTTP:
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* read_timeout
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* write_timeout
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Hard timeout:
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* exec_timeout
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To make use of these just add them to your Dockerfile when needed as ENV variables.
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> [Function watchdog reference](https://github.com/alexellis/faas/tree/master/watchdog)
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