This cookbook demonstrates how to enrich a stream of JSON documents with HTTP services. This method also works with AWS Lambda functions, subprocesses, etc.
We will start off by configuring a single enrichment, then we will move onto a workflow of enrichments with a network of dependencies.
Each enrichment will be performed in parallel across a pre-batched stream of documents. Workflow enrichments that do not depend on each other will also be performed in parallel, making this orchestration method very efficient.
The imaginary problem we are going to solve is applying a set of NLP based enrichments to a feed of articles in order to detect fake news. We will be consuming and writing to Kafka, but the example works with any input and output combination.
Articles are received over the topic
articles and look like this:
To start us off we will configure a single enrichment, which is an imaginary 'claims detector' service. This is an HTTP service that wraps a trained machine learning model to extract claims that are made within a body of text.
The service expects a
POST request with JSON payload of the form:
And returns a JSON payload of the form:
Since each request only applies to a single document we will make this enrichment scale by deploying multiple HTTP services and hitting those instances in parallel across our document batches.
We configure the
http processor to send a batch of documents out
in parallel, but if we were instead using the
subprocess processors to hit an enrichment we could wrap them
parallel processor for the same result.
With this pipeline our documents will come out looking something like this:
Extracting the claims of an article isn't enough for us to detect fake news, for that we need to add two more enrichments.
Next up is a 'hyperbole detector' that takes a
POST request containing the
article contents and returns a hyperbole score between 0 and 1. This time the
format is array-based and therefore supports calculating multiple documents
in a single request, making better use of the host machines GPU.
A request should take the following form:
And the response looks like this:
In order to create a single request from a batch of documents, and subsequently
map the result back into our batch, we will use the
unarchive processors in our
process_map flow, like this:
The purpose of the
archive processor is to take a batch of
JSON documents and place them into a single document as an array. Subsequently,
we then send one single request for each batch.
After the request is made we do the opposite with the
unarchive processor in
order to convert it back into a batch of the original size.
Fake News Detector
Finally, we are going to use a 'fake news detector' that takes the article contents as well as the output of the previous two enrichments and calculates a fake news rank between 0 and 1.
This service behaves similarly to the claims detector service and takes a document of the form:
And returns an object of the form:
We then wish to map the field
fake_news_rank from that result into the
original document at the path
process_map block for this enrichment would look like this:
Note that in our
premap we are targeting fields that are populated from the
previous two enrichments.
If we were to execute all three enrichments in order we'll end up with a document looking like this:
Since the contents of
tmp won't be required downstream we can remove it after
our enrichments with a
Combining into a Workflow
Since the dependency graph of our enrichments is simple it would be sufficient to simply configure these three enrichments sequentially such that the 'fake news detector' is run last.
However, if we configure our enrichments within a
processor we can use Benthos to automatically detect our dependency graph,
giving us two key benefits:
- Enrichments at the same level of a dependency graph (claims and hyperbole) will be executed in parallel.
- When introducing more enrichments to our pipeline the added complexity of resolving the dependency graph is handled automatically by Benthos.
You can read more about workflows and the advantages of this method in this article.
process_dag processor for our enrichments makes our
final pipeline configuration look like this:
catch processor was added at the end of the pipeline which
catches documents that failed enrichment. You can replace the log event with a
wide range of recovery actions such as sending to a dead-letter/retry queue,
dropping the message entirely, etc. You can read more about error handling
in this article.