.outbound

Outbound Push: Exchanging data between CHT applications and other tools

Outbound is only available in CHT Core 3.5.0 and above

Outbound push allows configurers to have the creation or editing of CouchDB documents trigger outbound REST requests using the data in that document. For example, upon receiving a referral report you could send that referral to an external facility system that will manage and process that event.

These triggers can apply to all document types (not just common types such as reports or contacts) and as such care should be taken to only send the documents you intend (see configuration of relevant_to below).

Configuration

For outbound pushes to occur, you must enable the mark_for_outbound transition in config:

{
  "transitions": {
    "mark_for_outbound": true
  }
}

The rest of the configuration is against the outbound configuration property, which allows you to configure as many outbound pushes as you like, keyed off a unique name:

{
  "outbound": {
    "first config": {
      "relevant_to": "...",
      "destination": {},
      "mapping": {}
    },
    "second config": { }
  }
}

Each outbound push configuration contains the following properties: relevant_to, destination and mapping.

relevant_to

An “expression” (some JS code that resolves to a truthy or falsy value) that determines whether this configuration is relevant to a document. The document is passed to the expression as doc, and if relevant is fully hydrated before being passed (i.e. the attached contact, its parents etc are fully attached instead of just being stubs).

Example: you want to send a referral to a facility’s EMR system when a CHW refers a patient:

{
  "relevant_to": "doc.type === 'data_record' && doc.form === 'referral'"
}

Note: all documents that Sentinel processes can be picked up by your configuration, so it’s important to correctly configure relevant_to. Checking the document type as shown above is probably a good start.

destination

A complex property that defines the details of the connection to the external service. It currently supports several authentication types: basic authentication, HTTP authorization request header, and a custom authentication mode for Muso SIH.

Basic auth example:

{
  "destination": {
    "base_url": "https://example.com",
    "auth": {
      "type": "basic",
      "username": "admin",
      "password_key": "example.com"
    },
    "path": "/api/v1/referral"
  }
}

Here password_key is a key used to find the password in CouchDB’s node-based configuration. See Credentials section below.

If you don’t provide an authentication parameter then the request will be sent without authentication.

As of 3.9, the header type is also supported, which sends authentication credentials via a HTTP request header: Authorization: '<value>'. The value is set in the CouchDB configuration, and referred to by the value_key, similarly to the password_key. The value must match the credentials needed for the third party tool, and is generally formatted as <type> <credentials>. For instance, to send data to RapidPro, the value in the configuration would be set to the complete RapidPro API Token: eg Token 123456789abcdef.

Header auth example:

{
  "destination": {
    "base_url": "https://example.com",
    "auth": {
      "type": "header",
      "name": "Authorization",
      "value_key": "example.com"
    },
    "path": "/api/v1/referral"
  }
}

mapping

A complex property that declares how the payload to be sent to the destination should be created.

Each key is a string object path to a location in the payload, and each value is either:

a string object path to the location of the source data in the report being processed, where the value is required to exist
an object with either a path property that represents a string object path as above, or an expr property which is an expression similar to relevant_to to determine the resulting value. If you wish for the value to be optional (that is to say it’s OK if path or expr evaluate to undefined) you may also set optional to true

A mapping example

Given the following example (incomplete) report:

{
  "id": "abc-1234",
  "type": "data_record",
  "form": "referral",
  "reported_date": 1555069530966,
  "fields": {
    "patient_id": "12345",
    "patient_temp_deg_F": 100,
    "danger_signs": ["V", "BL", "D", "IG"]
  },
  "contact": {
    "_id": "def-5678",
    "name": "Jane CHW",
    "parent": {
      "_id": "hij-9012",
      "name": "..."
    }
  }
}

The following mapping configuration:

{
  "mapping": {
    "patient_id": "doc.fields.patient_id",
    "chw_id": "doc.contact._id",
    "event.temp_c": {
      "expr": "((doc.fields.patient_temp_deg_F - 32) * (5.0/9.0)).toFixed(2)"
    },
    "event.in_danger": {
      "expr": "doc.fields.danger_signs.length >= 3 ? true : undefined",
      "optional": true
    },
    "event.additional_notes": {
      "path": "doc.fields.notes",
      "optional": true
    }
  }
}

Would create the following JSON payload to send:

{
  "patient_id": "12345",
  "chw_id": "def-5678",
  "event": {
    "temp_c": 37.78,
    "in_danger": true
  }
}

This example makes a few points:

The report that is being used to generate the outbound push is referenced as doc in both path and expr properties
To define a property that is itself an object, you can make the mapping key a JSON path.
If you define a property as optional, it won’t exist at all in the payload if the resulting value is undefined, either because that is the result of executing the expr, or the path doesn’t exist. Note that if the event.in_danger expression was instead doc.fields.danger_signs.length >= 3 the property in_danger would always exist and would either be true or false

Other Notes

Your report will be hydrated before being passed to the mapper. This gives you access to the contact and its parents
object paths that may have undefined properties need to be dealt with differently depending on if you are using a path or an expr. Given doc.foo.bar.smang as a path where any of those properties may not exist in the doc:
If you’re using path just use the path as is, if any part of the path is undefined the resulting value will safely be undefined
However, in expr you do need to handle this situation: doc.foo && doc.foo.bar && doc.foo.bar.smang
If any of your expr expressions throw an exception (for example because you didn’t handle potentially undefined properties as noted above) your push will fail
If any of your path declarations result in an undefined value and you have not also declared that property optional your push will fail

Credentials

To securely store credentials, we’ll be using CouchDB’s config storage, as this is a convenient location that only CouchDB administrators can access.

Passwords are stored under the medic-credentials section, under the key declared in config.

In the following example:

{
  "destination": {
    "base_url": "https://example.com",
    "auth": {
      "type": "basic",
      "username": "admin",
      "password_key": "example.com"
    },
    "path": "/api/v1/referral"
  }
}

We have our key configured to example.com. This means that in CouchDB’s admin config we would expect to find a password at medic-credentials/example.com.

To add the credential to the admin config you need to either PUT the value using curl or similar:

curl -X PUT https://<user>:<pass>@<domain>/_node/couchdb@127.0.0.1/_config/medic-credentials/example.com -d '"the-real-password"'

(Note that couchdb@127.0.0.1 is the local node name, and may be different for you depending on your setup.)

You can also add it via Fauxton:

Navigate to the Config screen
Click Add Option
The Section should be medic-credentials, the Name should be (in this example) example.com and the value should be the password
Click Create
You should then be able to see your credential in the list of configuration shown\

How Outbound messages are sent

Send semantics have changed over the course of developing this feature, and are important to understand for your deployment to be successful.

In 3.10 and above

Outbound messages are sent immediately
If there is an error in sending it will be added to a send queue to be retried every 5 minutes.
When it does finally send it will include any new changes to the document that have occurred in that time.
Documents can be sent again, as long as the resulting payload (as defined in the configuration’s mapping property) is different from the most recent outbound push performed for this document and configuration.

It’s important to understand that if your mapping configuration produces a different result every time it’s run you may experience Outbound sending the “same” data many more times than you’d expect.

For example, if you want a timestamp in your payload you could configure it like this:

{
  "timestamp": {"expr": "new Date()"}
}

Outbound may send your request multiple times even if the user just hit save once. If this is a problem for your deployment, consider using values on the document itself that will not change every time your mapping is executed:

{
  "timestamp": "doc.timestamp"
}

In 3.9

Outbound messages are sent immediately
If there is an error in sending it will be added to a send queue to be retried every 5 minutes.
When it does finally send it will include any new changes to the document that have occurred in that time.
Documents are only ever sent once for configuration

In 3.4-3.8

Outbound messages are added to a send queue that is executed once every 5 minutes or so.
If there is an error in sending it will be kept in the queue to be retried in another 5 minutes.
When it does finally send it will include any new changes to the document that have occurred in that time.
Once the document has successfully sent if the document is changed again it will be sent again, using the same rules as above.

Inbound?

The outbound feature is used for sending data to an external service. If you are looking to receive data from an external service, take a look at the records api.

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Last modified 03.03.2021: Change Medic 3.5 to cht-core 3.5 (5bef6ae)

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