Entry Points

There are many entry points for Ions.

This section covers:

Invoke a Lambda

Lambda entry points can be invoked from the AWS CLI. First, call get-schema. In the command below, replace $(GROUP) with the name of your compute group:

aws lambda invoke --function-name $(GROUP)-get-schema --payload '' /dev/stdout

This may return pending while AWS creates or configures external resources.

On success, this call will print your lambda's response, plus some AWS CLI status information:

(#:db{:id 39,
      :ident :fressian/tag,
      :valueType :db.type/keyword,
      :cardinality :db.cardinality/one,
      "Keyword-valued attribute of a value type that specifies the underlying fressian type used for serialization."}
 ;; more schema elided
 #:db{:id 80,
      :ident :inv/count,
      :valueType :db.type/long,
      :cardinality :db.cardinality/one})
    "StatusCode": 200,
    "ExecutedVersion": "$LATEST"

On your first invocation, this call may take a while due to Lambda cold start. Outside of dev, most lambda invocations are warm, so try calling the function a second time to see typical production performance.

To see a function that takes an argument, try get-items-by-type.

If aws --version returns version 2, then add the flag --cli-binary-format raw-in-base64-out to the command:

aws lambda invoke --function-name $(GROUP)-get-items-by-type --payload '"shirt"' /dev/stdout

On success, this will return details about shirts:

[[#:inv{:sku "SKU-28", :size :xlarge, :color :green}]
 ;; more shirt details
 [#:inv{:sku "SKU-56", :size :large, :color :yellow}]]
    "StatusCode": 200,
    "ExecutedVersion": "$LATEST"

Add an Attribute Predicate

You can use ions to deploy functions for use as attribute predicates, entity predicates, transaction functions, or query functions.

When you deployed the tutorial application, your ion-config.edn file allowed a valid-sku? function suitable for an attribute predicate.

(defn valid-sku?
  (boolean (re-matches #"SKU-(\d+)" s)))

You can now test this function at the REPL:

(load-file "siderail/user.repl")

;; try the fn at the REPL
(attrs/valid-sku? "SKU-112")
=> true
(attrs/valid-sku? "SKU-1B")
=> false

Then you can install valid-sku as a predicate for :inv/sku:

(def conn (starter/get-connection))

(def tx [{:db/ident :inv/sku
          :db.attr/preds 'datomic.ion.starter.attributes/valid-sku?}])
(d/transact conn {:tx-data tx})

After you install the function, you can use a with-db to prove that the predicate is in effect:

(def with-db (d/with-db conn))
(d/with with-db {:tx-data [{:db/id "should-not-work"
                            :inv/sku "not-a-sku"}]})
=> Entity -9223301668109598141 attribute :inv/sku value not-a-sku failed pred datomic.ion.starter.attributes/valid-sku?

HTTP Direct

Invoking an Ion via HTTP Direct is a simple http request.

Find your IonApiGatewayEndpoint in your compute group's CloudFormation template outputs.

Since HTTP Direct is a simple http request, it can be invoked from any platform that supports such requests. Try entering your IonApiGatewayEndpoint and data of :hat below.

HTTP Direct Results displayed here

On success, this will return an EDN representation of inventory data for a particular type.

The above XHR request would normally require that CORS for your API Gateway is setup with an allowed Origin of "https://docs.datomic.com".

The demo above sends the request to an Ion we've setup with the appropriate CORS headers. This intermediate Ion makes the request to your supplied endpoint and returns the result.

If your API Gateway was setup with the appropriate CORS response then you could make the request directly to your IonApiGatewayEndpoint endpoint.

This is equivalent to invoking your Ion through HTTP Direct with curl:

curl https://$(IonApiGatewayEndpoint) -d :hat
#{{:color :red, :type :hat, :size :medium, :sku "SKU-7"}
  {:color :blue, :type :hat, :size :small, :sku "SKU-35"}}

Now delete your system and conclude this tutorial.