Enable topic based subscription for Observation

zenproject/zen-package.edn

@@ -1 +1,3 @@
-{:deps {}}
+{:deps
+ {fhir.topic-based-subscription
+  "https://github.com/zen-fhir/hl7-fhir-uv-subscriptions-backport-r4b.git"}}

zenproject/zrc/system.edn

@@ -1,6 +1,71 @@
 {ns system
- import #{aidbox}
+ import #{aidbox
+          fhir.topic-based-subscription
+          hl7-fhir-uv-subscriptions-backport-r4b}
+
+ observation-topic
+ {:zen/tags #{fhir.topic-based-subscription/topic-definition}
+  ;; SubscriptionTopic url should be an absolute URI (globally unique)
+  :url "urn:aidbox-python-sdk:SubscriptionTopic:observations"
+  :resourceTrigger [
+                    ;; an SubscriptionTopic may consist 
+                    ;; of any number of resources
+                    {:resource "Observation"
+                     :fhirPathCriteria "%current.value.ofType(Quantity).value > 10"}]
+  :canFilterBy [{:resource        "Observation"
+                 :filterParameter "value"
+                 ;; _fhirPath specifies how to calculate value for the filter
+                 :_fhirPath       "%current.value.ofType(Quantity).value"
+                 :modifier        ["eq" "gt" "lt" "ge" "le"]}
+
+                {:resource        "Observation"
+                 :filterParameter "value-increase"
+                 ;; both %current and %previous state of the 
+                 ;; resource are available
+                 :_fhirPath       "%current.value.ofType(Quantity).value > %previous.value.ofType(Quantity).value"
+                 :modifier        ["eq"]}]}
+
+
+ postgres-observation-topic-storage
+ {:zen/tags #{fhir.topic-based-subscription/topic-storage}
+  ;; At the moment only PostgreSQL is available as a storage
+  :storage-type fhir.topic-based-subscription/postgres
+  ;; The name of the table which will be created to store topic events:
+  :table-name "observation_topic"
+  ;; Possible value for maxContent are: "empty" | "id-only" | "full-resource"
+  ;; The actual Resource is only stored in queue when "full-resource" value 
+  ;; are specified. When deciding which payload type to request, 
+  ;; systems SHOULD consider both ease of processing and security of PHI. 
+  ;; To mitigate the risk of information leakage, systems SHOULD use the 
+  ;; minimum level of detail consistent with the use case. 
+  ;; In practice, id-only provides a good balance between security 
+  ;; and performance for many real-world scenarios.
+  :maxContent "full-resource"
+  ;; The period, in seconds, during which events from the replication slot 
+  ;; will be buffered before being written to storage:
+  :timeout  10
+  ;; The maximum number of events the replication slot will buffer before
+  ;; writing to storage:
+  :maxCount 100
+  ;; Interval in seconds periodic heartbeat record generation 
+  ;; in cdc_topic_heartbeat_table, to reclaim the WAL space:
+  :heartbeat-rate 120
+  ;; The number of workers responsible for notification delivery. 
+  ;; min number 4 is advised. One worker can handle up to 1024 subsrciptions:
+  :senders-number 4}
+
+
+ ;; Service which binds storage with topic definition
+ observation-topic-srv
+ {:zen/tags #{aidbox/service}
+  :engine fhir.topic-based-subscription/change-data-capture-service-engine
+  :topic-definition observation-topic
+  :topic-storage postgres-observation-topic-storage}
+
+
+ ;; Entrypoint for the instance with corresponding service
 
  box
  {:zen/tags #{aidbox/system}
+  :services {:observation-topic-srv observation-topic-srv}
   :zen/desc "Test python sdk"}}