Add broadcast state case

README.md

@@ -217,3 +217,42 @@ The processed events are sent back to a Kafka topic (*SINK_TOPIC*), consumed by
   LOCATION "/processed_events"
 ```
   where *LOCATION* path is the HDFS location where processed events are stored.
+
+  ## Fifth one (Flink broadcast state)
+
+  There is IoT device sending messages to Kafka in Avro type with the value of some metric that has to be within some limits:
+
+  ```avro
+  {
+    "namespace": "net.zylklab.flink.sandbox.broadcaststate.pojo",
+	"type": "record",
+	"name": "Event",
+	"fields": 
+	[
+		{"name": "var_id",			"type": ["null","string"],	"default": null},
+		{"name": "var_name",			"type": ["null","string"],		"default": null},
+		{"name": "value",			"type": ["null","double"],	"default": null},
+		{"name": "ts",		"type": ["null","long"],	"default": null}
+	]
+}
+```
+
+These value's max and min limit could change over time so there is another Kafka topic where limit changes are published also in Avro type:
+
+```avro
+{
+    "namespace": "net.zylklab.flink.sandbox.broadcaststate.pojo",
+	"type": "record",
+	"name": "Limit",
+	"fields": 
+	[
+		{"name": "var_id",			"type": ["null","string"],	"default": null},
+		{"name": "var_name",			"type": ["null","string"],		"default": null},
+		{"name": "max_limit",			"type": ["null","double"],	"default": null},
+		{"name": "min_limit",			"type": ["null","double"],	"default": null}
+	]
+}
+```
+
+The Flink job consumes from both topics and process events comparing its values with its limits. When a new limit is published to Kafka, the job updates the limit without the need of restarting the job.
+