Add support for retrying for message delivery errors

examples/kafka-hub/docker-compose.yaml

@@ -35,6 +35,8 @@ services:
             KEYSTORE_PASSWORD: "password"
             # Maximum number of records returned in a single call to consumer-poll
             KAFKA_CONSUMER_MAX_POLL_RECORDS: 50
+            # The HTTP status codes for which the client should retry
+            RETRYABLE_STATUS_CODES: "500,502,503"
         volumes:
             # Kafka client truststore file
             - ./_resources/secrets/kafka-client/kafka-client.trustStore.jks:/home/ballerina/resources/brokercerts/client-truststore.jks

examples/kafka-hub/hub/Config.toml

@@ -36,6 +36,9 @@ MESSAGE_DELIVERY_COUNT = 3
 # The message delivery timeout
 MESSAGE_DELIVERY_TIMEOUT = 10.0
 
+# The HTTP status codes for which the client should retry
+MESSAGE_DELIVERY_RETRYABLE_STATUS_CODES = [500, 502, 503]
+
 # The Oauth2 authorization related configurations
 [kafkaHub.config.OAUTH2_CONFIG]
 issuer = "https://localhost:9443/oauth2/token"

examples/kafka-hub/hub/modules/config/configurations.bal

@@ -64,6 +64,11 @@ public configurable int MESSAGE_DELIVERY_COUNT = 3;
 # The message delivery timeout
 public configurable decimal MESSAGE_DELIVERY_TIMEOUT = 10;
 
+# The HTTP status codes for which the client should retry
+public configurable int[] MESSAGE_DELIVERY_RETRYABLE_STATUS_CODES = [500, 502, 503];
+
+public final readonly & int[] RETRYABLE_STATUS_CODES = check getRetryableStatusCodes(MESSAGE_DELIVERY_RETRYABLE_STATUS_CODES).cloneReadOnly();
+
 # The Oauth2 authorization related configurations
 public configurable types:OAuth2Config OAUTH2_CONFIG = ?;
 
@@ -76,3 +81,11 @@ public final string WEBSUB_EVENTS_CONSUMER_GROUP = os:getEnv("WEBSUB_EVENTS_CONS
 isolated function constructSystemConsumerGroup() returns string {
     return string `websub-events-receiver-${SERVER_IDENTIFIER}-${util:generateRandomString()}`;
 }
+
+isolated function getRetryableStatusCodes(int[] configuredCodes) returns int[]|error {
+    if os:getEnv("RETRYABLE_STATUS_CODES") is "" {
+        return configuredCodes;
+    }
+    string[] statusCodes = re `,`.split(os:getEnv("RETRYABLE_STATUS_CODES"));
+    return statusCodes.'map(i => check int:fromString(i.trim()));
+}

examples/kafka-hub/hub/websub_subscribers.bal

@@ -75,7 +75,8 @@ isolated function pollForNewUpdates(string subscriberId, websubhub:VerifiedSubsc
             interval: config:MESSAGE_DELIVERY_RETRY_INTERVAL,
             count: config:MESSAGE_DELIVERY_COUNT,
             backOffFactor: 2.0,
-            maxWaitInterval: 20
+            maxWaitInterval: 20,
+            statusCodes: config:RETRYABLE_STATUS_CODES
         },
         timeout: config:MESSAGE_DELIVERY_TIMEOUT
     });