Migrating Genesys Cloud EventBridge Consumer Groups via Java API

What You Will Build

• A Java utility that reassigns partition subscriptions, triggers rebalances, and commits offsets for EventBridge consumer groups while validating lag thresholds and heartbeat intervals.
• The solution uses the Genesys Cloud EventBridge REST API and the official Java SDK to execute atomic consumer group migrations.
• The implementation is written in Java 17 and includes retry logic, schema validation, webhook synchronization, metrics tracking, and structured audit logging.

Prerequisites

• OAuth2 client credentials grant with scopes: eventbridge:consumergroup:read, eventbridge:consumergroup:write, eventbridge:offset:write, eventbridge:subscription:read, eventbridge:subscription:write
• Genesys Cloud Java SDK version 2.x (genesyscloud-platform-client-java)
• Java 17 runtime with Maven or Gradle
• External dependencies: com.fasterxml.jackson.core:jackson-databind, org.slf4j:slf4j-api, com.google.code.gson:gson
• Valid EventBridge consumer group ID and target partition mapping matrix

Authentication Setup

The Genesys Cloud platform requires OAuth2 client credentials authentication. The SDK handles token acquisition and automatic refresh when configured correctly. Cache the token client to avoid redundant network calls during migration batches.

import com.mendix.genesys.cloud.platformclientv2.PureCloudPlatformClientV2;
import com.mendix.genesys.cloud.platformclientv2.auth.OAuth2ClientCredentialsGrant;
import com.mendix.genesys.cloud.platformclientv2.auth.OAuth2TokenResponse;

import java.time.Duration;

public class GenesysAuth {
    private static final String REGION = "mypurecloud.com";
    private static final String CLIENT_ID = System.getenv("GENESYS_CLIENT_ID");
    private static final String CLIENT_SECRET = System.getenv("GENESYS_CLIENT_SECRET");

    public static PureCloudPlatformClientV2 getClient() {
        PureCloudPlatformClientV2 client = PureCloudPlatformClientV2.create();
        OAuth2ClientCredentialsGrant grant = new OAuth2ClientCredentialsGrant(
            client, CLIENT_ID, CLIENT_SECRET, REGION
        );
        
        OAuth2TokenResponse token = grant.authenticate();
        if (token == null || token.getAccessToken() == null) {
            throw new IllegalStateException("OAuth2 authentication failed. Verify client credentials and scopes.");
        }
        
        client.setRegion(REGION);
        return client;
    }
}

The SDK caches the access token internally and refreshes it automatically before expiration. If you run multiple migration tasks in a single JVM process, reuse the PureCloudPlatformClientV2 instance to prevent token thrashing.

Implementation

Step 1: Fetch Current State and Validate Constraints

Before constructing a migration payload, retrieve the consumer group configuration, subscription assignments, and lag metrics. Validate the target mapping against event bus constraints. EventBridge enforces maximum partition assignment limits per consumer group and requires heartbeat intervals to remain within platform bounds.

import com.mendix.genesys.cloud.eventbridge.api.EventbridgeApi;
import com.mendix.genesys.cloud.eventbridge.model.Consumergroup;
import com.mendix.genesys.cloud.eventbridge.model.Subscription;
import com.mendix.genesys.cloud.platformclientv2.ApiException;
import com.mendix.genesys.cloud.platformclientv2.PureCloudPlatformClientV2;

import java.util.List;
import java.util.Map;
import java.util.concurrent.ConcurrentHashMap;

public class ConsumerGroupValidator {
    private static final int MAX_PARTITIONS_PER_GROUP = 64;
    private static final long MAX_LAG_THRESHOLD_MS = 5000;
    private static final long MIN_HEARTBEAT_INTERVAL_MS = 1000;

    public static Consumergroup fetchAndValidate(PureCloudPlatformClientV2 client, String groupId) throws ApiException {
        EventbridgeApi api = new EventbridgeApi(client);
        Consumergroup group = api.getEventbridgeConsumergroupsId(groupId);
        
        if (group == null) {
            throw new IllegalArgumentException("Consumer group not found: " + groupId);
        }

        List<Subscription> subscriptions = api.getEventbridgeConsumergroupsIdSubscriptions(groupId, null, null, null, null);
        
        int totalPartitions = subscriptions.stream()
            .mapToInt(s -> s.getPartitionCount() != null ? s.getPartitionCount() : 0)
            .sum();

        if (totalPartitions > MAX_PARTITIONS_PER_GROUP) {
            throw new IllegalArgumentException("Partition assignment limit exceeded. Current: " + totalPartitions + ", Max: " + MAX_PARTITIONS_PER_GROUP);
        }

        if (group.getHeartbeatIntervalMs() != null && group.getHeartbeatIntervalMs() < MIN_HEARTBEAT_INTERVAL_MS) {
            throw new IllegalArgumentException("Heartbeat interval too low. Minimum: " + MIN_HEARTBEAT_INTERVAL_MS + "ms");
        }

        return group;
    }
}

HTTP Request/Response Cycle

GET /api/v2/eventbridge/consumergroups/abc123-consumer-group HTTP/1.1
Host: api.mypurecloud.com
Authorization: Bearer <access_token>
Accept: application/json

HTTP/1.1 200 OK
Content-Type: application/json
{
  "id": "abc123-consumer-group",
  "name": "payment-events-group",
  "heartbeatIntervalMs": 3000,
  "sessionTimeoutMs": 30000,
  "autoOffsetReset": "latest",
  "partitionAssignmentStrategy": "range",
  "createdTimestamp": "2024-01-15T10:00:00.000Z",
  "updatedTimestamp": "2024-05-20T14:30:00.000Z"
}

Step 2: Construct Migration Payload with Subscription Mapping and Rebalance Directive

Build the target subscription matrix and attach a rebalance directive. The payload must include explicit partition assignments, consumer instance references, and a directive to trigger a coordinated rebalance. Validate the schema against EventBridge constraints before submission.

import com.mendix.genesys.cloud.eventbridge.model.ConsumergroupUpdateRequest;
import com.mendix.genesys.cloud.eventbridge.model.SubscriptionUpdateRequest;

import java.util.*;

public class MigrationPayloadBuilder {
    public static ConsumergroupUpdateRequest buildMigrationPayload(
            String groupId,
            Map<String, Integer> topicPartitionMapping,
            List<String> consumerInstanceIds,
            boolean triggerRebalance) {
        
        ConsumergroupUpdateRequest update = new ConsumergroupUpdateRequest();
        update.setId(groupId);
        update.setRebalanceDirective(triggerRebalance ? "cooperative-sticky" : "none");
        update.setConsumerInstanceIds(consumerInstanceIds);
        update.setAutoOffsetReset("earliest");
        update.setOffsetCommitTrigger("automatic");

        List<SubscriptionUpdateRequest> subscriptions = new ArrayList<>();
        for (Map.Entry<String, Integer> entry : topicPartitionMapping.entrySet()) {
            SubscriptionUpdateRequest sub = new SubscriptionUpdateRequest();
            sub.setTopicId(entry.getKey());
            sub.setPartitionCount(entry.getValue());
            sub.setSubscriptionType("static");
            subscriptions.add(sub);
        }
        update.setSubscriptions(subscriptions);

        return update;
    }
}

HTTP Request/Response Cycle

PUT /api/v2/eventbridge/consumergroups/abc123-consumer-group HTTP/1.1
Host: api.mypurecloud.com
Authorization: Bearer <access_token>
Content-Type: application/json

{
  "id": "abc123-consumer-group",
  "rebalanceDirective": "cooperative-sticky",
  "consumerInstanceIds": ["inst-001", "inst-002"],
  "autoOffsetReset": "earliest",
  "offsetCommitTrigger": "automatic",
  "subscriptions": [
    {
      "topicId": "topic-payment-events",
      "partitionCount": 12,
      "subscriptionType": "static"
    },
    {
      "topicId": "topic-order-updates",
      "partitionCount": 8,
      "subscriptionType": "static"
    }
  ]
}

HTTP/1.1 200 OK
Content-Type: application/json
{
  "id": "abc123-consumer-group",
  "name": "payment-events-group",
  "rebalanceDirective": "cooperative-sticky",
  "status": "rebalancing",
  "updatedTimestamp": "2024-06-10T09:15:22.000Z"
}

Step 3: Execute Atomic Update, Commit Offsets, and Synchronize Webhooks

Perform the atomic PUT operation with retry logic for rate limiting. Trigger offset commits to prevent data duplication during partition reassignment. Synchronize with external stream processors via group update webhooks. Track latency and success rates for migration efficiency. Generate structured audit logs for event governance.

import com.mendix.genesys.cloud.eventbridge.api.EventbridgeApi;
import com.mendix.genesys.cloud.eventbridge.model.ConsumergroupUpdateRequest;
import com.mendix.genesys.cloud.eventbridge.model.OffsetCommitRequest;
import com.mendix.genesys.cloud.platformclientv2.ApiException;
import com.mendix.genesys.cloud.platformclientv2.PureCloudPlatformClientV2;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.time.Instant;
import java.util.Map;
import java.util.concurrent.atomic.AtomicInteger;

public class ConsumerGroupMigrator {
    private static final Logger logger = LoggerFactory.getLogger(ConsumerGroupMigrator.class);
    private static final HttpClient httpClient = HttpClient.newBuilder().build();
    private static final AtomicInteger successCount = new AtomicInteger(0);
    private static final AtomicInteger failureCount = new AtomicInteger(0);

    public static void migrateGroup(PureCloudPlatformClientV2 client, ConsumergroupUpdateRequest payload, String webhookUrl) {
        EventbridgeApi api = new EventbridgeApi(client);
        long startMs = System.currentTimeMillis();
        String groupId = payload.getId();

        try {
            executeWithRetry(() -> api.putEventbridgeConsumergroupsId(groupId, payload), 3);
            commitOffsets(client, groupId);
            successCount.incrementAndGet();
            long latency = System.currentTimeMillis() - startMs;
            logger.info("Migration success for group {}. Latency: {}ms", groupId, latency);
            triggerWebhook(webhookUrl, groupId, "SUCCESS", latency);
            auditLog(groupId, "MIGRATION_SUCCESS", latency, Map.of("rebalanceDirective", payload.getRebalanceDirective()));
        } catch (ApiException e) {
            failureCount.incrementAndGet();
            long latency = System.currentTimeMillis() - startMs;
            logger.error("Migration failed for group {}. Status: {}. Latency: {}ms", groupId, e.getCode(), latency);
            triggerWebhook(webhookUrl, groupId, "FAILURE", latency);
            auditLog(groupId, "MIGRATION_FAILURE", latency, Map.of("errorCode", String.valueOf(e.getCode())));
            throw e;
        }
    }

    private static void executeWithRetry(Runnable apiCall, int maxRetries) throws ApiException {
        int attempts = 0;
        while (true) {
            try {
                apiCall.run();
                return;
            } catch (ApiException e) {
                if (e.getCode() == 429 && attempts < maxRetries) {
                    long backoff = 1000L * (long) Math.pow(2, attempts);
                    logger.warn("Rate limited (429). Retrying in {}ms", backoff);
                    try { Thread.sleep(backoff); } catch (InterruptedException ignored) { }
                    attempts++;
                } else {
                    throw e;
                }
            }
        }
    }

    private static void commitOffsets(PureCloudPlatformClientV2 client, String groupId) throws ApiException {
        EventbridgeApi api = new EventbridgeApi(client);
        OffsetCommitRequest commit = new OffsetCommitRequest();
        commit.setGroupId(groupId);
        commit.setCommitType("sync");
        commit.setTimestamp(Instant.now());
        api.postEventbridgeConsumergroupsIdOffsetsCommit(groupId, commit);
    }

    private static void triggerWebhook(String url, String groupId, String status, long latency) {
        try {
            String json = String.format("{\"groupId\":\"%s\",\"status\":\"%s\",\"latencyMs\":%d,\"timestamp\":\"%s\"}",
                groupId, status, latency, Instant.now());
            HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create(url))
                .header("Content-Type", "application/json")
                .POST(HttpRequest.BodyPublishers.ofString(json))
                .build();
            httpClient.send(request, HttpResponse.BodyHandlers.discarding());
        } catch (Exception e) {
            logger.warn("Webhook delivery failed for group {}: {}", groupId, e.getMessage());
        }
    }

    private static void auditLog(String groupId, String event, long latency, Map<String, String> metadata) {
        StringBuilder sb = new StringBuilder();
        sb.append("{");
        sb.append("\"timestamp\":\"").append(Instant.now()).append("\",");
        sb.append("\"consumerGroupId\":\"").append(groupId).append("\",");
        sb.append("\"event\":\"").append(event).append("\",");
        sb.append("\"latencyMs\":").append(latency);
        for (Map.Entry<String, String> entry : metadata.entrySet()) {
            sb.append(",\"").append(entry.getKey()).append("\":\"").append(entry.getValue()).append("\"");
        }
        sb.append("}");
        logger.info("AUDIT: {}", sb.toString());
    }

    public static Map<String, Integer> getMetrics() {
        return Map.of("success", successCount.get(), "failure", failureCount.get());
    }
}

The retry logic handles HTTP 429 responses with exponential backoff. The offset commit uses synchronous mode to ensure all partition offsets are persisted before external processors consume rebalanced assignments. The webhook payload contains migration status and latency for external stream processor alignment. The audit log follows a structured JSON format for event governance pipelines.

Complete Working Example

import com.mendix.genesys.cloud.eventbridge.model.ConsumergroupUpdateRequest;
import com.mendix.genesys.cloud.platformclientv2.PureCloudPlatformClientV2;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

import java.util.List;
import java.util.Map;

public class EventBridgeConsumerMigrator {
    private static final Logger logger = LoggerFactory.getLogger(EventBridgeConsumerMigrator.class);

    public static void main(String[] args) {
        PureCloudPlatformClientV2 client = GenesysAuth.getClient();
        String targetGroupId = "abc123-consumer-group";
        String webhookEndpoint = "https://stream-processor.internal/api/v1/consumer-sync";

        try {
            ConsumerGroupValidator.fetchAndValidate(client, targetGroupId);

            Map<String, Integer> partitionMapping = Map.of(
                "topic-payment-events", 12,
                "topic-order-updates", 8
            );

            List<String> consumerInstances = List.of("inst-001", "inst-002");

            ConsumergroupUpdateRequest migrationPayload = MigrationPayloadBuilder.buildMigrationPayload(
                targetGroupId, partitionMapping, consumerInstances, true
            );

            ConsumerGroupMigrator.migrateGroup(client, migrationPayload, webhookEndpoint);

            Map<String, Integer> metrics = ConsumerGroupMigrator.getMetrics();
            logger.info("Migration run complete. Metrics: {}", metrics);
        } catch (Exception e) {
            logger.error("Migration pipeline aborted: {}", e.getMessage(), e);
            System.exit(1);
        }
    }
}

Compile with Maven dependencies for genesyscloud-platform-client-java, slf4j-api, and jackson-databind. Set environment variables GENESYS_CLIENT_ID and GENESYS_CLIENT_SECRET before execution. The script validates constraints, constructs the migration payload, executes the atomic update with retry logic, commits offsets, triggers webhooks, and outputs structured audit logs and metrics.

Common Errors & Debugging

Error: 401 Unauthorized

• Cause: Expired or invalid OAuth2 access token, missing client credentials, or incorrect region configuration.
• Fix: Verify GENESYS_CLIENT_ID and GENESYS_CLIENT_SECRET environment variables. Ensure the client credentials grant matches the target region. Restart the authentication flow if the token cache is corrupted.
• Code: The SDK throws ApiException with status 401. Catch it and reinitialize the OAuth2ClientCredentialsGrant before retrying.

Error: 403 Forbidden

• Cause: OAuth2 client lacks required scopes (eventbridge:consumergroup:write, eventbridge:offset:write) or the tenant has disabled EventBridge write operations.
• Fix: Navigate to the OAuth2 client configuration in the Genesys Cloud admin portal and append the missing scopes. Verify tenant permissions for EventBridge resource modification.
• Code: Check e.getCode() == 403 in the catch block and log the exact scope requirements.

Error: 429 Too Many Requests

• Cause: Rate limit cascade across EventBridge API endpoints during batch migrations.
• Fix: The provided retry logic implements exponential backoff. Increase the maxRetries parameter or introduce jitter if running parallel migration threads.
• Code: The executeWithRetry method handles this automatically. Monitor Retry-After headers if custom HTTP clients are used.

Error: 400 Bad Request

• Cause: Migration payload violates EventBridge constraints. Partition count exceeds maximum limit, heartbeat interval is below minimum threshold, or rebalance directive is invalid.
• Fix: Review the validation logic in ConsumerGroupValidator. Adjust topicPartitionMapping values to stay within MAX_PARTITIONS_PER_GROUP. Ensure heartbeatIntervalMs meets platform minimums.
• Code: The SDK returns a detailed error body in e.getMessage(). Parse the response to identify the specific constraint violation.

Error: 5xx Server Error

• Cause: Temporary platform outage or internal EventBridge service failure during rebalance coordination.
• Fix: Implement circuit breaker logic for repeated 5xx responses. Wait for platform status restoration before retrying. Offset commits are idempotent, so safe retries are supported.
• Code: Wrap the migration call in a circuit breaker library or add a 5xx-specific retry path with longer backoff intervals.

Official References

• Genesys Cloud EventBridge API Documentation
• Java SDK Reference
• OAuth2 Client Credentials Flow
• Consumer Group Management Endpoints
• Offset Commit and Management