Hot-Swapping Cognigy.AI Model Versions via REST API with Java
What You Will Build
- The code executes a zero-downtime model version swap by constructing a validated traffic directive payload, verifying schema compatibility against runtime engine constraints, and executing an atomic PATCH cutover operation.
- This uses the Cognigy.AI REST API v2 model management, deployment routing, and audit endpoints.
- The implementation is written in Java 17 using the standard
java.net.httpclient with built-in retry logic, latency tracking, and webhook synchronization.
Prerequisites
- OAuth client type: Confidential client registered in Cognigy.AI with
model:read,model:write,deployment:write,routing:read,audit:writescopes. - API version: Cognigy.AI REST API v2.
- Language/runtime: Java 17 or higher.
- External dependencies: None. The tutorial uses only JDK standard libraries (
java.net.http,java.time,java.util,java.util.logging).
Authentication Setup
Cognigy.AI uses standard OAuth 2.0 client credentials flow. You must cache the access token and refresh it before expiration to avoid 401 interruptions during swap operations.
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;
public class CognigyAuth {
private final HttpClient httpClient;
private final String clientId;
private final String clientSecret;
private final String tokenEndpoint;
private String cachedToken;
private Instant tokenExpiry;
public CognigyAuth(String clientId, String clientSecret, String baseUrl) {
this.httpClient = HttpClient.newHttpClient();
this.clientId = clientId;
this.clientSecret = clientSecret;
this.tokenEndpoint = baseUrl + "/oauth/token";
this.tokenExpiry = Instant.now().minusSeconds(1);
}
public String getAccessToken() throws Exception {
if (cachedToken != null && Instant.now().isBefore(tokenExpiry)) {
return cachedToken;
}
String body = "grant_type=client_credentials&client_id=" + clientId + "&client_secret=" + clientSecret;
HttpRequest request = HttpRequest.newBuilder()
.uri(URI.create(tokenEndpoint))
.header("Content-Type", "application/x-www-form-urlencoded")
.POST(HttpRequest.BodyPublishers.ofString(body))
.build();
HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
if (response.statusCode() != 200) {
throw new RuntimeException("OAuth token request failed with status " + response.statusCode() + ": " + response.body());
}
Map<String, Object> tokenMap = parseSimpleJson(response.body());
this.cachedToken = (String) tokenMap.get("access_token");
long expiresIn = ((Number) tokenMap.get("expires_in")).longValue();
this.tokenExpiry = Instant.now().plusSeconds(expiresIn - 30); // 30s buffer
return cachedToken;
}
// Minimal JSON parser for token response to avoid external dependencies
private static Map<String, Object> parseSimpleJson(String json) {
// In production, use Jackson/Gson. This is a simplified extractor for tutorial clarity.
return Map.of(
"access_token", extractJsonValue(json, "access_token"),
"expires_in", extractJsonLong(json, "expires_in")
);
}
private static String extractJsonValue(String json, String key) {
int start = json.indexOf("\"" + key + "\":\"") + key.length() + 3;
int end = json.indexOf("\"", start);
return json.substring(start, end);
}
private static long extractJsonLong(String json, String key) {
int start = json.indexOf("\"" + key + "\":") + key.length() + 2;
int end = start;
while (end < json.length() && Character.isDigit(json.charAt(end))) end++;
return Long.parseLong(json.substring(start, end));
}
}
Required OAuth Scopes for Authentication: model:read, model:write, deployment:write, routing:read, audit:write
Implementation
Step 1: Construct Swap Payload and Validate Runtime Constraints
Before initiating a swap, you must verify that the target model version exists, that the deployment has not exceeded the maximum concurrent version limit, and that the schema is compatible with the runtime engine. Cognigy.AI enforces a default limit of five active versions per deployment.
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.util.List;
import java.util.Map;
import java.util.logging.Logger;
import java.util.logging.Level;
public class CognigyModelValidator {
private static final Logger logger = Logger.getLogger(CognigyModelValidator.class.getName());
private final HttpClient httpClient;
private final String baseUrl;
private final CognigyAuth auth;
public CognigyModelValidator(HttpClient httpClient, String baseUrl, CognigyAuth auth) {
this.httpClient = httpClient;
this.baseUrl = baseUrl;
this.auth = auth;
}
public Map<String, Object> validateSwap(String modelId, String targetVersion, String deploymentId) throws Exception {
String token = auth.getAccessToken();
// Fetch active versions to enforce max version count limit
String versionsUrl = baseUrl + "/api/v2/models/" + modelId + "/versions?status=active";
HttpRequest versionsReq = HttpRequest.newBuilder()
.uri(URI.create(versionsUrl))
.header("Authorization", "Bearer " + token)
.header("Accept", "application/json")
.GET()
.build();
HttpResponse<String> versionsResp = httpClient.send(versionsReq, HttpResponse.BodyHandlers.ofString());
if (versionsResp.statusCode() == 429) {
throw new RuntimeException("Rate limited on version fetch. Implement exponential backoff.");
}
if (versionsResp.statusCode() != 200) {
throw new RuntimeException("Version fetch failed: " + versionsResp.statusCode());
}
int activeCount = parseActiveVersionCount(versionsResp.body());
if (activeCount >= 5) {
throw new IllegalStateException("Maximum version count limit (5) reached. Cannot hot-swap until older versions are pruned.");
}
// Validate schema compatibility against runtime engine
String schemaUrl = baseUrl + "/api/v2/models/" + modelId + "/versions/" + targetVersion + "/schema/validate";
HttpRequest schemaReq = HttpRequest.newBuilder()
.uri(URI.create(schemaUrl))
.header("Authorization", "Bearer " + token)
.header("Content-Type", "application/json")
.POST(HttpRequest.BodyPublishers.ofString("{\"runtimeEngine\": \"cognigy-runtime-v2\", \"strictMode\": true}"))
.build();
HttpResponse<String> schemaResp = httpClient.send(schemaReq, HttpResponse.BodyHandlers.ofString());
if (schemaResp.statusCode() != 200) {
throw new RuntimeException("Schema validation failed for version " + targetVersion + ": " + schemaResp.body());
}
// Construct atomic swap payload with traffic directive and canary routing
String swapPayload = """
{
"modelId": "%s",
"targetVersion": "%s",
"deploymentId": "%s",
"trafficDirective": {
"type": "canary",
"initialWeight": 0.1,
"rampUpIntervalSeconds": 60,
"maxWeight": 1.0
},
"fallbackModelId": "%s",
"validateBeforeCutover": true,
"auditMetadata": {
"initiatedBy": "automated-pipeline",
"pipelineRunId": "run-%d"
}
}
""".formatted(modelId, targetVersion, deploymentId, modelId + "_v1.0.0", System.currentTimeMillis());
return Map.of(
"payload", swapPayload,
"activeVersionCount", activeCount,
"schemaValid", true
);
}
private static int parseActiveVersionCount(String json) {
// Simplified parser for tutorial. Extracts "count" or array length.
int countIdx = json.indexOf("\"count\":");
if (countIdx != -1) {
int start = countIdx + 7;
int end = start;
while (end < json.length() && Character.isDigit(json.charAt(end))) end++;
return Integer.parseInt(json.substring(start, end));
}
return 0;
}
}
Required OAuth Scopes: model:read, routing:read
Expected Response for Schema Validation:
{
"valid": true,
"compatible": true,
"warnings": [],
"engineConstraints": {
"maxConcurrentVersions": 5,
"supportedFormats": ["cognigy-json", "openapi-3.0"]
}
}
Step 2: Execute Atomic PATCH Operation with Retry and Latency Tracking
The cutover operation uses an atomic PATCH request. You must implement retry logic for 429 responses and track latency to measure swap efficiency. The request triggers automatic canary routing based on the traffic directive.
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.util.concurrent.TimeUnit;
import java.util.logging.Logger;
public class CognigyModelSwapper {
private static final Logger logger = Logger.getLogger(CognigyModelSwapper.class.getName());
private final HttpClient httpClient;
private final String baseUrl;
private final CognigyAuth auth;
public CognigyModelSwapper(HttpClient httpClient, String baseUrl, CognigyAuth auth) {
this.httpClient = httpClient;
this.baseUrl = baseUrl;
this.auth = auth;
}
public Map<String, Object> executeCutover(String deploymentId, String payload) throws Exception {
String token = auth.getAccessToken();
String cutoverUrl = baseUrl + "/api/v2/deployments/" + deploymentId + "/cutover";
long startNanos = System.nanoTime();
int maxRetries = 3;
long baseDelayMs = 1000;
for (int attempt = 1; attempt <= maxRetries; attempt++) {
HttpRequest request = HttpRequest.newBuilder()
.uri(URI.create(cutoverUrl))
.header("Authorization", "Bearer " + token)
.header("Content-Type", "application/json")
.header("X-Request-Id", "swap-" + System.currentTimeMillis())
.header("Idempotency-Key", "idemp-" + deploymentId + "-" + payload.hashCode())
.method("PATCH", HttpRequest.BodyPublishers.ofString(payload))
.build();
HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());
long elapsedMs = TimeUnit.NANOSECONDS.toMillis(System.nanoTime() - startNanos);
if (response.statusCode() == 200 || response.statusCode() == 202) {
logger.info("Cutover successful. Status: " + response.statusCode() + " | Latency: " + elapsedMs + "ms");
return Map.of(
"success", true,
"statusCode", response.statusCode(),
"responseBody", response.body(),
"latencyMs", elapsedMs,
"attempts", attempt
);
}
if (response.statusCode() == 429) {
long delay = baseDelayMs * (long) Math.pow(2, attempt - 1);
logger.warning("Rate limited (429). Retrying in " + delay + "ms (attempt " + attempt + ")");
Thread.sleep(delay);
continue;
}
throw new RuntimeException("Cutover failed with status " + response.statusCode() + ": " + response.body());
}
throw new RuntimeException("Max retries exceeded for cutover operation.");
}
}
Required OAuth Scopes: deployment:write, routing:read
Expected Response for PATCH Cutover:
{
"deploymentId": "dep-88a7c2",
"status": "cutover_initiated",
"cutoverId": "cut-99f1d4",
"trafficDirective": {
"type": "canary",
"currentWeight": 0.1,
"nextAdjustmentAt": "2024-05-20T14:35:00Z"
},
"estimatedCompletionSeconds": 120,
"auditTrail": {
"timestamp": "2024-05-20T14:34:00Z",
"action": "model_hot_swap",
"operator": "automated-pipeline"
}
}
Step 3: Verify Fallback Model and Synchronize Webhooks
After the atomic PATCH succeeds, you must verify that the fallback model is healthy and trigger webhooks to align external deployment pipelines (including NICE CXone routing configuration). This step ensures continuous service availability and generates governance audit logs.
import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.util.Map;
import java.util.logging.Logger;
public class CognigySwapOrchestrator {
private static final Logger logger = Logger.getLogger(CognigySwapOrchestrator.class.getName());
private final HttpClient httpClient;
private final String baseUrl;
private final CognigyAuth auth;
public CognigySwapOrchestrator(HttpClient httpClient, String baseUrl, CognigyAuth auth) {
this.httpClient = httpClient;
this.baseUrl = baseUrl;
this.auth = auth;
}
public void postSwapVerificationAndSync(String deploymentId, String modelId, Map<String, Object> cutoverResult) throws Exception {
String token = auth.getAccessToken();
// 1. Verify fallback model health
String fallbackUrl = baseUrl + "/api/v2/models/" + modelId + "/versions/fallback/health";
HttpRequest fallbackReq = HttpRequest.newBuilder()
.uri(URI.create(fallbackUrl))
.header("Authorization", "Bearer " + token)
.GET()
.build();
HttpResponse<String> fallbackResp = httpClient.send(fallbackReq, HttpResponse.BodyHandlers.ofString());
if (fallbackResp.statusCode() != 200) {
throw new RuntimeException("Fallback model verification failed: " + fallbackResp.body());
}
logger.info("Fallback model verified. Status: " + fallbackResp.body());
// 2. Generate audit log entry
String auditPayload = """
{
"event": "MODEL_HOT_SWAP_COMPLETED",
"deploymentId": "%s",
"modelId": "%s",
"cutoverId": "%s",
"latencyMs": %d,
"successRate": %s,
"timestamp": "%s"
}
""".formatted(
deploymentId,
modelId,
extractValue(cutoverResult, "responseBody", "cutoverId"),
cutoverResult.get("latencyMs"),
cutoverResult.get("success"),
java.time.Instant.now().toString()
);
// 3. Trigger webhook for external pipeline sync (CXone alignment)
String webhookUrl = baseUrl + "/api/v2/webhooks/deployments/sync";
String webhookPayload = """
{
"source": "cognigy-ai",
"action": "routing_update",
"targetPlatform": "nice-cxone",
"cxoneRoutingConfig": {
"queueId": "queue-ai-fallback",
"priority": 1,
"enable": true
},
"swapAudit": %s
}
""".formatted(auditPayload);
HttpRequest webhookReq = HttpRequest.newBuilder()
.uri(URI.create(webhookUrl))
.header("Authorization", "Bearer " + token)
.header("Content-Type", "application/json")
.POST(HttpRequest.BodyPublishers.ofString(webhookPayload))
.build();
HttpResponse<String> webhookResp = httpClient.send(webhookReq, HttpResponse.BodyHandlers.ofString());
if (webhookResp.statusCode() >= 400) {
logger.warning("Webhook sync returned " + webhookResp.statusCode() + ": " + webhookResp.body());
} else {
logger.info("External pipeline synchronized successfully.");
}
}
private static String extractValue(Map<String, Object> map, String key, String jsonPath) {
String body = (String) map.get(key);
int start = body.indexOf("\"" + jsonPath + "\":\"") + jsonPath.length() + 3;
int end = body.indexOf("\"", start);
return body.substring(start, end);
}
}
Required OAuth Scopes: model:read, audit:write, webhook:write
Expected Webhook Response:
{
"webhookId": "wh-77b3e1",
"status": "dispatched",
"targets": ["nice-cxone-routing-sync"],
"deliveryLatencyMs": 142,
"syncConfirmation": true
}
Complete Working Example
import java.net.http.HttpClient;
import java.util.Map;
public class CognigyHotSwapRunner {
public static void main(String[] args) throws Exception {
if (args.length < 3) {
throw new IllegalArgumentException("Usage: java CognigyHotSwapRunner <clientId> <clientSecret> <baseUrl>");
}
String clientId = args[0];
String clientSecret = args[1];
String baseUrl = args[2].replace("https://", "").replace("http://", "");
String fullBaseUrl = "https://" + baseUrl;
String modelId = "mdl-44a9c1";
String deploymentId = "dep-88a7c2";
String targetVersion = "2.4.1";
HttpClient client = HttpClient.newBuilder()
.followRedirects(HttpClient.Redirect.NORMAL)
.build();
CognigyAuth auth = new CognigyAuth(clientId, clientSecret, fullBaseUrl);
CognigyModelValidator validator = new CognigyModelValidator(client, fullBaseUrl, auth);
CognigyModelSwapper swapper = new CognigyModelSwapper(client, fullBaseUrl, auth);
CognigySwapOrchestrator orchestrator = new CognigySwapOrchestrator(client, fullBaseUrl, auth);
try {
System.out.println("Validating model swap constraints...");
Map<String, Object> validation = validator.validateSwap(modelId, targetVersion, deploymentId);
System.out.println("Active versions: " + validation.get("activeVersionCount"));
System.out.println("Schema valid: " + validation.get("schemaValid"));
System.out.println("Executing atomic cutover...");
Map<String, Object> cutoverResult = swapper.executeCutover(deploymentId, (String) validation.get("payload"));
System.out.println("Cutover latency: " + cutoverResult.get("latencyMs") + "ms");
System.out.println("Response: " + cutoverResult.get("responseBody"));
System.out.println("Verifying fallback and synchronizing pipelines...");
orchestrator.postSwapVerificationAndSync(deploymentId, modelId, cutoverResult);
System.out.println("Hot-swap completed successfully.");
} catch (Exception e) {
System.err.println("Swap operation failed: " + e.getMessage());
e.printStackTrace();
}
}
}
Common Errors & Debugging
Error: 409 Conflict - Version Limit or Schema Mismatch
- What causes it: The deployment already contains five active versions, or the target version schema contains incompatible node definitions that violate runtime engine constraints.
- How to fix it: Prune older versions via
DELETE /api/v2/models/{modelId}/versions/{versionId}or update the model schema to match the runtime specification. - Code showing the fix:
// Prune oldest version before swap
HttpRequest pruneReq = HttpRequest.newBuilder()
.uri(URI.create(baseUrl + "/api/v2/models/" + modelId + "/versions/v1.0.0"))
.header("Authorization", "Bearer " + token)
.DELETE()
.build();
httpClient.send(pruneReq, HttpResponse.BodyHandlers.ofString());
Error: 422 Unprocessable Entity - Invalid Traffic Directive Format
- What causes it: The
trafficDirectiveJSON object contains invalid weight values (outside 0.0 to 1.0) or missing required fields likerampUpIntervalSeconds. - How to fix it: Validate the payload structure against the Cognigy.AI routing schema before sending. Ensure
initialWeightandmaxWeightare decimal numbers. - Code showing the fix:
// Validate weight bounds before constructing payload
if (initialWeight < 0.0 || initialWeight > 1.0) {
throw new IllegalArgumentException("Traffic directive weight must be between 0.0 and 1.0");
}
Error: 503 Service Unavailable - Runtime Engine Busy
- What causes it: The inference cluster is undergoing internal scaling or garbage collection. The atomic PATCH cannot acquire a write lock on the routing table.
- How to fix it: Implement exponential backoff with jitter. The provided
executeCutovermethod already handles429retries. For503, wrap the call in a retry loop with a longer base delay. - Code showing the fix:
if (response.statusCode() == 503) {
long delay = 5000 * (long) Math.pow(2, attempt - 1);
Thread.sleep(delay + (long)(Math.random() * 1000)); // Add jitter
continue;
}