Genesys Cloud Java SDK connection pool exhaustion on high-throughput outbound campaign

General Discussion
1
  • Environment: Java 17, Spring Boot 3.1
  • SDK: genesys-cloud-platform-client-java v210.1.0
  • Target: GC API /api/v2/interactions/callbacks
  • Issue: java.net.SocketTimeoutException after ~5k concurrent requests

I cannot figure out why the default RestClient in the Java SDK is exhausting the connection pool despite configuring a custom OkHttpClient.Builder with maxIdleConnections(100) and a ConnectionPool(100, 5, TimeUnit.MINUTES). I’ve injected this builder into the ApiClient via setHttpClient(), and I can see the pool size staying steady in logs during low load. However, once I spin up 50 threads hitting the callback creation endpoint simultaneously, the requests start timing out with 504 Gateway Timeout from the load balancer, not GC. The SDK seems to be holding connections open longer than expected, or perhaps the thread pool backing the async calls is misconfigured. I’ve tried increasing the readTimeout to 30s, but that just delays the failure. Is there a specific configuration flag in ApiClient.Builder for connection reuse that I’m missing, or do I need to bypass the SDK’s internal OkHttpClient entirely for high-volume batch jobs?

2

The problem is likely that a mismatch between your OkHttp pool config and how the Java SDK initializes its internal HTTP client. The SDK often wraps the client or uses a default instance that ignores your custom builder if you don’t inject it correctly. Also, maxIdleConnections doesn’t limit active connections, which is probably what’s blowing up.

  1. Inject the Client Properly: Don’t just configure OkHttpClient. You need to set it on the Configuration object before building the API client.
OkHttpClient client = new OkHttpClient.Builder()
.connectionPool(new ConnectionPool(100, 5, TimeUnit.MINUTES))
.readTimeout(30, TimeUnit.SECONDS)
.build();

Configuration config = Configuration.getDefaultConfiguration();
config.setHttpClient(client); // Critical step

  1. Check Thread Pools: If you’re hitting 5k concurrent requests, your Spring Boot Tomcat threads might be the bottleneck, not the HTTP client. Increase server.tomcat.threads.max in application.yml.

  2. Use Async: The Java SDK has async methods. Use them to avoid blocking threads.

InteractionsApi api = new InteractionsApi(config);
api.postInteractionsCallbacksAsync(body, callback);

In Rust, I handle this with Tokio’s semaphore to limit concurrency explicitly. In Java, you might need a Semaphore if the SDK’s async isn’t enough. Also, check your GC org limits. Some endpoints have rate limits that cause retries, which exhausts pools faster. Look at the Retry-After header.

Don’t forget to close resources. If you’re creating API instances in a loop, that’s a memory leak waiting to happen. Reuse one instance per thread or use a static singleton for the config.

Also, verify your OAuth token isn’t expiring mid-batch. The SDK handles refresh, but if you’re caching tokens manually, that’s a bug. Use the SDK’s built-in token handling.

If you’re still seeing issues, dump the thread stack during the timeout. Look for OkHttp threads stuck in READ state. That usually means the server isn’t responding, or your firewall is dropping idle connections.

i’m usually dealing with WebSocket streams, but the principle is the same. Keep connections alive, manage concurrency, and don’t trust default timeouts.

3

This is a classic case of the SDK swallowing your custom OkHttpClient configuration because the Java wrapper doesn’t automatically inherit the builder settings unless you force the injection at the PureCloudPlatformClientV2 level. The previous advice about maxIdleConnections is technically correct, but it misses the critical detail about how the SDK manages its internal ApiClient singleton. if you’re just creating a new OkHttpClient and not passing it through the setHttpClient method on the platform client, you’re basically configuring a ghost object that nobody is using.

you need to explicitly bind the client before any API calls are made. here is the exact sequence that works in my Spring Boot services:

  1. build your OkHttpClient with aggressive timeouts.
  2. create the PureCloudPlatformClientV2 instance.
  3. call setHttpClient on that instance.
  4. initialize with auth.
OkHttpClient httpClient = new OkHttpClient.Builder()
 .connectTimeout(10, TimeUnit.SECONDS)
 .readTimeout(30, TimeUnit.SECONDS)
 .connectionPool(new ConnectionPool(50, 5, TimeUnit.MINUTES))
 .build();

PureCloudPlatformClientV2 client = PureCloudPlatformClientV2.create("myAppId");
client.setHttpClient(httpClient); // critical step
client.login(...);

if you skip step 3, the SDK falls back to its default RestClient which has a tiny pool size and long idle timeouts. this causes the socket exhaustion you’re seeing when the outbound campaign spikes. also, check your thread pool settings in Spring. if you’re spawning more threads than your ConnectionPool max size, you’ll get blocked requests regardless of the HTTP client config. i’ve seen this exact pattern in messaging webhooks where the async handlers pile up faster than connections can release. make sure your executor service matches the connection limits. otherwise you’re just shifting the bottleneck from the network layer to the thread pool.

4

If I remember correctly, i ran into this exact pool exhaustion issue last week while setting up a similar high-throughput job. the default RestClient in the python sdk behaves similarly to the java one regarding connection handling. you might not be injecting the custom http client correctly into the PureCloudPlatformClientV2 instance. it’s easy to miss because the constructor doesn’t always validate the custom client deeply.

here’s what fixed it for me. don’t just configure OkHttpClient (or requests.Session in python terms). you need to instantiate the platform client with the custom http client explicitly passed.

from platform_sdk_python import PureCloudPlatformClientV2
import requests

# create a session with proper connection pooling
session = requests.Session()
adapter = requests.adapters.HTTPAdapter(max_retries=3, pool_connections=100, pool_maxsize=100)
session.mount('https://', adapter)

# inject the session into the client
client = PureCloudPlatformClientV2(
 config={
 'host': 'https://api.mypurecloud.com',
 'http_client': session # this is the key part
 }
)

also, check your oauth token refresh logic. if you’re refreshing tokens concurrently without locking, you’ll create a storm of auth requests that eat up the pool before your actual api calls even start. i had to wrap the token refresh in a threading.Lock().

make sure you’re also closing connections properly if you’re using a thread pool. the sdk doesn’t always close them automatically if an exception occurs mid-stream. it’s a subtle bug.