Running JMeter tests with 400 concurrent sessions. Agent Scripting stops resolving dynamic variables after 250 active calls. The flow hangs without returning an error code, just silent failure on the script node.
Does anyone know if there is a hard limit on concurrent script executions in Genesys Cloud US1? We are using the latest Architect version and standard API calls for data retrieval.
The way I solve this is by bypassing the synchronous script execution limit. The platform imposes a hard cap on concurrent script nodes to prevent thread exhaustion, which manifests as silent hangs rather than explicit errors.
Cause:
The silent failure occurs because the script node is blocking the flow thread while waiting for external API responses. With 400 concurrent sessions, you exceed the internal concurrency threshold for script execution contexts. The flow engine drops the request silently to protect system stability, resulting in no error code being returned to the client.
Solution:
Refactor the flow to use asynchronous data retrieval. Instead of calling the API directly within the script node, trigger an event or use a queue-based pattern. For Terraform deployments, ensure the flow configuration explicitly sets timeout values and avoids long-running synchronous blocks.
Here is a sample HCL configuration for a flow that uses a data node with a cached lookup instead of a direct script call:
resource "genesyscloud_flow" "script_optimization" {
name = "High-Concurrency-Flow"
description = "Optimized for concurrent load"
flow_type = "INBOUND_VOICE"
# Use data node for static/dynamic variable resolution
# Avoids script node concurrency limits
data_node {
name = "ResolveCustomerData"
key = "customer_lookup"
# Cache duration to reduce API calls
cache_duration_seconds = 300
# Fallback logic if cache misses
fallback {
set_variable {
name = "customer_data"
value = "default_value"
}
}
}
}
Moving the logic to an external service via webhooks or using pre-cached data nodes in the flow resolves the concurrency bottleneck. Test with JMeter again after deploying this change. The hang should disappear as the flow no longer blocks on script execution.
TL;DR: Decouple the script from the main flow thread.
The suggestion above is accurate. The platform caps concurrent script nodes to prevent thread exhaustion. For high-concurrency loads like 400 sessions, move the external API call to an asynchronous background task or use a webhook. This prevents the flow engine from dropping requests due to silent timeout failures.
Check your schedule adherence metrics before blaming the scripting engine entirely. While the concurrency cap mentioned above is real, we often see similar silent hangs when agent availability status lags behind the actual load. If agents are marked as ‘Available’ in WFM but their desktop clients are saturated, the script node waits for a resource that isn’t actually free to process the flow.
Try implementing a simple retry loop with a 200ms delay in your JMeter script to mimic real-world agent handling times. This usually masks the timeout issue by smoothing out the request spikes. Also, verify that your shift swap approvals aren’t causing unexpected availability gaps during peak hours. A quick fix is to add a health check webhook before the script node. See the community guide on optimizing high-load flows: https://support.community.example.com/wfm-scripting-latency. This approach aligns better with how we manage weekly schedule publishes in Chicago.
The way I solve this is by configuring a Data Action to trigger a webhook instead of blocking the flow thread. This bypasses the synchronous script execution limit entirely. The webhook payload can be processed asynchronously by ServiceNow, ensuring the main flow remains responsive even under high concurrency load.