Quick question about BYOC trunk registration stability when simulating high-concurrent outbound calls from the ap-southeast-1 region.
Running a JMeter script to test API throughput for call creation. The setup involves a single BYOC trunk with a max concurrency of 50. When the thread group ramps up to 40 concurrent users within 10 seconds, the first 20 calls connect fine. However, the subsequent requests to POST /api/v2/architect/flows/{flowId}/actions/call start returning 409 Conflict errors. The error message indicates ‘Trunk capacity exceeded’ even though the actual active calls on the trunk are only at 15-20.
The JMeter config uses a simple loop controller with a 5-second pause between iterations. No WebSocket drops are observed in the logs. Is there a hidden queue or buffer limit on the BYOC side that triggers these 409s before the actual SIP trunk is saturated? Or is the rate limiter for the Architect API throttling the call creation requests faster than the trunk can register them?
Looking for insights on how to tune the load test to match the platform’s actual ingestion capacity for BYOC trunks.
The quickest way to solve this is to align your JMeter thread group ramp-up strategy with the BYOC trunk’s actual registration and concurrency limits. The 409 Conflict errors during the ramp-up phase typically indicate that the platform is rejecting new call attempts because the trunk has not yet completed its SIP registration handshake or has hit a soft concurrency ceiling before the underlying media servers are ready.
In Terraform, ensure the genesyscloud_byoc_trunk resource explicitly defines the max_concurrency and includes proper health check intervals. Here is the recommended configuration:
resource "genesyscloud_byoc_trunk" "test_trunk" {
name = "LoadTest-AP-Southeast-1"
description = "Trunk for high-concurrency JMeter testing"
max_concurrency = 50
# Critical for stability during rapid ramp-up
health_check_interval_seconds = 30
registration_timeout_seconds = 60
sip_proxy_host = "proxy.ap-southeast-1.genesys.cloud"
# Ensure proper codec negotiation to avoid media setup failures
supported_codecs = ["G711U", "G711A", "OPUS"]
}
Warning: Do not rely solely on the UI-defined concurrency limits during automated load tests. The API may reject requests faster than the SIP stack can process registrations, leading to transient 409s.
In JMeter, configure the HTTP Request Default Configurator to include a constant timer of at least 500ms between iterations. This mimics realistic call setup latency and prevents the API gateway from throttling requests. Additionally, verify that the genesyscloud_byoc_trunk resource is deployed in the same region as the JMeter test agents to minimize network latency during the SIP registration phase. If the issue persists, check the Genesys Cloud logging for specific SIP response codes (e.g., 486 Busy Here or 503 Service Unavailable) which provide more granular insight into trunk registration failures.
This issue stems from the performance dashboard interpreting the rapid spike in outbound attempts as a queue congestion event, triggering failover logic before the BYOC trunk registration stabilizes. The 409 Conflict is not merely a SIP handshake failure but a result of the platform rejecting calls due to perceived capacity limits during the ramp-up phase.
To mitigate this, adjust the JMeter configuration to introduce a slight delay between call creations, allowing the Genesys Cloud edge to register each trunk session properly. Ensure the payload includes explicit timeout parameters to prevent premature timeouts.
{
"to": "+15550100",
"timeout": 60,
"wait_for_answer": true,
"play_prompt": false
}
Review the Queue Activity view in the Performance Dashboard to confirm that the concurrency metrics align with the actual trunk registration state. This approach ensures that the load test reflects realistic usage patterns rather than overwhelming the initial registration process.