Scaling Your Contact Center with VICIdial

VICIdial supports deployments ranging from small teams to global enterprises. This guide provides a deep dive into scaling strategies—including architectural topologies, database replication setups, API and SIP load balancing, high-availability clusters, proactive monitoring, and disaster recovery planning.

Prerequisites

• VICIdial Administrator (Level 9) access to infrastructure and application tiers
• Multiple servers or VMs provisioned for web, dialer, and database roles
• External load balancer (HAProxy, NGINX, or dedicated appliance)
• MariaDB/MySQL replication configured (master-slave or Group Replication)
• Monitoring stack (Prometheus + Grafana, Zabbix, or ELK)
• Configuration management tool (Ansible, Terraform, or similar)

1  Architectural Topologies

Select the topology that meets your scale, redundancy, and budget requirements:

2  Database Replication & Consistency

A robust database layer underpins scaling:

• Master-Slave Replication: One write master, multiple read replicas. Configure `read_only` on slaves to offload reporting.
• Group Replication: Multi-master writes with automatic failover. Requires `gtid_mode=ON` and consistent versioning.
• Replication Monitoring: Use `SHOW SLAVE STATUS\G` or exporters (mysqld_exporter) to track `Seconds_Behind_Master` (< 1 s ideal).
• Backup Strategy: Leverage `mysqldump --single-transaction` or filesystem snapshots (LVM/ZFS) during low traffic windows.
• Failover Orchestration: Tools like Orchestrator or MHA automate master elections and DNS updates.

3  Load Balancing Web & API Tiers

Ensure high throughput and availability for HTTP(S) and API endpoints:

• HAProxy Configuration: Use `balance leastconn` for evenly distributed sessions. Enable `option httpchk GET /vicidial/non_agent_api.php HTTP/1.0` for health checks.
• Session Persistence: Employ `cookie SERVERID insert indirect nocache` or `balance source` to maintain agent sessions.
• SSL Termination: Offload TLS at LB; forward traffic in plaintext to internal nodes.
• Autoscaling: In cloud environments, integrate with AWS ASG or GCP MIG to add/remove web nodes based on CPU or request metrics.
• API Rate Limits: Throttle calls to `agent_api.php` to protect backend and prevent overload.

4  Scaling Dialer & SIP Trunking

Handle large call volumes while maintaining audio quality:

1. SIP Proxy Layer: Deploy Kamailio or OpenSIPS to front VICIdial dialers. Use `dispatcher` module for least-loaded node routing.
2. Trunk Distribution: Implement hashing on caller ID or trunk weight balancing in proxy to distribute outbound calls evenly.
3. RTP Load: Separate media relay nodes (RTPengine) to offload CPU and optimize packet transit.
4. Call Concurrency Tracking: Monitor `Active Channels` per node; scale dialers when concurrency reaches thresholds.
5. Global SIP Resilience: Use failover lists in proxy config to reroute trunks if primary gateway fails.

5  High-Availability & Failover

Minimize downtime and data loss:

• VIP Failover: Configure keepalived or Pacemaker/Corosync to failover Virtual IPs between nodes.
• Database Semi-Sync: Use semi-synchronous replication plugins to ensure commit safety before returning success.
• Service Supervision: Run critical services under systemd with `Restart=on-failure` and alerting on frequent restarts.
• Automated Playbooks: Use Ansible playbooks to deploy or reconfigure nodes automatically during failover.
• Chaos Testing: Periodically simulate node failures to validate recovery procedures and runbooks.

6  Monitoring & Observability

Visibility into system health drives proactive operations:

• Metrics Collection: Use node_exporter, mysqld_exporter, and custom VICIdial exporters to gather CPU, memory, disk I/O, DB stats, in-queue, and agent status.
• Dashboarding: Create Grafana dashboards showing call volume trends, drop rates, agent utilization, and replication lag.
• Alerting: Define Prometheus Alertmanager rules for conditions like drop % > 3 %, replication lag > 5 s, service down, or high Syslog error rates.
• Log Aggregation: Centralize VICIdial logs using Filebeat and ELK/Graylog for quick root-cause analysis.
• Tracing & Profiling: Instrument critical paths (API calls) with Jaeger or Zipkin to diagnose latency issues.

7  Disaster Recovery Planning

Ensure business continuity in worst-case scenarios:

1. Define RTO/RPO objectives and align backup frequency accordingly.
2. Store backups offsite or in object storage (S3, GCS) with encryption.
3. Test full restores quarterly to validate backup integrity.
4. Maintain secondary DR site with up-to-date replication streams.
5. Document DR playbooks with step-by-step failover instructions and contact lists.

Best Practices

1. Conduct capacity planning based on SIPp load testing and projected growth.
2. Adopt Infrastructure-as-Code for reproducible environments.
3. Version control all configuration and dialplan files (Git).
4. Secure all inter-node communication with VPNs or SSH tunnels.
5. Regularly review and update runbooks after any major architecture change.

Next Steps

• Explore containerized VICIdial deployments with Docker Compose or Kubernetes operators.
• Integrate auto-remediation scripts to self-heal common faults.
• Implement canary releases for configuration changes.
• Schedule annual architecture reviews and load tests.

For further architecture examples and configuration snippets, consult the VICIdial Manager Manual and community repositories on GitHub.