OPC UA Load Balancer for Redundant Server Failover
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Solution Overview
Problem
OPC UA clients cannot communicate with a redundant server set due to the inability to designate multiple endpoint URLs, limiting communication with redundant OPC UA servers.
Innovation Solution
A system using a load balancer (LB) to proxy connections between the OPC UA client and a redundant server set, where the LB switches active and standby servers during failover operations, allowing seamless communication by shifting the endpoint URL from the active to the standby server.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an OPC UA client designates a single endpoint URL to communicate with OPC UA servers, then the client can establish a connection, but the client cannot communicate with redundant server sets for failover operations
Solution Approach 1:
The patent introduces a load balancer as an intermediary component between the OPC UA client and the redundant server set. The load balancer receives the single endpoint URL from the client and internally manages connections to multiple servers (active and standby). This mediator enables the client to communicate with redundant servers without requiring the client to designate multiple URLs, thus resolving the contradiction between reliability and ease of operation.
2Reliability
If the OPC UA client directly connects to multiple endpoint URLs of redundant servers, then failover communication is enabled, but the system complexity increases
Solution Approach 1:
The load balancer serves as a centralized intermediary that manages all connections to the redundant server set. Instead of the client directly managing multiple connections to multiple servers, the load balancer handles connection routing, server status monitoring, and failover logic. This concentrates the complexity in a single component rather than distributing it across the client and multiple servers, thus enabling failover capability while controlling system complexity.
Solution Approach 2:
The patent segments the system into distinct functional components: the OPC UA client, the load balancer, and the server set (with active and standby servers). The load balancer is segmented as a separate entity responsible for connection management, while servers are segmented into active and standby roles. This segmentation allows each component to have a specific, simplified function, reducing overall system complexity while maintaining failover capability.
3Reliability
If the endpoint URL is directly associated with the active server, then direct server access is enabled, but transparent failover cannot be achieved
Solution Approach 1:
The load balancer acts as an intermediary that decouples the endpoint URL from the specific active server. The client communicates with the load balancer using a stable endpoint URL, while the load balancer dynamically routes this URL to the current active server. This intermediary layer enables transparent failover because the client's URL remains unchanged even when the active server changes, and the load balancer handles the complexity of URL management and server mapping internally.
Data Source
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AI summary
A system that operates using Open Platform Communications (OPC) Unified Architecture (UA) includes: a redundant server set including a first OPC UA server and a second OPC UA server; an OPC UA client configured to designate an endpoint Uniform Resource Locator (URL) to communicate with the redundant server set; and a load balancer (LB) connected between the redundant server set and the OPC UA client. The OPC UA client is configured to send a request for connection to the endpoint URL. The first OPC UA server is an active server. The second OPC UA server is a standby server. The LB is configured to proxy the connection to the first OPC UA server. The end point ULR is different from a URL of each of the first OPC UA server and the second OPC UA server.