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Marc SchierandCopilot
3c4661d2bf
## Failure MCP auto-accept mutated the shared application certificate manager and accepted every certificate error, so one permissive connection could affect concurrent or later strict sessions. The durable-subscription sample also serialized complete user identity tokens, including user-name passwords and issued bearer tokens. ## Fix - Isolate auto-accept certificate managers/configurations per connection and keep their lifetime with the managed session. - Auto-accept only `BadCertificateUntrusted`; retain strict validation for all other certificate errors and shared sessions. - Version the durable store and reject the previous unsafe format. - Remove user-name passwords before persistence and reject issued-token subscriptions rather than storing bearer credentials. - Add focused tools tests plus solution, project, and durable-subscription docs. ## Reference - OPC 10000-4 Session identity-token and application-certificate security. - Split from #4021. ## Tests - `Opc.Ua.Tools.Tests` Release: 7 passed on net10.0; 4 passed on net48. - `Quickstarts.Servers` Release builds passed on net10.0 and net48 with zero warnings/errors. - `Opc.Ua.Mcp` Release net10.0 build passed with zero warnings/errors. --------- Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
39 lines
3.6 KiB
Markdown
39 lines
3.6 KiB
Markdown
# Durable Subscription
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## Overview
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The durable subscriptions service enables long lifetimes of subscriptions with big queue sizes and therefore zero-dataloss scenarios.
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If the connection to the client fails the server continues to sample values. On reconnect the client can use the transfer subscription service to gain access to the missed values.
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## Fix an existing server with minimal changes
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- If a custom implementation of `INodeManager` is used, or the Method `CreateMonitoredItems` is overridden, add the new parameter `createDurable`. As long as durable Subscriptions are not enabled in the configuration this parameter can be ignored.
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- Implement`INodeManager.RestoreMonitoredItems`, this method is only called if durable subscriptions are enabled in the server configuration.
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- If a custom `IMonitoredItem` implementation is used, set `IsDurable` to false. Implement a `Dispose` method.
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## Enabling durable subscriptions on an existing server
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Typically the following porting steps are necessary:
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- Provide an implementation of `IMonitoredItemQueueFactory` that sets `SupportsDurableQueues` to true. This factory returns your own implementation of `IMonitoredItemQueue` that persists values to storage and supports large queue sizes. As a reference see [DurableMonitoredItemQueueFactory](../../samples/Quickstats.Servers/DurableSubscription/DurableMonitoredItemQueueFactory.cs).
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- Register the `IMonitoredItemQueueFactory` by overriding the StandardServer method `CreateMonitoredItemQueueFactory`.
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- Provide an implementation of `ISubscriptionStore` that persists and restores subscriptions to storage to continue them after a server restart. The subscription store shall also enshure persistent queues are provided to the monitored items after a restore.
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- - Register the `ISubscriptionStore` by overriding the StandardServer method `CreateSubscriptionStore`.
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- If a custom implementation of `INodeManager` is used, or the Method `CreateMonitoredItems` is overridden, add the new parameter `createDurable`. Pass the value of this parameter to the MonitoredItem constructor. If a custom queue length check if performed for durable subscriptions check against the durable queue length from SererConfiguration.
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- If a custom `IMonitoredItem` implementation is used, implement the `IsDurable` property. Implement a `Dispose` method. Add a `createDurable` paramter to the constructor.
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- Make the custom `MonitoredItem` use the `IMonitoredItemQueueFactory` from `IServerInternal.MonitoredItemQueueFactory` to get the registerd durable queues instead of using internal queues for events & value changes.
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- To test custom queues use the unit tests in Server Test Project in the file monitoredItemTests and adapt to use your own queue by providing your `IMonitoredItemQueueFactory` in the constructor.
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Extend the ServerConfiguration
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- Set `DurableSubscriptionsEnabled` to true
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- Set `MaxDurableNotificationQueueSize` to the desired value
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- Set `MaxDurableEventQueueSize` to the desired value
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- Set `MaxDurableSubscriptionLifetime` to the desired value
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## Known limitations and issues
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- Subscriptions are only persistet on a gracefuls shutdown. If the server crashes or needs to be shut down forcefully all `Subscriptions` / `MonitoredItems` are lost.
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- The Quickstarts durable-subscription store uses a versioned format and rejects files written by the previous unsafe format. User-name passwords are removed before persistence, and issued-token subscriptions are not persisted because their bearer token is the identity.
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- **Breaking change**: The Interfaces for INodeManager & IMonitoredItem were extended to support durable subscriptions.
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