mirror of
https://github.com/OPCFoundation/UA-.NETStandard.git
synced 2026-10-26 04:19:53 +08:00
Marc Schier
03777ecb09
- **Collections overhaul** — new/rewritten collection types (`ArrayOf`, `Collections` commits)
- **`Variant` builder/accessor** — new APIs for constructing and accessing Variants
- **`NodeId` operators made explicit** — breaking change for implicit conversions
- **Version bumped to 1.6** with preview build support
- **NumericRange** uses Variant
- **object** type accessors and general usage removed.
### 🏗️ Infrastructure
- Build config updated; `.NET 10` targeting
- InternalsVisibleTo moved to `.csproj`
- Pipeline/CI adjustments
38 lines
3.3 KiB
Markdown
38 lines
3.3 KiB
Markdown
# Durable Subscription
|
|
|
|
## Overview
|
|
|
|
The durable subscriptions service enables long lifetimes of subscriptions with big queue sizes and therefore zero-dataloss scenarios.
|
|
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.
|
|
|
|
## Fix an existing server with minimal changes
|
|
|
|
- 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.
|
|
- Implement`INodeManager.RestoreMonitoredItems`, this method is only called if durable subscriptions are enabled in the server configuration.
|
|
- If a custom `IMonitoredItem` implementation is used, set `IsDurable` to false. Implement a `Dispose` method.
|
|
|
|
## Enabling durable subscriptions on an existing server
|
|
|
|
Typically the following porting steps are necessary:
|
|
|
|
- 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](../../Applications/Quickstats.Servers/DurableSubscription/DurableMonitoredItemQueueFactory.cs).
|
|
- Register the `IMonitoredItemQueueFactory` by overriding the StandardServer method `CreateMonitoredItemQueueFactory`.
|
|
- 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.
|
|
- - Register the `ISubscriptionStore` by overriding the StandardServer method `CreateSubscriptionStore`.
|
|
- 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.
|
|
- If a custom `IMonitoredItem` implementation is used, implement the `IsDurable` property. Implement a `Dispose` method. Add a `createDurable` paramter to the constructor.
|
|
- 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.
|
|
- 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.
|
|
|
|
Extend the ServerConfiguration
|
|
|
|
- Set `DurableSubscriptionsEnabled` to true
|
|
- Set `MaxDurableNotificationQueueSize` to the desired value
|
|
- Set `MaxDurableEventQueueSize` to the desired value
|
|
- Set `MaxDurableSubscriptionLifetime` to the desired value
|
|
|
|
## Known limitations and issues
|
|
|
|
- Subscriptions are only persistet on a gracefuls shutdown. If the server crashes or needs to be shut down forcefully all `Subscriptions` / `MonitoredItems` are lost.
|
|
- **Breaking change**: The Interfaces for INodeManager & IMonitoredItem were extended to support durable subscriptions.
|