To ensure data consistency, it is recommended to use a distributed cache solution. In summary, using private cache solutions like Node-Cache in multi-instance environments can cause issues. Azure provides several options for distributed caching, including Azure Cache for Redis and Azure Cosmos DB. A distributed cache stores data in a centralized location accessible to all instances, ensuring that all requests have access to the same data. To avoid this issue, it is recommended to use a distributed cache solution instead of private cache solutions. Python: cachetools, discache and joblib.Memory This issue may also occur with other private cache libraries for different languages, such as: You will also see the instance is different from the one that saved the cache. Then, if you open a new InPrivate window of your browser (or you have ARR infinity disabled) and browse to you may occasionally see that the value is undefined by refreshing the page a few times.It will be saved and displayed with the instance name together. When you send a GET request to the root URL for this application, the application will generate a key-value cache – the key is the current Unix timestamp, and the value is its date-time in a friendly format.Step 4: Close and reopen the Firefox app to finish. Step 3: Uncheck all the boxes except for Cache in the tab and tap the Clear data button. Step 2: Go to Settings and tap Clear private data. You may observe the following behavior after deploying this application to a multi-instance app service: Step 1: Open the Firefox app and tap the Menu(three dots) in the bottom-right corner. Here's a JavaScript code snippet for an Express application to demonstrate this behavior:Ĭonst unixTimestamp = Math.floor(Date.now() / 1000) Ĭonst friendlyDateTime = date.toLocaleString(undefined, options) In this case, you may fail to get the value of this cache or get an incorrect value. Then, a request tries to read this value from another instance. However, in a multi-instance environment like a multi-instance App Service, using a private cache can lead to inconsistent behavior and data inconsistency.įor example, you save a value in one cache in an instance. The private cache works properly when running on a single instance, as all requests are handled by the same process and have access to the same cache. This behavior occurs because Node-Cache and other private cache solutions are designed to store data in the memory of a single process. However, the module worked fine on my local environment, single virtual machine, or single-instance app service. I recently encountered an issue when attempting to read cache values using the Node-Cache module on an app service running on multiple instances.
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