--- title: Archive Documents After Expiration description: When a document in an existing collection is about to expire, use the Eventing Service to create an archived copy of that document in a different collection. pubDate: 2026-08-17T09:53:44.266Z antora: editUrl: https://github.com/couchbaselabs/docs-devex/edit/capella/modules/eventing/pages/eventing-examples-docarchive.adoc xref: xref:cloud:eventing:eventing-examples-docarchive.adoc[] --- [Consult the llms.txt file for a full list of contents](/llms.txt) [View original HTML](/cloud/eventing/eventing-examples-docarchive.html) # Archive Documents After Expiration > When a document in an existing collection is about to expire, use the Eventing Service to create an archived copy of that document in a different collection. This example is similar to the [Create Documents After Expiration](eventing-examples-docexpiry.md) example, but has the following differences: * It archives a perfect copy in the target collection * It does not log errors unless a document is missing when the callback function to archive the document is triggered * Does not rely on a Couchbase SDK - instead, it relies on the expiry set on the source collection, where all documents have an expiration of 10 minutes from the time of their first mutation The `OnUpdate` JavaScript handler runs whenever a document is created or mutated. The Eventing Function calls a Timer, which executes a callback function 2 minutes before a document expires and archives an identical document with the same key in a specified target bucket. The original document in the source bucket does not change, but is deleted following the bucket's expiration date. ## [](#prerequisites)Prerequisites Before trying out the examples on this page, you must first: * Import the `tavel-sample` sample bucket. * Create two new buckets called `bulk` and `rr100` with a minimum size of 100MB. * Inside the `bulk` bucket, create two keyspaces called `bulk.data.source` and `bulk.data.target`. * Update the `source` collection's TTL (Time-to-Live) to **600**. * Inside the `rr100` bucket, create one keyspace called `rr100.eventing.metadata`. For more information about creating buckets, scopes, and collections, see [Manage Buckets](../clusters/data-service/manage-buckets.md). > [!NOTE] > Do not add, modify, or delete documents in the Eventing storage keyspace `rr100.eventing.metadata` while your Eventing Functions are in a deployed state. ## [](#example-archive-documents-after-expiration)Example: Archive Documents After Expiration This example walks you through how to archive documents after they have expired. ### [](#create-an-eventing-function)Create an Eventing Function To create a new Eventing Function: 1. Go to **Data Tools** **Eventing**. 2. Click **Add Function**. 3. In the **Settings** page, enter the following Function settings: * **archive\_before\_expiry** under **Name**. * **Archive all documents in a collection before a document expires.** under **Description**. * The keyspace `bulk.data.source` under **Listen to Location**. * The keyspace `rr100.eventing.metadata` under **Eventing Storage**. 4. Click **Next**. 5. In the **Bindings** page, click **Add Binding** and create two bindings. * For the first binding: * Select **Bucket**. * Enter **src** as the **Alias Name**. * Enter the keyspace `bulk.data.source` under **Bucket**, **Scope**, and **Collection**. * Select **Read Only** under **Permission**. * For the second binding: * Select **Bucket**. * Enter **tgt** as the **Alias Name**. * Enter the keyspace `bulk.data.target` under **Bucket**, **Scope**, and **Collection**. * Select **Read and Write** under **Permission**. 6. Click **Next**. 7. In the code editor, replace the placeholder JavaScript code with the following code sample: ```javascript function OnUpdate(doc, meta) { // Only processes documents that have a non-zero TTL if (meta.expiration == 0 ) return; // Note: JavaScript Data() is in milliseconds and meta.expiration is in seconds if (new Date().getTime()/1000 > (meta.expiration - 120)) { // If within the 120 second limit for expiry, creates a copy now // Creates a new document with the same ID in the target collection // log('OnUpdate: copy src to tgt for DocId:', meta.id); tgt[meta.id] = doc; } else { // Computes 120 seconds before the TTL (note that JavaScript Date() is in milliseconds) var twoMinsPrior = new Date((meta.expiration - 120) * 1000); // Creates a Timer with a context to run in the future, 120 seconds before the expiry // log('OnUpdate: create Timer '+meta.expiration+' - 120, for DocId:', meta.id); createTimer(DocTimerCallback, twoMinsPrior , meta.id, meta.id); } } function DocTimerCallback(context) { // This context is the key to the document that expires in 120 seconds var doc = src[context]; if (doc) { // Creates a new document with the same ID in the target collection // log('DocTimerCallback: copy src to tgt for DocId:', context); tgt[context] = doc; } else { log('DocTimerCallback: issue missing value for DocId:', context); } } ``` 8. Click **Create function** to create your Eventing Function. The `OnUpdate` handler creates a Timer that fires 2 minutes before the document's expiration time. ### [](#deploy-the-eventing-function)Deploy the Eventing Function Deploy your Eventing Function: 1. Go to **Data Tools** **Eventing**. 2. Click **More Options (⋮)** next to **archive\_before\_expiry**. 3. Click **Deploy** to deploy your Function. After it's deployed, the Eventing Function executes on all existing documents and any documents you create in the future. ### [](#insert-documents-into-source-bucket)Insert Documents into Source Bucket To insert documents into your **source** bucket: 1. Go to **Data Tools** **Query**. 2. For the **Query Context**, select **travel-sample** as the bucket and **\_default** as the scope. 3. In the code editor, enter the following query to locate a large set of data in the sample bucket: ```sqlpp SELECT COUNT(*) FROM `travel-sample`.`_default`.`_default` where type = 'airport' ``` 4. Click **Run** to run the query. 5. In the code editor, replace the previous query with the following query to insert documents from the **\_default** collection of the **travel-sample** bucket into the **source** collection you created earlier: ```sqlpp INSERT INTO `bulk`.`data`.`source`(KEY _k, VALUE _v) SELECT META().id _k, _v FROM `travel-sample`.`_default`.`_default` _v WHERE type="airport"; ``` 6. Click **Run** to run the query. 7. Go to **Data Tools** **Eventing**. 8. Click the **archive\_before\_expiry** function. The number under **Successes** should be 1968, which is the same number of documents inserted into the **source** collection from the **\_default** collection of the **travel-sample** bucket. ### [](#check-document-archival)Check Document Archival To check that your Eventing Function is running properly and archiving documents: 1. Go to **Data Tools** **Documents**. 2. Expand the **rr100** bucket and the **eventing** scope. The **metadata** collection should have 1280 documents in it that are related to your Eventing Function, and 4192 documents that are related to active Timers. 3. Expand the **bulk** bucket and the **data** scope. The **source** collection should have 1968 documents in it, inserted through the SQL++ query earlier. 4. Wait a few minutes and check the **Documents** tab again. The Timer has fired and executed the `DocTimerCallback` function, which archives the documents from the **source** collection into the **target** collection. You should see the following: * 1968 documents in the **source** collection. * 1968 documents in the **target** collection. 5. Go to **Data Tools** **Eventing**. 6. Click the **archive\_before\_expiry** function. The number under **Successes** should have doubled to 3936. If you wait a few more minutes until the 120 second expiry window is reached, the documents inside the **source** collection are no longer accessible because of the collection's pre-defined TTL. The 1968 archived documents are still in the **target** collection, but the original documents in the **source** collection have expired.