revalidate Function

The revalidate function is a powerful tool in CommandKit's caching system that allows you to refresh cached data on-demand. Unlike invalidate which simply removes cached data, revalidate fetches fresh data and updates the cache in a single operation.

Basic Usage

The revalidate function refreshes a specific cached entry and returns the updated data:

import { revalidate } from '@commandkit/cache';

// Fetch fresh data and update the cache
const freshData = await revalidate('user:123');

Passing Arguments to the Cached Function

The revalidate function also accepts additional arguments that will be passed to the original cached function:

import { revalidate } from '@commandkit/cache';

// Pass additional arguments to the cached function during revalidation
const freshData = await revalidate('userPosts', userId, { limit: 10 });

This is particularly useful when:

1. Your cached function requires arguments to execute
2. You need to pass different arguments than what was used in the original cache
3. You want to update cache with different parameters

How revalidate Works

When you call revalidate with a cache key, it:

1. Finds the original function that generated the cached data
2. Executes that function to get fresh data, passing along any provided arguments
3. Updates the cache with this fresh data
4. Returns the fresh data to you

This is different from manually invalidating and then fetching, as it's done in a single operation.

Benefits of Using revalidate

1. Simplified Code

   No need to write separate invalidation and fetching logic.

2. Consistent Cache State

   The cache is always left in a valid state with fresh data.

3. Performance

   Other parts of your application can continue using the cached data without interruption.

When to Use revalidate

The revalidate function is ideal for scenarios where you need fresh data but also want to ensure the cache remains populated:

1. Periodic Refreshes

   When you want to update cached data at regular intervals:

   // Set up a periodic refresh of leaderboard data
   setInterval(
     async () => {
       await revalidate('leaderboard:global');
       console.log('Global leaderboard refreshed');
     },
     60 * 60 * 1000,
   ); // Refresh hourly

2. Triggered Updates

   When specific actions should result in refreshed cached data:

   async function completeUserQuest(userId: string, questId: string) {
     // Process the quest completion
     await database.completeQuest(userId, questId);
   
     // Refresh the user's quest data in the cache
     const updatedQuestData = await revalidate(`quests:${userId}`);
   
     return updatedQuestData;
   }

3. Revalidating with Different Parameters

   When you need to refresh cache with specific parameters:

   // Original cached function might have been called with default parameters
   // Now we want to revalidate with specific parameters
   const updatedUserData = await revalidate('userData', userId, {
     includeDetails: true,
   });

Revalidating Multiple Items

You can revalidate multiple cache items at once by passing an array of keys:

import { revalidate } from '@commandkit/cache';

const [freshUserData, freshGuildData] = await Promise.all([
  revalidate(`user:${userId}`),
  revalidate(`guild:${guildId}`),
]);

Conditional Revalidation

Sometimes, you may want to revalidate cache only under certain conditions:

import { revalidate } from '@commandkit/cache';

async function getUserProfile(userId: string, forceRefresh = false) {
  const cacheKey = `user:${userId}`;

  if (forceRefresh) {
    return await revalidate(cacheKey);
  }

  // Use the regular cached function (defined elsewhere)
  return await getCachedUserProfile(userId);
}

Error Handling

As with any asynchronous operation, proper error handling is important:

try {
  const freshData = await revalidate('user:123');
  console.log('Cache revalidated successfully:', freshData);
} catch (error) {
  console.error('Failed to revalidate cache:', error);
  // Handle error gracefully - perhaps fall back to stale data
}

Combining with Other Caching Functions

You can use revalidate in conjunction with other caching functions for more complex scenarios:

import { revalidate } from '@commandkit/cache';

async function refreshAndExtendCache(userId: string) {
  // Revalidate the data with these new settings
  return await revalidate(`user:${userId}`);
}

Best Practices

1. Use Strategically

   revalidate is more resource-intensive than a simple cache read, so use it only when fresh data is truly needed.

2. Respect Rate Limits

   Be mindful of rate limits when revalidating data that requires API calls.

3. Implement Throttling

   Consider adding throttling to prevent abuse of revalidation, especially in user-triggered scenarios.

4. Consider Stale-While-Revalidate Pattern

   For UI operations, consider showing stale data immediately while revalidating in the background:

   async function getUserDataWithRefresh(userId: string) {
     // Get potentially stale data immediately
     const staleData = await getUserData(userId);
   
     // Revalidate in the background for next time
     revalidate(`user:${userId}`).catch(console.error);
   
     // Return the stale data for now
     return staleData;
   }

5. Pass Appropriate Arguments

   When revalidating functions that require arguments, make sure to provide all necessary parameters:

   // If the cached function requires specific arguments
   const cachedFetchItems = cache(async (category: string, limit: number) => {
     return await api.fetchItems(category, limit);
   });
   
   // When revalidating, provide all required arguments
   const freshItems = await revalidate('items:electronics', 'electronics', 10);

6. Monitor Revalidation Performance

   Keep track of how long revalidations take and adjust your strategy if they become too slow.

Conclusion

The revalidate function provides a powerful way to refresh your cached data while maintaining the performance benefits of caching. By using it strategically and passing appropriate arguments when needed, you can ensure your bot always presents fresh information for critical operations while still benefiting from cache performance for most requests.