Migrating from App Engine Memcache to Cloud Memorystore (Module 13)

Posted by Wesley Chun (@wescpy), Developer Advocate, Google Cloud

The earlier Module 12 episode of the Serverless Migration Station video sequence demonstrated tips on how to add App Engine Memcache utilization to an present app that has transitioned from the webapp2 framework to Flask. At the moment’s Module 13 episode continues its modernization by demonstrating tips on how to migrate that app from Memcache to Cloud Memorystore. Transferring from legacy APIs to standalone Cloud providers makes apps extra transportable and gives a better transition from Python 2 to three. It additionally makes it doable to shift to different Cloud compute platforms ought to that be desired or advantageous. Builders profit from upgrading to fashionable language releases and acquire added flexibility in application-hosting choices.

Whereas App Engine Memcache gives a primary, low-overhead, serverless caching service, Cloud Memorystore “takes it to the subsequent stage” as a standalone product. Quite than a proprietary caching engine, Cloud Memorystore offers customers the choice to pick from a pair of open supply engines, Memcached or Redis, every of which gives extra options unavailable from App Engine Memcache. Cloud Memorystore is often extra value environment friendly at-scale, presents excessive availability, gives computerized backups, and so forth. On prime of this, one Memorystore occasion can be utilized throughout many functions in addition to incorporates enhancements to reminiscence dealing with, configuration tuning, and so forth., gained from expertise managing an enormous fleet of Redis and Memcached cases.

Whereas Memcached is extra just like Memcache in utilization/options, Redis has a a lot richer set of knowledge buildings that allow highly effective utility performance if utilized. Redis has additionally been acknowledged because the most beloved database by builders in StackOverflow’s annual builders survey, and it is an awesome ability to choose up. For these causes, we selected Redis because the caching engine for our pattern app. Nonetheless, in case your apps’ utilization of App Engine Memcache is deeper or extra advanced, a migration to Cloud Memorystore for Memcached could also be a greater possibility as a better analog to Memcache.

Performing the migration

The pattern utility registers particular person net web page “visits,” storing customer info comparable to IP tackle and consumer agent. Within the authentic app, the latest visits are cached into Memcache for an hour and used for show if the identical consumer repeatedly refreshes their browser throughout this era; caching is a one strategy to counter this abuse. New guests or cache expiration outcomes new visits in addition to updating the cache with the latest visits. Such performance have to be preserved when migrating to Cloud Memorystore for Redis.

Under is pseudocode representing the core a part of the app that saves new visits and queries for the latest visits. Earlier than, you possibly can see how the latest visits are cached into Memcache. After finishing the migration, the underlying caching infrastructure has been swapped out in favor of Memorystore (by way of language-specific Redis consumer libraries). On this migration, we selected Redis model 5.0, and we advocate the most recent variations, 5.0 and 6.x on the time of this writing, as the most recent releases characteristic extra efficiency advantages, fixes to enhance availability, and so forth. Within the code snippets under, discover how the calls between each caching programs are almost equivalent. The bolded traces characterize the migration-affected code managing the cached knowledge.

Switching from App Engine Memcache to Cloud Memorystore for Redis