This article provides a solution for when the page cache is warming up and there is a stuck deployment or site down.
Affected products and versions
- Magento Commerce Cloud, all supported versions.
Issue
The cache warm up script, at the end of the post-deploy phase, sends requests at such a high rate that certain instances, like 4-cpu ones, cannot cope. Their nginx exhausts the number of workers.
Steps to reproduce
Start cache warmup operations.
Expected result
Pages or whole site loads.
Actual result
The site is unavailable or the response time is too high.
Solution
Limit the number of concurrent connections during the cache warm up. This requires adding the WARM_UP_CONCURRENCY post-deploy variable, to specify the number of warm-up requests that the cache warm up script can send concurrently. Setting this option can help manage load on Magento Cloud infrastructure. For steps, refer to Magento DevDocs > Post-deploy variables > WARM_UP_CONCURRENCY.