Error: dokku redis can't save in background fork cannot allocate memory

What's Causing This Error

The error "dokku redis can't save in background fork cannot allocate memory" occurs when Redis fails to create a child process (fork) to handle the saving of data in the background. This failure is due to insufficient system memory available for the fork operation. Redis requires enough memory to create a copy of its entire dataset during the fork, as it uses a Copy-On-Write (COW) mechanism to save data efficiently without affecting the main process.

Solution - Here's How To Resolve It

To resolve this issue, you have several options:

  1. Increase the available system memory: You could either upgrade your server's RAM or free up some memory by stopping other memory-consuming processes running on the same machine.
  2. Optimize Redis memory usage: Review your Redis configuration settings and adjust them to minimize memory consumption, such as using maxmemory and maxmemory-policy directives.
  3. Adjust overcommit settings: Modify the vm.overcommit_memory kernel parameter to allow Redis to allocate more memory for the fork operation. Set it to 1 to allow more aggressive allocation, but be cautious as this might lead to out-of-memory problems.
  4. Reduce the frequency of data persistence: Alter the Redis configuration settings that control how often data is saved (e.g., by modifying save directives). Be aware that doing so may increase the risk of data loss in case of a crash.

Note that depending on your specific use case and needs, you may need to combine multiple approaches to resolve the issue effectively.

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Dragonfly is fully compatible with the Redis ecosystem and requires no code changes to implement.