Redis notes

Introduction

This program extensively uses a runtime cache based on Redis.

Data durability

To make this work best, you should enable data durability with your Redis instance.

The append-only file is an alternative, fully durable strategy for Redis. It became available in version 1.1. You can turn on the AOF in your Redis configuration file (e.g. /etc/redis/redis.conf):

appendonly yes

Running

In order to run Redis from your local working tree, you might want to invoke:

echo 'dir ./var/lib\nappendonly yes' | redis-server -

Looking glass

In order to look into what is going on at the Redis substrate, you might want to invoke:

redis-cli monitor

Please take care, the output is noisy.

Running in production

We experienced infrequent crashes of our Redis instance on CentOS Linux 7.6.1810. In order to work around that problem, we configured systemd to restart the Redis instance on failure by adding a file to the /etc directory as outlined below.

cat /etc/systemd/system/redis.service.d/restart.conf:

[Service]
# https://jonarcher.info/2015/08/ensure-systemd-services-restart-on-failure/
# Please run "systemctl daemon-reload" after making changes to this file.
Restart=always
RestartSec=3

Please run systemctl daemon-reload after adding this file or making changes to it.

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We have been tracking this issue at [1].

[1] https://github.com/earthobservations/luftdatenpumpe/issues/7