This really shouldn’t happen as there is (should be) an entry in the /lib/systemd/system/redis-server.service file requiring network to be running. If this was an issue, I’d have expected the wider community to have squealed.
After=network.target
Looks like the Redis service file has changed @TrystanLea and that could be the issue. Below my file for Redis-server V3.2.6 installed on a DietPi OS. Quite different to the service file on an old system running redis-server V2.8.17.
When we looked into the MQTT service, I wrote a longer bit on my research into systemd service startup here (I am no expert), which may provide a solution for a replacement file for the EmonPi if necessary.
Redis-server V3.2.6 service file
[Unit]
Description=Advanced key-value store
After=network.target
Documentation=http://redis.io/documentation, man:redis-server(1)
[Service]
Type=forking
ExecStart=/usr/bin/redis-server /etc/redis/redis.conf
PIDFile=/var/run/redis/redis-server.pid
TimeoutStopSec=0
Restart=always
User=redis
Group=redis
RunTimeDirectory=redis
ExecStartPre=-/bin/run-parts --verbose /etc/redis/redis-server.pre-up.d
ExecStartPost=-/bin/run-parts --verbose /etc/redis/redis-server.post-up.d
ExecStop=-/bin/run-parts --verbose /etc/redis/redis-server.pre-down.d
ExecStop=/bin/kill -s TERM $MAINPID
ExecStopPost=-/bin/run-parts --verbose /etc/redis/redis-server.post-down.d
UMask=007
PrivateTmp=yes
LimitNOFILE=65535
PrivateDevices=yes
ProtectHome=yes
ReadOnlyDirectories=/
ReadWriteDirectories=-/var/lib/redis
ReadWriteDirectories=-/var/log/redis
ReadWriteDirectories=-/var/run/redis
CapabilityBoundingSet=~CAP_SYS_PTRACE
# redis-server writes its own config file when in cluster mode so we allow
# writing there (NB. ProtectSystem=true over ProtectSystem=full)
ProtectSystem=true
ReadWriteDirectories=-/etc/redis
[Install]
WantedBy=multi-user.target
Alias=redis.service