A cache that survives losing the box it runs on.

Drop the servers that should copy this one and press Add. What runs then is one job with the order written on it, because the order is the whole trick: the primary first, listening on its address with the set's password on its default user. Then the firewall — every member lets every other in on 6379 and 26379, all at once. Then each replica, its wire to the primary proved from its own box before it is told to follow, then made to replicate and waited for until the link is up. Then a sentinel beside each member, watching the primary with a quorum Vigia works out from the count.

Nothing restarts. Vigia writes each sentinel's file once and Sentinel owns it from then on. And the same honesty as the install: it runs from this console over the shells, so keep Vigia open until it finishes — closed halfway it stops between boxes, and the same button carries on from where it stopped.

Two more boxes? Drop them on the set. Each takes a row and is read at once — its cache, a shell on its saved login — and if one of them has no Redis, Vigia installs it first. Nothing is written until you press Add. Then they are filed as replicas and the set is built again from the top: the firewall opened between every member including the new ones, each new box proved and attached, a sentinel beside each, the quorum recalculated.

And the wires are re-proved. Five members is twenty wires; seven is forty-two — every member to every other on the port, each one tried from the box it starts at, not guessed from a config file. The header says how many are talking and when it was last checked.

This is the part most tools get wrong by pretending they are in charge. They are not: when enough sentinels agree the primary has been gone for five seconds, they promote the replica most in sync, point the others at it, and Sentinel-aware apps follow within seconds. Failover now simply asks them to do it now — and the log names the box they chose, not the box Vigia expected.

Which means the filing on your computer can disagree with reality, and Vigia says so instead of hiding it: this box is filed as the primary but copies another one — the sentinels moved it. Read again files what they say, or Apply puts the filing back on the boxes. Two buttons, two honest choices: accept what happened, or put it back deliberately. The old primary becomes a replica the moment it answers again.

Performance is the numbers that answer a real question: operations per second and the total since start, the hit ratio, memory with its RSS and fragmentation beside it, evictions, clients blocked and rejected, bytes in and out. Under them, the slow commands — when, how long, the command itself and which client sent it — with the sentence that saves an afternoon: the usual names here are the ones that walk everything, and an app user without the dangerous category cannot run them at all. And the open connections, each with what it is doing and a Close beside it.

Settings is the configuration as rows in words. What the address means, what protected mode is a seatbelt against, what the eviction policy actually does to your keys, why a cache wants a limit and a store wants durability. Each row says whether the change is live or waits for a restart, whether Vigia set it or the distribution did, and offers to put it back to the default.