# Meanwhile, back at the database: Galactus DB 1.6.2 to 1.6.5 The last time we wrote, in [1.6.1](/blog/galactus-db-1-6-1-nobody-waits), readers stopped waiting for writers, and we signed off with "nobody waits for anybody, including you". We meant it. Four days and four releases later, here's everything that happened while nobody was waiting. The short version: a faster way across a map, an Explorer you can put on the internet, backups that no longer stop the database, and replicas that live on another server. Also, we now host it for you, if you'd rather we did. ## 1.6.2: the scenic route, fixed Sat-navs sometimes take the scenic route. Ours did too, without telling anyone. `gdb.astar` added straight-line distance in metres to relationship weights in whatever units you had used. Weight your roads in kilometres, and it believed every destination was a thousand times further away than it was. It still found a path, just not always the shortest: Exeter to Newcastle came back as 634 km instead of 624. Ten kilometres is a nice walk, but it isn't what "shortest path" promises. A* now scales its guesses to your units, so it's exact again. While we were in there, A* learned to read `Geography` and `Geometry` points as well as `point()`. Before, it quietly ignored them and became a plain Dijkstra search, which is correct but rather misses the point of A*. Then the headline act: **Hourglass**, a new exact shortest-path algorithm, now built in as `gdb.shortestPath.hourglass`. It searches from both ends at once, keeps the two searches in balance, and sorts the frontier into buckets instead of a heap, so the two sides meet in the middle. It works on directed or undirected graphs, with or without locations, as long as the weights are whole numbers. You can watch it race across a road network in the [Hourglass demo](/demos/hourglass), and the [pathfinding guide](/docs/gds/pathfinding#hourglass) has the Cypher. Explorer also got a haircut: the new Node G mark, the `GALACTUS/DB` wordmark and a lime favicon you can find among forty open tabs. ## 1.6.3: Explorer goes outside Galactus Explorer used to be a homebody. Point it at any address and it would happily connect, which is lovely on your laptop and much less lovely on a public website, where "any address" includes the machine it runs on. 1.6.3 adds `GDB_EXPLORER_ALLOWED_HOSTS`. Give it a list such as `*.db.galactusdb.com:7687`, and Explorer only connects to those hosts, only over verified TLS, and only to public internet addresses. No sneaking round the back to the private network or the cloud's metadata service. It also learned to open the login form already filled in, from a link: `/login?endpoint=bolt%2Bs://HOST:7687&user=NAME&name=LABEL`. The password is never taken from the URL, because some things should be typed. ## 1.6.4: backups without the hush Until 1.6.4, taking a backup was like vacuuming during a dinner party: everyone stopped talking until you'd finished. A dump took the whole database for itself, and every reader and writer queued politely until it was done. Now a dump reads a snapshot of the database as it was when the dump began, using the same machinery that let readers stop waiting in 1.6.1. It takes the database for one batch of 1,024 nodes or relationships at a time, and writes carry on in between. The file holds exactly the moment it started: nothing half-written, nothing from anyone else's unfinished transaction. There is one catch, and we'd rather tell you than have you find it. While a dump runs, every change to data it hasn't reached yet keeps the old value in memory, so the dump can still copy it. If a busy writer makes that pile grow past half of `GDB_SNAPSHOT_MAX_BYTES`, writers start pausing briefly after each commit, and pause for longer the fuller it gets. Think of it as the vacuum on its quiet setting. Dumps themselves are slower than before, and the database is a little slower while one runs, but nobody has to stop talking. ## 1.6.5: a replica with its own postcode Since 1.4.0, Galactus DB has kept [replicas](/blog/galactus-db-replicas-and-pub-sub): read-only copies that follow a database a few milliseconds behind. Until now they had to live on the same server, like a backup singer who refused to leave the stage. In 1.6.5 a replica can follow a database on another Galactus DB server, over Bolt: ```cypher CREATE DATABASE orders_ro AS REPLICA OF 'bolt+s://primary.example.com:7687/orders'; ``` It starts from the non-blocking snapshot that 1.6.4 introduced, so the source carries on serving while the copy is taken. After that it applies every transaction, schema changes included, under the same transaction numbers as the source. `PAUSE`, `RESUME`, `RESYNC`, `PROMOTE`, delayed replicas and the rest all work as before. A few thoughtful touches: - **The source keeps your place.** If a replica pauses or loses its connection, the source holds its change stream from wherever the replica got to, so it catches up without starting again. It lets go when the replica is promoted or dropped, or after 24 hours of silence. That's enough time for a long weekend, though not for a fortnight in Portugal. - **Idle replicas sit quietly.** A replica with nothing to do asks for news and waits a couple of seconds for an answer, rather than asking "anything yet?" over and over like a child in the back of the car. - **Credentials stay out of the database.** The replica reads its user and password from the environment each time it connects, and never stores them. `bolt+s://` checks the source's certificate, and you can trust your own certificate authority with `GDB_REPLICA_SOURCE_CA_FILE`. - **`CALL gdb.replication.followers()`** on the source shows who's following and how far behind they are. Building this turned up a bug in `RESYNC` that dated back to 1.4.0. A replica that was copied again kept its old transaction numbering, and could skip the first transaction that followed. That's fixed for every replica, same-server or not. If it can't line up exactly with the source, a copy now fails loudly instead of skipping quietly. The [replicas guide](/docs/operations/replicas#replicas-on-another-instance) has the setup. The server being copied needs an Enterprise licence; the replicas themselves are happy on Commercial. Both servers need `GDB_REPLICATION=on`. The server is about 0.3 MB bigger for it: the Bolt client a replica uses, and the list of certificate authorities it trusts. We've decided we can live with that. ## Elsewhere in the galaxy - **[Galactus Cloud](/cloud) is in beta.** If you'd rather not run a server at all, we'll run one for you: a dedicated machine with its own TLS hostname, daily backups you can download, an optional IP allowlist, and six regions at the same price. Ordering takes a few minutes, and you connect with any Bolt driver or with Explorer, with the login already filled in (that's where 1.6.3 earned its keep). - **There's an Enterprise licence.** It's everything in Commercial, plus replicas on other servers and support from the people who wrote it. See [pricing](/pricing), or [get in touch](/contact?topic=enterprise). ## Upgrading Pull and restart: ```text docker pull ianknowles/galactus-db:1.6.5 ``` The data, commit log, snapshot and dump formats haven't changed since 1.6.1, so any 1.6 release opens the others' databases, and there's nothing to migrate. Remote replicas are off until you set `GDB_REPLICATION=on`. ## What's next Replicas on another server are the first step towards **Nebula**: a cluster of Galactus DB servers that keeps running when one of them doesn't. One server fails, another takes over, and nobody has to get up at 3am. Four releases in four days. We're going to have a cup of tea now.