In the example below, we are going to set up a three node CouchDB cluster. (Three is the minimum number needed to support clustering features.) We'll also set up a separate, single machine for making backups. In this example we will be using LXD.
We launch a (single) new container, install couchdb via snap from the store and enable interfaces, open up the bind address and set a admin password.
1. localhost> lxc launch ubuntu:18.04 couchdb-c1 1. localhost> lxc exec couchdb-c1 bash 1. couchdb-c1> apt update 1. couchdb-c1> snap install couchdb --edge 1. couchdb-c1> snap connect couchdb:mount-observe 1. couchdb-c1> snap connect couchdb:process-control 1. couchdb-c1> curl -X PUT http://localhost:5984/_node/_local/_config/httpd/bind_address -d '"0.0.0.0"' 1. couchdb-c1> curl -X PUT http://localhost:5984/_node/_local/_config/admins/admin -d '"Be1stDB"' 1. couchdb-c1> exit
Back on localhost, we can then use the LXD copy function to speed up installation:
$ lxc copy couchdb-c1 couchdb-c2 $ lxc copy couchdb-c1 couchdb-c3 $ lxc copy couchdb-c1 couchdb-bkup $ lxc start couchdb-c2 $ lxc start couchdb-c3 $ lxc start couchdb-bkup
We are going to need the IP addresses:
$ lxc list
Now, again from localhost, and using the lxc exec commond, we will use the snap configuration tool to set the various configuration files.
$ lxc exec couchdb-c1 snap set couchdb name=couchdb@10.210.199.73 setcookie=monster $ lxc exec couchdb-c2 snap set couchdb name=couchdb@10.210.199.221 setcookie=monster $ lxc exec couchdb-c3 snap set couchdb name=couchdb@10.210.199.121 setcookie=monster
The backup machine we will configure as a single instance (n=1).
$ lxc exec couchdb-bkup snap set couchdb name=couchdb@127.0.0.1 setcookie=monster $ lxc exec couchdb-bkup -- curl -X PUT http://admin:Be1stDB@localhost:5984/_node/_local/_config/cluster/n -d '"1"' $ lxc exec couchdb-bkup -- curl -X PUT http://admin:Be1stDB@localhost:5984/_node/_local/_config/cluster/q -d '"1"'
Each snap must be restarted for the new configurations to take affect.
$ lxc exec couchdb-c1 snap restart couchdb $ lxc exec couchdb-c2 snap restart couchdb $ lxc exec couchdb-c3 snap restart couchdb $ lxc exec couchdb-bkup snap restart couchdb
The configuration files are stored here.
$ lxc exec couchdb-bkup cat /var/snap/couchdb/current/etc/vm.args
Any changes to couchdb from the http configutation tool are made here
$ lxc exec couchdb-bkup cat /var/snap/couchdb/current/etc/local.ini
Now we set up the cluster via the http front-end. This only needs to be run once on the first machine. The last command syncs with the other nodes and creates the standard databases.
$ curl -X POST -H "Content-Type: application/json" http://admin:Be1stDB@10.210.199.73:5984/_cluster_setup -d '{"action": "add_node", "host":"10.210.199.221", "port": "5984", "username": "admin", "password":"Be1stDB"}' $ curl -X POST -H "Content-Type: application/json" http://admin:Be1stDB@10.210.199.73:5984/_cluster_setup -d '{"action": "add_node", "host":"10.210.199.121", "port": "5984", "username": "admin", "password":"Be1stDB"}' $ curl -X POST -H "Content-Type: application/json" http://admin:Be1stDB@10.210.199.73:5984/_cluster_setup -d '{"action": "finish_cluster"}'
Now we have a functioning three node cluster.
Let's create an example database ...
$ curl -X PUT http://admin:Be1stDB@10.210.199.73:5984/example $ curl -X PUT http://admin:Be1stDB@10.210.199.73:5984/example/aaa -d '{"test":1}' -H "Content-Type: application/json" $ curl -X PUT http://admin:Be1stDB@10.210.199.73:5984/example/aab -d '{"test":2}' -H "Content-Type: application/json" $ curl -X PUT http://admin:Be1stDB@10.210.199.73:5984/example/aac -d '{"test":3}' -H "Content-Type: application/json"
... And see that it is created on all three nodes.
$ curl -X GET http://admin:Be1stDB@10.210.199.73:5984/example/_all_docs $ curl -X GET http://admin:Be1stDB@10.210.199.221:5984/example/_all_docs $ curl -X GET http://admin:Be1stDB@10.210.199.121:5984/example/_all_docs
Our backup server is on 10.210.199.242. We will manually replicate to this from one (can be any one) of the nodes.
$ curl -X POST http://admin:Be1stDB@10.210.199.242:5984/_replicate -d '{"source":"http://10.210.199.73:5984/example", "target":"example", "continuous":false,"create_target":true}' -H "Content-Type: application/json" $ curl -X GET http://admin:Be1stDB@10.210.199.242:5984/example/_all_docs
Whereas the data store for the clusters nodes is sharded:
$ lxc exec couchdb-c1 ls /var/snap/couchdb/common/data/shards/
The backup database is a single directory:
$ lxc exec couchdb-bkup ls /var/snap/couchdb/common/data/shards/
The logs, by default, are captured by journald. First connect to the node in question: $ lxc exec couchdb-c1 bash Then, show logs as usual. couchdb is likely prefixed with ‘snap’ and suffix may vary depending on the version of snap. $ journalctl -u snap.couchdb* -f