Project: Stolon (App Definition and Development / Database)
File: simplecluster.md

These are the steps to setup and test a simple cluster. This example assumes a running etcd 3.x server on localhost. We'll use the etcd v3 api to store stolon data inside etcd. Note: under ubuntu the `initdb` command is not provided in the path. You should updated the exported `PATH` env variable or provide the `--pg-bin-path` command line option to the `stolon-keeper` command. The first step is to initialize a cluster with a cluster specification. For now we'll just initialize a cluster without providing a cluster specification but using a default one that will just start with an empty database cluster. ``` ./bin/stolonctl --cluster-name stolon-cluster --store-backend=etcdv3 init ``` If you want to automate this step you can just pass an initial cluster specification to the sentinels with the `--initial-cluster-spec` option. The sentinel will become the sentinels leader for the cluster named `stolon-cluster`. ``` ./bin/stolon-sentinel --cluster-name stolon-cluster --store-backend=etcdv3 ``` ``` sentinel id id=66613766 Trying to acquire sentinels leadership sentinel leadership acquired ``` ``` ./bin/stolon-keeper --cluster-name stolon-cluster --store-backend=etcdv3 --uid postgres0 --data-dir data/postgres0 --pg-su-password=supassword --pg-repl-username=repluser --pg-repl-password=replpassword --pg-listen-address=127.0.0.1 ``` This will start a stolon keeper with id `postgres0` listening by default on localhost:5431, it will setup and initialize a postgres instance inside `data/postgres0/postgres/` ``` exclusive lock on data dir taken keeper uid uid=postgres0 stopping database our keeper data is not available, waiting for it to appear our keeper data is not available, waiting for it to appear current db UID different than cluster data db UID db= cdDB=2a87ea79 initializing the database cluster cannot get configured pg parameters error=dial tcp 127.0.0.1:5432: getsockopt: connection refused starting database error getting pg state error=pq: password authentication failed for user "repluser" setting roles setting superuser password superuser password set creating replication role replication role created role=repluser stopping database our db requested role is master starting database already master postgres parameters changed, reloading postgres instance reloading database configuration ``` The sentinel will elect it as the master instance: ``` trying to find initial master initializing cluster keeper=postgres0 received db state for unexpected db uid receivedDB= db=2a87ea79 waiting for db db=2a87ea79 keeper=postgres0 waiting for db db=2a87ea79 keeper=postgres0 waiting for db db=2a87ea79 keeper=postgres0 db initialized db=2a87ea79 keeper=postgres0 ``` Now we can start the proxy ``` ./bin/stolon-proxy --cluster-name stolon-cluster --store-backend=etcdv3 --port 25432 ``` ``` proxy id id=63323266 Starting proxying master address address=127.0.0.1:5432 ``` Since this simple cluster is running on localhost, the current user (which started the first keeper) is the same superuser created at db initialization and the default pg_hba.conf trusts it, you can login without a

``` psql --host localhost --port 25432 postgres psql (9.4.5, server 9.4.4) Type "help" for help. postgres=# ``` Connect to the db. Create a test table and do some inserts (we use the "postgres" database for these tests but usually this shouldn't be done). ``` postgres=# create table test (id int primary key not null, value text not null); CREATE TABLE postgres=# insert into test values (1, 'value1'); INSERT 0 1 postgres=# select * from test; id | value -+-- 1 | value1 (1 row) ``` ``` ./bin/stolon-keeper --cluster-name stolon-cluster --store-backend=etcdv3 --uid postgres1 --data-dir data/postgres1 --pg-su-password=supassword --pg-repl-username=repluser --pg-repl-password=replpassword --pg-listen-address=127.0.0.1 --pg-port 5435 ``` This instance will start replicating from the master (postgres0) ``` exclusive lock on data dir taken keeper uid uid=postgres1 stopping database our keeper data is not available, waiting for it to appear our keeper data is not available, waiting for it to appear current db UID different than cluster data db UID db= cdDB=63343433 database cluster not initialized our db requested role is standby followedDB=2a87ea79 running pg_basebackup sync succeeded starting database postgres parameters changed, reloading postgres instance reloading database configuration our db requested role is standby followedDB=2a87ea79 already standby ``` You can now try killing the actual keeper managing the master postgres instance (if killed with SIGKILL it'll leave an unmanaged postgres instance, if you terminate it with SIGTERM it'll also stop the postgres instance before exiting) (if you just kill postgres, it'll be restarted by the keeper usually before the sentinels declares it as not healty) noticing that the sentinels will: declare the master as not healty. elect the standby as the new master. Remove the proxyconf. The current `psql` connection will be dropped. Wait for the new master to be ready. Update the proxyconf with the new master address. ``` no keeper info available db=2a87ea79 keeper=postgres0 no keeper info available db=2a87ea79 keeper=postgres0 master db is failed db=2a87ea79 keeper=postgres0 trying to find a standby to replace failed master electing db as the new master db=63343433 keeper=postgres1 ``` Now, inside the previous `psql` session you can redo the last select. The first time `psql` will report that the connection was closed and then it successfully reconnected: ``` postgres=# select * from test; server closed the connection unexpectedly This probably means the server terminated abnormally before or while processing the request. The connection to the server was lost. Attempting reset: Succeeded. postgres=# select * from test; id | value -+-- 1 | value1 (1 row) ``` If you start the `postgres0` keeper it'll read the new cluster view and make the old master become a standby of the new master.