peza / streaming-replication-docker-

TimescaleDB Streaming Replication in Docker

Streaming Replication Container Setup for TimescaleDB

Use this repository to launch a streaming replication enabled TimescaleDB cluster with 1 primary and 1 replica. It is based off of the latest-pg10 TimescaleDB docker image.

The Dockerfile takes advantage of PostgreSQL's init script hooks and runs replication.sh after the database has been initialized to configure the replication settings. replication.sh uses the variables defined in primary.env and replica.env, which are meant to be configured depending on your desired replication settings, credentials, and networking preferences.

WARNING: While replication.sh gets run as the postgres user since it is part of a PostgreSQL entrypoint script, the current TimescaleDB image logs in as root by default. Be careful if making changes through docker exec or similar commands, as making permissions changes with root will likely break things for the postgres user. We recommend either running docker exec with --user=postgres or running su postgres inside of the interactive shell.

Running

The containers can either be created through regular Docker commands or through Docker Swarm / Docker Compose using the stack.yml file.

Run with Docker

start_containers.sh creates a Docker network bridge to connect the primary and replica then uses the Dockerfile to run replication.sh against both database instances.

After ensuring the variables in primary.env and replica.env match your desired configuration, simply run:

./start_containers.sh

This will create and run 2 replication-ready containers named timescale-primary and timescale-replica.

Run with Docker Swarm

Provided you already have a swarm intialized, you can deploy the stack using stack.yml after building the image:

docker build -t timescale-replication .
docker stack deploy replication --compose-file stack.yml

stack.yml uses primary.env and replica.env for its environment variables, so make changes in those files to tweak the settings.

NOTE: The stack.yml file sets the REPLICATION_SUBNET on the primary to 10.0.0.0/24 by default, allowing all traffic within the service's internal network to connect as the replica user. To tweak this ACL, change the REPLICATION_SUBNET variable in stack.yml. Note, however, that the technique we use for the regular Docker setup (using getent to resolve the Docker hostname to an exact IP -- see replication.sh) does not work inside of Swarm. The Docker hostname resolves to Docker's service IP, which points to the same container, but the container itself connects from a separate internal IP, which will render any /32 subnet on the primary ineffective.

Run with Docker Compose

To run with Docker Compose, run:

docker build -t timescale-replication .
docker-compose -f stack.yml up

NOTE: By default stack.yml sets the REPLICATION_SUBNET (used by pg_hba to authorize IPs for replication) to 10.0.0.0/24 for compatibility with Docker Swarm (see above). Depending on your network configuration this may not work with Docker Compose. Either overwrite it with an appropriate subnet setting (172.0.0.0/8 will allow all containers on the default Docker network bridge to connect as replicas) or remove the variable altogether to force the replication.sh to use the full IP of the replica, which should work with Docker Compose, but will not work with Docker Swarm.

Configuration

Configure various replication settings via the primary.env and replica.env files. Whether the replication is synchronous or asynchronous (and to what degree) can be tuned using the SYNCRHONOUS_COMMIT variable in primary.env. The setting defaults to off, enabling fully asynchronous streaming replication. The other valid values are on, local, remote_write, and remote_apply. Consult our [documentation][timescale-streamrep-docs] for further details about trade-offs (i.e., performance vs. lag time, etc).