Read replicas¶
Table of contents
Introduction¶
Hasura Cloud can load balance queries and subscriptions across read replicas while sending all mutations and metadata API calls to the primary.
Adding read replica urls¶
Currently it is only possible to add read replicas for a database at the time of connecting.
Head to Data -> Manage -> Connect database
You can add read replicas for a database by adding their config to the /metadata/databases/database.yaml file:
- name: <db-name>
kind: postgres
configuration:
connection_info:
database_url:
from_env: <DATABASE_URL_ENV>
pool_settings:
idle_timeout: 180
max_connections: 50
retries: 1
read_replicas:
- database_url:
from_env: <DATABASE_REPLICA_URL_ENV>
pool_settings:
idle_timeout: 180
max_connections: 50
retries: 1
Apply the metadata by running:
hasura metadata apply
Currently it is only possible to add read replicas for a database at the time of connecting using the pg_add_source metadata API
POST /v1/metadata HTTP/1.1
Content-Type: application/json
X-Hasura-Role: admin
{
"type": "pg_add_source",
"args": {
"name": "<db_name>",
"configuration": {
"connection_info": {
"database_url": {
"from_env": "<DATABASE_URL_ENV>"
}
},
"read_replicas": [
{
"database_url": {
"from_env": "<DATABASE_REPLICA_URL_ENV>"
},
"pool_settings": {
"retries": 1,
"idle_timeout": 180,
"max_connections": 50
}
}
]
}
}
For existing v1.3 projects
If you have configured your Postgres instances with replicas, the replica URLs can be added to Hasura using the following environment variable in your project ENV Vars tab:
HASURA_GRAPHQL_READ_REPLICA_URLS=postgres://user:password@replica-host:5432/db
If you have multiple replicas, their urls can be added as comma separated values.
Additional environment variables for read replicas specifically:
HASURA_GRAPHQL_CONNECTIONS_PER_READ_REPLICA
HASURA_GRAPHQL_STRIPES_PER_READ_REPLICA
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