graphql-engine/docs/graphql/cloud/read-replicas.rst
2020-08-25 21:51:21 +05:30

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.. meta::
:description: Hasura Cloud read replicas
:keywords: hasura, docs, cloud, read replicas, connections, pool
.. _read_replicas:
Read replicas
=============
.. contents:: Table of contents
:backlinks: none
:depth: 1
:local:
Introduction
------------
Hasura Cloud can load balance queries and subscriptions across read replicas while sending all mutations and metadata API calls to the master.
Adding read replica urls
------------------------
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:
.. code-block:: bash
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.
Connection pool parameters
--------------------------
Additional environment variables for connection pools, and for read replicas specifically:
``HASURA_GRAPHQL_PG_STRIPES``
``HASURA_GRAPHQL_PG_CONNECTIONS``
``HASURA_GRAPHQL_CONNECTIONS_PER_READ_REPLICA``
``HASURA_GRAPHQL_STRIPES_PER_READ_REPLICA``