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Federation driver: redis

A full-featured federation driver that keeps track of Keppel accounts in a Redis that's shared between all participating Keppel instances. You probably want a clustered Redis setup like Dynomite to avoid a single point of failure, but a single Redis instance also works fine as long as all Keppels can reach it. The Redis is only read from and written when creating or deleting accounts and when issuing sublease tokens.

Server-side configuration

export KEPPEL_DRIVER_FEDERATION='{"type":"redis","params":{...}}'

The following parameters may be supplied in $KEPPEL_DRIVER_FEDERATION (in JSON format):

Field Type Explanation
env_prefix string A common prefix for all environment variables checked by this driver. Defaults to KEPPEL_FEDERATION_REDIS.
key_prefix string A prefix string that is prepended to all keys that this driver accesses in the Redis. This is useful for separating QA from productive deployments etc. Defaults to keppel.

The following environment variables may be supplied:

Variable Default Explanation
${params.env_prefix}_HOSTNAME (required) Hostname identifying the location of the shared Redis instance. This is separate from KEPPEL_REDIS_HOSTNAME since that one is usually local to the current Keppel instance whereas the federation Redis is shared among all Keppel instances in your deployment.
${params.env_prefix}_PORT 6379 Port on which the shared Redis instance is running on.
${params.env_prefix}_DB_NUM 0 Database number.
${params.env_prefix}_PASSWORD (optional) Password for the authentication.
${params.env_prefix}_PREFIX keppel A prefix string that is prepended to all keys that this driver accesses in the Redis. This is useful for separating QA from productive deployments etc.

In Redis, the driver accesses the following keys:

Key Type Explanation
${params.key_prefix}-primary-${NAME} string The hostname of the keppel-api hosting the primary account with that name.
${params.key_prefix}-replicas-${NAME} array of strings The hostnames of the keppel-apis hosting replica accounts with that name.
${params.key_prefix}-sublease-token-${NAME} string The sublease token that was most recently issued by the keppel-api hosting the primary account with that name. Will be replaced with the empty string when the token is redeemed to create a replica account.