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Persistence & Data storage

Background​

Pomerium keeps persistent state out of most components, but an identity-aware access proxy must maintain some data about every user's session. Historically, all user/session related data was stored in cookies, but this quickly became challenging.

  • Cookie and header limits would impact large organizations and some IdPs
  • SPAs would break when session cookies expired
  • No central visibility or management of existing sessions
  • Group membership was fixed from session creation
  • Slow initial authentication flow to fetch user data

To address these limitations, the Pomerium databroker service runs a number of internal services responsible for maintaining data and state.

Design​

The databroker is responsible for providing a stateful storage layer. Services which require high performance maintain a streaming local cache of the contents of the databroker, while others may call databroker in real time. Only the databroker is expected to maintain authoritative state.

Persistence​

At this time, most data stored by Pomerium is externally sourced and recoverable at startup (eg, group membership). The notable exception is user sessions. If the data hosted by the databroker is lost, users will need to log in through their IdP again at next session expiration.

To prevent early session loss in production deployments, persistent storage backends are available for configuration in the databroker. Use of these is strongly encouraged, but smaller or non-production deployments can make use of an in-memory storage layer if external dependencies are not practical or justifiable.

Backends​

Configuration options for each backend are detailed in databroker configuration reference.

In all backends, Pomerium encrypts record values. This ensures security of all records at rest, regardless of data store capabilities. While this prevents many classes of attack vector, additional security measures should always be taken to secure data in transit and minimize access to the backends themselves.

Please see Pomerium backend and upstream storage system documentation for best practices.

In-Memory​

  • Data Broker Service HA: no
  • Data Store HA: no
  • Data Persistence: no

The default storage backend for databroker is memory based. This backend provides easy deployment semantics but is not persistent or highly available. Running more than one databroker instance configured for memory backed storage is not supported and will lead to non-deterministic behavior.

Postgres​

  • Data Broker Service HA: yes
  • Data Store HA: yes
  • Data Persistence: yes

The Postgres based backend supports multiple databroker instances and persistence across restarts. We recommend a dedicated Postgres instance for Pomerium to provide the strongest security and performance guarantees.

Example configuration:

databroker_storage_type: postgres
databroker_storage_connection_string: postgres://user:pass@dbhost.internal.mydomain.com/pomerium?sslmode=disable

The connection string for postgres follows the same conventions as libpq:

postgresql://[userspec@][hostspec][/dbname][?paramspec]

where userspec is:

user[:password]

and hostspec is:

[host][:port][,...]

and paramspec is:

name=value[&...]

When using multiple hosts make sure to specify target_session_attrs=read-write so that the Databroker does not attempt to write to a read-only replica.

Redis​

Previous versions of Pomerium suggested Redis as a databroker back-end. This is no longer recommended for version >=18. You can review Archived Versions of our docs for more information on Redis as a databroker storage solution.

High Availability​

Redis should be configured to provide high availability via replication and failover.

Security​

Pomerium supports and strongly encourages ACL based authentication. To set up an ACL for pomerium, use the following template:

ACL setuser pomerium on >[PASSWORD] ~* +@all -@scripting -@dangerous -@admin -@connection

Pomerium supports and strongly encourages TLS support in Redis version 6. Both traditional and mutual TLS are supported.

Example secure configuration:

databroker_storage_type: redis
databroker_storage_connection_string: rediss://pomerium:PASSWORD@[HOST]:6379/
databroker_storage_cert_file: /tls/client.pem
databroker_storage_key_file: /tls/client.key
databroker_storage_ca_file: /tls/ca.pem
tip

the second s in rediss is intentional and turns on TLS support

Troubleshooting​

Most issues with the Databroker service are caused by a shared_secret mismatch between services. See Troubleshooting - Shared Secret Mismatch for details.