New reva config

[gmgigi96]

Context and Problem Statement

The configuration process for reva presents significant challenges due to its microservice architecture, which necessitates the repetition of configuration parameters across different parts of the services. To enable various drivers of the same service provider, such as LDAP, OIDC, and public shares as authentication providers, different TOML files are needed for each service.

Additionally, each microservice within reva requires the specification of a unique address, which demands a deep understanding of the reva architecture.

Collectively, these issues make it arduous for users to deploy a simplified (mono-process) version of reva.

Decision drivers

• Repeated configurations across microservices
• Different configuration files just to enable one service (and its dependencies)

Decision Outcome

The configuration will contain a new [vars] section, containing all the common parameters used by different services.
These variables, in the form of name:value, can be recalled by a different part of the configuration, as values, using the sintax {{ vars.name }}. The values can be of any type.
For example:

[vars]
db_hostname = "database.cern.ch"
db_password = "secret-password"
db_port     = 10

[grpc.services.usershareprovider]
db_hostname = "{{ vars.db_hostname }}"
db_password = "{{ vars.db_password }}"
db_port     = "{{ vars.db_port }}"
...

[grpc.services.publicshareprovider]
db_hostname = "{{ vars.db_hostname }}"
db_password = "{{ vars.db_password }}"
db_port     = "{{ vars.db_port }}"
...

To enable different drivers of the same provider, every provider configuration is a list:

[[grpc.services.authprovider]]
driver = "oidc"

[[grpc.services.authprovider]]
driver = "machine"

It is still possible to declare only one provider, if it will be the only one in the configuration file.

[grpc.services.authprovider]
driver = "oidc"

Because the same provider cannot listen on the same port, every provider allow to specify an address in the form host:port.

[[grpc.services.authprovider]]
driver  = "oidc"
address = "localhost:9000"

[[grpc.services.authprovider]]
driver  = "machine"
address = "localhost:9001"

If the address variable is not provided, the runtime will allocate a random one. If other services have to refer to a provider address, the template {{ grpc.services.<name>[<index>].address }} can be used. The list is 0-based indexed, and the order reflects the same as in the configuration file.

[[grpc.services.authprovider]]
driver = "oidc"

[[grpc.services.authprovider]]
driver = "machine"

[grpc.services.authregistry.driver.static]
machine = "{{ grpc.services.authprovider[1].address }}"

A common address for all the services defined in the same toml file can be provider in the [grpc] section:

[grpc]
address = "localhost:9142"

[grpc.services.storageprovider]
...

[grpc.services.authprovider]
...

Having a list of providers with the grpc.address variable is not allowed.