Replace zap with zerolog.
zerolog has a cleaner interface and can be easily configured with custom
error chain printing using a new error handling library that will be
implemented in another PR.
* Create an APIError that should only be used for api returned errors.
It'll wrap an error and can have different Kinds and optional code and
message.
* The http handlers will use the first APIError available in the
error chain and generate a json response body containing the code and
the user message. The wrapped error is internal and is not sent in the
response.
If no api error is available in the chain a generic internal
server error will be returned.
* Add a RemoteError type that will be created from remote services calls
(runservice, configstore). It's similar to the APIError but a
different type to not propagate to the caller response and it'll not
contain any wrapped error.
* Gateway: when we call a remote service, by default, we'll create a
APIError using the RemoteError Kind (omitting the code and the
message that usually must not be propagated).
This is done for all the remote service calls as a starting point, in
future, if this default behavior is not the right one for a specific
remote service call, a new api error with a different kind and/or
augmented with the calling service error codes and user messages could
be created.
* datamanager: Use a dedicated ErrNotExist (and converting objectstorage
ErrNotExist).
Implement runservice maintenance mode and export/import.
When runservice is set in maintenance mode it'll start only the maintenance and
export/import handlers.
Setting maintenance mode will set a key in etcd so all the runservice instances
will detect it and enter in maintenance mode. This is done asyncronously so it
could take some time (future improvements will add some api to show all the
runservice states)
Export is always available and will export the datamanager contents. Currently
only datamanager contents are exported (no logs and workspace archives).
Import is available only during maintenance, given a datamanager export will
import it and reset etcd to this import state.
Simone Gotti