graphql-engine/server/src-lib/Hasura/RemoteSchema/MetadataAPI/Core.hs
Auke Booij cdac24c79f server: delete the Cacheable type class in favor of Eq
What is the `Cacheable` type class about?
```haskell
class Eq a => Cacheable a where
  unchanged :: Accesses -> a -> a -> Bool
  default unchanged :: (Generic a, GCacheable (Rep a)) => Accesses -> a -> a -> Bool
  unchanged accesses a b = gunchanged (from a) (from b) accesses
```
Its only method is an alternative to `(==)`. The added value of `unchanged` (and the additional `Accesses` argument) arises _only_ for one type, namely `Dependency`. Indeed, the `Cacheable (Dependency a)` instance is non-trivial, whereas every other `Cacheable` instance is completely boilerplate (and indeed either generated from `Generic`, or simply `unchanged _ = (==)`). The `Cacheable (Dependency a)` instance is the only one where the `Accesses` argument is not just passed onwards.

The only callsite of the `unchanged` method is in the `ArrowCache (Rule m)` method. That is to say that the `Cacheable` type class is used to decide when we can re-use parts of the schema cache between Metadata operations.

So what is the `Cacheable (Dependency a)` instance about? Normally, the output of a `Rule m a b` is re-used when the new input (of type `a`) is equal to the old one. But sometimes, that's too coarse: it might be that a certain `Rule m a b` only depends on a small part of its input of type `a`. A `Dependency` allows us to spell out what parts of `a` are being depended on, and these parts are recorded as values of types `Access a` in the state `Accesses`.

If the input `a` changes, but not in a way that touches the recorded `Accesses`, then the output `b` of that rule can be re-used without recomputing.

So now you understand _why_ we're passing `Accesses` to the `unchanged` method: `unchanged` is an equality check in disguise that just needs some additional context.

But we don't need to pass `Accesses` as a function argument. We can use the `reflection` package to pass it as type-level context. So the core of this PR is that we change the instance declaration from
```haskell
instance (Cacheable a) => Cacheable (Dependency a) where
```
to
```haskell
 instance (Given Accesses, Eq a) => Eq (Dependency a) where
```
and use `(==)` instead of `unchanged`.

If you haven't seen `reflection` before: it's like a `MonadReader`, but it doesn't require a `Monad`.

In order to pass the current `Accesses` value, instead of simply passing the `Accesses` as a function argument, we need to instantiate the `Given Accesses` context. We use the `give` method from the `reflection` package for that.
```haskell
give :: forall r. Accesses -> (Given Accesses => r) -> r

unchanged :: (Given Accesses => Eq a) => Accesses -> a -> a -> Bool
unchanged accesses a b = give accesses (a == b)
```
With these three components in place, we can delete the `Cacheable` type class entirely.

The remainder of this PR is just to remove the `Cacheable` type class and its instances.

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/6877
GitOrigin-RevId: 7125f5e11d856e7672ab810a23d5bf5ad176e77f
2022-11-21 16:35:37 +00:00

213 lines
7.2 KiB
Haskell

{-# LANGUAGE TemplateHaskell #-}
module Hasura.RemoteSchema.MetadataAPI.Core
( AddRemoteSchemaQuery (..),
RemoteSchemaNameQuery (..),
runAddRemoteSchema,
runRemoveRemoteSchema,
dropRemoteSchemaInMetadata,
runReloadRemoteSchema,
runIntrospectRemoteSchema,
dropRemoteSchemaPermissionInMetadata,
dropRemoteSchemaRemoteRelationshipInMetadata,
runUpdateRemoteSchema,
)
where
import Data.Aeson.TH qualified as J
import Data.Environment qualified as Env
import Data.HashMap.Strict qualified as Map
import Data.HashMap.Strict.InsOrd qualified as OMap
import Data.HashSet qualified as S
import Data.Text.Extended
import Hasura.Base.Error
import Hasura.EncJSON
import Hasura.GraphQL.RemoteServer
import Hasura.Prelude
import Hasura.RQL.Types.Common
import Hasura.RQL.Types.Metadata
import Hasura.RQL.Types.Metadata.Object
import Hasura.RQL.Types.SchemaCache
import Hasura.RQL.Types.SchemaCache.Build
import Hasura.RQL.Types.SchemaCacheTypes
import Hasura.RemoteSchema.Metadata
import Hasura.RemoteSchema.SchemaCache.Build (addRemoteSchemaP2Setup)
import Hasura.RemoteSchema.SchemaCache.Types
import Hasura.Session
import Hasura.Tracing qualified as Tracing
import Network.HTTP.Client.Manager (HasHttpManagerM (..))
-- | The payload for 'add_remote_schema', and a component of 'Metadata'.
data AddRemoteSchemaQuery = AddRemoteSchemaQuery
{ -- | An internal identifier for this remote schema.
_arsqName :: RemoteSchemaName,
_arsqDefinition :: RemoteSchemaDef,
-- | An opaque description or comment. We might display this in the UI, for instance.
_arsqComment :: Maybe Text
}
deriving (Show, Eq, Generic)
instance NFData AddRemoteSchemaQuery
$(J.deriveJSON hasuraJSON ''AddRemoteSchemaQuery)
newtype RemoteSchemaNameQuery = RemoteSchemaNameQuery
{ _rsnqName :: RemoteSchemaName
}
deriving (Show, Eq)
$(J.deriveJSON hasuraJSON ''RemoteSchemaNameQuery)
runAddRemoteSchema ::
( QErrM m,
CacheRWM m,
MonadIO m,
HasHttpManagerM m,
MetadataM m,
Tracing.MonadTrace m
) =>
Env.Environment ->
AddRemoteSchemaQuery ->
m EncJSON
runAddRemoteSchema env (AddRemoteSchemaQuery name defn comment) = do
addRemoteSchemaP1 name
void $ addRemoteSchemaP2Setup env name defn
buildSchemaCacheFor (MORemoteSchema name) $
MetadataModifier $
metaRemoteSchemas %~ OMap.insert name remoteSchemaMeta
pure successMsg
where
-- NOTE: permissions here are empty, manipulated via a separate API with
-- runAddRemoteSchemaPermissions below
remoteSchemaMeta = RemoteSchemaMetadata name defn comment mempty mempty
addRemoteSchemaP1 ::
(QErrM m, CacheRM m) =>
RemoteSchemaName ->
m ()
addRemoteSchemaP1 name = do
remoteSchemaNames <- getAllRemoteSchemas <$> askSchemaCache
when (name `elem` remoteSchemaNames) $
throw400 AlreadyExists $
"remote schema with name "
<> name <<> " already exists"
runRemoveRemoteSchema ::
(QErrM m, UserInfoM m, CacheRWM m, MetadataM m) =>
RemoteSchemaNameQuery ->
m EncJSON
runRemoveRemoteSchema (RemoteSchemaNameQuery rsn) = do
void $ removeRemoteSchemaP1 rsn
withNewInconsistentObjsCheck $
buildSchemaCache $
dropRemoteSchemaInMetadata rsn
pure successMsg
removeRemoteSchemaP1 ::
(UserInfoM m, QErrM m, CacheRM m) =>
RemoteSchemaName ->
m [RoleName]
removeRemoteSchemaP1 rsn = do
sc <- askSchemaCache
let rmSchemas = scRemoteSchemas sc
void $
onNothing (Map.lookup rsn rmSchemas) $
throw400 NotExists "no such remote schema"
let depObjs = getDependentObjs sc remoteSchemaDepId
roles = mapMaybe getRole depObjs
nonPermDependentObjs = filter nonPermDependentObjPredicate depObjs
-- report non permission dependencies (if any), this happens
-- mostly when a remote relationship is defined with
-- the current remote schema
-- we only report the non permission dependencies because we
-- drop the related permissions
unless (null nonPermDependentObjs) $ reportDependentObjectsExist nonPermDependentObjs
pure roles
where
remoteSchemaDepId = SORemoteSchema rsn
getRole depObj =
case depObj of
SORemoteSchemaPermission _ role -> Just role
_ -> Nothing
nonPermDependentObjPredicate (SORemoteSchemaPermission _ _) = False
nonPermDependentObjPredicate _ = True
runReloadRemoteSchema ::
(QErrM m, CacheRWM m, MetadataM m) =>
RemoteSchemaNameQuery ->
m EncJSON
runReloadRemoteSchema (RemoteSchemaNameQuery name) = do
remoteSchemas <- getAllRemoteSchemas <$> askSchemaCache
unless (name `elem` remoteSchemas) $
throw400 NotExists $
"remote schema with name " <> name <<> " does not exist"
let invalidations = mempty {ciRemoteSchemas = S.singleton name}
metadata <- getMetadata
withNewInconsistentObjsCheck $
buildSchemaCacheWithOptions (CatalogUpdate Nothing) invalidations metadata
pure successMsg
runIntrospectRemoteSchema ::
(CacheRM m, QErrM m) => RemoteSchemaNameQuery -> m EncJSON
runIntrospectRemoteSchema (RemoteSchemaNameQuery rsName) = do
sc <- askSchemaCache
RemoteSchemaCtx {..} <-
Map.lookup rsName (scRemoteSchemas sc) `onNothing` throw400 NotExists ("remote schema: " <> rsName <<> " not found")
pure $ encJFromLBS _rscRawIntrospectionResult
runUpdateRemoteSchema ::
( QErrM m,
CacheRWM m,
MonadIO m,
HasHttpManagerM m,
MetadataM m,
Tracing.MonadTrace m
) =>
Env.Environment ->
AddRemoteSchemaQuery ->
m EncJSON
runUpdateRemoteSchema env (AddRemoteSchemaQuery name defn comment) = do
remoteSchemaNames <- getAllRemoteSchemas <$> askSchemaCache
remoteSchemaMap <- _metaRemoteSchemas <$> getMetadata
let metadataRMSchema = OMap.lookup name remoteSchemaMap
metadataRMSchemaPerms = maybe mempty _rsmPermissions metadataRMSchema
-- `metadataRMSchemaURL` and `metadataRMSchemaURLFromEnv` represent
-- details that were stored within the metadata
metadataRMSchemaURL = (_rsdUrl . _rsmDefinition) =<< metadataRMSchema
metadataRMSchemaURLFromEnv = (_rsdUrlFromEnv . _rsmDefinition) =<< metadataRMSchema
-- `currentRMSchemaURL` and `currentRMSchemaURLFromEnv` represent
-- the details that were provided in the request
currentRMSchemaURL = _rsdUrl defn
currentRMSchemaURLFromEnv = _rsdUrlFromEnv defn
unless (name `elem` remoteSchemaNames) $
throw400 NotExists $
"remote schema with name " <> name <<> " doesn't exist"
rsi <- validateRemoteSchemaDef env defn
-- we only proceed to fetch the remote schema if the url has been updated
unless
( (isJust metadataRMSchemaURL && isJust currentRMSchemaURL && metadataRMSchemaURL == currentRMSchemaURL)
|| (isJust metadataRMSchemaURLFromEnv && isJust currentRMSchemaURLFromEnv && metadataRMSchemaURLFromEnv == currentRMSchemaURLFromEnv)
)
$ do
httpMgr <- askHttpManager
void $ fetchRemoteSchema env httpMgr name rsi
-- This will throw an error if the new schema fetched in incompatible
-- with the existing permissions and relations
withNewInconsistentObjsCheck $
buildSchemaCacheFor (MORemoteSchema name) $
MetadataModifier $
metaRemoteSchemas %~ OMap.insert name (remoteSchemaMeta metadataRMSchemaPerms)
pure successMsg
where
remoteSchemaMeta perms = RemoteSchemaMetadata name defn comment perms mempty