graphql-engine/server/src-lib/Hasura/RemoteSchema/SchemaCache/Build.hs
Antoine Leblanc 6e574f1bbe harmonize network manager handling
## Description

### I want to speak to the `Manager`

Oh boy. This PR is both fairly straightforward and overreaching, so let's break it down.

For most network access, we need a [`HTTP.Manager`](https://hackage.haskell.org/package/http-client-0.1.0.0/docs/Network-HTTP-Client-Manager.html). It is created only once, at the top level, when starting the engine, and is then threaded through the application to wherever we need to make a network call. As of main, the way we do this is not standardized: most of the GraphQL execution code passes it "manually" as a function argument throughout the code. We also have a custom monad constraint, `HasHttpManagerM`, that describes a monad's ability to provide a manager. And, finally, several parts of the code store the manager in some kind of argument structure, such as `RunT`'s `RunCtx`.

This PR's first goal is to harmonize all of this: we always create the manager at the root, and we already have it when we do our very first `runReaderT`. Wouldn't it make sense for the rest of the code to not manually pass it anywhere, to not store it anywhere, but to always rely on the current monad providing it? This is, in short, what this PR does: it implements a constraint on the base monads, so that they provide the manager, and removes most explicit passing from the code.

### First come, first served

One way this PR goes a tiny bit further than "just" doing the aforementioned harmonization is that it starts the process of implementing the "Services oriented architecture" roughly outlined in this [draft document](https://docs.google.com/document/d/1FAigqrST0juU1WcT4HIxJxe1iEBwTuBZodTaeUvsKqQ/edit?usp=sharing). Instead of using the existing `HasHTTPManagerM`, this PR revamps it into the `ProvidesNetwork` service.

The idea is, again, that we should make all "external" dependencies of the engine, all things that the core of the engine doesn't care about, a "service". This allows us to define clear APIs for features, to choose different implementations based on which version of the engine we're running, harmonizes our many scattered monadic constraints... Which is why this service is called "Network": we can refine it, moving forward, to be the constraint that defines how all network communication is to operate, instead of relying on disparate classes constraint or hardcoded decisions. A comment in the code clarifies this intent.

### Side-effects? In my Haskell?

This PR also unavoidably touches some other aspects of the codebase. One such example: it introduces `Hasura.App.AppContext`, named after `HasuraPro.Context.AppContext`: a name for the reader structure at the base level. It also transforms `Handler` from a type alias to a newtype, as `Handler` is where we actually enforce HTTP limits; but without `Handler` being a distinct type, any code path could simply do a `runExceptT $ runReader` and forget to enforce them.

(As a rule of thumb, i am starting to consider any straggling `runReaderT` or `runExceptT` as a code smell: we should not stack / unstack monads haphazardly, and every layer should be an opaque `newtype` with a corresponding run function.)

## Further work

In several places, i have left TODOs when i have encountered things that suggest that we should do further unrelated cleanups. I'll write down the follow-up steps, either in the aforementioned document or on slack. But, in short, at a glance, in approximate order, we could:

- delete `ExecutionCtx` as it is only a subset of `ServerCtx`, and remove one more `runReaderT` call
- delete `ServerConfigCtx` as it is only a subset of `ServerCtx`, and remove it from `RunCtx`
- remove `ServerCtx` from `HandlerCtx`, and make it part of `AppContext`, or even make it the `AppContext` altogether (since, at least for the OSS version, `AppContext` is there again only a subset)
- remove `CacheBuildParams` and `CacheBuild` altogether, as they're just a distinct stack that is a `ReaderT` on top of `IO` that contains, you guessed it, the same thing as `ServerCtx`
- move `RunT` out of `RQL.Types` and rename it, since after the previous cleanups **it only contains `UserInfo`**; it could be bundled with the authentication service, made a small implementation detail in `Hasura.Server.Auth`
-  rename `PGMetadaStorageT` to something a bit more accurate, such as `App`, and enforce its IO base

This would significantly simply our complex stack. From there, or in parallel, we can start moving existing dependencies as Services. For the purpose of supporting read replicas entitlement, we could move `MonadResolveSource` to a `SourceResolver` service, as attempted in #7653, and transform `UserAuthenticationM` into a `Authentication` service.

PR-URL: https://github.com/hasura/graphql-engine-mono/pull/7736
GitOrigin-RevId: 68cce710eb9e7d752bda1ba0c49541d24df8209f
2023-02-22 15:55:54 +00:00

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{-# LANGUAGE Arrows #-}
module Hasura.RemoteSchema.SchemaCache.Build
( buildRemoteSchemas,
addRemoteSchemaP2Setup,
)
where
import Control.Arrow.Extended
import Control.Arrow.Interpret
import Control.Monad.Trans.Control (MonadBaseControl)
import Data.Aeson
import Data.ByteString.Lazy qualified as BL
import Data.Environment qualified as Env
import Data.HashMap.Strict.Extended qualified as M
import Data.Text.Extended
import Hasura.Base.Error
import Hasura.GraphQL.RemoteServer
import Hasura.Incremental qualified as Inc
import Hasura.Prelude
import Hasura.RQL.DDL.Schema.Cache.Common
import Hasura.RQL.DDL.Schema.Cache.Permission
import Hasura.RQL.Types.Metadata.Object
import Hasura.RQL.Types.Roles
import Hasura.RQL.Types.Roles.Internal (CheckPermission (..))
import Hasura.RQL.Types.SchemaCache
import Hasura.RQL.Types.SchemaCache.Build
import Hasura.RemoteSchema.Metadata
import Hasura.RemoteSchema.SchemaCache.Permission (resolveRoleBasedRemoteSchema)
import Hasura.RemoteSchema.SchemaCache.Types
import Hasura.Services
import Hasura.Session
import Hasura.Tracing qualified as Tracing
-- Resolves a user specified `RemoteSchemaMetadata` into information rich `RemoteSchemaCtx`
-- However, given the nature of remote relationships, we cannot fully 'resolve' them, so
-- we resolve of remote relationships as much as possible.
buildRemoteSchemas ::
( ArrowChoice arr,
Inc.ArrowDistribute arr,
ArrowWriter (Seq (Either InconsistentMetadata MetadataDependency)) arr,
Inc.ArrowCache m arr,
MonadIO m,
MonadBaseControl IO m,
Eq remoteRelationshipDefinition,
ToJSON remoteRelationshipDefinition,
MonadError QErr m,
ProvidesNetwork m
) =>
Env.Environment ->
( (Inc.Dependency (HashMap RemoteSchemaName Inc.InvalidationKey), OrderedRoles, Maybe (HashMap RemoteSchemaName BL.ByteString)),
[RemoteSchemaMetadataG remoteRelationshipDefinition]
)
`arr` HashMap RemoteSchemaName (PartiallyResolvedRemoteSchemaCtxG remoteRelationshipDefinition, MetadataObject)
buildRemoteSchemas env =
buildInfoMapPreservingMetadata _rsmName mkRemoteSchemaMetadataObject buildRemoteSchema
where
-- We want to cache this call because it fetches the remote schema over
-- HTTP, and we dont want to re-run that if the remote schema definition
-- hasnt changed.
buildRemoteSchema = Inc.cache proc ((invalidationKeys, orderedRoles, storedIntrospection), remoteSchema@(RemoteSchemaMetadata name defn _comment permissions relationships)) -> do
Inc.dependOn -< Inc.selectKeyD name invalidationKeys
remoteSchemaContextParts <-
(|
withRecordInconsistency
( liftEitherA <<< bindA
-< runExceptT
case M.lookup name =<< storedIntrospection of
Nothing -> noopTrace $ addRemoteSchemaP2Setup env name defn
Just rawIntro -> do
rsDef <- validateRemoteSchemaDef env defn
(ir, rsi) <- stitchRemoteSchema rawIntro name rsDef
pure (ir, rawIntro, rsi)
)
|) (mkRemoteSchemaMetadataObject remoteSchema)
case remoteSchemaContextParts of
Nothing -> returnA -< Nothing
Just (introspection, rawIntrospection, remoteSchemaInfo) -> do
-- we then resolve permissions
resolvedPermissions <- buildRemoteSchemaPermissions -< ((name, introspection, orderedRoles), fmap (name,) permissions)
-- resolve remote relationships
let transformedRelationships = relationships <&> \RemoteSchemaTypeRelationships {..} -> PartiallyResolvedRemoteRelationship _rstrsName <$> _rstrsRelationships
remoteSchemaContext =
RemoteSchemaCtx
{ _rscName = name,
_rscIntroOriginal = introspection,
_rscInfo = remoteSchemaInfo,
_rscRawIntrospectionResult = rawIntrospection,
_rscPermissions = resolvedPermissions,
_rscRemoteRelationships = transformedRelationships
}
returnA -< Just remoteSchemaContext
-- TODO continue propagating MonadTrace up calls so that we can get tracing
-- for remote schema introspection. This will require modifying CacheBuild.
noopTrace = Tracing.runTraceTWithReporter Tracing.noReporter Tracing.sampleNever "buildSchemaCacheRule"
mkRemoteSchemaMetadataObject remoteSchema =
MetadataObject (MORemoteSchema (_rsmName remoteSchema)) (toJSON remoteSchema)
-- | Resolves a RemoteSchemaPermission metadata object into a 'GraphQL schema'.
buildRemoteSchemaPermissions ::
( ArrowChoice arr,
Inc.ArrowDistribute arr,
ArrowWriter (Seq (Either InconsistentMetadata MetadataDependency)) arr,
ArrowKleisli m arr,
MonadError QErr m
) =>
-- this ridiculous duplication of [(RemoteSchemaName, RemoteSchemaPermissionMetadata)]
-- instead of just [RemoteSchemaName] is because buildInfoMap doesn't pass `e` to the
-- mkMetadataObject function. However, that change is very invasive.
((RemoteSchemaName, IntrospectionResult, OrderedRoles), [(RemoteSchemaName, RemoteSchemaPermissionMetadata)]) `arr` M.HashMap RoleName IntrospectionResult
buildRemoteSchemaPermissions = proc ((remoteSchemaName, originalIntrospection, orderedRoles), permissions) -> do
metadataPermissionsMap <- do
buildInfoMap (_rspmRole . snd) mkRemoteSchemaPermissionMetadataObject buildRemoteSchemaPermission
-<
(originalIntrospection, permissions)
-- convert to the intermediate form `CheckPermission` whose `Semigroup`
-- instance is used to combine permissions
let metadataCheckPermissionsMap = CPDefined <$> metadataPermissionsMap
allRolesUnresolvedPermissionsMap <-
bindA
-<
foldM
( \accumulatedRolePermMap (Role roleName (ParentRoles parentRoles)) -> do
rolePermission <- onNothing (M.lookup roleName accumulatedRolePermMap) $ do
parentRolePermissions <-
for (toList parentRoles) $ \role ->
onNothing (M.lookup role accumulatedRolePermMap) $
throw500 $
"remote schema permissions: bad ordering of roles, could not find the permission of role: " <>> role
let combinedPermission = sconcat <$> nonEmpty parentRolePermissions
pure $ fromMaybe CPUndefined combinedPermission
pure $ M.insert roleName rolePermission accumulatedRolePermMap
)
metadataCheckPermissionsMap
(_unOrderedRoles orderedRoles)
-- traverse through `allRolesUnresolvedPermissionsMap` to record any inconsistencies (if exists)
resolvedPermissions <-
interpretWriter
-< for (M.toList allRolesUnresolvedPermissionsMap) \(roleName, checkPermission) -> do
let inconsistentRoleEntity = InconsistentRemoteSchemaPermission remoteSchemaName
resolvedCheckPermission <- resolveCheckPermission checkPermission roleName inconsistentRoleEntity
return (roleName, resolvedCheckPermission)
returnA -< catMaybes $ M.fromList resolvedPermissions
where
buildRemoteSchemaPermission = proc (originalIntrospection, (remoteSchemaName, remoteSchemaPerm)) -> do
let RemoteSchemaPermissionMetadata roleName defn _ = remoteSchemaPerm
metadataObject = mkRemoteSchemaPermissionMetadataObject (remoteSchemaName, remoteSchemaPerm)
schemaObject = SORemoteSchemaPermission remoteSchemaName roleName
providedSchemaDoc = _rspdSchema defn
addPermContext err = "in remote schema permission for role " <> roleName <<> ": " <> err
(|
withRecordInconsistency
( do
(resolvedSchemaIntrospection, dependency) <-
liftEitherA <<< bindA
-<
runExceptT $ modifyErr addPermContext $ resolveRoleBasedRemoteSchema roleName remoteSchemaName originalIntrospection providedSchemaDoc
recordDependencies -< (metadataObject, schemaObject, pure dependency)
returnA -< resolvedSchemaIntrospection
)
|) metadataObject
mkRemoteSchemaPermissionMetadataObject ::
(RemoteSchemaName, RemoteSchemaPermissionMetadata) ->
MetadataObject
mkRemoteSchemaPermissionMetadataObject (rsName, (RemoteSchemaPermissionMetadata roleName defn _)) =
let objectId = MORemoteSchemaPermissions rsName roleName
in MetadataObject objectId $ toJSON defn
addRemoteSchemaP2Setup ::
(QErrM m, MonadIO m, ProvidesNetwork m, Tracing.MonadTrace m) =>
Env.Environment ->
RemoteSchemaName ->
RemoteSchemaDef ->
m (IntrospectionResult, BL.ByteString, RemoteSchemaInfo)
addRemoteSchemaP2Setup env name def = do
rsi <- validateRemoteSchemaDef env def
fetchRemoteSchema env name rsi