graphql-engine/server/src-lib/Hasura/RQL/DDL/Schema/Catalog.hs
Lyndon Maydwell 59c01786fe Optimistic Metadata Locking
Add optimistic concurrency control to the ‘replace_metadata’ call.

Prevents users from submitting out-of-date metadata to metadata-mutating APIs.

See https://github.com/hasura/graphql-engine-mono/issues/472 for details.

GitOrigin-RevId: 5f220f347a3eba288a9098b01e9913ffd7e38166
2021-02-19 02:40:23 +00:00

70 lines
2.8 KiB
Haskell

-- | Functions for fetching and updating @'Metadata' in the catalog.
module Hasura.RQL.DDL.Schema.Catalog
( fetchMetadataFromCatalog
, setMetadataInCatalog
, bumpMetadataVersionInCatalog
) where
import Hasura.Prelude
import qualified Database.PG.Query as Q
import Hasura.Backends.Postgres.Connection
import Hasura.RQL.Types.Error
import Hasura.RQL.Types.Metadata
import Data.Int (Int64)
fetchMetadataFromCatalog :: Q.TxE QErr (Metadata, MetadataResourceVersion)
fetchMetadataFromCatalog = do
rows <- Q.withQE defaultTxErrorHandler
[Q.sql|
SELECT metadata, resource_version from hdb_catalog.hdb_metadata
|] () True
case rows of
[] -> pure (emptyMetadata, initialResourceVersion)
[(Q.AltJ metadata, resourceVersion)] -> pure (metadata, MetadataResourceVersion resourceVersion)
_ -> throw500 "multiple rows in hdb_metadata table"
-- Used to increment metadata version when no other changes are required
bumpMetadataVersionInCatalog :: Q.TxE QErr ()
bumpMetadataVersionInCatalog = do
Q.unitQE defaultTxErrorHandler
[Q.sql|
UPDATE hdb_catalog.hdb_metadata
SET resource_version = hdb_catalog.hdb_metadata.resource_version + 1
|] () True
setMetadataInCatalog :: Maybe MetadataResourceVersion -> Metadata -> Q.TxE QErr ()
setMetadataInCatalog mResourceVersion metadata = case mResourceVersion of
-- If a resource version isn't specified update the metadata and bump the version
Nothing ->
Q.unitQE defaultTxErrorHandler
[Q.sql|
INSERT INTO hdb_catalog.hdb_metadata(id, metadata)
VALUES (1, $1::json)
ON CONFLICT (id) DO UPDATE SET
metadata = $1::json,
resource_version = hdb_catalog.hdb_metadata.resource_version + 1
|] (Identity $ Q.AltJ metadata) True
-- If a resource version is specified, check that it matches and...
-- If so: Update the metadata and bump the version
-- If not: Throw a 409 error
Just resourceVersion -> do
rows <- Q.withQE defaultTxErrorHandler
[Q.sql|
INSERT INTO hdb_catalog.hdb_metadata(id, metadata)
VALUES (1, $1::json)
ON CONFLICT (id) DO UPDATE SET
metadata = $1::json,
resource_version = hdb_catalog.hdb_metadata.resource_version + 1
WHERE hdb_catalog.hdb_metadata.resource_version = $2
RETURNING 1
|] (Q.AltJ metadata, getMetadataResourceVersion resourceVersion) True
case rows of
[] -> throw409 $ "metadata resource version referenced (" <> tshow (getMetadataResourceVersion resourceVersion) <> ") did not match current version"
[Identity (_::Int64)] -> pure ()
_ -> throw500 "multiple rows in hdb_metadata table"