postgraphile-plugin-atomic-mutations
This Postgraphile plugin allows you to enable mutation atomicity with GraphQL
requests containing multiple mutations.
It's ideal if you would like to have client request repeatability when at least
one mutation in the GraphQL request fails. This would guarantee that either all
the mutations in the request are committed
when successful, or all are
rolled back
if at least one is erroneous.
Installing
yarn add postgraphile-plugin-atomic-mutations
npm install postgraphile-plugin-atomic-mutations
Usage as Library
import { makePluginHook } from 'postgraphile';
import {
AtomicMutationsHook,
AtomicMutationsPlugin,
getMutationAtomicityContext,
} from 'postgraphile-plugin-atomic-mutations';
const app = express();
const pluginHook = makePluginHook([AtomicMutationsHook]);
app.use(
postgraphile(pgConfig, schema, {
appendPlugins: [AtomicMutationsPlugin],
pluginHook,
async additionalGraphQLContextFromRequest(req, res) {
return {
mutationAtomicityContext: getMutationAtomicityContext(req),
};
},
}),
);
app.listen(5000);
Usage from Client
The plugin allows the client to decide when the mutation atomicity should be
applied per GraphQL request, using a custom HTTP header
'X-Mutation-Atomicity'
, which can be set to either 'on'
or 'off'
.
mutation MultipleMutationOperation {
createTenant(input: {tenant: {name: "New Tenant"}}) {
tenant {
id
}
}
updateTenant(input: {patch: {name: "Updated Tenant Name"}, id: "dd0f6631-3905-4cc0-bc75-6c7b1dcafa89"}) {
tenant {
name
}
}
deleteTenant(input: {id: "761aa030-6965-4cfe-90cf-00d2dec41c61"}) {
tenant {
name
}
}
}
In the above example of a multiple mutation request, if we didn't use the plugin
at all, the outcome would be that Mutations #1
& #3
will be committed to the
database, while #2
will be rolled back due to its hypothetical error. But if
the same request is sent again from the client, there will be new exceptions
caused by mutations #1
& #3
(possibly for duplicate key violation, and no
matching criteria).
Now instead if we use the plugin, and the same request is made with the
'X-Mutation-Atomicity: on'
HTTP header set by the client, the Mutations #1
&
#3
will never be committed to the database since Mutation #2
caused an
error, guaranteeing atomicity for the set of Mutations. If the client decides to
re-run the same request again, the outcome will be the same.
If the 'X-Mutation-Atomicity'
is set to 'off
or not set at all, the plugin
will be disabled.
Limitations
-
If there already exists plugins which are used in postgraphile options,
AtomicMutationsPlugin
must be appended after them - i.e.
appendPlugins: [SomePlugin, AnotherPlugin, AtomicMutationsPlugin]
.
-
As with any transaction management mechanism, the individual mutations must
not contain any explicit commit
or rollback
commands.
-
Postgraphile v4 has an experimental feature
enableQueryBatching
which is currently not supported by the plugin.
Todo
- Introduce plugin options to control default behavior.
- When the client does not specify a
'X-Mutation-Atomicity'
header.
- Improve tests to have more code coverage.
Contributing
This project uses yarn
as the package manager, so make sure that pre-requisite
is installed.
npm install -g yarn
Then clone
& run yarn