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fix(router): avoid subscription clients on subgraphs with no subscriptions #3094

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48 changes: 33 additions & 15 deletions router/core/factoryresolver.go
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Original file line number Diff line number Diff line change
Expand Up @@ -48,7 +48,7 @@ type InstanceData struct {
}

type FactoryResolver interface {
ResolveGraphqlFactory(subgraphName string) (plan.PlannerFactory[graphql_datasource.Configuration], error)
ResolveGraphqlFactory(subgraphName string, hasSubscriptions bool) (plan.PlannerFactory[graphql_datasource.Configuration], error)
ResolveStaticFactory() (plan.PlannerFactory[staticdatasource.Configuration], error)
InstanceData() InstanceData
}
Expand Down Expand Up @@ -167,7 +167,18 @@ func NewDefaultFactoryResolver(
}
}

func (d *DefaultFactoryResolver) ResolveGraphqlFactory(subgraphName string) (plan.PlannerFactory[graphql_datasource.Configuration], error) {
// hasSubscriptionRootNodes reports whether a data source's root nodes include
// any Subscription fields.
func hasSubscriptionRootNodes(rootNodes []*nodev1.TypeField) bool {
for _, node := range rootNodes {
if node.TypeName == "Subscription" && len(node.FieldNames) > 0 {
return true
}
}
return false
Comment on lines +172 to +178

@coderabbitai coderabbitai Bot Jul 17, 2026

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🎯 Functional Correctness | 🟠 Major | 🏗️ Heavy lift

🧩 Analysis chain

🏁 Script executed:

#!/bin/bash
set -euo pipefail

# Map relevant files and inspect the resolver helper and its callers.
git ls-files | rg '(^|/)(factoryresolver\.go|.*engine.*|.*schema.*|.*graphql.*|.*nodev1.*)\.go$' || true

printf '\n--- factoryresolver outline ---\n'
ast-grep outline router/core/factoryresolver.go --view expanded || true

printf '\n--- search for hasSubscriptionRootNodes and hasSubscriptions ---\n'
rg -n "hasSubscriptionRootNodes|hasSubscriptions|ResolveGraphqlFactory|Subscription" router/core -g '*.go' || true

printf '\n--- inspect relevant slices of factoryresolver.go ---\n'
sed -n '1,260p' router/core/factoryresolver.go

printf '\n--- search for RootNodes generation / normalization ---\n'
rg -n "RootNodes|TypeField|subscription:|Subscription" . -g '*.go' || true

Repository: wundergraph/cosmo

Length of output: 50374

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '\n--- factoryresolver.go relevant lines ---\n'
sed -n '160,220p' router/core/factoryresolver.go | cat -n

printf '\n--- root-node generation / schema metadata path ---\n'
rg -n "RootNodes|TypeName:|FieldNames:|subscription:" router -g '*.go' | head -n 200

printf '\n--- inspect any schema-to-root-node conversion helpers ---\n'
rg -n "TypeField|RootNodes" router/core router -g '*.go' | head -n 200

Repository: wundergraph/cosmo

Length of output: 41770

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '\n--- schemaloader loader root-node construction ---\n'
sed -n '150,240p' router/pkg/schemaloader/loader.go | cat -n

printf '\n--- inspect router config client root-node examples ---\n'
sed -n '1,140p' router/pkg/routerconfig/client.go | cat -n

printf '\n--- search for schema root type handling in router/pkg/schemaloader and router/core ---\n'
rg -n "subscription:|query:|mutation:|RootNodes|TypeName.*Subscription|TypeName.*Query|TypeName.*Mutation" router/pkg/schemaloader router/core -g '*.go'

Repository: wundergraph/cosmo

Length of output: 9624

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '\n--- schemaloader loader.go around root-node usage ---\n'
sed -n '160,230p' router/pkg/schemaloader/loader.go | cat -n

printf '\n--- schemaloader tests with subscription schemas ---\n'
rg -n "subscription:" router/pkg/schemaloader/loader_test.go router/pkg/schemaloader -g '*.go' -A 6 -B 6

printf '\n--- search for custom subscription root names in generated config/tests ---\n'
rg -n 'TypeName:\s*"Subscription"|subscription:\s*[A-Za-z_][A-Za-z0-9_]*' router -g '*.go' -A 4 -B 4

Repository: wundergraph/cosmo

Length of output: 3242

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '\n--- production code that writes DataSourceConfiguration.RootNodes ---\n'
rg -n "RootNodes:\s*\[\]\*nodev1.TypeField|RootNodes:\s*\[\]plan.TypeField|RootNodes:\s*make\(" router -g '*.go' -A 4 -B 4

printf '\n--- inspect surrounding code in likely builders ---\n'
sed -n '1,220p' router/pkg/routerconfig/client.go | cat -n
sed -n '560,660p' router/core/factoryresolver.go | cat -n

Repository: wundergraph/cosmo

Length of output: 39251

🏁 Script executed:

#!/bin/bash
set -euo pipefail

printf '\n--- search for custom operation root types in schemas/configs/tests ---\n'
rg -n 'schema\s*\{[^}]*subscription:\s*[A-Za-z_][A-Za-z0-9_]*|schema\s*\{[^}]*query:\s*[A-Za-z_][A-Za-z0-9_]*|schema\s*\{[^}]*mutation:\s*[A-Za-z_][A-Za-z0-9_]*' router -g '*.go' -g '*.graphql' -g '*.gql' -A 3 -B 3

printf '\n--- search for explicit EventStream or non-Subscription root type names ---\n'
rg -n 'EventStream|type\s+Subscription\b|subscription:\s*[A-Za-z_][A-Za-z0-9_]*' router -g '*.go' -g '*.graphql' -g '*.gql' -A 3 -B 3

Repository: wundergraph/cosmo

Length of output: 5781

Detect the configured subscription root type, not a hard-coded Subscription. dataSourceMetaData copies TypeName verbatim, so a valid schema like schema { subscription: EventStream } will be treated as subscription-free and the planner will skip the subscription client. Add a case for a custom subscription root type.

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@router/core/factoryresolver.go` around lines 172 - 178, Update
hasSubscriptionRootNodes to recognize the configured subscription root type in
addition to the default "Subscription". Use the schema/root-type configuration
available to the resolver when comparing node.TypeName, so custom declarations
such as EventStream are detected and subscription planning remains enabled.

}

func (d *DefaultFactoryResolver) ResolveGraphqlFactory(subgraphName string, hasSubscriptions bool) (plan.PlannerFactory[graphql_datasource.Configuration], error) {
if d.connector != nil {
// If the connector is not nil, we try to get the provider for the subgraph.
// In case of a provider, we use the gRPC client provider to create the factory.
Expand All @@ -183,9 +194,13 @@ func (d *DefaultFactoryResolver) ResolveGraphqlFactory(subgraphName string) (pla

if d.transportFactory == nil || d.baseTransport == nil {
// dummy implementation for plan generator that doesn't make requests
subscriptionClient := graphql_datasource.NewGraphQLSubscriptionClient(d.engineCtx,
d.subscriptionClientOptions...,
)
var subscriptionClient graphql_datasource.GraphQLSubscriptionClient
if hasSubscriptions {
subscriptionClient = graphql_datasource.NewGraphQLSubscriptionClient(d.engineCtx,
d.subscriptionClientOptions...,
)
}

return graphql_datasource.NewFactory(d.engineCtx, http.DefaultClient, subscriptionClient)
}

Expand All @@ -194,14 +209,17 @@ func (d *DefaultFactoryResolver) ResolveGraphqlFactory(subgraphName string) (pla
Transport: d.transportFactory.RoundTripper(d.baseTransport),
}

streamingClient := &http.Client{
Transport: d.transportFactory.RoundTripper(d.baseTransport),
}
var subscriptionClient graphql_datasource.GraphQLSubscriptionClient
if hasSubscriptions {
streamingClient := &http.Client{
Transport: d.transportFactory.RoundTripper(d.baseTransport),
}

subscriptionClient := graphql_datasource.NewGraphQLSubscriptionClient(
d.engineCtx,
append([]graphql_datasource.SubscriptionClientOption{graphql_datasource.WithUpgradeClient(defaultHTTPClient), graphql_datasource.WithStreamingClient(streamingClient)}, d.subscriptionClientOptions...)...,
)
subscriptionClient = graphql_datasource.NewGraphQLSubscriptionClient(
d.engineCtx,
append([]graphql_datasource.SubscriptionClientOption{graphql_datasource.WithUpgradeClient(defaultHTTPClient), graphql_datasource.WithStreamingClient(streamingClient)}, d.subscriptionClientOptions...)...,
)
}

if subgraphClient, ok := d.subgraphHTTPClients[subgraphName]; ok {
// it's intentional that we're not using the subgraphClient for subscriptions
Expand Down Expand Up @@ -355,7 +373,7 @@ func (l *Loader) Load(engineConfig *nodev1.EngineConfiguration, subgraphs []*nod
return nil, providers, err
}

out, err = plan.NewDataSourceConfiguration[staticdatasource.Configuration](
out, err = plan.NewDataSourceConfiguration(
in.Id,
factory,
l.dataSourceMetaData(in),
Expand Down Expand Up @@ -483,12 +501,12 @@ func (l *Loader) Load(engineConfig *nodev1.EngineConfiguration, subgraphs []*nod

dataSourceName := l.subgraphName(subgraphs, in.Id)

factory, err := l.resolver.ResolveGraphqlFactory(dataSourceName)
factory, err := l.resolver.ResolveGraphqlFactory(dataSourceName, hasSubscriptionRootNodes(in.RootNodes))
if err != nil {
return nil, providers, err
}

out, err = plan.NewDataSourceConfigurationWithName[graphql_datasource.Configuration](
out, err = plan.NewDataSourceConfigurationWithName(
in.Id,
dataSourceName,
factory,
Expand Down
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