priority: add policy config parsing (#3936)
diff --git a/xds/internal/balancer/priority/config.go b/xds/internal/balancer/priority/config.go
new file mode 100644
index 0000000..da08590
--- /dev/null
+++ b/xds/internal/balancer/priority/config.go
@@ -0,0 +1,64 @@
+/*
+ *
+ * Copyright 2020 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package priority
+
+import (
+ "encoding/json"
+ "fmt"
+
+ internalserviceconfig "google.golang.org/grpc/internal/serviceconfig"
+ "google.golang.org/grpc/serviceconfig"
+)
+
+type child struct {
+ Config *internalserviceconfig.BalancerConfig
+}
+
+type lbConfig struct {
+ serviceconfig.LoadBalancingConfig
+
+ // Children is a map from the child balancer names to their configs. Child
+ // names can be found in field Priorities.
+ Children map[string]*child
+ // Priorities is a list of child balancer names. They are sorted from
+ // highest priority to low. The type/config for each child can be found in
+ // field Children, with the balancer name as the key.
+ Priorities []string
+}
+
+func parseConfig(c json.RawMessage) (*lbConfig, error) {
+ var cfg lbConfig
+ if err := json.Unmarshal(c, &cfg); err != nil {
+ return nil, err
+ }
+
+ prioritiesSet := make(map[string]bool)
+ for _, name := range cfg.Priorities {
+ if _, ok := cfg.Children[name]; !ok {
+ return nil, fmt.Errorf("LB policy name %q found in Priorities field (%v) is not found in Children field (%+v)", name, cfg.Priorities, cfg.Children)
+ }
+ prioritiesSet[name] = true
+ }
+ for name := range cfg.Children {
+ if _, ok := prioritiesSet[name]; !ok {
+ return nil, fmt.Errorf("LB policy name %q found in Children field (%v) is not found in Priorities field (%+v)", name, cfg.Children, cfg.Priorities)
+ }
+ }
+ return &cfg, nil
+}
diff --git a/xds/internal/balancer/priority/config_test.go b/xds/internal/balancer/priority/config_test.go
new file mode 100644
index 0000000..15c4069
--- /dev/null
+++ b/xds/internal/balancer/priority/config_test.go
@@ -0,0 +1,107 @@
+/*
+ *
+ * Copyright 2020 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+package priority
+
+import (
+ "testing"
+
+ "github.com/google/go-cmp/cmp"
+ "google.golang.org/grpc/balancer/roundrobin"
+ internalserviceconfig "google.golang.org/grpc/internal/serviceconfig"
+)
+
+func TestParseConfig(t *testing.T) {
+ tests := []struct {
+ name string
+ js string
+ want *lbConfig
+ wantErr bool
+ }{
+ {
+ name: "child not found",
+ js: `{
+ "priorities": ["child-1", "child-2", "child-3"],
+ "children": {
+ "child-1": {"config": [{"round_robin":{}}]},
+ "child-3": {"config": [{"round_robin":{}}]}
+ }
+}
+ `,
+ wantErr: true,
+ },
+ {
+ name: "child not used",
+ js: `{
+ "priorities": ["child-1", "child-2"],
+ "children": {
+ "child-1": {"config": [{"round_robin":{}}]},
+ "child-2": {"config": [{"round_robin":{}}]},
+ "child-3": {"config": [{"round_robin":{}}]}
+ }
+}
+ `,
+ wantErr: true,
+ },
+ {
+ name: "good",
+ js: `{
+ "priorities": ["child-1", "child-2", "child-3"],
+ "children": {
+ "child-1": {"config": [{"round_robin":{}}]},
+ "child-2": {"config": [{"round_robin":{}}]},
+ "child-3": {"config": [{"round_robin":{}}]}
+ }
+}
+ `,
+ want: &lbConfig{
+ Children: map[string]*child{
+ "child-1": {
+ &internalserviceconfig.BalancerConfig{
+ Name: roundrobin.Name,
+ },
+ },
+ "child-2": {
+ &internalserviceconfig.BalancerConfig{
+ Name: roundrobin.Name,
+ },
+ },
+ "child-3": {
+ &internalserviceconfig.BalancerConfig{
+ Name: roundrobin.Name,
+ },
+ },
+ },
+ Priorities: []string{"child-1", "child-2", "child-3"},
+ },
+ wantErr: false,
+ },
+ }
+ for _, tt := range tests {
+ t.Run(tt.name, func(t *testing.T) {
+ got, err := parseConfig([]byte(tt.js))
+ if (err != nil) != tt.wantErr {
+ t.Errorf("parseConfig() error = %v, wantErr %v", err, tt.wantErr)
+ return
+ }
+ if diff := cmp.Diff(got, tt.want); diff != "" {
+ t.Errorf("parseConfig() got = %v, want %v, diff: %s", got, tt.want, diff)
+ }
+ })
+ }
+}
diff --git a/xds/internal/balancer/priority/doc.go b/xds/internal/balancer/priority/doc.go
new file mode 100644
index 0000000..53bd270
--- /dev/null
+++ b/xds/internal/balancer/priority/doc.go
@@ -0,0 +1,24 @@
+/*
+ *
+ * Copyright 2020 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+// Package priority implements the priority balancer.
+//
+// This balancer will be kept in internal until we use it in the xds balancers,
+// and are confident its functionalities are stable. It will then be exported
+// for more users.
+package priority
