experimental support for query batching

.changesets/exp_garypen_126_query_batching.md

@@ -0,0 +1,21 @@
+### query batching prototype ([Issue #126](https://github.com/apollographql/router/issues/126))
+
+An experimental implementation of query batching which adds support for client request batching to the Apollo Router.
+
+If you’re using Apollo Client, you can leverage the in-built support for batching to reduce the number of individual requests sent to the Apollo Router.
+
+Once [configured](https://www.apollographql.com/docs/react/api/link/apollo-link-batch-http/), Apollo Client will automatically combine multiple operations into a single HTTP request. The number of operations within a batch is client configurable, including the maximum number of operations in a batch and the maximum duration to wait for operations to accumulate before sending the batch request. 
+
+The Apollo Router must be configured to receive batch requests, otherwise it rejects them. When processing a batch request, the router deserializes and processes each operation of a batch independently, and it responds to the client only after all operations of the batch have been completed.
+
+```yaml
+experimental_batching:
+  enabled: true
+  mode: batch_http_link
+```
+
+All operations within a batch will execute concurrently with respect to each other.
+
+Do not attempt to use subscriptions or `@defer` queries within a batch as they are not supported.
+
+By [@garypen](https://github.com/garypen) in https://github.com/apollographql/router/pull/3837

apollo-router/feature_discussions.json

@@ -3,7 +3,8 @@
     "experimental_retry": "https://github.com/apollographql/router/discussions/2241",
     "experimental_response_trace_id": "https://github.com/apollographql/router/discussions/2147",
     "experimental_logging": "https://github.com/apollographql/router/discussions/1961",
-    "experimental_http_max_request_bytes": "https://github.com/apollographql/router/discussions/3220"
+    "experimental_http_max_request_bytes": "https://github.com/apollographql/router/discussions/3220",
+    "experimental_batching": "https://github.com/apollographql/router/discussions/3840"
   },
   "preview": {
     "preview_directives": "https://github.com/apollographql/router/discussions/3754"

apollo-router/src/configuration/metrics.rs

@@ -313,6 +313,12 @@ impl Metrics {
             opt.tracing.zipkin,
             "$.tracing.zipkin[?(@.endpoint)]"
         );
+        log_usage_metrics!(
+            value.apollo.router.config.batching,
+            "$.experimental_batching[?(@.enabled == true)]",
+            opt.mode,
+            "$.mode"
+        );
     }
 }
 

apollo-router/src/configuration/mod.rs

@@ -185,6 +185,10 @@ pub struct Configuration {
 
     #[serde(default, skip_serializing, skip_deserializing)]
     pub(crate) notify: Notify<String, graphql::Response>,
+
+    /// Batching configuration.
+    #[serde(default)]
+    pub(crate) experimental_batching: Batching,
 }
 
 impl PartialEq for Configuration {
@@ -234,6 +238,7 @@ impl<'de> serde::Deserialize<'de> for Configuration {
             limits: Limits,
             experimental_chaos: Chaos,
             experimental_graphql_validation_mode: GraphQLValidationMode,
+            experimental_batching: Batching,
         }
         let ad_hoc: AdHocConfiguration = serde::Deserialize::deserialize(deserializer)?;
 
@@ -252,6 +257,7 @@ impl<'de> serde::Deserialize<'de> for Configuration {
             .chaos(ad_hoc.experimental_chaos)
             .uplink(ad_hoc.uplink)
             .graphql_validation_mode(ad_hoc.experimental_graphql_validation_mode)
+            .experimental_batching(ad_hoc.experimental_batching)
             .build()
             .map_err(|e| serde::de::Error::custom(e.to_string()))
     }
@@ -288,6 +294,7 @@ impl Configuration {
         chaos: Option<Chaos>,
         uplink: Option<UplinkConfig>,
         graphql_validation_mode: Option<GraphQLValidationMode>,
+        experimental_batching: Option<Batching>,
     ) -> Result<Self, ConfigurationError> {
         #[cfg(not(test))]
         let notify_queue_cap = match apollo_plugins.get(APOLLO_SUBSCRIPTION_PLUGIN_NAME) {
@@ -322,6 +329,7 @@ impl Configuration {
             },
             tls: tls.unwrap_or_default(),
             uplink,
+            experimental_batching: experimental_batching.unwrap_or_default(),
             #[cfg(test)]
             notify: notify.unwrap_or_default(),
             #[cfg(not(test))]
@@ -360,6 +368,7 @@ impl Configuration {
         chaos: Option<Chaos>,
         uplink: Option<UplinkConfig>,
         graphql_validation_mode: Option<GraphQLValidationMode>,
+        experimental_batching: Option<Batching>,
     ) -> Result<Self, ConfigurationError> {
         let configuration = Self {
             validated_yaml: Default::default(),
@@ -382,6 +391,7 @@ impl Configuration {
             apq: apq.unwrap_or_default(),
             preview_persisted_queries: persisted_query.unwrap_or_default(),
             uplink,
+            experimental_batching: experimental_batching.unwrap_or_default(),
         };
 
         configuration.validate()
@@ -1273,3 +1283,23 @@ fn default_graphql_path() -> String {
 fn default_graphql_introspection() -> bool {
     false
 }
+
+#[derive(Clone, Debug, Default, Error, Display, Serialize, Deserialize, JsonSchema)]
+#[serde(deny_unknown_fields, rename_all = "snake_case")]
+pub(crate) enum BatchingMode {
+    /// batch_http_link mode
+    #[default]
+    BatchHttpLink,
+}
+
+/// Configuration for Batching
+#[derive(Debug, Clone, Default, Deserialize, Serialize, JsonSchema)]
+#[serde(deny_unknown_fields)]
+pub(crate) struct Batching {
+    /// Activates Batching (disabled by default)
+    #[serde(default)]
+    pub(crate) enabled: bool,
+
+    /// Batching mode
+    pub(crate) mode: BatchingMode,
+}

apollo-router/src/configuration/snapshots/apollo_router__configuration__metrics__test__metrics@batching.router.yaml.snap

@@ -0,0 +1,8 @@
+---
+source: apollo-router/src/configuration/metrics.rs
+expression: "&metrics.metrics"
+---
+value.apollo.router.config.batching:
+  - 1
+  - opt__mode__: batch_http_link
+

apollo-router/src/configuration/snapshots/apollo_router__configuration__tests__schema_generation.snap

@@ -1009,6 +1009,37 @@ expression: "&schema"
       },
       "additionalProperties": false
     },
+    "experimental_batching": {
+      "description": "Batching configuration.",
+      "default": {
+        "enabled": false,
+        "mode": "batch_http_link"
+      },
+      "type": "object",
+      "required": [
+        "mode"
+      ],
+      "properties": {
+        "enabled": {
+          "description": "Activates Batching (disabled by default)",
+          "default": false,
+          "type": "boolean"
+        },
+        "mode": {
+          "description": "Batching mode",
+          "oneOf": [
+            {
+              "description": "batch_http_link mode",
+              "type": "string",
+              "enum": [
+                "batch_http_link"
+              ]
+            }
+          ]
+        }
+      },
+      "additionalProperties": false
+    },
     "experimental_chaos": {
       "description": "Configuration for chaos testing, trying to reproduce bugs that require uncommon conditions. You probably don’t want this in production!",
       "default": {

apollo-router/src/configuration/testdata/metrics/batching.router.yaml

@@ -0,0 +1,3 @@
+experimental_batching:
+  enabled: true
+  mode: batch_http_link

apollo-router/src/plugins/telemetry/tracing/apollo_telemetry.rs

@@ -208,11 +208,12 @@ impl Exporter {
         })
     }
 
-    fn extract_root_trace(
+    fn extract_root_traces(
         &mut self,
         span: &LightSpanData,
         child_nodes: Vec<TreeData>,
-    ) -> Result<Box<proto::reports::Trace>, Error> {
+    ) -> Result<Vec<proto::reports::Trace>, Error> {
+        let mut results: Vec<proto::reports::Trace> = vec![];
         let http = extract_http_data(span);
         let mut root_trace = proto::reports::Trace {
             start_time: Some(span.start_time.into()),
@@ -235,17 +236,19 @@ impl Exporter {
                     client_version,
                     duration_ns,
                 } => {
-                    if http.method != Method::Unknown as i32 {
-                        let root_http = root_trace
-                            .http
-                            .as_mut()
-                            .expect("http was extracted earlier, qed");
-                        root_http.request_headers = http.request_headers;
-                        root_http.response_headers = http.response_headers;
+                    for trace in results.iter_mut() {
+                        if http.method != Method::Unknown as i32 {
+                            let root_http = trace
+                                .http
+                                .as_mut()
+                                .expect("http was extracted earlier, qed");
+                            root_http.request_headers = http.request_headers.clone();
+                            root_http.response_headers = http.response_headers.clone();
+                        }
+                        trace.client_name = client_name.clone().unwrap_or_default();
+                        trace.client_version = client_version.clone().unwrap_or_default();
+                        trace.duration_ns = duration_ns;
                     }
-                    root_trace.client_name = client_name.unwrap_or_default();
-                    root_trace.client_version = client_version.unwrap_or_default();
-                    root_trace.duration_ns = duration_ns;
                 }
                 TreeData::Supergraph {
                     operation_signature,
@@ -258,6 +261,7 @@ impl Exporter {
                         variables_json,
                         operation_name,
                     });
+                    results.push(root_trace.clone());
                 }
                 TreeData::Execution(operation_type) => {
                     if operation_type == OperationKind::Subscription.as_apollo_operation_type() {
@@ -281,21 +285,17 @@ impl Exporter {
             }
         }
 
-        Ok(Box::new(root_trace))
+        Ok(results)
     }
 
-    fn extract_trace(&mut self, span: LightSpanData) -> Result<Box<proto::reports::Trace>, Error> {
-        self.extract_data_from_spans(&span)?
-            .pop()
-            .and_then(|node| {
-                match node {
-                    TreeData::Request(trace) | TreeData::SubscriptionEvent(trace) => {
-                        Some(trace)
-                    }
-                    _ => None
-                }
-            })
-            .expect("root trace must exist because it is constructed on the request or subscription_event span, qed")
+    fn extract_traces(&mut self, span: LightSpanData) -> Result<Vec<proto::reports::Trace>, Error> {
+        let mut results = vec![];
+        for node in self.extract_data_from_spans(&span)? {
+            if let TreeData::Request(trace) | TreeData::SubscriptionEvent(trace) = node {
+                results.push(*trace?)
+            }
+        }
+        Ok(results)
     }
 
     fn extract_data_from_spans(&mut self, span: &LightSpanData) -> Result<Vec<TreeData>, Error> {
@@ -416,11 +416,11 @@ impl Exporter {
                 });
                 child_nodes
             }
-            _ if span.attributes.get(&APOLLO_PRIVATE_REQUEST).is_some() => {
-                vec![TreeData::Request(
-                    self.extract_root_trace(span, child_nodes),
-                )]
-            }
+            _ if span.attributes.get(&APOLLO_PRIVATE_REQUEST).is_some() => self
+                .extract_root_traces(span, child_nodes)?
+                .into_iter()
+                .map(|node| TreeData::Request(Ok(Box::new(node))))
+                .collect(),
             ROUTER_SPAN_NAME => {
                 child_nodes.push(TreeData::Router {
                     http: Box::new(extract_http_data(span)),
@@ -549,9 +549,10 @@ impl Exporter {
                         .to_string(),
                 ));
 
-                vec![TreeData::SubscriptionEvent(
-                    self.extract_root_trace(span, child_nodes),
-                )]
+                self.extract_root_traces(span, child_nodes)?
+                    .into_iter()
+                    .map(|node| TreeData::SubscriptionEvent(Ok(Box::new(node))))
+                    .collect()
             }
             _ => child_nodes,
         })
@@ -704,12 +705,14 @@ impl SpanExporter for Exporter {
             if span.attributes.get(&APOLLO_PRIVATE_REQUEST).is_some()
                 || span.name == SUBSCRIPTION_EVENT_SPAN_NAME
             {
-                match self.extract_trace(span.into()) {
-                    Ok(mut trace) => {
-                        let mut operation_signature = Default::default();
-                        std::mem::swap(&mut trace.signature, &mut operation_signature);
-                        if !operation_signature.is_empty() {
-                            traces.push((operation_signature, *trace));
+                match self.extract_traces(span.into()) {
+                    Ok(extracted_traces) => {
+                        for mut trace in extracted_traces {
+                            let mut operation_signature = Default::default();
+                            std::mem::swap(&mut trace.signature, &mut operation_signature);
+                            if !operation_signature.is_empty() {
+                                traces.push((operation_signature, trace));
+                            }
                         }
                     }
                     Err(Error::MultipleErrors(errors)) => {