Add a histogram metric tracking evaluated query plans

the `experimental_plans_limit` option can be used to limit the number of query plans evaluated for a query, but there was no way to know what is a reasonable value for that option. This adds a histogram metric tracking the number of evaluated query plans, which should give more context to configure this.
apollographql · Aug 23, 2024 · ae3f9ec · ae3f9ec
1 parent a0a98d4
commit ae3f9ec
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Showing 3 changed files with 37 additions and 3 deletions.
diff --git a/Cargo.lock b/Cargo.lock
@@ -335,7 +335,7 @@ dependencies = [
  "reqwest",
  "rhai",
  "rmp",
- "router-bridge",
+ "router-bridge 0.5.30+v2.8.3 (git+https://github.com/apollographql/federation-rs?branch=geal/plan-count)",
  "rowan",
  "rstack",
  "rust-embed",
@@ -5803,6 +5803,29 @@ dependencies = [
  "which",
 ]
 
+[[package]]
+name = "router-bridge"
+version = "0.5.30+v2.8.3"
+source = "git+https://github.com/apollographql/federation-rs?branch=geal/plan-count#2883d18d519b13a0d6830898c0eb197b59ad4571"
+dependencies = [
+ "anyhow",
+ "async-channel 1.9.0",
+ "deno_console",
+ "deno_core",
+ "deno_url",
+ "deno_web",
+ "deno_webidl",
+ "rand 0.8.5",
+ "serde",
+ "serde_json",
+ "thiserror",
+ "tokio",
+ "tower",
+ "tower-service",
+ "tracing",
+ "which",
+]
+
 [[package]]
 name = "router-fuzz"
 version = "0.0.0"
@@ -5818,7 +5841,7 @@ dependencies = [
  "libfuzzer-sys",
  "log",
  "reqwest",
- "router-bridge",
+ "router-bridge 0.5.30+v2.8.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "schemars",
  "serde",
  "serde_json",

diff --git a/apollo-router/Cargo.toml b/apollo-router/Cargo.toml
@@ -198,7 +198,8 @@ regex = "1.10.5"
 reqwest.workspace = true
 
 # note: this dependency should _always_ be pinned, prefix the version with an `=`
-router-bridge = "=0.5.30+v2.8.3"
+#router-bridge = "=0.5.30+v2.8.3"
+router-bridge = { git = "https://github.com/apollographql/federation-rs", branch = "geal/plan-count" }
 
 rust-embed = { version = "8.4.0", features = ["include-exclude"] }
 rustls = "0.21.12"

diff --git a/apollo-router/src/query_planner/bridge_query_planner.rs b/apollo-router/src/query_planner/bridge_query_planner.rs
@@ -315,6 +315,8 @@ impl PlannerMode {
                         query_plan: QueryPlan {
                             node: root_node.map(Arc::new),
                         },
+                        evaluated_plan_count: plan.statistics.evaluated_plan_count.into_inner()
+                            as u64,
                     },
                 })
             }
@@ -554,13 +556,20 @@ impl BridgeQueryPlanner {
                     QueryPlanResult {
                         query_plan: QueryPlan { node: Some(node) },
                         formatted_query_plan,
+                        evaluated_plan_count,
                     },
                 mut usage_reporting,
             } => {
                 if let Some(sig) = operation_signature {
                     usage_reporting.stats_report_key = sig;
                 }
 
+                u64_histogram!(
+                    "apollo.router.query_planning.evaluated_plans",
+                    "Number of query plans evaluated for a query before choosing the best one",
+                    evaluated_plan_count
+                );
+
                 if matches!(
                     self.configuration
                         .experimental_apollo_metrics_generation_mode,
@@ -949,6 +958,7 @@ impl BridgeQueryPlanner {
 pub struct QueryPlanResult {
     pub(super) formatted_query_plan: Option<Arc<String>>,
     pub(super) query_plan: QueryPlan,
+    pub(super) evaluated_plan_count: u64,
 }
 
 impl QueryPlanResult {