Honor HTTP-date Retry-After values in OtlpExporter

.changeset/quiet-otters-retry.md

@@ -0,0 +1,5 @@
+---
+"effect": patch
+---
+
+Honor HTTP-date `Retry-After` values when retrying OTLP exports.

packages/effect/src/unstable/observability/OtlpExporter.ts

@@ -26,6 +26,24 @@ import * as HttpClientError from "../../unstable/http/HttpClientError.ts"
 import * as HttpClientRequest from "../../unstable/http/HttpClientRequest.ts"
 import type { HttpBody } from "../http/HttpBody.ts"
 
+const retryAfterDelay = (value: string | undefined): Effect.Effect<Duration.Duration> => {
+  const seconds = Option.fromUndefinedOr(value).pipe(Option.flatMap(Num.parse))
+  if (Option.isSome(seconds)) {
+    return Effect.succeed(Duration.seconds(seconds.value))
+  }
+  if (value === undefined) {
+    return Effect.succeed(Duration.seconds(5))
+  }
+  const timestamp = Date.parse(value)
+  if (Number.isNaN(timestamp)) {
+    return Effect.succeed(Duration.seconds(5))
+  }
+  return Effect.map(
+    Clock,
+    (clock) => Duration.millis(Math.max(timestamp - clock.currentTimeMillisUnsafe(), 1))
+  )
+}
+
 const policy = Schedule.forever.pipe(
   Schedule.passthrough,
   Schedule.addDelay(({ output: error }) => {
@@ -34,11 +52,7 @@ const policy = Schedule.forever.pipe(
       && error.reason._tag === "StatusCodeError"
       && error.reason.response.status === 429
     ) {
-      const retryAfter = Option.fromUndefinedOr(error.reason.response.headers["retry-after"]).pipe(
-        Option.flatMap(Num.parse),
-        Option.getOrElse(() => 5)
-      )
-      return Effect.succeed(Duration.seconds(retryAfter))
+      return retryAfterDelay(error.reason.response.headers["retry-after"])
     }
     return Effect.succeed(Duration.seconds(1))
   })

packages/effect/test/unstable/observability/OtlpExporter.test.ts

@@ -270,6 +270,27 @@ describe("OtlpExporter", () => {
       })
     ))
 
+  it.effect("retries status 429 with HTTP-date retry-after delay", () =>
+    Effect.scoped(
+      Effect.gen(function*() {
+        const { attempts, httpClient } = yield* makeHttpClient("Thu, 01 Jan 1970 00:01:00 GMT")
+        const exporter = yield* makeExporter(httpClient)
+
+        exporter.push({ value: 1 })
+        yield* yieldNowN(3)
+
+        assert.strictEqual(yield* Ref.get(attempts), 1)
+
+        yield* TestClock.adjust("5 seconds")
+        yield* yieldNowN(2)
+        assert.strictEqual(yield* Ref.get(attempts), 1)
+
+        yield* TestClock.adjust("55 seconds")
+        yield* yieldNowN(2)
+        assert.strictEqual(yield* Ref.get(attempts), 2)
+      })
+    ))
+
   it.effect("uses fallback retry-after delay when header is non-numeric", () =>
     Effect.scoped(
       Effect.gen(function*() {