Fix MethodError when an armed retry is abandoned at the request deadline

src/http_client_retry.jl

@@ -206,7 +206,7 @@ function _arm_request_retry!(
         _sleep_retry_delay!(request, delay_ns) || return false, nothing, delay_ns
         ok = true
     finally
-        ok || (bucket !== nothing && token !== nothing && release(bucket::RetryBucket, token, nothing))
+        ok || (bucket !== nothing && token !== nothing && release(bucket::RetryBucket, token, _retry_bucket_failure_cost(nothing)))
     end
     controller.remaining -= 1
     return true, token, delay_ns

test/http_retry_tests.jl

@@ -511,6 +511,39 @@ end
     end
 end
 
+@testset "retry arming refunds the bucket when the deadline preempts the backoff" begin
+    listener = ND.listen("tcp", "127.0.0.1:0"; backlog = 8)
+    address = ND.join_host_port("127.0.0.1", Int((NC.addr(listener)::NC.SocketAddrV4).port))
+    base_url = "http://$(address)"
+    seen = Tuple{String, String, String}[]
+    server_task = _serve_retry_sequence(listener, [
+        (status = 503, reason = "Service Unavailable"),
+    ], seen)
+    try
+        # A backoff far beyond the request deadline means the armed retry is
+        # abandoned before it sleeps. The bucket reservation must be refunded
+        # rather than the release erroring (it used to be called with `nothing`
+        # as the failure cost, which has no method).
+        bucket = HT.RetryBucket(capacity = 15, backoff_scale_factor_ms = 60_000, max_backoff_secs = 60)
+        response = HT.get(
+            "$(base_url)/deadline";
+            retries = 2,
+            retry_bucket = bucket,
+            request_timeout = 1,
+            status_exception = false,
+        )
+        @test response.status == 503
+        _wait_task_retry!(server_task)
+        @test seen == [("GET", "/deadline", "")]
+        # Full refund: with capacity 15 a second reservation (cost 10) only
+        # succeeds if the abandoned one returned its 10.
+        token = Base.acquire(bucket, only(keys(bucket.partitions)))
+        Base.release(bucket, token, 0)
+    finally
+        HTTP.@try_ignore NC.close(listener)
+    end
+end
+
 @testset "HTTP.open retries idempotent buffered requests" begin
     listener = ND.listen("tcp", "127.0.0.1:0"; backlog = 8)
     address = ND.join_host_port("127.0.0.1", Int((NC.addr(listener)::NC.SocketAddrV4).port))