if I just read the docs, I would have figured this out sooner :|

src/main.rs

@@ -7,7 +7,7 @@ pub mod speak_proxy;
 
 use anyhow::Result as AnyhowResult;
 use crate::newrelic_logger::{NewRelicLogger, MaybeNewRelicTransaction};
-use crate::speak_proxy::speak_proxy;
+use crate::speak_proxy::{speak_proxy, speak_proxy_with_retry};
 use futures::future::{self, Future};
 use hyper::Method;
 use hyper::header::HeaderValue;
@@ -179,7 +179,7 @@ fn main() -> AnyhowResult<()> {
       match (req.method(), req.uri().path()) {
         (&Method::POST, "/speak") => {
           let nr_transaction = newrelic_logger3.web_transaction("/speak");
-          speak_proxy(req, remote_addr.clone(), router3, nr_transaction, "/speak")
+          speak_proxy_with_retry(req, remote_addr.clone(), router3, nr_transaction, "/speak")
         },
         (&Method::POST, "/speak_spectrogram") => {
           let nr_transaction = newrelic_logger3.web_transaction("/speak_spectrogram");

src/speak_proxy.rs

@@ -17,6 +17,7 @@ use std::fmt::Display;
 use std::net::SocketAddr;
 use std::str::FromStr;
 use std::sync::Arc;
+use futures::IntoFuture;
 
 /// NB: This much match the shape of SpeakRequest in the 'voder/tts_service' code.
 /// This is used for both /speak and /speak_spectrogram requests.
@@ -33,6 +34,23 @@ struct RequestDetails {
   pub speaker: String,
 }
 
+pub fn speak_proxy_with_retry(
+  req: Request<Body>,
+  remote_addr: SocketAddr,
+  router: Arc<Router>,
+  transaction: MaybeNewRelicTransaction,
+  endpoint: &'static str) -> BoxFut
+{
+  speak_proxy(req, remote_addr, router, transaction, endpoint)
+    .then(|result| {
+      match result {
+        Ok(t) => future::ok(t),
+        Err(t) => future::err(t),
+      }
+    })
+    .boxed()
+}
+
 pub fn speak_proxy(
   req: Request<Body>,
   remote_addr: SocketAddr,