When booting a session, retry every five seconds if unable to send the request.

This is intended to transparently resume the session (using `boot` to start over) after more serious connection interruptions. It interacts with the heartbeat timeout: we let the browser try to reconnect through `EventSource` on its own for up to 30 seconds, before intervening, closing the event source, and starting attempts to call `boot`.

This covers both initial boot, which will now hang if the server is unavailable (sorry), and reconnection after an event timeout. No other operations are retried (particularly, sending a message is _not_ retried).

1 files changed, 21 insertions, 0 deletions

diff --git a/ui/lib/retry.js b/ui/lib/retry.js
new file mode 100644
index 0000000..777f1be
--- /dev/null
+++ b/ui/lib/retry.js
@@ -0,0 +1,21 @@
+export async function retry(callback, retryCond, delay) {
+  while (true) {
+    try {
+      return await callback();
+    } catch (err) {
+      if (retryCond(err)) {
+        await delay();
+      } else {
+        throw err;
+      }
+    }
+  }
+}
+
+export function delay(millis) {
+  return async () => await sleep(millis);
+}
+
+function sleep(millis) {
+  return new Promise((resolve) => setTimeout(resolve, millis));
+}