retry requests to rtcv if failing

Author: mjarkk

client.ts

@@ -3,6 +3,7 @@ export { newCvToScan, LangLevel } from './cv.ts'
 
 import { envT, readEnv, serverT } from './env.ts'
 import { CVToScan } from './cv.ts'
+import { fetchWithRetry } from './utils.ts'
 
 import { Sha512 } from "https://deno.land/std@0.143.0/hash/sha512.ts"
 
@@ -110,8 +111,7 @@ class ServerConn {
             body: body ? JSON.stringify(body) : undefined,
         }
 
-        const req = await fetch(url, options)
-        // TODO retry if server is not available
+        const req = await fetchWithRetry(url, options)
         if (req.status >= 400) {
             const text = await req.text()
             throw `server responsed with [${req.status}] ${req.statusText}: ${text}`

utils.ts

@@ -0,0 +1,20 @@
+export async function fetchWithRetry(input: string | Request, init?: RequestInit) {
+    let attempt = 0
+    let lastError: unknown
+    while (attempt <= 4) {
+        if (attempt > 0) {
+            const seconds = attempt * 4
+            console.warn(`fetch failed to RTCV, retrying after ${seconds} seconds`)
+            await sleep(seconds * 1000)
+        }
+        try {
+            return await fetch(input, init)
+        } catch (e) {
+            attempt++
+            lastError = e
+        }
+    }
+    throw `fetch failed to RTCV, retried 4 times. ${lastError}`
+}
+
+export const sleep = (timeout: number) => new Promise((res) => setTimeout(res, timeout))