chore: improve tryFetch documentation and handling

packages/daemon/src/util/tryFetch.ts

@@ -1,50 +1,64 @@
 import { LoggerService } from '@pockethost/common'
-import fetch from 'node-fetch'
-import { AsyncContext } from './AsyncContext'
+import fetch, { Response } from 'node-fetch'
 
 export const TRYFETCH_RETRY_MS = 50
 
-export type Config = Required<AsyncContext> & {
+export type Config = {
   preflight: () => Promise<boolean>
   retryMs: number
 }
 
+/**
+ *
+ * @param url The URL to fetch
+ * @param config { preflight: ()=>Promise<boolean>, retryMs: number}
+ * @returns Promise<Response>
+ *
+ * tryFetch will contiously try to fetch a URL every `retryMs`, with an optinoal `preflight`.
+ * If `preflight` is specificed, it must resolve to `true` before tryFetch
+ * will attempt to fetch the URL. If `preflight` resolves to `false`, tryFetch
+ * will delay by `retryMs` and then check again. If `preflight` rejects,
+ * then tryFetch rejects and exits.
+ *
+ * Note: tryFetch exits ONLY on success or a rejected preflight.
+ */
 export const tryFetch = async (url: string, config?: Partial<Config>) => {
-  const { logger, preflight, retryMs }: Config = {
-    logger: LoggerService().create(`tryFetch`),
+  const { preflight, retryMs }: Config = {
     preflight: async () => true,
     retryMs: TRYFETCH_RETRY_MS,
     ...config,
   }
-  const _logger = logger.create(`tryFetch`)
-  const { dbg } = _logger
-  return new Promise<void>((resolve, reject) => {
-    const tryFetch = async () => {
+  const logger = LoggerService().create(`tryFetch`).breadcrumb(url)
+  const { dbg } = logger
+  return new Promise<Response>((resolve, reject) => {
+    const again = () => setTimeout(_real_tryFetch, retryMs)
+    const _real_tryFetch = async () => {
       if (preflight) {
-        dbg(`Checking preflight`)
         try {
+          dbg(`Preflight: CHECK`)
           const shouldFetch = await preflight()
           if (!shouldFetch) {
-            reject(new Error(`failed preflight, aborting`))
+            dbg(`Preflight: NOT READY`)
+            again()
             return
           }
+          dbg(`Preflight: READY`)
         } catch (e) {
-          reject(new Error(`preflight threw error, aborting`))
+          dbg(`Preflight: ABORT`)
+          reject(e)
           return
         }
       }
       try {
-        dbg(`Trying to fetch ${url} `)
+        dbg(`Fetch: START`)
         const res = await fetch(url)
-        dbg(`Fetch ${url} successful`)
-        resolve()
+        dbg(`Fetch: SUCCESS`)
+        resolve(res)
       } catch (e) {
-        dbg(
-          `Could not fetch ${url}, trying again in ${retryMs}ms. Raw error ${e}`,
-        )
-        setTimeout(tryFetch, retryMs)
+        dbg(`Fetch: ERROR: trying again in ${retryMs}ms | ${e}`)
+        again()
       }
     }
-    tryFetch()
+    _real_tryFetch()
   })
 }