Add retry-on-failed download

[nickheyer]

Just got an error while attempting to curling https://nodejs.org/dist/v10.15.0/node-v10.15.0-linux-x64.tar.xz...
Transfer closed with xxxxxxx bytes remaining to read. Ie: Connection timed out for whatever reason.

In a prod env, when we are unable to control unknown variables like a stable network for the servers hosting node's repos, or even our own network on occasion, the solution is to almost always retry (with a back-off delay). You should add such a delay to the default behavior, or better yet add alternate mirrors to use on failed downloads, etc.

16:23:03 #7 2.290 1 of 2: 10.15.0...
16:23:03 #7 2.314 installing : node-v10.15.0
16:23:03 #7 2.412 mkdir : /home/tester/n/n/versions/node/10.15.0
16:23:03 #7 2.416 fetch : https://nodejs.org/dist/v10.15.0/node-v10.15.0-linux-x64.tar.xz
16:23:04 #7 3.350 curl: (18) transfer closed with 3224425 bytes remaining to read
16:23:04 #7 3.366 xz: (stdin): Unexpected end of input
16:23:04 #7 3.369 tar: Unexpected EOF in archive
16:23:04 #7 3.369 tar: Unexpected EOF in archive
16:23:04 #7 3.369 tar: Error is not recoverable: exiting now
16:23:04 #7 3.370
16:23:04 #7 3.370 Error: failed to download archive for 10.15.0
16:23:04 #7 3.370
16:23:04 #7 3.371 n-install: WARNING: Failed to install version '10.15.0'.
16:23:04 #7 3.371 2 of 2: 6.11.2...
16:23:04 #7 3.387 installing : node-v6.11.2
16:23:04 #7 3.451 mkdir : /home/tester/n/n/versions/node/6.11.2
16:23:04 #7 3.455 fetch : https://nodejs.org/dist/v6.11.2/node-v6.11.2-linux-x64.tar.xz
16:23:05 #7 4.519 copying : node/6.11.2
16:23:06 #7 5.240 installed : v6.11.2 (with npm 3.10.10)
16:23:06 #7 5.251 === n successfully installed.
16:23:06 #7 5.251 The active Node.js version is: v6.11.2
16:23:06 #7 5.251
16:23:06 #7 5.251 Run n -h for help.
16:23:06 #7 5.251 To update n later, run n-update.
16:23:06 #7 5.251 To uninstall, run n-uninstall.
16:23:06 #7 5.251
16:23:06 #7 5.251 IMPORTANT: OPEN A NEW TERMINAL TAB/WINDOW or run . /home/tester/.bashrc
16:23:06 #7 5.251 before using n and Node.js.
16:23:06 #7 5.251 ===
16:23:06 #7 DONE 5.9s

[shadowspawn]

Related upstream issue: tj/n#784

For interest, NodeJS are in the process of improving their web infrastructure so that updates to their web site and downloads do not cause a brief outage while the cache is refreshed.

[mklement0]

Thanks for the additional info, @shadowspawn.

@nickheyer, I think @shadowspawn's comment on the linked issue applies analogously to this project in this case:

I currently don't think a retry is appropriate in the n code. There are lots of things that can go wrong, including systematic problems that need fixing before an attempt can work. I prefer failing fast and leaving it up to the caller to decide how to proceed.