Investigate flaky test-fs-read-buffer-tostring-fail on Raspberry Pi

[Trott]

https://ci.nodejs.org/job/node-test-binary-arm/2326/RUN_SUBSET=2,label=pi1-raspbian-wheezy/console

not ok 45 parallel/test-fs-read-buffer-tostring-fail
# (node:9636) DeprecationWarning: fs.read's legacy String interface is deprecated. Use the Buffer API as mentioned in the documentation instead.
# 
# /home/iojs/build/workspace/node-test-binary-arm/RUN_SUBSET/2/label/pi1-raspbian-wheezy/test/parallel/test-fs-read-buffer-tostring-fail.js:56
#   throw err;
#   ^
# AssertionError: '"toString()" failed' === 'EBUSY: resource busy or locked, read'
#     at /home/iojs/build/workspace/node-test-binary-arm/RUN_SUBSET/2/label/pi1-raspbian-wheezy/test/parallel/test-fs-read-buffer-tostring-fail.js:31:12
#     at /home/iojs/build/workspace/node-test-binary-arm/RUN_SUBSET/2/label/pi1-raspbian-wheezy/test/common.js:407:15
#     at callback (fs.js:663:23)
#     at FSReqWrap.wrapper [as oncomplete] (fs.js:681:17)
  ---
  duration_ms: 58.419

[rvagg]

@Trott any other instances of this failure? It's possibly related to the Pi's all running their build/ directory on NFS, perhaps there was a momentary hiccup, I did have a whole lot of networking trouble a couple of days ago and had to shut everything down to deal with it, perhaps this is related.

[Trott]

@Trott any other instances of this failure?

Not that I've noticed, but I haven't been paying attention to specific failures on Raspberry Pi the last few days. I'll run a stress test and if it doesn't show any problems, then let's close this issue.

Stress test: https://ci.nodejs.org/job/node-stress-single-test/752/nodes=pi1-raspbian-wheezy/console

(Aside: These aren't really "stress tests" but I can't think of a better term that is sufficiently succinct. Suggestions welcome.)

[Trott]

Oof, that job went offline after 10 hours and it was still compiling. Let's try again and hope some of that compilation is cached...

https://ci.nodejs.org/job/node-stress-single-test/753/nodes=pi1-raspbian-wheezy/console

[Trott]

The test takes more than a minute to run on these devices, so I'm content with stopping it after 500 successful consecutive runs rather than waiting another 10 hours to get another 500 runs. Closing!

[Trott]

Argh. It came back. https://ci.nodejs.org/job/node-test-binary-arm/2674/RUN_SUBSET=5,label=pi2-raspbian-wheezy/console

not ok 45 parallel/test-fs-read-buffer-tostring-fail
# TIMEOUT
# (node:28761) DeprecationWarning: fs.read's legacy String interface is deprecated. Use the Buffer API as mentioned in the documentation instead.
  ---
  duration_ms: 120.184

[Trott]

Might the thing to do here be to check common.enoughTestMem and skip the test if there isn't enough memory? @nodejs/testing

[Trott]

It takes ~90s to run normally and the test runner times out at 120s. That seems like not a lot of headroom to me. I'm inclined to do the skip-based-on-memory thing as I imagine this is a memory-intensive test.

[Trott]

Proposed fix: #7575