Bug 13470

If worker A deletes a file which is still being used by worker B, it loses the file rather than it sticking around until its closed.

Documenting this here so we have it recorded somewhere.

pokybuild@debian9-ty-2:/srv/autobuilder/buildhistory/test$ python3 test.py 
['.nfs000000000e48e34100004463', 'test1.py', 'test.py']

then once test.py is started, running test1.py:

[pokybuild@centos7-ty-4 test]$ python3 test1.py 
df69a7bdf92bbdffdae594f12d8efc2aa6c11eb40fa46af36a06c4d8e95b7338
Traceback (most recent call last):
  File "test1.py", line 22, in <module>
    for chunk in iter(lambda: f.read(4096), b""):
  File "test1.py", line 22, in <lambda>
    for chunk in iter(lambda: f.read(4096), b""):
OSError: [Errno 116] Stale file handle

which represents the problem.

[pokybuild@centos7-ty-4 test]$ cat test1.py 
#!/usr/bin/env python3
import subprocess
import time
import os
import hashlib

h = hashlib.sha256()

testdir = "/srv/autobuilder/buildhistory/test"
#subprocess.check_call("cp /usr/bin/zip %s/zip" % testdir, shell=True)
with open(testdir + "/zip", "rb") as f:
    foo = f.read(4096)
    h.update(foo)
    print(h.hexdigest())
    #subprocess.check_call("rm %s/zip" % testdir, shell=True)
    time.sleep(30)
    foo2 = f.read(4096)
    h.update(foo2)
    time.sleep(5)
    foo3 = f.read(4096)
    h.update(foo3)
    for chunk in iter(lambda: f.read(4096), b""):
        h.update(chunk)
    print(h.hexdigest())
    foo3 = f.seek(0)
    foo3 = f.read(4096)
    print(str(os.listdir(testdir)))

#!/usr/bin/env python3
import subprocess
import time
import os

testdir = "/srv/autobuilder/buildhistory/test"
subprocess.check_call("cp /usr/bin/zip %s/zip" % testdir, shell=True)
time.sleep(10)
with open(testdir + "/zip", "rb") as f:
    foo = f.read(4096)
    time.sleep(5)
    subprocess.check_call("rm %s/zip" % testdir, shell=True)
    foo2 = f.read(4096)
    time.sleep(5)
    foo3 = f.read(4096)
    print(str(os.listdir(testdir)))

An example build failure this causes are the WARNING in:

https://autobuilder.yoctoproject.org/typhoon/#/builders/53/builds/847

step1b: WARNING: Logfile for failed setscene task is /home/pokybuild/yocto-worker/qemuarm/build/build/tmp/work/x86_64-linux/python3-setuptools-native/41.0.1-r0/temp/log.do_populate_sysroot_setscene.47244
step1b: WARNING: Setscene task (virtual:native:/home/pokybuild/yocto-worker/qemuarm/build/meta/recipes-devtools/python/python3-setuptools_41.0.1.bb:do_populate_sysroot_setscene) failed with exit code '1' - real task will be run instead

where the setscene log would show a stale file handle.

I'd swear the NFS used to keep the file around until all open handles were closed.