[OpenAFS] Using a file lock to avoid race conditions?
Edgecombe, Jason
jwedgeco@uncc.edu
Tue, 15 Mar 2011 12:14:32 -0400
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Hi everyone,
=20
We're working on a script to fetch mail from an IMAP server and put it
into a web-based ticketing system. The script should be run from one of
our five Linux web servers in our fail-over pool. The script should
still run even if one server is down. A late run of 2-3 times the
frequency is acceptable.
=20
I'm thinking of using a file lock (i.e. flock) in AFS to determine who
fetches the email, but I need to know about the failure scenarios. Does
the lock persist if the machine freezes or dies? Will an orphaned lock
expire, and if so, how long does it take to expire?
=20
Any other suggestions are welcome.
=20
Sincerely,
Jason
=20
------------------------------------------------------------------------
---
Jason Edgecombe | Linux and Solaris Administrator
UNC Charlotte | The William States Lee College of Engineering
9201 University City Blvd. | Charlotte, NC 28223-0001
jwedgeco@uncc.edu <mailto:jwedgeco@uncc.edu> | http://coe.uncc.edu
<http://coe.uncc.edu/> | <https://www.facebook.com/UNCCEngr> =20
Facebook <https://www.facebook.com/UNCCEngr>=20
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vlink=3Dpurple><div class=3DWordSection1><p class=3DMsoNormal><span =
style=3D'font-size:10.0pt'>Hi everyone,<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:10.0pt'><o:p> </o:p></span></p><p =
class=3DMsoNormal><span style=3D'font-size:10.0pt'>We’re working =
on a script to fetch mail from an IMAP server and put it into a =
web-based ticketing system. The script should be run from one of our =
five Linux web servers in our fail-over pool. The script should still =
run even if one server is down. A late run of 2-3 times the frequency is =
acceptable.<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:10.0pt'><o:p> </o:p></span></p><p =
class=3DMsoNormal><span style=3D'font-size:10.0pt'>I’m thinking of =
using a file lock (i.e. flock) in AFS to determine who fetches the =
email, but I need to know about the failure scenarios. Does the lock =
persist if the machine freezes or dies? Will an orphaned lock expire, =
and if so, how long does it take to expire?<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:10.0pt'><o:p> </o:p></span></p><p =
class=3DMsoNormal><span style=3D'font-size:10.0pt'>Any other suggestions =
are welcome.<o:p></o:p></span></p><p class=3DMsoNormal><span =
style=3D'font-size:10.0pt'><o:p> </o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:10.0pt'>Sincerely,<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:10.0pt'>Jason<o:p></o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:10.0pt'><o:p> </o:p></span></p><p =
class=3DMsoNormal><span =
style=3D'font-size:9.0pt;font-family:"Arial","sans-serif"'>--------------=
-------------------------------------------------------------<o:p></o:p><=
/span></p><p class=3DMsoNormal style=3D'text-autospace:none'><span =
style=3D'font-size:9.0pt;font-family:"Arial","sans-serif"'>Jason =
Edgecombe <b>| </b>Linux and Solaris =
Administrator<o:p></o:p></span></p><p class=3DMsoNormal =
style=3D'text-autospace:none'><span =
style=3D'font-size:9.0pt;font-family:"Arial","sans-serif"'>UNC Charlotte =
<b>| </b>The William States Lee College of =
Engineering<o:p></o:p></span></p><p class=3DMsoNormal =
style=3D'text-autospace:none'><span =
style=3D'font-size:9.0pt;font-family:"Arial","sans-serif"'>9201 =
University City Blvd. <b>| </b>Charlotte, NC =
28223-0001<o:p></o:p></span></p><p class=3DMsoNormal =
style=3D'text-autospace:none'><span =
style=3D'font-size:9.0pt;font-family:"Arial","sans-serif"'><a =
href=3D"mailto:jwedgeco@uncc.edu"><span =
style=3D'color:windowtext'>jwedgeco@uncc.edu</span></a> <b>| </b><a =
href=3D"http://coe.uncc.edu/"><span =
style=3D'color:blue'>http://coe.uncc.edu</span></a> | </span><a =
href=3D"https://www.facebook.com/UNCCEngr"><span =
style=3D'color:gray;text-decoration:none'><img border=3D0 width=3D16 =
height=3D16 id=3D"Picture_x0020_3" =
src=3D"cid:image001.gif@01CBE30A.4507FA80" =
alt=3Dfacebook-logo></span></a><span style=3D'color:gray'> <a =
href=3D"https://www.facebook.com/UNCCEngr"><span =
style=3D'color:gray'>Facebook</span></a></span><span =
style=3D'font-size:9.0pt;font-family:"Arial","sans-serif"'><o:p></o:p></s=
pan></p><p class=3DMsoNormal style=3D'text-autospace:none'><span =
style=3D'font-size:9.0pt;font-family:"Arial","sans-serif"'>--------------=
-------------------------------------------------------------<o:p></o:p><=
/span></p><p class=3DMsoNormal style=3D'text-autospace:none'><span =
style=3D'font-size:8.0pt;font-family:"Arial","sans-serif"'>If you are =
not the intended recipient of this transmission or a person responsible =
for delivering it to the intended recipient, any disclosure, copying, =
distribution, or other use of any of the information in this =
transmission is strictly prohibited. If you have received this =
transmission in error, please notify me immediately by reply e-mail or =
by telephone at 704-687-3514. Thank you.<o:p></o:p></span></p><p =
class=3DMsoNormal><o:p> </o:p></p></div></body></html>
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