Feature #3310
closed
nfd process: write PID to file
Added by Junxiao Shi almost 10 years ago.
Updated almost 10 years ago.
Description
Write the PID of nfd process to a file, so that it can be signaled with kill precisely.
Necessity:
In certain experiments including but not limited to Mini-NDN, multiple nfd processes can be running in the same PID namespace.
pkill and killall cannot precisely signal one nfd process without affecting other nfd processes.
This issue includes:
- design the format of PID file
- decide the location of PID file, whether and how it can be configured
- decide who should write the PID file
- implement the feature
- Description updated (diff)
file format
- Many applications write just the PID (in decimal), as a text file.
- Google Chrome for Ubuntu writes the machine name plus the PID (in decimal), as a symlink
$HOME/.config/google-chrome/SingletonLock.
Having the machine name allows Google Chrome to prompt user if the profile is being used on another machine sharing a folder over NFS, but this isn't important for NFD.
I'm unsure about the choice between a text file and a symlink.
location
The location must be configured, so that multiple nfd processes can have different PID files.
The choice is: whether to configure this in nfd.conf, or as a command line option (on either nfd or nfd-start+nfd-stop, depending on the next answer).
who writes PID file
Either nfd itself or nfd-start should write the PID file.
In nfd-start, it can know nfd's PID through $! variable.
Sounds like the wrong solution to me. Why can't the parent process (whatever spawns the nfd process) keep track of its PID? E.g. in bash there's $!, in python you can use subprocess.Popen objects, etc... What does having a PID file simplify?
Why can't the parent process (whatever spawns the nfd process) keep track of its PID?
In the case of nfd-start and nfd-stop, the parent process who spawns nfd is nfd-start, which has no way to pass the PID to nfd-stop which can be called in another console.
who said anything about nfd-start and nfd-stop? With the merging of nfd and nrd in one process, there's no reason for those scripts to exist anymore, we should get rid of them. nfd should be run directly.
- Status changed from New to Rejected
20151103 conference call agrees with note-3, so this is rejected.
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