Sage server launching script

[kwankyu]

Many users seem to write individually scripts starting and stopping a Sage server. It would be good that there is a place where these efforts can be combined.

Component: packages: experimental

Keywords: service daemon mode background

Author: Kwankyu Lee

Reviewer: Frédéric Chapoton

Issue created by migration from https://trac.sagemath.org/ticket/7893

[kwankyu]

comment:2

Anybody is welcome to upload an improved version of the script!

[kwankyu]

comment:3

I revised the script according Donald Alan Morrison's comments: 

1. The stop_server function does not do error checking to ensure that
   the pid contained in the pid file actually corresponds to a server
   process: https://github.com/sagemath/sage/files/ticket7893/sage-server.gz

30      def stop_server():
31          try:
32              # if sage notebook server is running, "twist.pid" is
created
33              file = open(os.environ!['HOME'] + '/.sage/
sage_notebook.sagenb/twistd.pid', 'r')
34              pid = file.readline()
35              file.close()
36              print "Stopping sage server..."
37              os.system('kill -INT ' + pid)
38          except IOError:
39              print "No sage server running."

Given the frequency of reboots for most users, and the cost to the
user of killing a random process, it would be good to error check
against the actual running process name.

2. It would be good to add some code that waits for SIG_TERM to
   complete, then optionally sends SIG_KILL.  One can't assume SIG_TERM
   will be handled correctly by the server, especially if it's in a bad
   state.

3. The script should verify the completion of !Notebook locking #2, then delete the pid
   files.

-Don

[jdemeyer]

comment:4

Using "screen" is not very portable, so I would avoid that.

[jdemeyer]

comment:5

Typo: twist.pid -> twistd.pid

[kwankyu]

comment:6

Further revised according to the comment :

Line 50 "blocks" (waits syncronously without checking status); also
half of a second may not be long enough if all memory was used up and
there was excessive paging in/out from the swap file.  One alternative
method is to check for the existence of the pid file periodically for
a longer period (possibly parameterized), and if it is deleted,
recheck that the twistd process has indeed exited else send SIGKILL.

Otherwise, good refactor. :-)

-Don

[cschwan]

comment:7

Look at #381 for a similar effort. On Gentoo I automatically start the Notebook with a runscript - I find it very useful because the only thing I have to do is to open a browser and type in the Notebook's address. It is also possible to access the server from a different PC. To make it a more secure it is run as a different user.

I just added a patch which lets one specify the location of twistd's PID file: #10131 - this might be of interest.

[cschwan]

Attachment: sage-notebook-server.gz

Runscript starting the Notebook server on Gentoo

[cschwan]

comment:8

It should be easy to port the runscript e.g. to debian - as far as I know Debian also has runscript/start-stop-daemon.

[nexttime]

comment:9

Ping. Shouldn't something like this get shipped with Sage?

Also, the Sage Installation Guide lacks this topic. (There's a reference from the online FAQ to #381 though.)

[nexttime]

Changed keywords from none to service daemon mode background

[kwankyu]

revised for Sage 5.4; removed "upgrade" command

[kwankyu]

Attachment: sage-server.gz

Attachment: sage-server.zip

revised for Sage 5.4; removed "upgrade" command

[kwankyu]

comment:11

Nowadays the goal of the script can be achieved easily on the OS level using tools such as Upstart in Ubuntu. Even I, the writer of the scipt, ceased using it long time ago.

[fchapoton]

comment:12

ok, then let us close that.

[fchapoton]

Reviewer: Frédéric Chapoton