[Spread-users] Spread as a real daemon

John Robinson jr at vertica.com
Wed Feb 14 01:15:04 EST 2007

Hi all,

We are looking to install the spread daemon as a real Linux daemon - you 
know, starts on reboot, can be cycled while the system is running, 
detaches itself from stdin/out/err.  We can do all this with a /etc/rc.d 
shell script riding above it [can share this if anyone is interested]. 
Target platforms are RHEL4, Fedora, and SuSe, if that matters.

Here's the issue:

We are happily using the cluster-reconfiguration feature of Spread 4.0. 
  This is one problem we have bumped into:

We would like to configure a new machine to add to the cluster by 
installing spread on it and starting its daemon, say with just a private 
Spread segment, then adding it to the existing segment with spmonitor. 
However, if we do this, it won't join the pre-existing segment without 
cycling its daemon, which requires root access, which we would prefer to 
avoid.  In other words, if there are two separate spread segments (one 
the singleton new machine), and we try to get them to combine into one 
segment with a matched config file, it doesn't succeed.  We have thought 
of a way to make this work by watching for the spread.conf file to 
appear, and then firing up the daemon at the right time (this would be a 
separete daemon-watching daemon, if you will).  Doesn't seem elegant.

What would help out here, and we have been tempted to put this into the 
spread daemon, is if the daemon can start with a non-existant config 
file (perhaps with an extra switch to say "keep running if the config 
file isn't there yet"), and then have it just wake up periodically to 
wait for the config file to appear and then go through all the rest of 
its initialization to join the (newly-expanded) segment.

Have we missed something obvious?  Has someone wrestled with this issue?

Many thanks; the product has been working great for us (thankfully, we 
have necesary flow control =:).


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