winston Overfull backlog dropped TraceBuf

[Philip Crotwell]

Hi all

So, I was applying patches to my earthworm machine, which required a reboot. So there was a small amount of downtime, maybe 10-20 minutes. Upon restarting earthworm and Winston, I got a lot of messages in the winston ImportEW.log file like:

2013-03-14 09:50:39: (FINE) Overfull backlog, dropped TraceBuf: PAULI$HHZ$CO$00
2013-03-14 09:50:39: (FINE) Overfull backlog, dropped TraceBuf: HODGE$HHZ$CO$00
2013-03-14 09:50:39: (FINE) Overfull backlog, dropped TraceBuf: HODGE$HHZ$CO$00
2013-03-14 09:50:39: (FINE) Overfull backlog, dropped TraceBuf: PAULI$HHZ$CO$00
2013-03-14 09:50:39: (FINE) Overfull backlog, dropped TraceBuf: HODGE$HHZ$CO$00
2013-03-14 09:50:39: (FINE) Overfull backlog, dropped TraceBuf: HODGE$HHZ$CO$00
2013-03-14 09:50:39: (FINE) Overfull backlog, dropped TraceBuf: HODGE$HHZ$CO$00

Since these are all Z channels, I suspect this is related to this setting in my ImportEW.config:
# Fast options (for writing tracebufs immediately to the database)
options=Fast
Fast.timeThreshold=1
Fast.traceBufThreshold=1
Fast.maxBacklog=200
Fast.rsam.delta=10
Fast.rsam.duration=60
Fast.applyTo=* ..Z * *

To be honest, I have this there because it was in the example and sounded like a good idea at the time, but not for any really good reason.

So, have others seen problems with the "fast" database writing? Should I disable this to avoid losing data? I have already increased the Fast.maxBacklog to 2000, so hopefully that will help.

Being fast seems like a good idea, but quickly throwing data into the trash is less appealing. :)

thanks,
Philip

PS, This is on the winston from the 7.6 earthworm release.

[Stefan Lisowski]

My understanding of the Fast option is Winston, is that it lets you add
certain channels that you really care about faster than other channels.
So maybe you occasionally have dropouts in the other ones, but the core
channels all get written to the DB.

If all channels are "fast" I don't think there's any particular benefit
t using this feature.

- Stefan

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[Philip Crotwell]

That was what I thought as well, which is why I set up the vertical to go fast, with the horizontals and other aux data to go regular. Maybe all verticals is too many channels, but I only have a dozen stations, so it seems like it should be able to handle it.

I should say that the stations with the drops are all Q330 digitizers. My experience is that when the Q330 reconnects, it pumps out the data backlog as fast as it can. My other stations, refteks and guralps, seems to catch up at a much more leisurely pace. Still seems weird to me that a station on a cell modem can send data in faster than winston can stuff it into the database! My earthworm/winston machine is brand new with plenty of memory, cpu and fast disk. Just odd. Maybe upping the maxBacklog will solve it.

thanks,

Philip

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[Parker, Thomas]

The Fast options attempt to get data into MySQL as quickly as
possible. However, that causes a lot of small writes, which can stress
disk I/O. Bumping Fast.timeThreshold and Fast.traceBufThreshold up a
bit should help.

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Tom Parker
U.S. Geological Survey
Alaska Volcano Observatory
4200 University Drive
Anchorage, AK 99508
tpa...@usgs.gov
907-786-7030 (phone)
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[Philip Crotwell]

So sounds like unless I really have a need to get the Z in the database asap, I am probably better off just letting everything go in via the regular spigot?

thanks
Philip

[Parker, Thomas]

Yep. Most of the Winston installs I've seen struggle with disk I/O.

I've often wondered if there's another SQL database that is easier on
disk than MySQL/MyISAM. Winston's queries are fairly simple and should
migrate easily if a better DB is found.