Nagios Support Forum

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On 22 Dec 2006, at 01:50, Ethan Galstad wrote:

> Based on the recent thread about hanging Nagios processes, I have
> removed the COMMAND_BUFFER_SLOTS and SERVICE_BUFFER_SLOTS definitions
> out to config file variables:
>
> external_command_buffer_slots=3D4096
> check_result_buffer_slots=3D4096
>
> I have also updated nagiostats to report the avail/used number of =20
> slots
> for graphing in MRTG. Could folks try out the latest 2.x CVS code and
> give it some testing?

Ethan,

Thanks for applying to CVS. Several comments:

- external_command_buffer_slots and check_result_buffer_slots only =20
needs to be an int as the circular_buffer struct only uses an int for =20=

items

- in xsddefault.c, when you print out external_command_buffer.items, =20
I think this is not thread-safe. My thread knowledge is pretty =20
limited, so please correct me if I am wrong. The main nagios process =20
writes the status data via xsddefault_save_status_data, which needs =20
to read the external_command_buffer variable. However, this variable =20
is written to by the command_file_worker_thread. So I think the =20
xsddefault_save_status_data routine needs a thread lock on =20
external_command_buffers before it can read the items data, otherwise =20=

there is the potential for corrupt data. Note, there is a cost to =20
that, especially if the status data is being written with =20
aggregate_status_updates =3D 0.

- your output to status.dat is different from mine. You are =20
outputting max_external_command_buffer_slots (the value defined in =20
nagios.cfg) and used_external_command_buffer_slots (the current =20
number of items in the buffer). In my patch, I had a different =20
definition: max_command_buffer_items meant the "maximum number of =20
items that has been in the buffer".

(I would prefer used_external_command_buffer_slots be changed to =20
current_external_command_buffer_slots because it more accurately =20
describes "this is the number I have now".)

=46rom now on, I'll call it high_external_command_buffer_items, as it =20=

can also be the "high water mark of the number of items in the =20
buffer". This is a useful statistic as it tells you what the =20
max_external_command_buffer_slots should be to get no holdups.

Also, it probably makes sense to put the high water mark within the =20
circular_buffer struct.

Please find a patch attached with these changes.

On my small test system, the used_check_result_buffer_slots is =20
usually 0. When I introduce 1 fake slave (128 results per 10 =20
seconds), used_check_result_buffer fluctuates from 0 to 20s to 30s. =20
Introducing a 2nd fake slave, the high mark moves up to 100s. A 3rd =20
slave moves the high mark to 192.

If I introduce NDO into the system, I get a large iowait time (in the =20=

80%s), presumably database writes. The status file is not updated as =20
regularly (one instance of 60 seconds between writes), but when it =20
does, then the high_* values jump up to the 200-300s. This is a =20
poorly configured database, so I'm guessing that there are delays due =20=

to the main nagios process passing data to the the broker module.

At the moment with 2 slaves sending 128 packets per 10 seconds, I'm =20
getting high values of 983 for external commands and 1405 for check =20
results.

I think these recent changes help with seeing if there are =20
bottlenecks at the reading of the command pipe, but I think there are =20=

possibly other slow downs further down the chain (which Nagios 3 may =20
aid with).

Ton

http://www.altinity.com
T: +44 (0)870 787 9243
F: +44 (0)845 280 1725
Skype: tonvoon

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This post was automatically imported from historical nagios-devel mailing list archives
Original poster: ton.voon@altinity.com