[Nagios-devel] Test Please: Buffer Slots Variable CVS Code
nagios at nagios.org
Wed Jan 3 03:12:33 UTC 2007
Ton Voon wrote:
> 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:
>> I have also updated nagiostats to report the avail/used number of slots
>> for graphing in MRTG. Could folks try out the latest 2.x CVS code and
>> give it some testing?
> Thanks for applying to CVS. Several comments:
> - external_command_buffer_slots and check_result_buffer_slots only needs
> to be an int as the circular_buffer struct only uses an int for items
> - in xsddefault.c, when you print out external_command_buffer.items, I
> think this is not thread-safe. My thread knowledge is pretty limited, so
> please correct me if I am wrong. The main nagios process writes the
> status data via xsddefault_save_status_data, which needs to read the
> external_command_buffer variable. However, this variable is written to
> by the command_file_worker_thread. So I think the
> xsddefault_save_status_data routine needs a thread lock on
> external_command_buffers before it can read the items data, otherwise
> there is the potential for corrupt data. Note, there is a cost to that,
> especially if the status data is being written with
> aggregate_status_updates = 0.
> - your output to status.dat is different from mine. You are outputting
> max_external_command_buffer_slots (the value defined in nagios.cfg) and
> used_external_command_buffer_slots (the current number of items in the
> buffer). In my patch, I had a different definition:
> max_command_buffer_items meant the "maximum number of items that has
> been in the buffer".
> (I would prefer used_external_command_buffer_slots be changed to
> current_external_command_buffer_slots because it more accurately
> describes "this is the number I have now".)
> From now on, I'll call it high_external_command_buffer_items, as it can
> also be the "high water mark of the number of items in the buffer". This
> is a useful statistic as it tells you what the
> max_external_command_buffer_slots should be to get no holdups.
> Also, it probably makes sense to put the high water mark within the
> circular_buffer struct.
> Please find a patch attached with these changes.
> On my small test system, the used_check_result_buffer_slots is usually
> 0. When I introduce 1 fake slave (128 results per 10 seconds),
> used_check_result_buffer fluctuates from 0 to 20s to 30s. Introducing a
> 2nd fake slave, the high mark moves up to 100s. A 3rd slave moves the
> high mark to 192.
> If I introduce NDO into the system, I get a large iowait time (in the
> 80%s), presumably database writes. The status file is not updated as
> regularly (one instance of 60 seconds between writes), but when it does,
> then the high_* values jump up to the 200-300s. This is a poorly
> configured database, so I'm guessing that there are delays due 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
> getting high values of 983 for external commands and 1405 for check results.
> I think these recent changes help with seeing if there are bottlenecks
> at the reading of the command pipe, but I think there are possibly other
> slow downs further down the chain (which Nagios 3 may aid with).
Good suggestions. I have applied almost identical patches to CVS based
on your comments. Thanks!
Email: nagios at nagios.org
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