Best Practice to analyse event "SYS_THREAD_HANG"?

[user54119]

We see this problem also again, here on V2.0-RC1 on Linux x64.

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[user55116]

As a workaround, i increased the polling interval (from 60->120 sec) for most of the DCIs.

No thread hang so far, but still a bit early to celebrate.

Size of my setup:

Total number of objects:     17788
Number of monitored nodes:   401
Number of collectable DCIs:  2959

[user55116]

@user55116 said in Best Practice to analyse event "SYS_THREAD_HANG"?:

As a workaround, i increased the polling interval (from 60->120 sec) for most of the DCIs.

No thread hang so far, but still a bit early to celebrate.

Size of my setup:

Total number of objects:     17788
Number of monitored nodes:   401
Number of collectable DCIs:  2959

Well, the error occurs every week now, not whenever the server feels like it, only I partially success. I can now schedule a restart to prevent this from happening, but I would still prefer a proper solution.

[user54119]

We also have no solution yet.

[victor]

Hi,

when you encounter hang next time, could you please capture process state using following instruction?

1. Check netxmsd PID
2. Run

gdb netxmsd

(use full path if necessary). It will show (gdb) prompt.

3. Within gdb run

attach <netxmsd_pid>

it should show (gdb) prompt again.

4.  Run

thread apply all bt

and send me the output (could be quite long, so make sure you have adequate buffer length in terminal).

5. Run

detach

to detach from netxmsd and let it run.

Best regards,
Victor

[user54119]

Hi Victor

Here the output.

thanks
Dani

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putty.log

[victor]

Hi,

from the trace I see that server is blocked on reading one of Service.Check(...) parameters (and I see there are lot of them) which probably takes some time to complete. As DCI is locked when it is being polled, when item poller thread attempts to access this DCI it locks, and so watchdog warning is triggered.
Actually new feature called "agent side DCI cache" introduced in 2.0-RC1 can help - you can turn on agent cache for those DCIs (or all DCIs). This will switch then from polling mode to push mode, thus eliminating long locks on server side.

Best regards,
Victor

[user54119]

Hi Victor

Thanks you for your analyse.
I changed all 'Service-Check'-DCIs to Agent Cache Mode = ON (are all DCIs with Soucre-node = NetXMS server). Seems to be the solution (ok a little bit early for all-clear)!

Is this feature fully implemented now in V2.0-RC1?
Is there also a disadvantage of Cache-mode=on or is it ok to change all agent-DCIs to cache-mode=on?
What are the possible values for server configuration variable "DefaultAgentCacheMode"? I couldn't found it in the Wiki.
Is there a short documentation of the agent-cache-mode feature?

thanks
Dani

[user54119]

Is there a documentation of the cache feature?
There are 3 level for this feature:

1. server default setting 'DefaultAgentCacheMode' (which number is which setting?)
2. settings on the agent (on, off, default, is default the setting from the server settings?
3. settings on the individual DCI (on, off, default)

Are there limitations with V2.0-RC2?

thanks
Dani

[victor]

Hi,

it should be fully functional in 2.0-RC2. We will update documentation soon. In short:

1. DefaultAgentCacheMode can be either 1 (on) or 2 (off);
2. agent level "default" means using DefaultAgentCacheMode settings;
3. DCI level "default" means using agent level settings.

Best regards,
Victor

[Borgso]

Sorry for necroing this topic, we have the same issue and just upgraded to 2.0.3 we are now able to use this AgentCache function.

On Source node, there is a script polling custom Services for values.
Without agent cache this would give 1 poll each second, with cache on it polls much more within one second.
But it does not save any data to DCI history, do "Origin" need to be "Push" and not "NetXMS agent" when AgentCache function is On?

Is this function the reason of SQLite requirment on agent and are there any agent side configuration needed (ie db location)?

[victor]

No, origin need to be "NetXMS agent". Yes, this is the main reason why agent needs SQLite. Usually no additional configuration required, agent will create local database in reasonable location ($install_prefix/var/lib/netxms if built from sources, /var/lib/netxms if installed from deb package).
There is a bug in 2.0.3 (fixed in 2.0.4) that cached mode actually works only for servers listed as MasterServers in agent configuration.

Best regards,
Victor