There are lots of factors that determine the system health of a server. The hardware capabilities - CPU, memory or disk - is an important one, but also the server load - number of devices (Nodes to be polled, updated, audited, synchronised), number of products (NMIS, OAE, opCharts, opHA - each running different processes), number of concurrent users.
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Some aprox. configurations:
| Number of nodes | Number of threads |
|---|---|
| 120 | 3-4 |
OMK has the equivalent parameter:
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| Code Block |
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omkd_max_requests |
MongoDB memory usage
MongoDB, in its default configuration, will use will use the larger of either 256 MB or ½ of (ram – 1 GB) for its cache size.
MongoDB cache size can be changed by adding the cacheSizeGB argument to the /etc/mongod.conf configuration file, as shown below.
| Code Block |
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storage:
dbPath: /var/lib/mongodb
journal:
enabled: true
wiredTiger:
engineConfig:
cacheSizeGB: 1 |
Here is an interesting information regarding how MongoDB reserves memory for internal cache and WiredTiger, the underneath technology. Also some adjustment that can be done: https://dba.stackexchange.com/questions/148395/mongodb-using-too-much-memory
Server examples
Two servers are compared in this section.
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- abort_after: From NMIS 8.6.8G there is a new command line option, abort_after, that prevents the main thread to run for a long time, preventing it to collide from the next cron job. By default, this parameter is 60 seconds, as the cron job is set to run every 60 minutes.
This option always needs to have also the option mthreads=true.
Code Block nmis8/bin/nmis.pl type=collect abort_after=60 mthread=true ignore_running=true;
- max_thread: The other important configuration option is max_thread, that will prevent the number of children of the main process be too big. Considerations:
- If the collect has a lot of nodes to process, the number of children won't reach the limit instantly. While the main thread is forking, the children complete their jobs and will exit. Also, the main process will wait for them to change their state so the number will increase slowly.
- NMIS can have more than one instance of the main process running, and the number of children could be higher that max_threads, as the limit is only per instance.
- sort_due_nodes: When NMIS decides what to poll it can do some in a pseudo random order which is the default, if your server is overloaded you will likely see some nodes never getting polled, hence pseudo random, so for heavily loaded servers, enable sort_due_nodes, in the NMIS configuration add with the value set to 1.
Gaps in Graphs
If the server takes a long time to collect and cannot complete any operation, an useful tool is nmis8/admin/polling_summary. Here we can see how many nodes have any late collect, and a summary of nodes being collected and not collected.
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