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PWH setting of max_connections

ksk_natsume
Inactive

Hi, This is Ryotaro.

I want to know about PWH setting of max_connections.

I asked before on

https://answers.dynatrace.com/spaces/148/uem-open-...

However, I want to know more detail.

this answer raising cases where there are many clients as an example, but our environment is three clients. However, If I open many chart dashlets, does the number of simultaneous connections increase?

■ Please tell me the conditions that will increase the number of concurrent database connections on one client.

■ Is there an upper limit on the number of DB simultaneous connections per client?

■ Please tell me about the behavior when I exceed the number of DB simultaneous connections.

Best Regards

Ryotaro

2 REPLIES 2

Hi Ryotaro,

internally we use a jdbc connection pool to handle these situations. When all connections are in use and a time out triggers, there will be an exception and the request will fail. This could be a charting request and then you'd not see all the data in the chart. That wouldn't be so bad. However, it could also be a writing or updating request, this could in extreme cases lead to some data loss or inconsistent data (if the situation persists; we usually recover fine if it only happens for a short peak time).

There is no per-client limit for the connections, only the global one. However, a client can only have 3 pending requests on a server, so there's an indirect limit.

All requests that trigger pwh operations contribute to the number of connections in use. For clients, this is mostly charting and incident requests. You will reach the limit if in total all your concurrent requests (for clients that mostly means "chart refreshes") sum 50. Typically the backend server will use 5 to 8 connections at a time without client interaction. Therefore, you'll typically have about 42 connections free. If you have 14 clients with the worst case of each client having open 3 (larger) charting requests simultaneously, you'll hit the limit. Most often, the consequence will be half-empty charts.

Hope that helps, best regards,

Peter

PS: As stated in the original answer, there's a setting to increase the default of 50 connections to a larger number. The effect of increasing this number will be increased load on the database.

ksk_natsume
Inactive

Hi Peter,

Thank you for your answer!