We have a JBoss application where the database connections are managed via C3PO. Recently the DB node (Oracle DB) had gone down and ever since the restart of the DB we are seeing intermittent timeouts during the DB call. Ideally new connections should've been made after the DB node had come back up but looks like the connections were still persistent and had gone idle.
C3PO configurations I think could be responsible:
hibernate.c3p0.timeout=300
hibernate.c3p0.idle_test_period=1800
Upon some research i read that the idle_test_period should not be higher than the c3p0.timeout. Does this hold good and if yes what's how do these values determine when a connection is idle and has to be removed from the pool?
Related
We have recently upgraded from Oracle.ManagedDataAccess.EntityFramework to Oracle.EntityFrameworkCore (we are on .net standard 2.0). When we connect to the database we use proxy credentials, with the following connection string:
User Id=changingUserId;Data Source=dbname;Proxy User Id=proxyUserId;Proxy Password=proxyUserPassword;
The UserID element changes based on who is connecting.
The problem we have is that the connection pools are no longer working as expected, with many connections being spawning and not closed - we very quickly reach the pool size limit and everything grinds to halt. Before the upgrade, pools would increase and decrease in size, but they now only grow!
Reading the oracle docs, it appears it requires the connection string to be identical for connection pooling to work correctly, but I don't see how this is possible when we are using proxy users. Has anyone else come across this/got around it or am I missing something?
Thanks
Chris
We have found a work around, adding the users password into the connection string makes it work as expected - no more filling up the connection pool/connection numbers are again rising and falling.
User Id=changingUserId;Password=usersPwd;Data Source=dbname;Proxy User Id=proxyUserId;Proxy Password=proxyUserPassword;
This isn't ideal for us - authentication/authorisation is handled elsewhere - but it will do for now. We are raising a call with Oracle as I suspect this is a bug in their library.
We have a Spring Boot application usin AWS Aurora serverless as a database. Our back-end is 99% of the time not used; therefore, we set the minimumidle parameter to 0 - hoping that Hikari would after a certain amount of time, close all the connections until they're needed again. That way our serverless database would also pause after a certain amount of inactive time.
Unfortunately, it's not working. We can see that Hikari is indeed closing the idle connections as we monitor our database. However, our serverless database isn't pausing due to inactivity.
My question is: Is Hikari is doing periodical polling to the database at certain intervals even after no idle/active connections are left? We suspect this is what's keeping our DB "active".
We're in the process of rewriting a web application in Java, coming from PHP. I think, but I'm not really sure, that we might run into problems in regard to connection pooling. The application in itself is multitenant, and is a combination of "Separate database" and "Separate schema".
For every Postgres database server instance, there can be more than 1 database (named schemax_XXX) holding more than 1 schema (where the schema is a tenant). On signup, one of two things can happen:
A new tenant schema is created in the highest numbered schema_XXX database.
The signup process sees that a database has been fully allocated and creates a new schemas_XXX+1 database. In this new database, the tenant schema is created.
All tenants are known via a central registry (also a Postgres database). When a session is established the registry will resolve the host, database and schema of the tenant and a database session is established for that HTTP request.
Now, the problem I think I'm seeing here is twofold:
A JDBC connection pool is defined when the application starts. With that I mean that all databases (host+database) are known at startup. This conflicts with the signup process.
When I'm writing this we have ~20 database servers with ~1000 databases (for a total sum of ~100k (tenant) schemas. Given those numbers, I would need 20*1000 data sources for every instance of the application. I'm assuming that all pools are also, at one time or another, also started. I'm not sure how much resources a pool allocates, but it must be a non trivial amount for 20k pools.
So, is it feasable to even assume that a connection pool can be used for this?
For the first problem, I guess that a pool with support for JMX can be used, and that we create a new datasource when and if a new schemas_XXX database is created. The larger issue is that of the huge amount of pools. For this, I guess, some sort of pool manager should be used that can terminate a pool that have no open connections (and on demand also start a pool). I have not found anything that supports this.
What options do I have? Or should I just bite the bullet and fall back to an out of process connection pool such as PgBouncer and establish a plain JDBC connection per request, similar to how we're handling it now with PHP?
A few things:
A Connection pool need not be instantiated only at application start-up. You can create or destroy them whenever you want;
You obviously don't want to eagerly create one Connection pool per database or schema to be open at all times. You'd need to keep at least 20000 or 100000 Connections open if you did, a nonstarter even before you get to the non-Connection resources used by the DataSource;
If, as is likely, requests for Connections for a particular tenant tend to cluster, you might consider lazily, dynamically instantiating pools, and destroying them after some timeout if they've not handled a request for a while.
Good luck!
I am using Pentaho-BI server installation in my web application as a third party installation.I am using its saiku analytics and reporting files by embedding their specific links in iframe of my application. Problem is I am not getting how it creates database connections, in terms of numbers?? Because many times it throws error regarding 'No connection is available in pool'. I know there are properties like max available connection, max idle connections , wait and sql validation. But How to release connections?? And if Pentaho handles it in its own way then how?? Because increasing number of max connections available will create load on database server, when many users are using my BI server.
One solution I found is just to restart my BI server, but It's not a valid solution for production environment. Other solution I think is scheduler, but I have no clues about it and not getting proper info on net.
The defaults for max connections are incredibly low. This is standard tomcat connection pooling stuff, I would definitely try increasing the default, see if that helps. you can monitor concurrent connections on the db side - just because you have 100 connections to the db it doesn't necessarily mean they'll be all used at once.
Also; Are you using mysql? You should try the c3po pooling driver it handles timeouts and things better than the standard driver so you shouldnt ever get dead connections sitting in the pool.
We have a web service written in Java and is connecting to Oracle database for data extraction. Recently, we encountered too many inactive session in Oracle database from JDBC which is our web service.
We are very sure that all the connection is being closed and set to null after every process.
Can anyone help us in this? Why is it causing inactive session in the database and what can be the solution to this.
Thank you.
What, exactly, is the problem?
Normally, the middle tier application server creates a connection pool. When your code requests a connection, it gets an already open connection from the pool rather than going through the overhead of spawning a new connection to the database. When your code closes a connection, the connection is returned to the pool rather than going through the overhead of physically closing the connection. That means that there will be a reasonable number of connections to the database where the STATUS in V$SESSION is "INACTIVE" at any given point in time. That's perfectly normal.
Even under load, most database connections from a middle tier are "INACTIVE" most of the time. A status of "INACTIVE" merely means that at the instant you ran the query, the session was not executing a SQL statement. Most connections will spend most of their time either sitting in the connection pool waiting for a Java session to open them or waiting on the Java session to do something with the data or waiting on the network to transfer data between the machines.
Are you actually getting an error (i.e. ORA-00020: maximum number of processes exceeded)? Or are you just confused by the number of entries in V$SESSION?