I am using JDBC with proxool connection pool to connect to mysql DB.
I am selecting large number of rows from multiple threads and after some time i get an error saying communication link failure, Last packet sent to the server was ...ago.
I am closing connection,statement,resultSet in every thread.
The fetching time increases gradually and the exception occurs after 5-10 minutes.
I doubt it is a memory leak, but cant find any clue.
Please let me know the possible reasons.
Thanks,
Kaka
it may related on your Connection Timeout, try to increase it.
con.setConnectionTimeout(X);
Related
I have been using oci8 for over a year now for several batch processes. There I used to make oracle calls based on a particular frequency without any high number of parallel requests. Recently I started using this driver to process multiple number of user requests in parallel using go routines. The connections go through 90% of the times but for remaining 10% I see an error driver: bad connection being thrown from this driver. This is generally happening in two situations:
When the connection was left idle for too long(happens for few requests).
When there is a spike in number of connections.
Actions taken:
Already checked with my oracle DB for connection/session limits. There is no such limit on it.
Tried forking the branch and adding error logs which didn't seem to compile.
Most of the people who have faced this issue mentioned wrong handling of multiple connections at the same time. For me that is something done by oci8.
Please help!
I am not able to understand the values in WAS PMI for ConnectionPoolModule.
In one application I am monitoring, I am getting perf metrics for "Allocate Count", and in other I am getting perf metrics for "Create Count"
In the case of the AllocateCount - i can see that this value keeps increasing over time, and not sure what the effects of this state is.
What are the differences between these count types?
What should I be looking for to review connection pools?
Why are these metrics not showing up at the same time?
Should I be bothered about the increase in AllocateCount, or should I match it with other metrics to review the application state?
Thanks!
With these metrics, an allocate is an application request for a connection, e.g. a DataSource.getConnection(). The WebSphere pool manager either satisfies the request with an already-pooled connection, or creates a new one, and in the latter case the create count gets incremented. So if your allocate and create counts were the same, you'd be doing no pooling, probably a bad thing!
But that's not necessarily the best thing to monitor. Things like the average wait time could be the best starting point.
Let me refer you to some other links to help you monitor WebSphere JDBC connection pool data:
JDBC chapter in WebSphere Application Server performance cookbook
WebSphere Application Server Performance Tuning Toolkit with video
Older but still relevant, some slides specifically detailing some connection pool monitoring techniques.
I have a ASP.Net MVC Application connecting to Oracle DB. I am using LINQ in my controller to pull data from Oracle DB.
If that page is loaded, after several minutes if its idle, it gives the above error.
Now I can't ask my DBA to increase the idle time. In my research I saw mention of Pooling in Web.config file. My understanding is that, because of Pooling, some of these connections are still active. I have removed this portion
Min Pool Size=1;Max Pool Size=20;Pooling=true
Do I have to explicitly say in my Web.config:
Pooling=false
I also have in my Controller, Dispose function as below but that doesn't help:
protected override void Dispose(bool disposing)
{
if (disposing)
{
db.Dispose();
}
base.Dispose(disposing);
}
Please help.
If the DBA sets an idle timeout on the server for connections then configure your connection pool with this option.
Min Pool Size=0;
The default is 1. This will keep the ODP.NET client from keeping any open idle connections in the pool while the application is idle. It will still increase the pool size when connection requests come in and it will likely be slightly less efficient at satisfying initial requests since it has to create those connections, but it will work and not have the idle timeout issue.
I agree with some of the comments that there shouldn't be an idle timeout set on the server for these cases, but I've found that some organizations insist on doing this for security reasons.
Here's an approach. When you resume using your connection after a potential idle delay, such as waiting for an incoming request, do this:
Run some cheap no-op query like SELECT 1 FROM DUAL;
If you get the error you mentioned, make sure the connection is completely closed, then open a new one.
Use the connection as normal.
This is a bit of a hack compared to organizing your connection pool properly, but it's better than opening up a new connection every time you need one.
I am an Oracle DBA and not a java developer or websphere expert. We recently started using websphere in our environment. So the developers are still learning it. So I may not word my question properly. I did search the forums and saw 2 other questions like this. My question is more about how to trouble shoot this.
Websphere 8.5.0.2
Oracle 11.2.0.3
I see 20 open connections in the database. All are inactive. So they are not processing. From oracle it is v$session. Inactive means, you are open and not doing anything. Basically it is idle.
If they are inactive and not processing, they should be available for the connection pool to give to a new requester, assuming the DAO the java developer is using is being closed when done (this includes try/catch block). We confirmed that he is closing his connections.
Checks so far:
1. We reviewed the developers code. He is using standard java DAOs. He is closing his connection. He has a try/catch block and the first thing he does in the catch is close the connection.
2. My assumption is that this should cover the code path.
We don't see any errors raised in a log about 'closing' a connection.
My understanding of how a connection pool works
1. Pool Manager opens a configurable set of connections to the database. In our case it is 20.
2. When an application requests a connection, the connection manager does a lookup of the pool for the next available connection, then passes a pointer to that connect to the requesting function.
Possibility:
1. really slow server. We are using VMs for development/test. We do not have visibility to the servers to see if they are busy. So another VM could be using up CPU or disk.
Though lookups for available connections are light weight, it is possible that the server is hung up at 100% cpu and we timeout. Problem is, I don't have a way to look at this. No privileges and no access to someone who does.
not closing connections: We checked pretty thoroughly. We don't see any code passes (including exceptions) where he is not closing connections. First thing he does in a catch, is close the connection.
Any suggestions on where to look? I think its an issue with a slow server, but I want to rule other stuff out. I would like to state again that I am not a java developer or a websphere expert. So my question may be worded poorly.
the first thing he does in the catch is close the connection
Get the developer to introduce finally block after catch block and close connection in finally block, instead of catch block. Flow will move to catch only in case of error, but on normal flow the connection will not be released soon.
try {
//do something
}
catch(Exception ex) {
// log error
}
finally {
//close connection here
}
The symptoms you've described indicate a connection leak. Leaks are easy to solve (see ad-inf's response), but it can be hard to locate the source of the leak. Luckily, WAS comes with ConnLeakLogic mechanism. After enabling it, in the trace.log you'll find entries related to connections which have been retrieved from pool by application and haven't been returned for longer period of time. That connection information will also print a stack trace of a Java thread from the time of obtaining the connection. Seeing that stack traces, Java developer should be able to identify offending code.
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?