this is my first question on the site so be patient if something is not correctly in it.
I have a problem with Hibernate in the Grails application. The application works with MySQL database. When it tries to perform save operation for one specific domain object (this class is very simple, just several fields and many to one relation with another domain class) it hangs. I am getting socket timeout exception no matter how big max connection and max socket timeout was set during connection.
The strangest thing is that this happens only with production server. On local environment this piece of code works fine. And other database operations are also executed fine.
I tried to perform generated by Hibernate insert statement manually and it works good. But Hibernate still fails to finish the operation no matter how long I wait.
Do you have any ideas what can cause such behavior?
Related
I have been trying to use MySql data with Spotfire, Had a connection established and managed to make a working dxp file. Tried to do the same with a second table and it threw this error
The following error message "Streaming result set com.mysql.jdbc.RowDataDynamic#XXXXXX is still active. No statements may be issued when any streaming result sets are open and in use on a given connection. Ensure that you have called .close() on any active streaming result sets before attempting more queries" comes from MySQL.
afterwards I opened my already working dxp file and the error popped again. It seems I somehow have a connection still open and active but spotfire is suppose to manage the connection as far as I know at least
After looking this up online some people say it's a bug, others say I need to close the connection, but I can't find a solution. Please help
Edit: changing the minimum connections number (which probably closes the open connections) makes ot possible for the dxp to run once but then it fails the second time (after closing and opening)
My app is working with MySQL database, to connection I'm using FireDAC components. Last time I have got a network problem, I test it and it is looks like (time to time) it losing 4 ping request. My app return me error: "[FireDAC][Phys][MySQL] Lost connection to MySQL server during query". Now the question: setting fdconnection.TFDUpdateOptions.LockWait to true (default is false) will resolve my problem or make new problems?
TFDUpdateOptions.LockWait has no effect on your connection to the database. It determines what happens when a record lock can't be obtained immediately. The documentation says it pretty clearly:
Use the LockWait property to control whether FireDAC should wait while the pessimistic lock is acquired (True), or return the error immediately (False) if the record is already locked. The default value is False.
The LockWait property is used only if LockMode = lmPessimistic.
FireDAC can't wait to get a lock if it loses the connection, as clearly there is no way to either request the lock or determine if it was obtained. Therefore, changing LockWait will not change the lost connection issue, and it may slow many other operations against the data.
The only solution to your lost ping requests is to fix your network connection so it stops dropping packets. Simply randomly changing options on TFDConnection isn't going to fix networking issues.
I have an application which connects to a MySql database using Delphi's TAdoConnection object. This is a very query intensive application. So I create the connection and keep it open to avoid the high resource expense of open/closing database connections. But obviously problems can arise (database restart, network connection failure, etc). So I have built in code to free my database object, recreate it, and reconnect when queries fail.
I have a common function to connect to the database. The relevant code is this:
try
AdoConnection.open;
result := Adoconnection.Connected
except
result := False;
......
end;
I ran some test by turning on and off the MySql database. Everything works fine if the database is off on application startup (i.e. it properly throws an exception). However, if I turn off the database after the application has already successfully connected, subsequent re-connections do not throw exceptions, and additionally falsley report true for AdoConnection.Connected. I am sure the connection object had been freed/recreated first.
It seems there is some sort of caching mechanism going on here (most likely at the hardware/driver level - not application level). Anyone have any ideas?
I observed this also.
Ideas for dealing with it:
If you get an error on running a query then check if it's a connection issue and if so try to reconnect and then run the query again.
If your program uses a timer and waits a while between running batches of queries then perform a simple query (maybe "select now()") before each batch and if this fails then try to reconnect.
I have developed a windows service using Delphi 2007. It connects to a remote MySql database via the internet using TAdoConnection and TAdoQuery. I have retained the default value of 30 seconds for CommandTimeout property. I also create the connection/query objects on each new query and free them when done (i.e. I don't create the database connection at startup and keep it open).
Every once in a while the service stops and the event viewer shows "Lost connection to MySQL server during query". I have everything wrapped in exceptions. My suspicion is that there is a drop in the network while the query is executing.
Anyone have any resolution/ideas?
What triggers windows to shutdown the service?
Also, I have the service "Recovery" set to restart the service but this never happens.
My next step will be to start logging when each query starts and compare this to the date/time of the shutdown. Because as of now I don't know how log this is.
This is may be not a direct answer, but I had same problem few days ago, and I have the mysql on local server, and I connect using Mydac components.
After many tries, I found the problem came from one table that has BLOB fields, I tried to query on the table like
select * from table
And I got this problem after the query fetch around 1600 rows, after few inspection I found the problem came from few records and seems they corrupted. so when I do query like
Select * from my table where id not
between 1599 and 1650
I had this problem, if I removed Not from they query which fetch only 51 records I got the error, which means there's some records are corrupted, also I did mysqlcheck but it didn't fix the problem, and I tried some other check tools and I got same result, I didn't tried to delete these records, because I need why this problem happen, but I got busy with other things so I left the server for a while.
BTW, I used MySql Query browser for trying to do the queries, because other tools will give me the errors without showing how many records fetched before mysql instance terminated unexpectedly.
One of the more interesting "features" in Coldfusion is how it handles external requests. The basic gist of it is that when a query is made to an external source through <cfquery> or or any other external request like that it passes the external request on to a specific driver and at that point CF itself is unable to suspend it. Even if a timeout is specified on the query or in the cfsetting it is flatly ignored for all external requests.
http://www.coldfusionmuse.com/index.cfm/2009/6/9/killing.threads
So with that in mind the issue we've run into is that somehow the communication between our CF server and our mySQL server sometimes goes awry and leaves behind hung threads. They have the following characteristics.
The hung thread shows up in CF and cannot be killed from FusionReactor.
There is no hung thread visible in mySQL, and no active running query (just the usual sleeps).
The database is responding to other calls and appears to be operating correctly.
Max connections have not been reached for the DB nor the user.
It seems to me the only likely candidate is that somehow CF is making a request, mySQL is responding to that request but with an answer which CF ignores and continues to keep the thread open waiting for a response from mySQL. That would explain why the database seems to show no signs of problems, but CF keeps a thread open waiting for the mysterious answer.
Usually these hung threads appear randomly on otherwise working scripts (such as posting a comment on a news article). Even while one thread is hung for that script, other requests for that script will go through, which would imply that the script isn't neccessarily at fault, but rather the condition faced when the script was executed.
We ran some test to determine that it was not a mysql generated max_connections error... we created a user, gave it 1 max connections, tied that connection with a sleep(1000) query and executed another query. Unfortunately, it correctly errored out without generating a hung thread.
So, I'm left at this point with absolutely no clue what is going wrong. Is there some other connection limit or timeout which could be causing the communication between the servers to go awry?
One of the things you should start to look at is the hardware between the two servers. It is possible that you have a router or bridge or NIC that is dropping occasional packets. This can result in the mySQL box thinking it has completed the task while the CF server sits there and waits for a complete response indefinitely, creating a hung thread.
3com has some details on testing for packet loss here: http://support.3com.com/infodeli/tools/netmgt/tncsunix/product/091500/c11ploss.htm#22128
We had a similar problem with a MS SQL server. There, the root cause was a known issue in which, for some reason, the server thinks it's shutting down, and the thread hangs (even though the server is, obviously, not shutting down).
We weren't able to eliminate the problem, but were able to reduce it by turning off pooled DB connections and fiddling with the connection refresh rate. (I think I got that label right -- no access to administrator at my new employment.) Both are in the connection properties in Administrator.
Just a note: The problem isn't entirely with CF. The problem, apparently, affects all Java apps. Which does not, in any way, reduce how annoyed I get by this.
Long story short, but I believe the caused was due to Coldfusion's CF8 image processing. It was just buggy and now in CF9 I have never seen that problem again.