[Opensim-dev] Opensim 0.7 tidying up the MySQL DB connection string

[Alex Ra]

DC> Since you were the one who wrote the newly introduced
DC> MySqlMigrations class, which uses the MySqlScript class, can you
DC> please explain how we can get around the issue that Frank is
DC> talking about?

Hello Diva,

I haven't looked how the timeouts are implemented in the driver,
the code I added/modified doesn't do anything about them.

MySqlScript class is ONLY needed if a proc needs to be defined.
Otherwise, the common Migration class can be used for mySQL just as
for all other DBs.

I'm not sure the regular MySqlCommand would work any
better with huge timeouts than MySqlScript.  If the timeout can be
extended beyond the "default default" of 30 sec but then hits a
limit, it sounds to me more like some server-side limitation
then something in MySqlScript.

I can look at the driver sources, but not today.

Re rolling back to the old driver:  the code changes that accompanied
the driver update can be found in r/12794, r/12795.  The converter
function in DBGuids.cs is supposed to convert between UUIDs and the
DB-specific representation more or less regardless of what the driver
returns (string or Guid). So it should be possible to rollback the
driver (or use "OldGuids" var) without actually touching the code.
MySqlMigration would have to be removed, though.

I wonder what could make the migration run so slow, may be it would
make sense to look into the migration scripts and try to optimize them
somehow (add/remove some indexes or whatever).  Most of the migration stuff is
just about adding/changing columns and for all I know a server should be
able to process quite a lot of data in 1 hour (like hundreds of
thousands rows).

Can Frank provide some details on what parts of the migration are
especially slow?

When people start migrating their DBs to 0.7, it would be nice to make
sure the scripts are reasonably efficient.


DC> Since you were the one who wrote the newly introduced
DC> MySqlMigrations class, which uses the MySqlScript class, can you
DC> please explain how we can get around the issue that Frank is
DC> talking about? It looks like the MySqlScript class has some
DC> hardcoded timeouts. Frank says that we might be able to specify a
DC> timeout between 0 and 1 hour, but not more. Some DB migrations,
DC> especially assets, might take more than 1 hour.

DC> I'm really considering rolling back to using the old driver
DC> because this one is causing too much grief and confusion at this
DC> critical time when we want things to be stable.
DC>  
DC> Any light on this new driver, especially its limitations/bugs,
DC> and how we can overcome them, would be very much appreciated so
DC> that we can try to continue to use it in dev code.

DC> Thanks.
DC> Crista


DC> On 6/18/2010 10:57 AM, Frank Nichols wrote: 
DC> The use of the MysqlScript class is at the heart of most of the
DC> problems I have seen with the migration of mysql databases from
DC> 0.6.9 to 0.7.0. The problem seems to be that the default command
DC> timeout value for processing a sql statement with this class is 30
DC> seconds, which is far to short to alter a table inserting a column
DC> when there are hundreds of thousands of rows in that table.  

DC> In researching this it appears that the devart version of the new
DC> MySql.data.dll has a version of the MysqlScript which allows you
DC> to set the command timeout programmatically, however the mysql
DC> version of this library does not have this property available. As
DC> far as I could see there is currently no way to set the command
DC> timeout. So, it would appear that automatic migrations are doomed
DC> to fail in any case where they take more than 30 seconds.

DC> Frank

DC> On Fri, Jun 18, 2010 at 7:13 AM, Michael Cerquoni <nebadon2025 at gmail.com> wrote:
DC> I have to say so far this new MySQL connector has been absolutely
DC> nothing but trouble for Frank Nichols and myself testing Migration
DC> from 0.6.9 to 0.7,  All throughout the testing we have had nothing
DC> but failure after failure from this new MySQL connector that has
DC> been introduced.  It has been nearly impossible to move forward on
DC> to 0.7 because of this,  I have no doubt that this will be a major
DC> problem for everyone to migrate over if you have even what seems
DC> like the most minimal amounts of data.   At this time i really
DC> have to give this new connector a -1.   Can someone please explain
DC> to me why the Original MySQL connector that seemed to work
DC> perfectly for years has now been replaced with one that constantly
DC> times out during migrations and gives nothing but trouble with
DC> DNS, requires us to use additional connection string settings, and
DC> basiclly makes moving on to 0.7 impossible for myself and others??
DC> I must be missing something here! 


DC> On Fri, Jun 18, 2010 at 6:06 AM, AlexRa <info at adeptsql.com> wrote:

AA>> But I note that I has "pooling=false;" in my own string though its
AA>> not been in the example ini files for a while.  Anyone know what this
AA>> does and if its wise to keep it in the string if I had a working
AA>> 0.6.9 system with it there before?

DC> Hello Ai,

DC> Can't tell you why the "pooling=false;" was there in the 1st place, but
DC> I've noticed that it did cause connection failures on a Windows box during
DC> performance testing (thousands mySQL requests in a loop, each with
DC> connect/disconnect). The error didn't happen without the "pooling=false;"
DC> option. I don't know if that affects mySQL on Linux as well.

DC> Best regards,

DC> Alex


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Best regards,

Alex