ColumnStore API : python program using columnstore api crashing when trying to run 2 instances

Atul Gore

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Jan 3, 2018, 4:27:33 AM1/3/18

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Hi,

I am trying to use the python binding of the maridb-columnstore-api to bulk load some data.

I have a 2 PM/UM system.

I am trying to load data into multiple tables.

The problem i see is following:

I run one instance of my python program to load data into tableA.

I run another instance of my python program to load data into tableB.

The second instance crashes with the error:

terminate called after throwing an instance of 'mcsapi::ColumnStoreNetworkError'

what(): Compressed data corruption

Aborted (core dumped)

However, no core file seems to be generated. I looked up the source code and the error seems to be coming from src/util_network.cpp in snappy uncompress method.

I am running this on Ubuntu 16.04 system.

I checked all the logs in /var/log/mariadb/columnstore but can't find anything that might point to the issue. Is there any other place that i can look?

I assume the columnstore system should allow 2 parallel loads to 2 different tables of the same database using 2 different processes simultaneously.

Any pointers to how to get past this errors would be of great help as I am having to do a single process batched.

Kindly let me know if any more information is required for getting to the root cause of this issue.

Thanks,

./a

Andrew Hutchings

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Jan 3, 2018, 5:49:46 AM1/3/18

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Hi Atul,

There were several bugs in the network packet handling and compression
that are fixed in the develop-1.1 branch (which will make up the 1.1.3
release). I think it is highly likely you are hitting one of those.

If you are able to compile it yourself please try using this branch:

https://github.com/mariadb-corporation/mariadb-columnstore-api/tree/develop-1.1

If you are still getting the crashes after that let me know and I'll
show you how to get some debugging information.

Kind Regards
Andrew

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Atul Gore

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Jan 3, 2018, 6:13:32 AM1/3/18

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Thanks for reverting so quickly Andrew!

I tried the build from develop-1.1 branch

Now its past that error and gives the following error:

terminate called after throwing an instance of 'mcsapi::ColumnStoreServerError'

what(): Error committing BRM

Let me know what information I can provide to help you debug this further.

Thanks,

./a

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Andrew Hutchings

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Jan 3, 2018, 7:00:47 AM1/3/18

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Hi Atul,

Excellent! Something new! :)

OK, if you could add the following flag when running cmake:

-DCMAKE_BUILD_TYPE=Debug

Then recompile it, upon executing there will be a huge amount of
debugging data spit out onto STDERR. This will basically state what
decisions were made and all the packet data.

If you could capture this and send this to me directly (since this will
likely have private information in it) I can take a look.

In addition can you please send me /var/log/mariadb/columnstore/err.log
for all your PM nodes that might also have some useful information.

Kind Regards
Andrew

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Andrew Hutchings

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Jan 8, 2018, 9:50:59 AM1/8/18

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For those in the list, debugging information was supplied offline and it
helped to find:

https://jira.mariadb.org/browse/MCOL-1147

The fix for this will be in the 1.1.3 release.

Kind Regards
Andrew

Atul Gore

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Jan 9, 2018, 12:11:19 AM1/9/18

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Thanks Andrew and Jens. I just took the update and the parallel load is progressing just fine.

Is there a date on the 1.1.3 release yet, so that I can consume the binaries in production?

Thanks,

./a

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Andrew Hutchings

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Jan 10, 2018, 3:16:17 AM1/10/18

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Hi Atul,

Unfortunately I cannot give you a release date at the moment. But it
will be soon. We are trying to wrap up the last tickets for it now.

Kind Regards
Andrew

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