DAP Client 1.0.0 change in processing???

After upgrading to the 1.0.0 DAP client yesterday, I'm now getting a very specific error:

ERROR - [Errno 28] No space left on device

It appears that the DAP client is now loading up my /tmp location (which is very limited) for holding and assembly of the various file parts prior to assembly and shipment to Postgres. If I'm wrong about this, please let me know, but it's certainly unexpected.

I can increase this location, but it would be nice to add this as an option in the DAP client so I don't have to modify multiple systems to allow for it. Right now I"m just looking for a "yea" or "nay" on this as to whether it's "by design".

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Accepted answers

reynlds

Confirmed. Following a FULL database refresh (complete removal of the DB along with a full "initdb" using DAP), along with "fixing" the data in Canvas (adding a name to an object that was created w/o one), has allowed this process to continue. However, it should still be that DAP logs these errors, and proceeds, rather than simply dumping out on anything that does not fit exactly as defined. Again, it's up to Instructure to modify Canvas to NOT allow blank (null) names on course sections.

All comments

LeventeHunyadi

Caching temporary data to disk was implemented in one of the more recent 0.3.x versions. Previously, DAP client library was operating in memory-only streaming mode, it was reading records from the network connection, and directly sending them to the database as they were incoming. In more recent versions of the DAP client library, this was changed to a buffered approach, whereby parts are first downloaded to the disk, and then inserted into the database by reading the files on disk.

The buffered approach was introduced in response to user complaints. Many users had a setup with a relatively slow database, and the database engine could not keep up with the speed records were being received over the network connection. This has resulted in a premature disconnect, and ultimately a poor user experience. Others had issues with the AWS pre-signed URL expiring by the time they got to downloading a file in the result-set other than the first two or three. All of these are eliminated with a buffered approach, and disk size seemed not to be a major concern for the majority of our users.

If the development team would want to re-introduce the streaming approach, they would have to carefully assess they do so in a way that doesn't resurface the network connectivity and URL expiry issues.

reynlds

@LeventeHunyadi

I finally woke up and harkened back to my "unix days" and changed the environment variable for TEMPDIR, which (thankfully) the DAP client is honoring. so no more warnings about running out of space. I'm currently running a full drop/init on each table and so far it's populating the new temp area with TSV files, and uploading them to the DB. Fingers crossed...

I still think a switch to redirect the temp files, that is built directly into the DAP client, would be very helpful/useful...especially for users that may not have access to modify their environment or exports:

dap initdb --namespace canvas --table assessment_questions --temp /var/lib/tmp

reynlds

Found the offending section (with no enrollments) and deleted it. It had been created without a name by the instructor. Will see if it init's in a few hours.

reynlds

dtod

initdb (and I assume syncdb) seems to download .tsv files to your /tmp, which if you have a big installation, can be a LOT of data for the larger tables. It consumed our tmp space.

IMO it should be using the .gz files and as necessary expanding each file temporarily. Alternatively, per reynlds

In Linux

export TMPDIR=/somecustom/dir/withlotsofspace

Also, data errors can be resolved for mysql by making sure you have the correct character set and collation, e.g.

ALTER table
    CD2.canvas__courses
    CHARACTER SET = utf8mb4
    COLLATE = utf8mb4_unicode_ci;

and/or similarly for the database.

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