[Glass] how to update models properly

Sebastian as you are not using seaside, you should read thru 

http://gemstonesoup.wordpress.com/2008/03/09/glass-101-simple-persistence/

and understand the part on object locking. 

So for example on an incoming request I take my handy unique identifier from the client, look it up, if found it's an update so I do 

basicDataChangedWithLock: fields

"WASessionLockNotAcquiredException when signalled will cause the initial HTTP request to be retried after

an abortTransaction"

System writeLock: self

ifDenied: [ 

WARetryHttpRequest signal: 'SerialNumber lock denied'.

"does not return"  ]

ifChanged: [ 

System addToCommitOrAbortReleaseLocksSet: self.

WARetryHttpRequest signal: 'SerialNumber lock changed'.

"does not return" ].

self basicDataChanged: fields.

System addToCommitOrAbortReleaseLocksSet: self.

The basicDataChanged: then takes the dictionary of key/value pairs and compares against the current data. Given I work with items such as the name of the iOS device I make heavy use of symbols to store that information. 

Other issues are relate to the backup, for that I have this script, which I think needs some work as it sometimes hangs in the while loop if a GemTools session is active. 

Also because I only have a few 10 of millions of objects I can do the "SystemRepository Audit"  This also then pushes the current backup to Amazon S3 which archives it after a week to Glacier.  Not shown is another script that takes the output log file and builds a JIRA entry so in the morning I can jump over to JIRA and confirm the backup worked as expected.  Note the s3cmd also does a PGP encryption on the data before sending, the --server-side-encryption is redundant but there out of habit. 

Note once a year or so the object audit reports an issue with a few objects, but running the audit again after taking the database out of production along with a page audit shows no issue. I was told it could be a transit issue.

/opt/gemstone/product/bin/topaz -l -T 50000 << EOF

set gemstone seaside

set username DataCurator

login

swordfish

output push backup.out

errorCount

run

 System waitForVoteStateIdle.

 [ System _deadNotReclaimedCount > 0 ] whileTrue: [ System sleep: 1.  System abortTransaction ].

%

send SystemRepository objectAudit

send SystemRepository startNewLog

run

 SystemRepository fullBackupCompressedTo: 

 '/opt/gemstone/backups/backup-' , 

 (DateTime now asSeconds // 60) printString.

%

logout

errorCount

exit

EOF

# cleanup backups

cat backup.out >> backupAll.out

cd /opt/gemstone/backups

ls -l 

find . -maxdepth 1 -daystart  -mtime -1  -type f -exec /usr/local/bin/s3cmd --server-side-encryption --reduced-redundancy -e put {} s3://foobartoobar \;

#

(ls -t backup* | head -n 2; ls backup*) | sort | uniq -u | xargs rm 

if [ "2" -le "`find . -mtime -2 -name 'backup*' | wc -l`" ]; then 

 cd /opt/gemstone/product/seaside/data

 find  . -maxdepth 1  -mtime +2  -name 'tranlog*' -exec rm {} \;

fi

On Wed, Oct 29, 2014 at 9:40 AM, Richard Sargent via Glass <[hidden email]> wrote:

Hi Sebastian,

If you replicate state between different memory spaces, you have the same kind of issues to deal with that GBS faces. There *are* a lot of complexities in the general case.

Ultimately, when you send the revised state back to the server, you need to ensure you update the existing server object with the replicated data. The Object database model is very different from the Relational database model (which has an essential indirection built-in).

It may be worth considering executing behaviours in the server against the object (and then replicating the new state back to the client).

On Wed, Oct 29, 2014 at 9:23 AM, Sebastian Heidbrink via Glass <[hidden email]> wrote:

Hi all,

I spent quite some time to get used to Gemstone now . Somehow I stumble across some questions and insecurities again and again.

I wonder if somebody can give me some hints on this.

I use Gemstone/Web without Seaside but with a ZincREST interface. Some of my data model objects a transfered via JSON or CSV betwenn db and client. Everytime the client wants to modify data on the server he sends a JSON representation of the object to the server and the server parses the json and creates a data model object from it.
Now I do have a persited version of my model object and the just newly created model object within the DB.
How would I update now? I can't replace the persisted object by the new one, because I might loose references to/from it... I will need to walk through all attributes compare them and replace just different ones?!
I feel like the whole approache is wrong and slow, isn't it? Wouldn't it be better to just parse the request's json into a JSONObject and do the synching after I located the persisted Object based on some hash values or id provided?

How do your strategies look like? I currently feel like producing too many temporary and unneeded objects.

Creade, Delete and Replace do not really provide such "imagination" issues like the Update... do they?

Any push into the right direction is highly appreciated!
Thanks and have fun at FAST if you'll be there!
Sebastian
_______________________________________________
Glass mailing list
[hidden email]
http://lists.gemtalksystems.com/mailman/listinfo/glass

_______________________________________________
Glass mailing list
[hidden email]
http://lists.gemtalksystems.com/mailman/listinfo/glass

--

===========================================================================
John M. McIntosh <[hidden email]> https://www.linkedin.com/in/smalltalk
===========================================================================