ArangoDB upgrade loses data - database

Question

I feel I'm doing something wrong with the ArangoDB upgrade process. The end result from the upgrade is that my databases exist, my users exist, my collections exist, but there are no documents in my collections. Obviously this is an issue. I've had this problem occur twice, upgrading from 2.3.1 -> 2.3.4, and 2.3.4 -> 2.4 in Windows. I used the same procedure in both cases:
Stopped the ArangoDB service
Made a backup copy of my ArangoDB directory from Program Files
Installed the new version of ArangoDB
Copied the contents of the database folder from the old ArangoDB directory to the new one, excluding the system database (I feel like this is where I go wrong...)
Then I open a command prompt to the bin directory and run arangod --upgrade
The upgrade output seems right to me, it finds the old databases and upgrades them, which is evident by the fact that they exist, along with the collections. But as stated before the collections are all empty. Thankfully this has been in a dev environment, but I worry about upgrading my production environment. Am I doing something wrong or is this a bug?

Answer 1

I've tried to reproduce this with the step 2.3.5 to 2.4.1 using the x64 Arango packages
What I did:
First, ran arangod from the shell with its own database directory outside of the program directory:
bin\arangod.exe c:\ee --console
Created a collection, inserted data (like the js/server/tests/aql-optimizer-rule-use-index-for-sort.js setUp()-function does)
then installed the new version, ran
bin\arangod.exe c:\ee --upgrade
then
bin\arangod.exe c:\ee --console
AQL_EXECUTE("for u in UnitTestsAqlOptimizeruse_index_for_sort_XX return u")
Which gave me all 100 documents which I put into the collection.
Next I tried with running the arangod service, with the var\lib folder inside of the Porgram Files folder. I connected using arangosh, inserted the documents into the collection again, verified with
db._query("for u in UnitTestsAqlOptimizeruse_index_for_sort_XX return u").toArray();
that all data was there.
Then stopped the service, installed 2.4.1, stopped the service, and used explorer to copy over the ArangoDB 2.4.1\var\lib directory, run the arangod --upgrade with success restarted the service, and used arangosh to successfully revalidate the collection and its documents again.
So, as this seems similar to what you did, can you try to reproduce this with a minimal set of data and send us your var\lib directory?

Answer 2

As it turns out the problem was related to replication. I would replicate data from the production db to use during development. Then when I would upgrade or stop the Arango service on the dev db all the documents would vanish. BUT when I used arango backup and restore to copy the production DB data, everything worked as expected. The newest version of Arango is supposed to have fixed the issue, but I haven't had any time to test it.