Calling Transaction::rollback() fails with assertion

[sync-by-unito]

This is an umbrella issue used to track the resolution of several issues we have seen including "Transaction::rollback" in the  stack trace. These are (please update if more are found):
#5585
https://github.com/realm/realm-swift/issues/7788 (now closed)

[sync-by-unito]

➤ On 2022-06-24, Jørgen Edelbo commented:

One theory could be that the call to "remap_and_update_refs" in Transaction::commit_and_continue_as_read could throw. If this happens we could get a stacktrace like the ones we have seen. I tried to create a test where I forced the function to throw and then I got this trace:

#4 0x00005555564abb84 in realm::util::terminate (message=0x55555676ed50 "Assertion failed: m_write_transaction_open",
file=0x55555676e2c0 "/home/jed/wip/realm-mono/src/realm/db.cpp", line=2091, values=...) at /home/jed/wip/realm-mono/src/realm/util/terminate.cpp:133
#5 0x00005555563390c2 in realm::DB::do_end_write (this=0x555556c9f220) at /home/jed/wip/realm-mono/src/realm/db.cpp:2091
#6 0x000055555633b9cc in realm::DB::end_write_on_correct_thread (this=0x555556c9f220) at /home/jed/wip/realm-mono/src/realm/db.cpp:2570
#7 0x000055555643dc71 in realm::Transaction::rollback (this=0x555556c990a0) at /home/jed/wip/realm-mono/src/realm/transaction.cpp:186
#8 0x000055555643d929 in realm::Transaction::close (this=0x555556c990a0) at /home/jed/wip/realm-mono/src/realm/transaction.cpp:126

This will effectively hide the underlying exception. The PR #5615 updates the transaction stage earlier so that this assertion will not fail.

I don't believe that this is the root cause, but the PR will rule it out.

[sync-by-unito]

➤ On 2022-06-24, Jørgen Edelbo commented:

I think the main question to ask is: How can it be that the transaction is still in writing stage after the call to "commit_and_continue_as_read"? It must be in writing stage, otherwise the rollback function would not be called when the transaction object is closed when going out of scope.

[jedelbo]

Links in GitHub:
#5585
realm/realm-swift#7788

[sync-by-unito]

➤ Finn Andersen commented:

We have merged #5615 so when released, these failed rollbacks should go away.

[sync-by-unito]

➤ Lee Maguire commented:

It looks like this issue has resurfaced after the fix was merged https://jira.mongodb.org/browse/HELP-36253

[sync-by-unito]

➤ Jørgen Edelbo commented:

[~lee.maguire@mongodb.com] the fix that Finn mentioned was not released in Swift until 10.28.4

[sync-by-unito]

➤ Finn Andersen commented:

Yeah, we should close this unless it is reported on a newer release.

[sync-by-unito]

➤ Finn Andersen commented:

Closing as presumably fixed