assert(), and SCYLLA_ASSERT() are evil (Refs #7871) because they can cause the entire Scylla cluster to crash mysteriously instead of cleanly failing the specific request that encountered a serious problem of failed pre-requisite.
In this two-patch series, in the first patch we introduce a new macro throwing_assert(), a convenient drop-in replacement for SCYLLA_ASSERT() but which has all the benefits of on_internal_error() instead of the dangers of SCYLLA_ASSERT().
In the second patch we use the new function to replace every call to SCYLLA_ASSERT() in Alternator by the new throwing_assert().
Here is an example from the second patch to demonstrate the power of this approach: The Alternator code uses the attrs_column() function to retrieve the ":attrs" column of a schema. Since every Alternator table always has an ":attrs" column in its schema, we felt safe to SCYLLA_ASSERT() that this column exists. However, imagine that one day because of a bug, one Alternator table is missing this column. Or maybe not a bug - maybe a malicious user on a shared cluster found a way to deliberately delete this column (e.g, with a CQL command!) and this check fails. Before this patch, the entire Scylla node will crash. If the same request is sent to all nodes - the entire cluster will crash. The user might not even know which request caused this crash. In contrast, after this patch, the specific operation - e.g., PutItem - will get an exception. Only this operation, and nothing else, will be aborted, and the user who sent this request will even get an "Internal Server Error" with the assertion-failure message, alerting them that this specific query is causing problems, while other queries might work normally.
There's no need to backport this patch - unless it becomes annoying that other branches don't have the throwing_assert() function and we want it to ease other backports.
Fixes#28308.
Closesscylladb/scylladb#28445
* github.com:scylladb/scylladb:
alternator: replace SCYLLA_ASSERT with throwing_assert
utils: introduce throwing_assert(), a safe replacement for assert
fcc570c697