keith-turner opened a new issue, #5442:
URL: https://github.com/apache/accumulo/issues/5442
**Is your feature request related to a problem? Please describe.**
Currently all fate table operations acquire a read lock on the namespace.
This may be unnecessary, it may be safe to only acquire the namespace readlock
in table operations that add/remove tables. If it is unnecessary, then its a
cost that frequent fate operations like compact or bulk import are paying when
they do not need to.
**Describe the solution you'd like**
Limit acquiring the namespace read lock to fate operations that add/remove
tables like create table, delete table, import table, and clone table. Remove
acquiring the namespace read lock from other table operations like bulk import,
compact, etc.
Assuming Accumulo will work like the following then a proof by contradiction
is one way to show its correct.
1. The delete namespace gets a write lock on the namespace its trying to
delete
2. Table operations that create/delete tables get a read lock on the
namespace and write lock on the table.
3. Other table operations only get a read lock on the table.
With the constraints above, assume that a namespace could be deleted while a
bulk import fate operation is running on a table in the namespace. This can
not happen because the namespace can not be deleted when it has tables (once
#5389 is fixed) . The table can not be deleted because the fate op can not get
a write lock on the table because the bulk import fate op has read lock on the
table.
With this change there would be transitive protection of namespaces being
deleted instead of direct protection.
**Describe alternatives you've considered**
None.
**Additional context**
Opened this issue based on conversations in #5334. Marked this as a 4.0
changes as it could be disruptive to make in a bug fix release because
namespace locks are persisted in zookeeper. Changing the persisted data
related to fate operations in bug fix releases is always tricky and hard to
test.
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