Stanislav Lukyanov created IGNITE-10563:
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Summary: Allow manual fsync for WAL
Key: IGNITE-10563
URL: https://issues.apache.org/jira/browse/IGNITE-10563
Project: Ignite
Issue Type: Improvement
Reporter: Stanislav Lukyanov
When walMode is set to LOG_ONLY or BACKGROUND there is a gap between successful
return of cache write operations and actual of the data to the persistent
memory. This gap is, while usually low, generally can be of any length and
depends on low-level system parameters (e.g. sysctl memory and IO settings on
Linux).
On the other hand, there are situations when a user may want to ensure that at
certain points all writes have been propagated to the disk.
For example, say a large batch of data is being inserted into Ignite from an
upstream system. After finishing the batch we want to ensure that all of the
data is secure, and after that we remove the batch from the upstream storage.
In other words, we want
{code}
map = upstream.getData();
cache.putAll(map);
cache.fsync(); // <-------
upstream.removeAll(map);
{code}
Currently there is no easy way to ensure that certain write (or all writes
until a point in time) has been flushed to a device. We can only rely on
settings like WAL sync interval, checkpoint timeout, etc.
It would be nice to have a way to manually call fsync() for WAL to have a
strong guarantee that all previous updates have been fully written on disk.
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