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Avoid writing the metadata file when it hasn't changed.

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This commit is contained in:
Heikki Linnakangas
2021-10-17 14:54:39 +03:00
parent ba557d126b
commit b405eef324
1 changed files with 43 additions and 39 deletions
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82
pageserver/src/layered_repository.rs
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@@ -1340,50 +1340,54 @@ impl LayeredTimeline {
timeline_dir.sync_all()?;
}
// Save the metadata, with updated 'disk_consistent_lsn', to a
// file in the timeline dir. After crash, we will restart WAL
// streaming and processing from that point.
// If we were able to advance 'disk_consistent_lsn', save it the metadata file.
// After crash, we will restart WAL streaming and processing from that point.
let old_disk_consistent_lsn = self.disk_consistent_lsn.load();
if disk_consistent_lsn != old_disk_consistent_lsn {
assert!(disk_consistent_lsn > old_disk_consistent_lsn);
// We can only save a valid 'prev_record_lsn' value on disk if we
// flushed *all* in-memory changes to disk. We only track
// 'prev_record_lsn' in memory for the latest processed record, so we
// don't remember what the correct value that corresponds to some old
// LSN is. But if we flush everything, then the value corresponding
// current 'last_record_lsn' is correct and we can store it on disk.
let ondisk_prev_record_lsn = if disk_consistent_lsn == last_record_lsn {
Some(prev_record_lsn)
} else {
None
};
// We can only save a valid 'prev_record_lsn' value on disk if we
// flushed *all* in-memory changes to disk. We only track
// 'prev_record_lsn' in memory for the latest processed record, so we
// don't remember what the correct value that corresponds to some old
// LSN is. But if we flush everything, then the value corresponding
// current 'last_record_lsn' is correct and we can store it on disk.
let ondisk_prev_record_lsn = if disk_consistent_lsn == last_record_lsn {
Some(prev_record_lsn)
} else {
None
};
let ancestor_timelineid = self.ancestor_timeline.as_ref().map(|x| x.timelineid);
let ancestor_timelineid = self.ancestor_timeline.as_ref().map(|x| x.timelineid);
let metadata = TimelineMetadata {
disk_consistent_lsn,
prev_record_lsn: ondisk_prev_record_lsn,
ancestor_timeline: ancestor_timelineid,
ancestor_lsn: self.ancestor_lsn,
};
LayeredRepository::save_metadata(
self.conf,
self.timelineid,
self.tenantid,
&metadata,
false,
)?;
if self.upload_relishes {
schedule_timeline_upload(())
// schedule_timeline_upload(
// self.tenantid,
// self.timelineid,
// layer_uploads,
// disk_consistent_lsn,
// });
let metadata = TimelineMetadata {
disk_consistent_lsn,
prev_record_lsn: ondisk_prev_record_lsn,
ancestor_timeline: ancestor_timelineid,
ancestor_lsn: self.ancestor_lsn,
};
LayeredRepository::save_metadata(
self.conf,
self.timelineid,
self.tenantid,
&metadata,
false,
)?;
// Also update the in-memory copy
self.disk_consistent_lsn.store(disk_consistent_lsn);
if self.upload_relishes {
schedule_timeline_upload(())
// schedule_timeline_upload(
// self.tenantid,
// self.timelineid,
// layer_uploads,
// disk_consistent_lsn,
// });
}
}
// Also update the in-memory copy
self.disk_consistent_lsn.store(disk_consistent_lsn);
Ok(())
}