We migrated satelliteDB off of Postgres and over to CockroachDB (crdb), but there was way too high contention for the injuredsegments table so we had to rollback to Postgres for the repair queue. A couple things contributed to this problem:
1) crdb doesn't support `FOR UPDATE SKIP LOCKED`
2) the original crdb Select query was doing 2 full table scans and not using any indexes
3) the SLC Satellite (where we were doing the migration) was running 48 repair worker processes, each of which run up to 5 goroutines which all are trying to select out of the repair queue and this was causing a ton of contention.
The changes in this PR should help to reduce that contention and improve performance on CRDB.
The changes include:
1) Use an update/set query instead of select/update to capitalize on the new `UPDATE` implicit row locking ability in CRDB.
- Details: As of CRDB v20.2.2, there is implicit row locking with update/set queries (contention reduction and performance gains are described in this blog post: https://www.cockroachlabs.com/blog/when-and-why-to-use-select-for-update-in-cockroachdb/).
2) Remove the `ORDER BY` clause since this was causing a full table scan and also prevented the use of the row locking capability.
- While long term it is very important to `ORDER BY segment_health`, the change here is only suppose to be a temporary bandaid to get us migrated over to CRDB quickly. Since segment_health has been set to infinity for some time now (re: https://review.dev.storj.io/c/storj/storj/+/3224), it seems like it might be ok to continue not making use of this for the short term. However, long term this needs to be fixed with a redesign of the repair workers, possible in the trusted delegated repair design (https://review.dev.storj.io/c/storj/storj/+/2602) or something similar to what is recommended here on how to implement a queue on CRDB https://dev.to/ajwerner/quick-and-easy-exactly-once-distributed-work-queues-using-serializable-transactions-jdp, or migrate to rabbit MQ priority queue or something similar..
This PRs improved query uses the index to avoid full scans and also locks the row its going to update and CRDB retries for us if there are any lock errors.
Change-Id: Id29faad2186627872fbeb0f31536c4f55f860f23
the immediate need is to be able to move the repair queue back out
of cockroach if we can't save it.
Change-Id: If26001a4e6804f6bb8713b4aee7e4fd6254dc326
We plan to add support for a new Reed-Solomon scheme soon, but our
repair queue orders segments by least number of healthy pieces first.
With a second RS scheme, fewer healthy pieces will not necessarily
correlate to lower health.
This change just adds the new column in a migration. A separate change
will add the new health function.
Right now, since we only support one RS scheme, behavior will not
change. Number of healthy pieces is being inserted as "segment health"
until the new health function is merged.
Segment health is calculated with a new priority function created in
commit 3e5640359. In order to use the function, a new config value is
added, called NodeFailureRate, representing the approximate probability
of any individual node going down in the duration of one checker run.
Change-Id: I51c4202203faf52528d923befbe886dbf86d02f2
* add monkit stat new_remote_segments_needing_repair, which reports the
number of new unhealthy segments in the repair queue since the previous
checker iteration
Change-Id: I2f10266006fdd6406ece50f4759b91382059dcc3
The migration was broken into one migration per table to reduce table locking and reduce the
chances of failure due to SQL timeouts.
Of the 14 fields that lacked time zones, only the 3 named 'interval_start` seemed to have non-UTC data in them.
These fields are fixed in the migration by removing the +00 and adding AT TIME ZONE current_setting('TIMEZONE')
Field with good data are migrated by adding AT TIME ZONE 'UTC'
Note that postgres's timezone() is different than cockroach's timezone() so AT TIME ZONE is used.
https://storjlabs.atlassian.net/browse/SM-104
Change-Id: I410f2f1d7c11b143f17844347f37e6f4b1e70fce
Add a column to the repair queue table in the satellite db for healthy
piece count. When an item is selected from the repair queue, the least
durable segment that has not been attempted in the past hour should be
selected first. This prevents our repairer from getting stuck doing work
on segments that are close to the repair threshold while allowing
segments that are more unhealthy to degrade further.
The migration also clears the repair queue so that the migration runs
quickly and we can properly account for segment health in future repair
work.
We do not select items off the repair queue that have been attempted in
the past six hours. This was changed from on hour to allow us time to
try a wider variety of segments when the repair queue is very large.
Change-Id: Iaf183f1e5fd45cd792a52e3563a3e43a2b9f410b
everyone was importing it as dbx anyway. why should it be
named satellitedb? so yeah just pass the "-p dbx" flag.
Change-Id: I5efa669f4f00f196b38a9acd0d402009475a936f
