See #3462 and related PRs.
We use a simple algorithm to calculate the level of affinity violation,
and then an optimizer that performs random swaps until things improve.
Display the nodes summary once the cluster is established using
redis-trib.rb
After the cluster meet and join was done, when the summary was shown, it
was giving info regarding the nodes. This fix ensures that confusion
where the slaves were shown as masters.
Fix would be to reset the nodes and reload the cluster information
before checking the cluster status after creating it.
This fix was suggested by Anthony LaTorre, that provided also a good
test case that was used to verify the fix.
The problem with the old implementation is that, the time returned by
a timer event (that is the time after it want to run again) is added
to the event *start time*. So if the event takes, in order to run, more
than the time it says it want to be scheduled again for running, an
infinite loop is triggered.
We use the new variadic/pipelined MIGRATE for faster migration.
Testing is not easy because to see the time it takes for a slot to be
migrated requires a very large data set, but even with all the overhead
of migrating multiple slots and to setup them properly, what used to
take 4 seconds (1 million keys, 200 slots migrated) is now 1.6 which is
a good improvement. However the improvement can be a lot larger if:
1. We use large datasets where a single slot has many keys.
2. By moving more than 10 keys per iteration, making this configurable,
which is planned.
Close#2710Close#2711
The introduction of --from --to --slots --yes options allow to reshard
from cli in an automated way from scripts. The code is ugly and needs
refactoring as soon as we get it in RC / stable release.
Will be configurable / adaptive at some point but let's start with a
saner value compared to 1 sec which is not a good idea for big data
structures stored into a single key.
redis-trib used to allocate slots not considering fractions of nodes
when computing the slots_per_node amount. So the fractional part was
carried over till the end of the allocation, where the last node
received a few more slots than any other (or a lot more if the cluster
was composed of many nodes).
The computation was changed to allocate slots more evenly when they are
not exactly divisible for the number of masters we have.
This got removed in 2e5c394 during a new feature addition.
The prior commit had "break if masters.length == masters_count"
but we are guaranteed to aready have that condition met since
otherwise we would haven't gotten this far.
Without this break statement, it's possible some masters may
be forgotten and have zero replicas while other masters have
more than their requested number of replicas.
Thanks to carlos for pointing out this regression at:
https://groups.google.com/forum/#!topic/redis-db/_WVVqDw5B7c
This bug was introduced in 2e5c394f during a refactor.
It took me a while to understand what was going on with
the code, so I've refactored it further by:
- Replacing boolean values with meaningful symbols
- Replacing 'i' with a meaningful variable name
- Adding the proper abort check
- Factoring out now duplicated conditionals
- Adding optional verbose logging (we're inside *four*
different looping constructs, so it takes a while to
figure out where all the moving parts are)
- Updating comment for the section
This fixes a problem when the number of master instances
equaled the number of replica instances. Before, when
there were equal numbers of both, nodes_count would go to
zero, but the while loop would spin in i < @replicas because
i would never be updated (because the nodes_list of each ip
was length == 0, which triggered an endless loop of
next -> i = 0 -> 0 < 1? -> true -> next -> i = 0 ...)
Thanks to carlo who found this problem at:
https://groups.google.com/forum/#!topic/redis-db/_WVVqDw5B7c
artix