Skip to content

EDITD/elasticsearch-rebalancer

develop
Switch branches/tags

Name already in use

A tag already exists with the provided branch name. Many Git commands accept both tag and branch names, so creating this branch may cause unexpected behavior. Are you sure you want to create this branch?
Code

Latest commit

 

Git stats

Files

Permalink
Failed to load latest commit information.
Type
Name
Latest commit message
Commit time
 
 
 
 
 
 
 
 
 
 

Elasticsearch Rebalancer

A script that attempts to re-balance Elasticsearch shards by size without changing the existing balancing.

By default ES balances shards over nodes by considering:

  • The number of shards / node
  • The number of shards / index / node

Which is great if every shard is the same size, but in reality this is not the case. Without considering the size of shards (except for watermarks) it's possible to end up with some nodes almost at watermark alongside others that are almost empty. This blog post describes it well - this script is inspired by that project. As well as size this logic can be applied to any weighting of shards. This diagram highlights the problem elasticsearch-rebalancer attempts to solve:

How does it work?

The script is based around the idea of "swaps" - pairs of shards to relocate between the two nodes. Each iteration the script identifies the most-full and least-full nodes, searching through their largest/smallest shards to find a suitable swap. Ideally the largest shard on the most-full node and the smallest shard on the least-full node swap.

To maintain existing ES balances, shards are only considered if the node to move to does not have any other shard from the same index. This means the shards per node and shards per index per node remain the same, so ES shouldn't do any additional rebalancing.

Usage

Usage: es-rebalance [OPTIONS] ES_HOST

Options:
  --iterations INTEGER  Number of iterations (swaps) to execute.
  --attr TEXT           Node attributes in form key=value.
  --commit              Execute the shard reroutes (default print only).
  --print-state         Print the current nodes & weights and exit.
  --index-name TEXT     Filter the indices for swaps by name, supports
                        wildcards.
  --max-node TEXT       Force the max node to consider for shard swaps.
  --min-node TEXT       Force the min node to consider for shard swaps.
  --one-way             Disables shard swaps and simply moves max -> min. Note
                        after ES rebalancing is restored ES will attempt to
                        rebalance itself according to it's own heuristics.
  --help                Show this message and exit.

Custom Weighting

By default the es-rebalance script uses shard size (in bytes) as the weight indicator. It is possible to customise this by writing your own CLI - for example:

from elasticsearch_rebalancer import make_rebalance_elasticsearch_cli

def get_shard_weight(shard):
    return 1

if __name__ == '__main__':
    rebalance_elasticsearch = make_rebalance_elasticsearch_cli(
        get_shard_weight_function=get_shard_weight,
    )
    rebalance_elasticsearch()

About

Pokes Elasticsearch to balance itself sensibly.

Resources

License

Stars

Watchers

Forks

Packages

No packages published

Languages