Today if sending file chunks is CPU-bound (e.g. when using compression)
then we tend to concentrate all that work onto relatively few threads,
even if `indices.recovery.max_concurrent_file_chunks` is increased. With
this commit we fork the transmission of each chunk onto its own thread
so that the CPU-bound work can happen in parallel.
This commit adds the `data_frozen` node role as part of the formalization of data tiers. It also
adds the `"frozen"` phase to ILM, currently allowing the same actions as the existing cold phase.
The frozen phase is intended to be used for data even less frequently searched than the cold phase,
and will eventually be loosely tied to data using partial searchable snapshots (as oppposed to full
searchable snapshots in the cold phase).
Relates to #60848
This commit sets the recovery rate for dedicated cold nodes. The goal is
here is enhance performance of recovery in a dedicated cold tier, where
we expect such nodes to be predominantly using searchable snapshots to
back the indices located on them. This commit follows a simple approach
where we increase the recovery rate as a function of the node size, for
nodes that appear to be dedicated cold nodes.
Today, we send operations in phase2 of peer recoveries batch by batch
sequentially. Normally that's okay as we should have a fairly small of
operations in phase 2 due to the file-based threshold. However, if
phase1 takes a lot of time and we are actively indexing, then phase2 can
have a lot of operations to replay.
With this change, we will send multiple batches concurrently (defaults
to 1) to reduce the recovery time.
Restoring from a snapshot (which is a particular form of recovery) does not currently take recovery throttling into account
(i.e. the `indices.recovery.max_bytes_per_sec` setting). While restores are subject to their own throttling (repository
setting `max_restore_bytes_per_sec`), this repository setting does not allow for values to be configured differently on a
per-node basis. As restores are very similar in nature to peer recoveries (streaming bytes to the node), it makes sense to
configure throttling in a single place.
The `max_restore_bytes_per_sec` setting is also changed to default to unlimited now, whereas previously it was set to
`40mb`, which is the current default of `indices.recovery.max_bytes_per_sec`). This means that no behavioral change
will be observed by clusters where the recovery and restore settings were not adapted.
Relates https://github.com/elastic/elasticsearch/issues/57023
Co-authored-by: James Rodewig <james.rodewig@elastic.co>
The `indices.recovery.max_bytes_per_sec` recovery bandwidth limit can differ
between nodes if it is not set dynamically, but today this is not obvious. This
commit adds a paragraph to its documentation clarifying how to set different
bandwidth limits on each node.
Co-Authored-By: James Rodewig <james.rodewig@elastic.co>
* Clarify that peer recovery settings apply to shard relocation
* Fix awkward wording of 1st sentence
* [DOCS] Remove snapshot recovery reference.
Call out link to [[cat-recovery]].
Separate expert settings.
Today file-chunks are sent sequentially one by one in peer-recovery. This is a
correct choice since the implementation is straightforward and recovery is
network bound in most of the time. However, if the connection is encrypted, we
might not be able to saturate the network pipe because encrypting/decrypting
are cpu bound rather than network-bound.
With this commit, a source node can send multiple (default to 2) file-chunks
without waiting for the acknowledgments from the target.
Below are the benchmark results for PMC and NYC_taxis.
- PMC (20.2 GB)
| Transport | Baseline | chunks=1 | chunks=2 | chunks=3 | chunks=4 |
| ----------| ---------| -------- | -------- | -------- | -------- |
| Plain | 184s | 137s | 106s | 105s | 106s |
| TLS | 346s | 294s | 176s | 153s | 117s |
| Compress | 1556s | 1407s | 1193s | 1183s | 1211s |
- NYC_Taxis (38.6GB)
| Transport | Baseline | chunks=1 | chunks=2 | chunks=3 | chunks=4 |
| ----------| ---------| ---------| ---------| ---------| -------- |
| Plain | 321s | 249s | 191s | * | * |
| TLS | 618s | 539s | 323s | 290s | 213s |
| Compress | 2622s | 2421s | 2018s | 2029s | n/a |
Relates #33844
Today we throttle recoveries only for incoming recoveries. Nodes that have a lot
of primaries can get overloaded due to too many recoveries. To still keep that at bay
we limit the number of threads that are sending files to the target to overcome this problem.
The right solution here is to also throttle the outgoing recoveries that are today unbounded on
the master and don't start the recovery until we have enough resources on both source and target nodes.
The concurrency aspects of the recovery source also added a lot of complexity and additional threadpools
that are hard to configure. This commit removes the concurrent streamns notion completely and sends files
in the thread that drives the recovery simplifying the recovery code considerably.
Outgoing recoveries are not throttled on the master via a allocation decider.
David Turner
Lee Hinman
Jason Tedor
James Rodewig
Nhat Nguyen
Yannick Welsch
James Rodewig
alamzeeshan
Simon Willnauer
Clinton Gormley