Skip to content

Commit

Permalink
Corrects setting names for segment replication backpressure (#5492)
Browse files Browse the repository at this point in the history
Signed-off-by: Fanit Kolchina <kolchfa@amazon.com>
(cherry picked from commit 5ebf909)
Signed-off-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
  • Loading branch information
github-actions[bot] committed Nov 2, 2023
1 parent d99f598 commit 291a178
Show file tree
Hide file tree
Showing 2 changed files with 12 additions and 12 deletions.
Original file line number Diff line number Diff line change
Expand Up @@ -9,20 +9,20 @@ grand_parent: Availability and recovery

# Segment replication backpressure

Segment replication backpressure is a shard-level rejection mechanism that dynamically rejects indexing requests as replica shards in your cluster fall behind primary shards. With segment replication backpressure, indexing requests are rejected when the percentage of stale shards in the replication group exceeds `MAX_ALLOWED_STALE_SHARDS` (50% by default). A replica is considered stale if it is behind the primary shard by the number of checkpoints that exceeds the `MAX_INDEXING_CHECKPOINTS` setting and its current replication lag is greater than the defined `MAX_REPLICATION_TIME_SETTING` field.
Segment replication backpressure is a shard-level rejection mechanism that dynamically rejects indexing requests as replica shards in your cluster fall behind primary shards. With segment replication backpressure, indexing requests are rejected when the percentage of stale shards in the replication group exceeds `segrep.pressure.replica.stale.limit` (50% by default). A replica is considered stale if it is behind the primary shard by the number of checkpoints that exceeds the `segrep.pressure.checkpoint.limit` setting and its current replication lag is greater than the defined `segrep.pressure.time.limit` field.

Replica shards are also monitored to determine whether the shards are stuck or lagging for an extended period of time. When replica shards are stuck or lagging for more than double the amount of time defined by the `MAX_REPLICATION_TIME_SETTING` field, the shards are removed and replaced with new replica shards.
Replica shards are also monitored to determine whether the shards are stuck or lagging for an extended period of time. When replica shards are stuck or lagging for more than double the amount of time defined by the `segrep.pressure.time.limit` field, the shards are removed and replaced with new replica shards.

## Request fields

Segment replication backpressure is disabled by default. To enable it, set `SEGMENT_REPLICATION_INDEXING_PRESSURE_ENABLED` to `true`. You can update the following dynamic cluster settings using the [cluster settings]({{site.url}}{{site.baseurl}}/api-reference/cluster-api/cluster-settings/) API endpoint.
Segment replication backpressure is disabled by default. To enable it, set `segrep.pressure.enabled` to `true`. You can update the following dynamic cluster settings using the [cluster settings]({{site.url}}{{site.baseurl}}/api-reference/cluster-api/cluster-settings/) API endpoint.

Field | Data type | Description
:--- | :--- | :---
SEGMENT_REPLICATION_INDEXING_PRESSURE_ENABLED | Boolean | Enables the segment replication backpressure mechanism. Default is `false`.
MAX_REPLICATION_TIME_SETTING | Time unit | The maximum amount of time that a replica shard can take to copy from the primary shard. Once `MAX_REPLICATION_TIME_SETTING` is breached along with `MAX_INDEXING_CHECKPOINTS`, the segment replication backpressure mechanism is initiated. Default is `5 minutes`.
MAX_INDEXING_CHECKPOINTS | Integer | The maximum number of indexing checkpoints that a replica shard can fall behind when copying from primary. Once `MAX_INDEXING_CHECKPOINTS` is breached along with `MAX_REPLICATION_TIME_SETTING`, the segment replication backpressure mechanism is initiated. Default is `4` checkpoints.
MAX_ALLOWED_STALE_SHARDS | Floating point | The maximum number of stale replica shards that can exist in a replication group. Once `MAX_ALLOWED_STALE_SHARDS` is breached, the segment replication backpressure mechanism is initiated. Default is `.5`, which is 50% of a replication group.
`segrep.pressure.enabled `| Boolean | Enables the segment replication backpressure mechanism. Default is `false`.
`segrep.pressure.time.limit` | Time unit | The maximum amount of time that a replica shard can take to copy from the primary shard. Once `segrep.pressure.time.limit` is breached along with `segrep.pressure.checkpoint.limit`, the segment replication backpressure mechanism is initiated. Default is `5 minutes`.
`segrep.pressure.checkpoint.limit` | Integer | The maximum number of indexing checkpoints that a replica shard can fall behind when copying from primary. Once `segrep.pressure.checkpoint.limit` is breached along with `segrep.pressure.time.limit`, the segment replication backpressure mechanism is initiated. Default is `4` checkpoints.
`segrep.pressure.replica.stale.limit `| Floating point | The maximum number of stale replica shards that can exist in a replication group. Once `segrep.pressure.replica.stale.limit` is breached, the segment replication backpressure mechanism is initiated. Default is `.5`, which is 50% of a replication group.

## Path and HTTP methods

Expand All @@ -40,4 +40,4 @@ shardId target_node target_host checkpoints_behind bytes_behind cur
[index-1][0] runTask-1 127.0.0.1 0 0b 0s 7ms 0
```

The `checkpoints_behind` and `current_lag` metrics are taken into consideration when initiating segment replication backpressure. They are checked against `MAX_INDEXING_CHECKPOINTS` and `MAX_REPLICATION_TIME_SETTING`, respectively.
The `checkpoints_behind` and `current_lag` metrics are taken into consideration when initiating segment replication backpressure. They are checked against `segrep.pressure.checkpoint.limit` and `segrep.pressure.time.limit`, respectively.
Original file line number Diff line number Diff line change
Expand Up @@ -59,13 +59,13 @@ For the best performance, we recommend enabling both of the following settings:
2. Balanced primary shard allocation:

```json
curl -X PUT "$host/_cluster/settings?pretty" -H 'Content-Type: application/json' -d'
{
"persistent": {
PUT /_cluster/settings
{
"persistent": {
"cluster.routing.allocation.balance.prefer_primary": true,
"segrep.pressure.enabled": true
}
}
}
```
{% include copy-curl.html %}

Expand Down

0 comments on commit 291a178

Please sign in to comment.