Synced flush was a brilliant idea. It supports instant recoveries with a
quite small implementation. However, with the presence of sequence
numbers and retention leases, it is no longer needed. This change
removes it from 8.0.
Relates #5077
* Add ILM histore store index
This commit adds an ILM history store that tracks the lifecycle
execution state as an index progresses through its ILM policy. ILM
history documents store output similar to what the ILM explain API
returns.
An example document with ALL fields (not all documents will have all
fields) would look like:
```json
{
"@timestamp": 1203012389,
"policy": "my-ilm-policy",
"index": "index-2019.1.1-000023",
"index_age":123120,
"success": true,
"state": {
"phase": "warm",
"action": "allocate",
"step": "ERROR",
"failed_step": "update-settings",
"is_auto-retryable_error": true,
"creation_date": 12389012039,
"phase_time": 12908389120,
"action_time": 1283901209,
"step_time": 123904107140,
"phase_definition": "{\"policy\":\"ilm-history-ilm-policy\",\"phase_definition\":{\"min_age\":\"0ms\",\"actions\":{\"rollover\":{\"max_size\":\"50gb\",\"max_age\":\"30d\"}}},\"version\":1,\"modified_date_in_millis\":1576517253463}",
"step_info": "{... etc step info here as json ...}"
},
"error_details": "java.lang.RuntimeException: etc\n\tcaused by:etc etc etc full stacktrace"
}
```
These documents go into the `ilm-history-1-00000N` index to provide an
audit trail of the operations ILM has performed.
This history storage is enabled by default but can be disabled by setting
`index.lifecycle.history_index_enabled` to `false.`
Resolves#49180
The freeze index API docs state that frozen indices are blocked for
write operations.
While this implies frozen indices are read-only, it does not explicitly
use the term "read-only", which is found in other docs, such as the
force merge docs.
This adds the "ready-only" term to the freeze index API docs as well
as other clarification.
The current snippets in the synced flush docs can cause conflicts with
other background syncs, such as the global checkpoint sync or retention
lease sync, in the docs tests.
This skips tests for those snippets to avoid conflicts.
We should only snapshot the index we're going to
restore in the next step. Otherwise, we will
potentially not get the correct response or
fail restoring outright due to internal indices
getting created concurrently when running against
the x-pack distribution.
Closes#46844
This commit updates the docs about translog retention and flushing to reflect
recent changes in how peer recoveries work. It also adds some docs to describe
how history is retained for replay using soft deletes and shard history
retention leases.
Relates #45473
