| = sstableofflinerelevel |
| |
| When using LeveledCompactionStrategy, sstables can get stuck at L0 on a |
| recently bootstrapped node, and compactions may never catch up. This |
| tool is used to bump sstables into the highest level possible. |
| |
| ref: https://issues.apache.org/jira/browse/CASSANDRA-8301 |
| |
| The way this is done is: sstables are storted by their last token. Given |
| an original leveling like this (note that [ ] indicates token |
| boundaries, not sstable size on disk; all sstables are the same size): |
| |
| .... |
| L3 [][][][][][][][][][][] |
| L2 [ ][ ][ ][ ] |
| L1 [ ][ ] |
| L0 [ ] |
| .... |
| |
| Will look like this after being dropped to L0 and sorted by last token |
| (and, to illustrate overlap, the overlapping ones are put on a new |
| line): |
| |
| .... |
| [][][] |
| [ ][][][] |
| [ ] |
| [ ] |
| ... |
| .... |
| |
| Then, we start iterating from the smallest last-token and adding all |
| sstables that do not cause an overlap to a level. We will reconstruct |
| the original leveling top-down. Whenever we add an sstable to the level, |
| we remove it from the sorted list. Once we reach the end of the sorted |
| list, we have a full level, and can start over with the level below. |
| |
| If we end up with more levels than expected, we put all levels exceeding |
| the expected in L0, for example, original L0 files will most likely be |
| put in a level of its own since they most often overlap many other |
| sstables. |
| |
| Cassandra must be stopped before this tool is executed, or unexpected |
| results will occur. Note: the script does not verify that Cassandra is |
| stopped. |
| |
| == Usage |
| |
| sstableofflinerelevel [--dry-run] <keyspace> <table> |
| |
| == Doing a dry run |
| |
| Use the --dry-run option to see the current level distribution and |
| predicted level after the change. |
| |
| Example: |
| |
| .... |
| sstableofflinerelevel --dry-run keyspace eventlog |
| For sstables in /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753: |
| Current leveling: |
| L0=2 |
| Potential leveling: |
| L0=1 |
| L1=1 |
| .... |
| |
| == Running a relevel |
| |
| Example: |
| |
| .... |
| sstableofflinerelevel keyspace eventlog |
| For sstables in /var/lib/cassandra/data/keyspace/eventlog-6365332094dd11e88f324f9c503e4753: |
| Current leveling: |
| L0=2 |
| New leveling: |
| L0=1 |
| L1=1 |
| .... |
| |
| == Keyspace or table not found |
| |
| If an invalid keyspace and/or table is provided, an exception will be |
| thrown. |
| |
| Example: |
| |
| .... |
| sstableofflinerelevel --dry-run keyspace evenlog |
| |
| Exception in thread "main" java.lang.IllegalArgumentException: Unknown keyspace/columnFamily keyspace1.evenlog |
| at org.apache.cassandra.tools.SSTableOfflineRelevel.main(SSTableOfflineRelevel.java:96) |
| .... |
