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In this section, I will explain the meaning of the metrics listed in the previous section.
num-immutable-mem-table
number of immutable memtables that have not yet been flushed.
mem-table-flush-pending
returns 1 if a memtable flush is pending; otherwhise, returns 0
compaction-pending
returns 1 if at least one compaction is pending; otherwise, return 0
background-errors
returns the accumulated number of background errors
cur-size-active-mem-table
returns approximate size of active memtable in bytes
cur-size-all-mem-tables
returns approximate size of active and unflushed immutable memtables
size-all-mem-tables
returns approximate size of active, unflushed immutable, and pinned immutable memtables (bytes).
num-entries-active-mem-table
returns total number of entries in the active memtable.
num-entries-imm-mem-tables
returns total number of entries in the unflushed immutable memtables.
num-deletes-active-mem-table
returns total number of delete entries in the active memtable.
num-deletes-imm-mem-tables
returns total number of delete entries in the unflushed immutable memtables.
estimate-num-keys
returns estimated number of total keys in the active and unflushed immutable memtables and storage.
estimate-table-readers-mem
returns estimated memory used for reading SST tables, excluding memory used in block cache (e.g., filter and index blocks).
num-live-versions
returns number of live versions. `Version` is an internal data structure. See version_set.h for details. More live versions often mean more SST files are held from being deleted, by iterators or unfinished compactions.
estimate-live-data-size
returns an estimate of the amount of live data in bytes.
min-log-number-to-keep
min-obsolete-sst-number-to-keep
total-sst-files-size
live-sst-files-size
base-level
estimate-pending-compaction-bytes
num-running-compactions
num-running-flushes
actual-delayed-write-rate
is-write-stopped
estimate-oldest-key-time
block-cache-capacity
block-cache-usage
block-cache-pinned-usage
memtables-size
Memory usage of all mem-tables. Mem-tables are in-memory write buffers. Each new key-value pair is first written to a mem-table and each read looks first into the mem-table before it looks on disk. Once a mem-table is full it becomes immutable and it is replaced by a new mem-table. A background thread flushes a mem-table asynchronously to disk. Additionally, mem-tables can also be flushed manually. RocksDB keeps in memory the currently active mem-tables, full but not yet flushed mem-tables, and flushed mem-tables that are kept around to maintain write history in memory.
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