Manage a KVDB

HSE requires minimal management beyond configuring mpool storage, creating a KVDB, and optionally defining an associated configuration file as previously described. The following examples illustrate the few other aspects of KVS and KVDB management.

Managing KVS

Most often a client application will use the HSE API to create and manage the one or more KVS it needs for storing collections of KV pairs in accordance with the HSE data model. However, KVS can also be managed from the hse CLI.

Create a KVS

Continuing with our example KVDB, we create three KVS.

$ hse kvs create mydb/docData docData.pfx_len=0
$ hse kvs create mydb/docIdx docIdx.pfx_len=16
$ hse kvs create mydb/docIdxAlt docIdxAlt.pfx_len=12

$ hse kvdb list -v
kvdbs:
- name: mydb
  label: raw
  kvslist:
    - mydb/docData
    - mydb/docIdx
    - mydb/docIdxAlt

Destroy a KVS

Similarly, we can remove a KVS from the KVDB, along with any KV data it stores.

$ hse kvs destroy mydb/docIdxAlt
$ hse kvdb list -v
kvdbs:
- name: mydb
  label: raw
  kvslist:
    - mydb/docData
    - mydb/docIdx

Managing KVDB

Most KVDB management is related to its lifecycle or storage.

View Parameters for a KVDB

The parameters for a KVDB can be specified via multiple sources, as previously discussed. You can view the parameters in effect for an active KVDB, including all of its KVS, as follows.

$ hse kvdb params mydb

Tip

For this command to work, the KVDB must be open by a client application.

Rename or Label a KVDB

As previously noted, the name and label of a KVDB are simply the name and label of the mpool that stores it. Hence, the mpool CLI is used to change the name or label of a KVDB. Note that an mpool (and hence KVDB) must be deactivated to rename it.

$ sudo mpool deactivate mydb
$ sudo mpool rename mydb docDB
$ sudo mpool activate docDB
$ sudo mpool set docDB label=Weather_Docs

$ hse kvdb list -v
kvdbs:
- name: docDB
  label: Weather_Docs
  kvslist:
    - docDB/docData
    - docDB/docIdx

Compact a KVDB

HSE implements the physical removal of logically deleted data as a background operation. Physical removal can also be forced from the hse CLI. This operation can take several minutes depending on the amount of data stored in the KVDB, among other factors, and so a timeout can be specified.

$ hse kvdb compact --timeout 120 docDB

If a KVDB is in use by an application, the compaction operation may continue past the timeout value (specified or default). In this case, the status of the compaction can be queried.

$ hse kvdb compact --status docDB

The compaction can also be canceled.

$ hse kvdb compact --cancel docDB

Destroy a KVDB

Finally, a KVDB is deleted by destroying the mpool that stores it.

$ sudo mpool destroy docDB
$ hse kvdb list
No KVDBs found