otp.ShowSnapshotList#

class ShowSnapshotList(snapshot_storage='all', **kwargs)#

Bases: onetick.py.core.source.Source

Outputs all snapshots names for global memory storage and/or for memory mapped files. These snapshots should be written there by the onetick.py.Source.save_snapshot(). Output ticks have SNAPSHOT_NAME, STORAGE_TYPE and DB_NAME fields.

Parameters

snapshot_storage ('memory' or 'memory_mapped_file') –

This parameter specifies the place of storage of the snapshot. Possible options are:

memory - the snapshot is stored in the dynamic (heap) memory of the process that ran (or is still running) the onetick.py.Source.save_snapshot() for the snapshot.
memory_mapped_file - the snapshot is stored in a memory mapped file. For each symbol to get the location of the snapshot in the file system, ReadSnapshot looks at the SAVE_SNAPSHOT_DIR parameter value in the locator section for the database of the symbol.
all - shows both, memory, memory_mapped_file snapshots.

Default: all

Examples

List snapshots from all snapshot storage types:

>>> src = otp.ShowSnapshotList(snapshot_storage='all')  
>>> otp.run(src)  
        Time SNAPSHOT_NAME        STORAGE_TYPE        DB_NAME
0 2003-12-01    snapshot_1              MEMORY        DEMO_L1
1 2003-12-01    snapshot_2              MEMORY        DEMO_L1
2 2003-12-01    snapshot_3  MEMORY_MAPPED_FILE  SNAPSHOT_DEMO

List snapshots from memory:

>>> src = otp.ShowSnapshotList(snapshot_storage='memory')  
>>> otp.run(src)  
        Time SNAPSHOT_NAME        STORAGE_TYPE        DB_NAME
0 2003-12-01    snapshot_1              MEMORY        DEMO_L1
1 2003-12-01    snapshot_2              MEMORY        DEMO_L1

List snapshots from memory mapped files:

>>> src = otp.ShowSnapshotList(snapshot_storage='memory_mapped_file')  
>>> otp.run(src)  
        Time SNAPSHOT_NAME        STORAGE_TYPE        DB_NAME
0 2003-12-01    snapshot_3  MEMORY_MAPPED_FILE  SNAPSHOT_DEMO