View Source snmpa_local_db (snmp v5.16)

The SNMP built-in database

The module snmpa_local_db contains functions for implementing tables (and variables) using the SNMP built-in database. The database exists in two instances, one volatile and one persistent. The volatile database is implemented with ets. The persistent database is implemented with dets.

There is a scaling problem with this database.

Insertions and deletions are inefficient for large tables.

This problem is best solved by using Mnesia instead.

The following functions describe the interface to snmpa_local_db. Each function has a Mnesia equivalent. The argument NameDb is a tuple {Name, Db} where Name is the symbolic name of the managed object (as defined in the MIB), and Db is either volatile or persistent. mnesia is not possible since all these functions are snmpa_local_db specific.

Common Data Types

In the functions defined below, the following limitation applies:

Db = volatile | persistent

Summary

Functions

dump()

This function can be used to manually dump the database to file.

match(Table, Pattern)

Performs an ets/dets matching on the table.

print()

Equivalent to print/2.

print(Table)

Equivalent to print/2.

print(Table, Db)

Prints the contents of the database on screen. This is useful for debugging since the STANDARD-MIB and OTP-SNMPEA-MIB (and maybe your own MIBs) are stored in snmpa_local_db.

table_create(Table)

Creates a table. If the table already exist, the old copy is destroyed.

table_create_row(Table, RowIndex, Row)

Creates a row in a table. Row is a tuple with values for all columns, including the index columns.

table_delete(Table)

Deletes a table.

table_delete_row(Table, RowIndex)

Deletes the row in the table.

table_exists(Table)

Checks if a table exists.

table_get_element(Table, RowIndex, Col)

Get a column value (element) from a row of the table.

table_get_row(Table, RowIndex)

Row is a tuple with values for all columns, including the index columns.

table_set_elements(Table, RowIndex, Cols)

Update the specified columnar objects of the row of this table.

Functions

dump()

-spec dump() -> ok | {error, Reason} when Reason :: term().

This function can be used to manually dump the database to file.

match(Table, Pattern)

-spec match(Table, Pattern) -> [Match]
               when
                   Table :: snmpa:name_db() | snmpa:name(),
                   Pattern :: ets:match_pattern(),
                   Match :: term().

Performs an ets/dets matching on the table.

See ets:match/2 for a description of Pattern and the return values.

print()

-spec print() -> term().

Equivalent to print/2.

print(Table)

-spec print(Table) -> term() when Table :: snmpa:name().

Equivalent to print/2.

print(Table, Db)

-spec print(Table, Db) -> term() when Table :: snmpa:name(), Db :: volatile | persistent.

Prints the contents of the database on screen. This is useful for debugging since the STANDARD-MIB and OTP-SNMPEA-MIB (and maybe your own MIBs) are stored in snmpa_local_db.

Table is an atom for a table in the database. When no name is supplied, the whole database is shown.

Note that these functions does not actually print, using io:format/2, instead they (just) return the information. If executed in a shell, the information will then be displayed (probably truncated) there.

A better use would be:

	  io:format("~p~n", [snmpa_local_db:print()]).

table_create(Table)

-spec table_create(Table) -> boolean() when Table :: snmpa:name_db() | snmpa:name().

Creates a table. If the table already exist, the old copy is destroyed.

Returns false if the NameDb argument is incorrectly specified, true otherwise.