snmpa_local_db
(snmp)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 types are used:
-
NameDb = {Name, Db}
-
Name = atom(), Db = volatile | persistent
-
RowIndex = [int()]
-
Cols = [Col] | [{Col, Value}], Col = int(), Value = term()
where RowIndex
denotes the last part of the OID, that
specifies the index of the row in the table. Cols
is a
list of column numbers in case of a get operation, and a list of
column numbers and values in case of a set operation.
Functions
dump() -> ok | {error, Reason}
Reason = term()
This function can be used to manually dump the database to file.
match(NameDb, Pattern)
Performs an ets/dets matching on the table.
See Stdlib documentation, module ets, for a description of
Pattern
and the return values.
print()
print(TableName)
print(TableName, Db)
TableName = atom()
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
.
TableName
is an atom for a table in the database.
When no name is supplied, the whole database is shown.
table_create(NameDb) -> bool()
Creates a table. If the table already exist, the old copy is destroyed.
Returns false
if the NameDb
argument is
incorrectly specified, true
otherwise.
table_create_row(NameDb, RowIndex, Row) -> bool()
Row = {Val1, Val2, ..., ValN}
Val1 = Val2 = ... = ValN = term()
Creates a row in a table. Row
is a tuple with
values for all columns, including the index columns.
table_delete(NameDb) -> void()
Deletes a table.
table_delete_row(NameDb, RowIndex) -> bool()
Deletes the row in the table.
table_exists(NameDb) -> bool()
Checks if a table exists.
table_get_row(NameDb, RowIndex) -> Row | undefined
Row = {Val1, Val2, ..., ValN}
Val1 = Val2 = ... = ValN = term()
Row
is a tuple with values for all columns,
including the index columns.
See Also
ets(3), dets(3), snmp_generic(3)