[Ericsson AB]

snmp_local_db

MODULE

snmp_local_db

MODULE SUMMARY

The SNMP built-in database

DESCRIPTION

The module snmp_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. It is possible to manually dump the database.

There are three scaling problems with this database.

All these problems are best solved by using Mnesia instead.

In order to know when the content of the database should be dumped, it is possible to register/unregister a notification client. This client will be notified of all persistent/permanent changes to the database by a call to:

Module:notify(Client,What)

Where the arguments are:

Note!

The snmp local db currently uses the defalt auto-save time of dets!

See register_notify_client/2 and unregister_notify_client/2 below for further information.

The following functions describe the interface to snmp_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 snmp_local_db specific.

Common Data Types

In the functions defined below, the following types are used:

where RowIndex denotes the last part of the OID, that specifies the index of the row in tha 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.

EXPORTS

dump() -> ok | {error, Reason}

This function can be used to dump the database at any time.

match(NameDb,Pattern)

Performs an ets matching on the table. See Stdlib documentation, module ets, for a description of Pattern and the return values.

print()
print(TableName)
print(TableName, Db)

Types:

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 snmp_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()

Types:

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

Types:

Row = {Val1, Val2, ..., ValN}
Val1 = Val2 = ... = ValN = term()

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

register_notify_client(Client,Module) -> ok | {error,Reason}

Types:

Client = term()
Module = atom()
Reason = {already_registered,CurrentModule}
CurrentModule = atom()

Register Client as notification client to snmp_local_db. Client is actually just used as an identity, but could e.g. be a pid(). When changes are made to the database (insert, delete or stop) notify clients will be notified.

unregister_notify_client(Client) -> ok | {error,Reason}

Types:

Client = term()
Reason = not_registered

Unregister Client as notification client to snmp_local_db.

See Also

ets(3), snmp_generic(3)

AUTHORS

Martin Björklund - support@erlang.ericsson.se
Klas Eriksson - support@erlang.ericsson.se

snmp 3.4.12
Copyright © 1991-2006 Ericsson AB