kamailio/modules/db_berkeley

Berkeley DB Module

Will Quan

Cisco Systems

Edited by

Will Quan

Copyright � 2007 Cisco Systems
__________________________________________________________________

Table of Contents

1. Admin Guide

1. Overview
2. Dependencies

2.1. Kamailio Modules
2.2. External Libraries or Applications

3. Parameters

3.1. auto_reload (integer)
3.2. log_enable (integer)
3.3. journal_roll_interval (integer seconds)

4. Functions
5. MI Commands

5.1. bdb_reload

6. Installation and Running
7. Database Schema and Metadata
8. METADATA_COLUMNS (required)
9. METADATA_KEYS (required)
10. METADATA_READONLY (optional)
11. METADATA_LOGFLAGS (optional)
12. DB Maintaince Script : kamdbctl
13. DB Recovery : kambdb_recover
14. Known Limitations

List of Examples

1.1. Set auto_reload parameter
1.2. Set log_enable parameter
1.3. Set journal_roll_interval parameter
1.4. METADATA_COLUMNS
1.5. contents of version table
1.6. METADATA_COLUMNS
1.7. METADATA_KEYS
1.8. METADATA_LOGFLAGS
1.9. kamdbctl
1.10. kambdb_recover usage

Chapter 1. Admin Guide

Table of Contents

1. Overview
2. Dependencies

2.1. Kamailio Modules
2.2. External Libraries or Applications

3. Parameters

3.1. auto_reload (integer)
3.2. log_enable (integer)
3.3. journal_roll_interval (integer seconds)

4. Functions
5. MI Commands

5.1. bdb_reload

6. Installation and Running
7. Database Schema and Metadata
8. METADATA_COLUMNS (required)
9. METADATA_KEYS (required)
10. METADATA_READONLY (optional)
11. METADATA_LOGFLAGS (optional)
12. DB Maintaince Script : kamdbctl
13. DB Recovery : kambdb_recover
14. Known Limitations

1. Overview

This is a module which integrates the Berkeley DB into SIP-router. It
implements the DB API defined in SIP-router.

2. Dependencies

2.1. Kamailio Modules
2.2. External Libraries or Applications

2.1. Kamailio Modules

The following modules must be loaded before this module:
* No dependencies on other Kamailio modules.

2.2. External Libraries or Applications

The following libraries or applications must be installed before
running Kamailio with this module loaded:
* Berkeley Berkeley DB - an embedded database. Version >= 4.6.

3. Parameters

3.1. auto_reload (integer)
3.2. log_enable (integer)
3.3. journal_roll_interval (integer seconds)

3.1. auto_reload (integer)

The auto-reload will close and reopen a Berkeley DB when the files
inode has changed. The operation occurs only duing a query. Other
operations such as insert or delete, do not invoke auto_reload.

Default value is 0 (1 - on / 0 - off).

Example 1.1. Set auto_reload parameter
...
modparam("db_berkeley", "auto_reload", 1)
...

3.2. log_enable (integer)

The log_enable boolean controls when to create journal files. The
following operations can be journaled: INSERT, UPDATE, DELETE. Other
operations such as SELECT, do not. This journaling are required if you
need to recover from a corrupt DB file. That is, kambdb_recover
requires these to rebuild the db file. If you find this log feature
useful, you may also be interested in the METADATA_LOGFLAGS bitfield
that each table has. It will allow you to control which operations to
journal, and the destination (like syslog, stdout, local-file). Refer
to bdblib_log() and documentation on METADATA.

Default value is 0 (1 - on / 0 - off).

Example 1.2. Set log_enable parameter
...
modparam("db_berkeley", "log_enable", 1)
...

3.3. journal_roll_interval (integer seconds)

The journal_roll_interval will close and open a new log file. The roll
operation occurs only at the end of writing a log, so it is not
guaranteed to to roll 'on time'.

Default value is 0 (off).

Example 1.3. Set journal_roll_interval parameter
...
modparam("db_berkeley", "journal_roll_interval", 3600)
...

4. Functions

No function exported to be used from configuration file.

5. MI Commands

5.1. bdb_reload

5.1. bdb_reload

Causes db_berkeley module to re-read the contents of specified table
(or dbenv). The db_berkeley DB actually loads each table on demand, as
opposed to loading all at mod_init time. The bdb_reload operation is
implemented as a close followed by a reopen. Note- bdb_reload will fail
if a table has not been accessed before (because the close will fail).

Name: bdb_reload

Parameters: tablename (or db_path); to reload a particular table
provide the tablename as the arguement (eg subscriber); to reload all
tables provide the db_path to the db files. The path can be found in
kamctlrc DB_PATH variable.

6. Installation and Running

First download, compile and install the Berkeley DB. This is outside
the scope of this document. Documentation for this procedure is
available on the Internet.

Next, prepare to compile SIP-router with the db_berkeley module. In the
directory /modules/db_berkeley, modify the Makefile to point to your
distribution of Berkeley DB. You may also define 'BDB_EXTRA_DEBUG' to
compile in extra debug logs. However, it is not a recommended
deployment to production servers.

Because the module dependes on an external library, the db_berkeley
module is not compiled and installed by default. You can use one of the
next options.
* edit the "Makefile" and remove "db_berkeley" from
"excluded_modules" list. Then follow the standard procedure to
install Kamailio: "make all; make install".
* from command line use: 'make all include_modules="db_berkeley";
make install include_modules="db_berkeley"'.

Installation of SIP-router is performed by simply running make install
as root user of the main directory. This will install the binaries in
/usr/local/sbin/. If this was successful, SIP-router control engine
files should now be installed as /usr/local/sbin/kamdbctl.

Decide where (on the filesystem) you want to install the Berkeley DB
files. For instance, '/usr/local/etc/kamailio/db_berkeley' directory.
Make note of this directory as we need to add this path to the kamctlrc
file. Note: SIP-router will not startup without these DB files.

Edit kamctlrc - There are two parameters in this file that should be
configured before kamdbctl script can work properly: DBENGINE and
DB_PATH. Edit file: '/usr/local/etc/sip-router/kamctlrc'
## database type: MYSQL, PGSQL, DB_BERKELEY, or DBTEXT, by defau
lt none is loaded
# DBENGINE=DB_BERKELEY

## database path used by dbtext or db_berkeley
# DB_PATH="/usr/local/etc/kamailio/db_berkeley"

(Optional) Pre creation step- Customize your meta-data. The DB files
are initially seeded with necessary meta-data. This is a good time to
review the meta-data section details, before making modifications to
your tables dbschema. By default, the files are installed in
'/usr/local/share/sip-router/db_berkeley/sip-router' By default these
tables are created Read/Write and without any journalling as shown.
These settings can be modified on a per table basis. Note: If you plan
to use kambdb_recover, you must change the LOGFLAGS.
METADATA_READONLY
0
METADATA_LOGFLAGS
0

Execute kamdbctl - There are three (3) groups of tables you may need
depending on your situation.
kamdbctl create (required)
kamdbctl presence (optional)
kamdbctl extra (optional)

Modify the SIP-router configuration file to use db_berkeley module. The
database URL for modules must be the path to the directory where the
Berkeley DB table-files are located, prefixed by "berkeley://", e.g.,
"berkeley:///usr/local/etc/kamailio/db_berkeley".

A couple other IMPORTANT things to consider are the 'db_mode' and the
'use_domain' modparams. The description of these parameters are found
in usrloc documentation.

Note on db_mode- The db_berkeley module will only journal the moment
usrloc writes back to the DB. The safest mode is mode 3 , since the
db_berkeley journal files will always be up-to-date. The main point is
the db_mode vs. recovery by journal file interaction. Writing journal
entries is 'best effort'. So if the hard drive becomes full, the
attempt to write a journal entry may fail.

Note on use_domain- The db_berkeley module will attempt natural joins
when performing a query. This is basically a lexigraphical string
compare using the keys provided. In most places in the db_berkeley
dbschema (unless you customize), the domainname is identified as a
natural key. Consider an example where use_domain = 0. In table
subscriber, the db will be keying on 'username|NULL' because the
default value will be used when that key column is not provided. This
effectivly means that later queries must consistently use the username
(w.o domain) in order to find a result to that particular subscriber
query. The main point is 'use_domain' can not be changed once the
db_berkeley is setup.

7. Database Schema and Metadata

All Berkeley DB tables are created via the kamdbctl script. This
section provides details as to the content and format of the DB file
upon creation.

Since the Berkeley DB stores key value pairs, the database is seeded
with a few meta-data rows . The keys to these rows must begin with
'METADATA'. Here is an example of table meta-data, taken from the table
'version'.

Note on reserved character- The '|' pipe character is used as a record
delimiter within the Berkeley DB implementation and must not be present
in any DB field.

Example 1.4. METADATA_COLUMNS
METADATA_COLUMNS
table_name(str) table_version(int)
METADATA_KEY
0

In the above example, the row METADATA_COLUMNS defines the column names
and type, and the row METADATA_KEY defines which column(s) form the
key. Here the value of 0 indicates that column 0 is the key(ie
table_name). With respect to column types, the db_berkeley modules only
has the following types: string, str, int, double, and datetime. The
default type is string, and is used when one of the others is not
specified. The columns of the meta-data are delimited by whitespace.

The actual column data is stored as a string value, and delimited by
the '|' pipe character. Since the code tokenizes on this delimiter, it
is important that this character not appear in any valid data field.
The following is the output of the 'db_berkeley.sh dump version'
command. It shows contents of table 'version' in plain text.

Example 1.5. contents of version table
VERSION=3
format=print
type=hash
h_nelem=21
db_pagesize=4096
HEADER=END
METADATA_READONLY
1
address|
address|3
aliases|
aliases|1004
dbaliases|
dbaliases|1
domain|
domain|1
gw_grp|
gw_grp|1
gw|
gw|4
speed_dial|
speed_dial|2
subscriber|
subscriber|6
uri|
uri|1
METADATA_COLUMNS
table_name(str) table_version(int)
METADATA_KEY
0
acc|
acc|4
grp|
grp|2
lcr|
lcr|2
location|
location|1004
missed_calls|
missed_calls|3
re_grp|
re_grp|1
silo|
silo|5
trusted|
trusted|4
usr_preferences|
usr_preferences|2
DATA=END

8. METADATA_COLUMNS (required)

The METADATA_COLUMNS row contains the column names and types. Each is
space delimited. Here is an example of the data taken from table
subscriber :

Example 1.6. METADATA_COLUMNS
METADATA_COLUMNS
username(str) domain(str) password(str) ha1(str) ha1b(str) first_name(str) last_
name(str) email_address(str) datetime_created(datetime) timezone(str) rpid(str)

Related (hardcoded) limitations:
* maximum of 32 columns per table.
* maximum tablename size is 64.
* maximum data length is 2048

Currently supporting these five types: str, datetime, int, double,
string.

9. METADATA_KEYS (required)

The METADATA_KEYS row indicates the indexes of the key columns, with
respect to the order specified in METADATA_COLUMNS. Here is an example
taken from table subscriber that brings up a good point:

Example 1.7. METADATA_KEYS
METADATA_KEY
0 1

The point is that both the username and domain name are require as the
key to this record. Thus, usrloc modparam use_domain = 1 must be set
for this to work.

10. METADATA_READONLY (optional)

The METADATA_READONLY row contains a boolean 0 or 1. By default, its
value is 0. On startup the DB will open initially as read-write (loads
metadata) and then if this is set=1, it will close and reopen as read
only (ro). I found this useful because readonly has impacts on the
internal db locking etc.

11. METADATA_LOGFLAGS (optional)

The METADATA_LOGFLAGS row contains a bitfield that customizes the
journaling on a per table basis. If not present the default value is
taken as 0. Here are the masks so far (taken from bdb_lib.h):

Example 1.8. METADATA_LOGFLAGS
#define JLOG_NONE 0
#define JLOG_INSERT 1
#define JLOG_DELETE 2
#define JLOG_UPDATE 4
#define JLOG_STDOUT 8
#define JLOG_SYSLOG 16

This means that if you want to journal INSERTS to local file and syslog
the value should be set to 1+16=17. Or if you do not want to journal at
all, set this to 0.

12. DB Maintaince Script : kamdbctl

Use the kamdbctl script for maintaining SIP-router Berkeley DB tables.
This script assumes you have DBENGINE and DB_PATH setup correctly in
kamctlrc. Note Unsupported commands are- backup, restore, migrate,
copy, serweb.

Example 1.9. kamdbctl
usage: kamdbctl create
kamdbctl presence
kamdbctl extra
kamdbctl drop
kamdbctl reinit
kamdbctl bdb list (lists the underlying db files in DB_PATH)
kamdbctl bdb cat db (prints the contents of db file to STDOUT in pl
ain-text)
kamdbctl bdb swap db (installs db.new by db -> db.old; db.new -> db)
kamdbctl bdb append db datafile (appends data to a new instance of db;
output DB_PATH/db.new)
kamdbctl bdb newappend db datafile (appends data to a new instance of db;
output DB_PATH/db.new)

13. DB Recovery : kambdb_recover

The db_berkeley module uses the Concurrent Data Store (CDS)
architecture. As such, no transaction or journaling is provided by the
DB natively. The application kambdb_recover is specifically written to
recover data from journal files that SIP-router creates. The
kambdb_recover application requires an additional text file that
contains the table schema.

The schema is loaded with the '-s' option and is required for all
operations. Provide the path to the db_berkeley plain-text schema
files. By default, these install to
'/usr/local/share/kamailio/db_berkeley/kamailio/'.

The '-h' home option is the DB_PATH path. Unlike the Berkeley
utilities, this application does not look for the DB_PATH environment
variable, so you have to specify it. If not specified, it will assume
the current working directory. The last argument is the operation.
There are fundamentally only two operations- create and recover.

The following illustrates the four operations available to the
administrator.

Example 1.10. kambdb_recover usage
usage: ./kambdb_recover -s schemadir [-h home] [-c tablename]
This will create a brand new DB file with metadata.

usage: ./kambdb_recover -s schemadir [-h home] [-C all]
This will create all the core tables, each with metadata.

usage: ./kambdb_recover -s schemadir [-h home] [-r journal-file]
This will rebuild a DB and populate it with operation from journal-file.
The table name is embedded in the journal-file name by convention.

usage: ./kambdb_recover -s schemadir [-h home] [-R lastN]
This will iterate over all core tables enumerated. If journal files exis
t in 'home',
a new DB file will be created and populated with the data found in the l
ast N files.
The files are 'replayed' in chronological order (oldest to newest). This
allows the administrator to rebuild the db with a subset of all possible
operations if needed. For example, you may only be interested in
the last hours data in table location.

Important note- A corrupted DB file must be moved out of the way before
kambdb_recover is executed.

14. Known Limitations

The Berkeley DB does not nativly support an autoincrement (or sequence)
mechanism. Consequently, this version does not support surragate keys
in dbschema. These are the id columns in the tables.