32. Configuration File Shortcuts¶
This appendix describes features that AMPS provides for simplifying configuration.
AMPS Configuration File Special Characters¶
In AMPS there are a few special characters that you should be aware of when creating your configuration file. These characters can provide some handy shortcuts and make configuration creation easier, but you should also be aware of them so as not to introduce errors.
State of the World File Name¶
When specifying the file for a State of the World database, using the
%n
string in the file name specifies that the AMPS server will use
the message type and topic name in that position to create a unique
file name. The example below shows how to use this in the AMPS
configuration file.
<SOW>
<Topic>
<Topic>Customers</Topic>
<FileName>./sow/%n.sow</FileName>
<MessageType>json</MessageType>
<Key>/customerId</Key>
</Topic>
</SOW>
SOW file name tokens used in configuration file
Log Rotation Name¶
When specifying an AMPS log file which has RotationThreshold
specified, using the %n
string in the log file name is a useful
mechanism for ensuring the name of the log file is unique and
sequential. The example below shows a file name token replacement
in the AMPS configuration file.
<Logging>
<Target>
<Protocol>file</Protocol>
<Level>info</Level>
<FileName>log/log-%n.log</FileName>
<RotationThreshold>2G</RotationThreshold>
</Target>
</Logging>
Log file name used in configuration file
In the above example, a log file will be created in the AMPSDIR/log/
directory. The first time this file is created, it will be named
log-1.log
. Once the log file reaches the RotationThreshold
limit
of 2G, the previous log file will be saved, and the new log file name
will be incremented by one. Thus, the next log file will be named
AMPSDIR/log/log-2.log
.
Dates¶
AMPS allows administrators to use date based file names when specifying the file name in the configuration, as demonstrated in the example below.
<Logging>
<Target>
<Protocol>file</Protocol>
<Level>info</Level>
<FileName>
log/log-%Y-%m-%dT%H%M%S.log
</FileName>
<RotationThreshold>2G</RotationThreshold>
</Target>
</Logging>
Date tokens used in configuration file
In the above example, a log file will be created in the $AMPSDIR/log
named 2011-01-01-120000.log
if the log was created at noon on
January 1, 2011.
AMPS provides full support for the date tokens provided by the standard
strftime function, with the exception of %n
, as described above. The
following table shows some of the most commonly used tokens:
Token | Description | Example |
---|---|---|
%a | Short weekday name | Fri |
%A | Full weekday name | Friday |
%b | Short month name | Feb |
%B | Full month name | February |
%c | Simple date and time | Fri Feb 14 17:25:00 2014 |
%C | Century | 20 |
%d | Day of the month (leading zero if necessary) | 05 |
%D | Short date format (MM/DD/YY) | 02/20/14 |
%e | Day of the month (leading space if necessary) | 5 |
%F | Short date format (YYYY-MM-DD) | 2014-02-20 |
%H | Hour (00-23) | 17 |
%I | Hour (00-12) | 05 |
%j | Day of the year (001-366) | 051 |
%m | Month (01-12) | 02 |
%p | AM or PM | PM |
%r | Current time, 12 hour format | 05:25:00 pm |
%R | Current time, 24 hour format | 17:25 |
%T | ISO 8601 Time format | 17:25:00 |
%u | ISO 8601 day of the week (1-7, Monday = 1) | 5 |
%V | ISO 8601 week number (00-53) | 07 |
%y | Year, last two digits | 14 |
%Y | Year, four digits | 2014 |
%Z | Timezone name or abbreviation (blank if undetermined) | PST |
Using Units in the Configuration¶
To make configuration easy, AMPS permits the use of units to expand
values. For example, if a time interval is measured in seconds, then the
letter s
can be appended to the value. For example, the following
SOW topic definition uses the Expiration
tag to set the record
expiration to 86400 seconds (one day).
<SOW>
<Topic>
...
<Expiration>86400s</Expiration>
...
</Topic>
</SOW>
Expiration using seconds
An even easier way to specify an expiration of one day is to use the
following Expiration
:
<SOW>
<Topic>
...
<Expiration>1d</Expiration>
...
</Topic>
</SOW>
Expiration using days
The table below shows a listing of the time units AMPS supports in the configuration file.
Units | Description |
---|---|
ns |
nanoseconds |
us |
microseconds |
ms |
milliseconds |
s |
seconds |
m |
minutes |
h |
hours |
d |
days |
w |
weeks |
AMPS configuration supports a similar mechanism for byte-based units when specifying sizes in the configuration file. The table below shows a listing of the byte units AMPS supports in the configuration file.
Units | Description |
---|---|
kb |
kilobytes |
mb |
megabytes |
gb |
gigabytes |
tb |
terabytes |
Dealing with large numbers in AMPS configuration can also be simplified
by using common exponent values to handle raw values. This means that
instead of having to input 10000000
to represent ten million, a user
can input 10M
. The table below contains a list of the exponents
supported.
Units | Description |
---|---|
k | 103 - thousand |
M | 106 - million |
Tip
To make it easier for users to remember the units, AMPS interval and byte units are not case sensitive.
Environment Variables in AMPS Configuration¶
AMPS configuration also allows for environment variables to be used as
part of the data when specifying a configuration file. These variables
can be set in the environment when AMPS starts, or passed to AMPS using
the -D
option on the command line.
If a global system variable is commonly used in an organization, then it
may be useful to define this in one location and re-use it across
multiple AMPS installations or applications. AMPS will replace any token
wrapped in ${}
with the environment variable defined in the current
user operating system environment. The example below demonstrates how
the environment variable ENV_LOG
is used to define a global
environment variable for the location of the host logging.
<Logging>
<Target>
<Protocol>file</Protocol>
<FileName>${ENV_LOG}</FileName>
<Level>info</Level>
<RotationThreshold>2G</RotationThreshold>
</Target>
</Logging>
Environment variables in AMPS configuration
Internal Environment Variables¶
In addition to supporting custom environment variables, AMPS includes a set of environment variables automatically populated by the server.
These variables are listed below:
Variable Name | Contains |
---|---|
AMPS_CONFIG_DIRECTORY |
Directory in which the configuration file used to start AMPS is located. |
AMPS_CONFIG_PATH |
Full path to the configuration file used to start AMPS, including the file name. |
AMPS_VERSION |
Full version number of the AMPS server. |
When AMPS processes the configuration file, AMPS expands these variables just as though they were set in the environment. For example, assume that AMPS was started with the following command at the command prompt:
%>./ampServer ../amps/config/config.xml
Given this command, the log file configuration option shown in
the example below can be used to instruct AMPS to create the log files
in the same parent directory as the configuration file — in this case
../amps/config/logs/infoLog.log
.
<Logging>
<Target>
<Protocol>file</Protocol>
<FileName>${AMPS_CONFIG_DIRECTORY}/logs/infoLog.log</FileName>
<Level>info</Level>
<RotationThreshold>2G</RotationThreshold>
</Target>
</Logging>
AMPS_CONFIG_DIRECTORY environment variable example