Patterns

Simplified Pattern Syntax

The Simplified pattern syntax is available in boom because it provides a more readable form. In addition it allows defining names for custom variables. In most cases it is enough to have simple patterns to match incoming indications. On the other side, this format has sensitive limitations and might be not sufficient for real complex text processing.

Hint: The rules by which boom assigns strings to variables behaves like HP Operations Manager's algorithm. The HP Operations manager's pattern matching algorithm always scans both the input line and the pattern definition (including alternative expressions) from left to right. <*> expressions are assigned as few characters as possible. <#>, <@> and <_> expressions are assigned as many characters as possible (greedy).
Example: In matching the pattern <*.var1><*.var2> against the string "test", var1 will be assigned an empty string, var2 will be assigned the string "test".

It is possible to have inner capturing groups to parse additional variables from extracted parts.
For Example:

Incoming text:

--- 01/01/2008 x--x Error404 Page not found

<*><[Error<[<#.n><_><*.msg>]>].complete>

<$complete>=Error404 Page not found
<$dummy1>=404 Page not found
<$n>=404
<$msg>=Page not found
	  

The next example shows the use case where the goal of filtering is to match messages for all users except the following: {"root", "user1", and "user2"}.

The complexity of this task is that there are also users available with names like: "user10", "user112".

The proposed pattern do this job by using sub-pattern is:

[user[1|2]] combined with <![root].from>
	  

Java Patterns

Java patterns are used for the "Search Text" attribute of Indication or Hybrid Policies and a couple of bundled Java Monitors (Opm and LogFileMonitor). The full description of a Java pattern format can be found on Sun's Java Platform API page (see Pattern class).

The boom Java patterns also support variables but in a slightly different way than the 'Simplified Pattern Syntax'. By using the Java patterns you can not define custom names but you can use predefined names: <$var1>,<$var2>,<$var3>...

Hint: The rule by which the Java pattern matching algorithm assigns strings to variables is always greedy (expressions are assigned as many characters as possible).

Short overview about the Java Pattern Syntax: