Probe Vue - Description

Description

ProbeVue provides a series of probe point specifications that are potential events that can be probed. A script written in the Vue language allows the user to define a probe that is a block of code called an action block that will run when those events occur on the system. The execution of the action block can be limited to specific events by use of a conditional statement placed on the probe called a predicate. The code in the action block follows a C-like syntax with a limited set of built in functions.

The following is an example of a probe that is defined for whenever a process with a PID of 123456 enters the read system call. When that event happens this script will call the built-in printf function to print a message to its output trace buffers. The first line in the action block is a C-style comment and therefore will not execute in the ProbeVue environment.

@@syscall:*:read:entry when ( __pid == 123456) { /* This is a comment: The process with a PID of 123456 has called read; */ printf("read system call entered.\n"); }

Probes like the above sample can be written and run without the extensive testing normally required of a production system. The ProbeVue environment protects the user from errant code or resource hungry tracing frequently seen with previous IBM tracing tools. The runtime compile feature of ProbeVue provides a powerful ad-hoc environment for data gathering.