A tracepoint is basically a non-breaking remote breakpoint. Tracepoints differ from ordinary breakpoints in two ways. First, it doesn’t pause the code execution but just takes a screenshot of the variables when the code hits that line. Second, it’s integrated with Thundra’s distributed technology enabling the connection between several tracepoints in the same transaction.
When you put a tracepoint on a line, the Thundra agent on the corresponding remote application takes a snapshot of the local variables on that point when the execution passes from that point and sends them as tracepoint snapshot events back to the IntelliJ IDEA.
You can see the existing tracepoint associated with each application instance under the corresponding instance section on the main Thundra tool window: