strace - Trace system calls and signals. A diagnostic, debugging and instructional userspace utility.

Raygun - Raygun gives developers meaningful insights into problems affecting their applications. Discover issues - Understand the problem - Fix things faster.

perf - Perf is a simple app monitoring solution paired with meaningful alerts.

Sentry.io - From error tracking to performance monitoring, developers can see what actually matters, solve quicker, and learn continuously about their applications - from the frontend to the backend.

DTrace - DTrace is a performance analysis and troubleshooting tool for Solaris, Mac OS X and FreeBSD.

Kafka - Apache Kafka is publish-subscribe messaging rethought as a distributed commit log.