ConDep
ConDep is a open source infrastructure configuration and deployment DSL (Domain Specific Language) specifically targeted to (but not limited to) the Windows Server platform. If your familiar with tools like Chef and Puppet, ConDep does very much the same, but with native support for Windows.
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Gerrit
A Web based code review and project management system for Git projects
linux windows osx open-source scm java
Instrumental
Instrumental is a real-time, high-scale application and server monitoring tool with intelligent alerts, a powerful query language, and free development accounts.
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KairosDB
KairosDB is a fast distributed scalable time series database written on top of Cassandra. RESTful JSON-based query/results. Includes flot-based visualization.
linux windows osx open-source metrics visualization java cassandra
SSH KeyBox
An open-source jump box solution with auditing capabilities
linux open-source cloud monitoring security java