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Qorb

Qorb is a work-in-progress Connection Pooling library, heavily inspired by the "Cueball" connection pooling library.

Overview

Qorb's main interface is the link:Pool object.

This pool relies on two interfaces that can be customized:

• The link:Resolver interface identifies how to locate backend servers. link:DnsResolver provides a default implementation which queries DNS entries to access the set of backends.
• The link:Connector interface identifies how to connect to a single backend. Within this method, the connect method is essential, but the is_valid and on_recycle methods can optionally be implemented to perform (respectively) health checks and perform cleanup actions before used connections are returned to the pool.

Examples

To get up and running with a client, server, and DNS system, link:examples/README.adoc[refer to the README in the examples directory].

In particular, the link:examples/tcp_echo_workload/main.rs[TCP echo workload] example demonstrates how to create a connection pool with a custom TCP connection.

This provides a setup for generating a workload to an arbitrary number of backends, and then walks through the tools to inspect the connection pool.

Terminology

• Service: A named entity which refers to a program that is running with one or more instantiations as distinct backends.
• Backend: An specific instance of a program running a service. Each backend should provide the same interface, such that a client can access any one of the backends implementing a service interchangeably.
• Resolver: A client-side entity responsible for translating service name into backend location. A common example of a resolver is "DNS".
• Slot: An allocated commitment to create a connection to a particular backend. A slot may be "connected" if the connection has been established, or "connecting" if the backend hasn't yet been reached.
• Slot Set: A group of slots all attempting to access a particular backend. The number of slots which are allocated for each backend is controlled by qorb, but may be adjusted via user-configurable policy.
• Pool: The a group of connections to one or more backends, from which a client of qorb can "claim" a connection. The pool manages resolvers, finds backends, creates slots for backends, and vends out connected slots to clients.

TODO List

Things I'd like to do before getting more eyes on this:

• Add dtrace probes
• Add a baseline test suite