Threading model

Envoy uses a single process with multiple threads architecture. A single master thread controls various sporadic coordination tasks while some number of worker threads perform listening, filtering, and forwarding. Once a connection is accepted by a listener, the connection spends the rest of its lifetime bound to a single worker thread. This allows the majority of Envoy to be largely single threaded (embarrassingly parallel) with a small amount of more complex code handling coordination between the worker threads. Generally Envoy is written to be 100% non-blocking and for most workloads we recommend configuring the number of worker threads to be equal to the number of hardware threads on the machine.