.. _extending:

Extending Envoy for custom use cases

The Envoy architecture makes it fairly easily extensible via a variety of different extension types including:

• :ref:Access loggers <arch_overview_access_logs>
• :ref:Access log filters <arch_overview_access_log_filters>
• :ref:Clusters <arch_overview_service_discovery>
• :ref:Listener filters <arch_overview_listener_filters>
• :ref:Network filters <arch_overview_network_filters>
• :ref:HTTP filters <arch_overview_http_filters>
• :ref:gRPC credential providers <arch_overview_grpc>
• :ref:Health checkers <arch_overview_health_checking>
• :ref:Resource monitors <arch_overview_overload_manager>
• :ref:Retry implementations <arch_overview_http_routing_retry>
• :ref:Stat sinks <arch_overview_statistics>
• :ref:Tracers <arch_overview_tracing>
• :ref:Request ID <arch_overview_tracing>
• Transport sockets
• BoringSSL private key methods
• :ref:Watchdog action <envoy_v3_api_msg_config.bootstrap.v3.Watchdog.WatchdogAction>
• :ref:Internal redirect policy <envoy_v3_api_field_config.route.v3.InternalRedirectPolicy.predicates>
• :ref:Compression libraries <arch_overview_compression_libraries>
• :ref:Bootstrap extensions <envoy_v3_api_field_config.bootstrap.v3.Bootstrap.bootstrap_extensions>
• :ref:Fatal actions <envoy_v3_api_field_config.bootstrap.v3.Bootstrap.fatal_actions>
• :ref:Formatters <config_access_log_command_operators>
• :ref:Connection balance extensions <envoy_v3_api_field_config.listener.v3.Listener.ConnectionBalanceConfig.extend_balance>

As of this writing there is no high level extension developer documentation. The :repo:existing extensions <source/extensions> are a good way to learn what is possible.

An example of how to add a network filter and structure the repository and build dependencies can be found at envoy-filter-example <https://github.com/envoyproxy/envoy-filter-example>_.