Make zenoh router configurable using envar

README.md

@@ -45,7 +45,7 @@ source install/setup.bash
 > Note: Manually launching zenoh router won't be necessary in the future.
 ```bash
 # terminal 1
-ros2 run rmw_zenoh_cpp init_rmw_zenoh_router
+ros2 run rmw_zenoh_cpp rmw_zenohd
 ```
 
 > Note: Without the zenoh router, nodes will not be able to discover each other since multicast discovery is disabled by default in the node's session config. Instead, nodes will receive discovery information about other peers via the zenoh router's gossip functionality. See more information on the session configs [below](#config).
@@ -68,26 +68,36 @@ ros2 run demo_nodes_cpp listener
 The listener node should start receiving messages over the `/chatter` topic.
 > Note: Ignore all the warning printouts.
 
-### Graph introspection
-Presently we only support limited `ros2cli` commands to introspect the ROS graph such as `ros2 node list` and `ros2 topic list`.
+## Configuration
+`rmw_zenoh` relies on separate configurations files to configure the Zenoh `router` and `session` respectively.
+To understand more about `routers` and `sessions`, see [Zenoh documentation](https://zenoh.io/docs/getting-started/deployment/).
+For more information on the topology of Zenoh adopted in `rmw_zenoh`, please see [Design](#design).
+Default configuration files are used by `rmw_zenoh` however certain environment variables may be set to provide absolute paths to custom configuration files.
+The table below summarizes the default files and the environment variables for the `router` and `session`.
+For a complete list of configurable parameters, see [zenoh/DEFAULT_CONFIG.json5](https://github.com/eclipse-zenoh/zenoh/blob/main/DEFAULT_CONFIG.json5).
 
-## Config
-The [default configuration](rmw_zenoh_cpp/config/DEFAULT_RMW_ZENOH_SESSION_CONFIG.json5) sets up the zenoh sessions with the following main characteristics:
+|         |                                            Default config                                            |   Envar for custom config  |
+|---------|:----------------------------------------------------------------------------------------------------:|:--------------------------:|
+| Router  |  [DEFAULT_RMW_ZENOH_ROUTER_CONFIG.json5](rmw_zenoh_cpp/config/DEFAULT_RMW_ZENOH_ROUTER_CONFIG.json5)  |  `ZENOH_ROUTER_CONFIG_URI` |
+| Session | [DEFAULT_RMW_ZENOH_SESSION_CONFIG.json5](rmw_zenoh_cpp/config/DEFAULT_RMW_ZENOH_SESSION_CONFIG.json5) | `ZENOH_SESSION_CONFIG_URI` |
 
-Table:
-| Zenoh Config | Default |
-| :---:   | :---: |
-| udp_multicast | disabled |
-| gossip scouting | enabled |
-| connect | tcp/localhost:7447 |
-
-This assumes that there is a `zenohd` running in the system at port 7447.
-A custom configuration may be provided by setting the `RMW_ZENOH_CONFIG_FILE` environment variable to point to a custom zenoh configuration file.
+For example, to set the path to a custom `router` configuration file,
+```bash
+export ZENOH_ROUTER_CONFIG_URI=$HOME/MY_ZENOH_ROUTER_CONFIG.json5
+```
 
+### Connecting multiple hosts
+By default, all discovery traffic is local per host, where the host is the PC running a Zenoh `router`.
+To bridge communications across two hosts, the `router` configuration for one the hosts must be updated to connect to the other `router` at startup.
+This is done by specifying an endpoint in host's `router` configuration file to as seen below.
+In this example, the `router` will connect to the `router` running on a second host with IP address `192.168.1.1` and port `7447`.
+
+```json
+{
+  connect: {
+    endpoints: ["tcp/192.168.1.1:7447"],
+  },
+}
+```
 
-## TODO Features
-- [x] Publisher
-- [x] Subscription
-- [ ] Client
-- [ ] Service
-- [ ] Graph introspection
+> Note: To connect multiple hosts, include the endpoints of all routers in the network.

rmw_zenoh_cpp/CMakeLists.txt

@@ -95,16 +95,21 @@ install(
   DESTINATION share/${PROJECT_NAME}
 )
 
-add_executable(init_rmw_zenoh_router apps/init_rmw_zenoh_router.cpp)
+add_executable(rmw_zenohd
+  src/zenohd/main.cpp
+  src/detail/zenoh_config.cpp
+)
 
-target_link_libraries(init_rmw_zenoh_router
+target_link_libraries(rmw_zenohd
   PRIVATE
     ament_index_cpp::ament_index_cpp
+    rcutils::rcutils
+    rmw::rmw
     zenohc::lib
 )
 
 install(
-  TARGETS init_rmw_zenoh_router
+  TARGETS rmw_zenohd
   DESTINATION lib/${PROJECT_NAME}
 )
 

rmw_zenoh_cpp/src/detail/zenoh_config.cpp

@@ -22,48 +22,70 @@
 #include <ament_index_cpp/get_package_share_directory.hpp>
 #include <rmw/impl/cpp/macros.hpp>
 
-#include "identifier.hpp"
-
+///==============================================================================
 namespace
 {
+/// Map the configurable entity to a pair of environment variable name that
+/// stores the absolute path to the Zenoh config and the default config filename.
+/// Note: The default config file should be located within rmw_zenoh_cpp/config/.
+static const std::unordered_map<ConfigurableEntity,
+  std::pair<const char *, const char *>> envar_map = {
+  {ConfigurableEntity::Session,
+    {"ZENOH_SESSION_CONFIG_URI", "DEFAULT_RMW_ZENOH_SESSION_CONFIG.json5"}},
+  {ConfigurableEntity::Router, {"ZENOH_ROUTER_CONFIG_URI", "DEFAULT_RMW_ZENOH_ROUTER_CONFIG.json5"}}
+};
 
-/// Env var to set the path to the zenoh configuration file.
-static constexpr const char * kZenohConfigFileEnvVar = "RMW_ZENOH_CONFIG_FILE";
-/// The name of the default configuration file for the default zenoh session configuration.
-static constexpr const char * const kDefaultZenohConfigFileName =
-  "DEFAULT_RMW_ZENOH_SESSION_CONFIG.json5";
-
-}  // namespace
-
-rmw_ret_t get_z_config(z_owned_config_t * config)
+rmw_ret_t _get_z_config(
+  const char * envar_name,
+  const char * default_uri,
+  z_owned_config_t * config)
 {
-  const char * zenoh_config_path;
+  const char * configured_uri;
+  const char * envar_uri;
   // Get the path to the zenoh configuration file from the environment variable.
-  if (NULL != rcutils_get_env(kZenohConfigFileEnvVar, &zenoh_config_path)) {
+  if (NULL != rcutils_get_env(envar_name, &envar_uri)) {
     // NULL is returned if everything is ok.
     RCUTILS_LOG_ERROR_NAMED(
-      "ZenohConfiguration", "Env Var '%s' can't be read.", kZenohConfigFileEnvVar);
+      "rmw_zenoh_cpp", "Envar %s cannot be read.", envar_name);
     return RMW_RET_ERROR;
   }
-
   // If the environment variable contains a path to a file, try to read the configuration from it.
-  if (zenoh_config_path[0] != '\0') {
+  if (envar_uri[0] != '\0') {
     // If the environment variable is set, try to read the configuration from the file.
-    *config = zc_config_from_file(zenoh_config_path);
+    *config = zc_config_from_file(envar_uri);
+    configured_uri = envar_uri;
   } else {
     // If the environment variable is not set use internal configuration
-    static const std::string path_to_config_folder =
-      ament_index_cpp::get_package_share_directory(rmw_zenoh_identifier) + "/config/";
-    const std::string default_zconfig_path = path_to_config_folder + kDefaultZenohConfigFileName;
-    *config = zc_config_from_file(default_zconfig_path.c_str());
+    *config = zc_config_from_file(default_uri);
+    configured_uri = default_uri;
   }
-
   // Verify that the configuration is valid.
   if (!z_config_check(config)) {
     RCUTILS_LOG_ERROR_NAMED(
-      "ZenohConfiguration",
-      "Configuration is not valid. Please check the zenoh configuration file.");
+      "rmw_zenoh_cpp",
+      "Invalid configuration file %s", configured_uri);
     return RMW_RET_ERROR;
   }
+  RCUTILS_LOG_DEBUG_NAMED(
+    "rmw_zenoh_cpp",
+    "configured using configuration file %s", configured_uri);
   return RMW_RET_OK;
 }
+}  // namespace
+
+///==============================================================================
+rmw_ret_t get_z_config(const ConfigurableEntity & entity, z_owned_config_t * config)
+{
+  auto envar_map_it = envar_map.find(entity);
+  if (envar_map_it == envar_map.end()) {
+    RCUTILS_LOG_ERROR_NAMED(
+      "rmw_zenoh_cpp", "get_z_config called with invalid ConfigurableEntity.");
+    return RMW_RET_ERROR;
+  }
+  // Get the absolute path to the default configuration file.
+  static const std::string path_to_config_folder =
+    ament_index_cpp::get_package_share_directory("rmw_zenoh_cpp") + "/config/";
+  const std::string default_config_path = path_to_config_folder + envar_map_it->second.second;
+
+  return _get_z_config(envar_map_it->second.first, default_config_path.c_str(), config);
+}

rmw_zenoh_cpp/src/detail/zenoh_config.hpp

@@ -17,18 +17,30 @@
 
 #include <zenoh.h>
 
+#include <unordered_map>
+#include <utility>
+
 #include "rmw/ret_types.h"
 
-/// Get the zenoh configuration for a session.
+///==============================================================================
+enum class ConfigurableEntity : uint8_t
+{
+  Invalid = 0,
+  Session,
+  Router
+};
+
+///==============================================================================
+/// Get the zenoh configuration for a configurable entity.
 /// @details The behavior is as follows:
-///   - If the environment variable `RMW_ZENOH_CONFIG_FILE` is set, it will
-///     be used as the path to the zenoh configuration file.
-///     - In case there is an error reading the file, the internal configuration will be used.
-///   - If the environment variable `RMW_ZENOH_CONFIG_FILE` is not set, the
-///     configuration will be read from the internal configuration.
-///   - If internal configuration is not available, a zenoh default configuration is used.
+///   - If the environment variable for the entity is set, the z_owned_config_t
+///     is configured as per the configuration file retrieved.
+///   - If the environment variable is not set, the z_owned_config_t
+///     is configured using the rmw_zenoh default configuration file.
+/// @param entity The zenoh entity to be configured.
 /// @param config The zenoh configuration to be filled.
 /// @returns `RMW_RET_OK` if the configuration was successfully loaded.
-rmw_ret_t get_z_config(z_owned_config_t * config);
+[[nodiscard]]
+rmw_ret_t get_z_config(const ConfigurableEntity & entity, z_owned_config_t * config);
 
 #endif  // DETAIL__ZENOH_CONFIG_HPP_

rmw_zenoh_cpp/src/rmw_init.cpp

@@ -148,8 +148,8 @@ rmw_init(const rmw_init_options_t * options, rmw_context_t * context)
 
   // Initialize the zenoh configuration.
   z_owned_config_t config;
-  if ((ret = get_z_config(&config)) != RMW_RET_OK) {
-    RMW_SET_ERROR_MSG("Error setting up zenoh configuration for the session.");
+  if ((ret = get_z_config(ConfigurableEntity::Session, &config)) != RMW_RET_OK) {
+    RMW_SET_ERROR_MSG("Error configuring Zenoh session.");
     return ret;
   }
 

rmw_zenoh_cpp/apps/init_rmw_zenoh_router.cpp → rmw_zenoh_cpp/src/zenohd/main.cpp

@@ -31,6 +31,10 @@
 
 #include <ament_index_cpp/get_package_share_directory.hpp>
 
+#include "../detail/zenoh_config.hpp"
+
+#include "rmw/error_handling.h"
+
 static bool running = true;
 
 class KeyboardReader final
@@ -169,13 +173,13 @@ int main(int argc, char ** argv)
   (void)argc;
   (void)argv;
 
-  static const char * RMW_ZENOH_IDENTIFIER = "rmw_zenoh_cpp";
-  static const char * ZENOH_ROUTER_CONFIG_NAME = "DEFAULT_RMW_ZENOH_ROUTER_CONFIG.json5";
-  const std::string zenoh_router_config_path =
-    ament_index_cpp::get_package_share_directory(RMW_ZENOH_IDENTIFIER) +
-    "/config/" + std::string(ZENOH_ROUTER_CONFIG_NAME);
+  // Initialize the zenoh configuration for the router.
+  z_owned_config_t config;
+  if ((get_z_config(ConfigurableEntity::Router, &config)) != RMW_RET_OK) {
+    RMW_SET_ERROR_MSG("Error configuring Zenoh router.");
+    return 1;
+  }
 
-  z_owned_config_t config = zc_config_from_file(zenoh_router_config_path.c_str());
   z_owned_session_t s = z_open(z_move(config));
   if (!z_check(s)) {
     printf("Unable to open router session!\n");