Add 'best available' QoS policies

rmw/include/rmw/qos_profiles.h

@@ -100,6 +100,32 @@ static const rmw_qos_profile_t rmw_qos_profile_system_default =
   false
 };
 
+/// Match majority of endpoints currently available while maintaining the highest level of service
+/**
+ * Reliability, durability, deadline, liveliness, and liveliness lease duration policies will be
+ * chosen at the time of creating a subscription or publisher.
+ *
+ * The actual QoS policy can be retrieved after the endpoint is created with
+ * `rmw_get_subscriptions_info_by_topic` or `rmw_get_publishers_info_by_topic`.
+ *
+ * The middleware is not expected to update policies after creating a subscription or
+ * publisher, even if one or more policies are incompatible with newly discovered endpoints.
+ * Therefore, this profile should be used with care since non-deterministic behavior
+ * can occur due to races with discovery.
+ */
+static const rmw_qos_profile_t rmw_qos_profile_best_available =
+{
+  RMW_QOS_POLICY_HISTORY_KEEP_LAST,
+  10,
+  RMW_QOS_POLICY_RELIABILITY_BEST_AVAILABLE,
+  RMW_QOS_POLICY_DURABILITY_BEST_AVAILABLE,
+  RMW_QOS_DEADLINE_BEST_AVAILABLE,
+  RMW_QOS_LIFESPAN_DEFAULT,
+  RMW_QOS_POLICY_LIVELINESS_BEST_AVAILABLE,
+  RMW_QOS_LIVELINESS_LEASE_DURATION_BEST_AVAILABLE,
+  false
+};
+
 static const rmw_qos_profile_t rmw_qos_profile_unknown =
 {
   RMW_QOS_POLICY_HISTORY_UNKNOWN,

rmw/include/rmw/types.h

@@ -381,6 +381,22 @@ typedef enum RMW_PUBLIC_TYPE rmw_qos_reliability_policy_e
   /// Attempt to deliver samples, but some may be lost if the network is not robust
   RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT,
 
+  /// Will match the majority of endpoints and use a reliable policy if possible
+  /**
+   * A policy will be chosen at the time of creating a subscription or publisher.
+   * A reliable policy will by chosen if it matches with all discovered endpoints,
+   * otherwise a best effort policy will be chosen.
+   *
+   * The actual QoS policy can be retrieved after the endpoint is created with
+   * `rmw_get_subscriptions_info_by_topic` or `rmw_get_publishers_info_by_topic`.
+   *
+   * The middleware is not expected to update the policy after creating a subscription or
+   * publisher, even if the chosen policy is incompatible with newly discovered endpoints.
+   * Therefore, this policy should be used with care since non-deterministic behavior
+   * can occur due to races with discovery.
+   */
+  RMW_QOS_POLICY_RELIABILITY_BEST_AVAILABLE,
+
   /// Reliability policy has not yet been set
   RMW_QOS_POLICY_RELIABILITY_UNKNOWN
 } rmw_qos_reliability_policy_t;
@@ -413,6 +429,25 @@ typedef enum RMW_PUBLIC_TYPE rmw_qos_durability_policy_e
   /// Samples are not persistent
   RMW_QOS_POLICY_DURABILITY_VOLATILE,
 
+  /// Will match the majority of endpoints and use a transient local policy if possible
+  /**
+   * A policy will be chosen at the time of creating a subscription or publisher.
+   * A transient local policy will by chosen if it matches with all discovered endpoints,
+   * otherwise a volatile policy will be chosen.
+   *
+   * In the case that a volatile policy is chosen for a subscription, any messages sent before
+   * the subscription was created by transient local publishers will not be received.
+   *
+   * The actual QoS policy can be retrieved after the endpoint is created with
+   * `rmw_get_subscriptions_info_by_topic` or `rmw_get_publishers_info_by_topic`.
+   *
+   * The middleware is not expected to update the policy after creating a subscription or
+   * publisher, even if the chosen policy is incompatible with newly discovered endpoints.
+   * Therefore, this policy should be used with care since non-deterministic behavior
+   * can occur due to races with discovery.
+   */
+  RMW_QOS_POLICY_DURABILITY_BEST_AVAILABLE,
+
   /// Durability policy has not yet been set
   RMW_QOS_POLICY_DURABILITY_UNKNOWN
 } rmw_qos_durability_policy_t;
@@ -452,18 +487,72 @@ typedef enum RMW_PUBLIC_TYPE rmw_qos_liveliness_policy_e
   // Using `3` for backwards compatibility.
   RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC = 3,
 
+  /// Will match the majority of endpoints and use a manual by topic policy if possible
+  /**
+   * A policy will be chosen at the time of creating a subscription or publisher.
+   * A manual by topic policy will by chosen if it matches with all discovered endpoints,
+   * otherwise an automatic policy will be chosen.
+   *
+   * The actual QoS policy can be retrieved after the endpoint is created with
+   * `rmw_get_subscriptions_info_by_topic` or `rmw_get_publishers_info_by_topic`.
+   *
+   * The middleware is not expected to update the policy after creating a subscription or
+   * publisher, even if the chosen policy is incompatible with newly discovered endpoints.
+   * Therefore, this policy should be used with care since non-deterministic behavior
+   * can occur due to races with discovery.
+   */
+  RMW_QOS_POLICY_LIVELINESS_BEST_AVAILABLE = 4,
+
   /// Liveliness policy has not yet been set
-  RMW_QOS_POLICY_LIVELINESS_UNKNOWN = 4
+  RMW_QOS_POLICY_LIVELINESS_UNKNOWN = 5
 } rmw_qos_liveliness_policy_t;
 
 /// QoS Deadline default.
 #define RMW_QOS_DEADLINE_DEFAULT RMW_DURATION_UNSPECIFIED
+/// Will match the majority of endpoints while maintaining as strict a policy as possible
+/**
+ * Value is RMW_DURATION_INFINITE - 1.
+ *
+ * A policy will be chosen at the time of creating a subscription or publisher.
+ * For a subscription, the deadline will be the maximum value of all discovered publisher
+ * deadlines.
+ * For a publisher, the deadline will be the minimum value of all discovered subscription
+ * deadlines.
+ *
+ * The actual QoS policy can be retrieved after the endpoint is created with
+ * `rmw_get_subscriptions_info_by_topic` or `rmw_get_publishers_info_by_topic`.
+ *
+ * The middleware is not expected to update the policy after creating a subscription or
+ * publisher, even if the chosen policy is incompatible with newly discovered endpoints.
+ * Therefore, this policy should be used with care since non-deterministic behavior
+ * can occur due to races with discovery.
+ */
+#define RMW_QOS_DEADLINE_BEST_AVAILABLE {9223372036LL, 854775806LL}
 
 /// QoS Lifespan default.
 #define RMW_QOS_LIFESPAN_DEFAULT RMW_DURATION_UNSPECIFIED
 
 /// QoS Liveliness lease duration default.
 #define RMW_QOS_LIVELINESS_LEASE_DURATION_DEFAULT RMW_DURATION_UNSPECIFIED
+/// Will match the majority of endpoints while maintaining as strict a policy as possible
+/**
+ * Value is RMW_DURATION_INFINITE - 1.
+ *
+ * A policy will be chosen at the time of creating a subscription or publisher.
+ * For a subscription, the lease duration will be the maximum value of all discovered publisher
+ * lease durations.
+ * For a publisher, the lease duration will be the minimum value of all discovered subscription
+ * lease durations.
+ *
+ * The actual QoS policy can be retrieved after the endpoint is created with
+ * `rmw_get_subscriptions_info_by_topic` or `rmw_get_publishers_info_by_topic`.
+ *
+ * The middleware is not expected to update the policy after creating a subscription or
+ * publisher, even if the chosen policy is incompatible with newly discovered endpoints.
+ * Therefore, this policy should be used with care since non-deterministic behavior
+ * can occur due to races with discovery.
+ */
+#define RMW_QOS_LIVELINESS_LEASE_DURATION_BEST_AVAILABLE {9223372036LL, 854775806LL}
 
 /// ROS MiddleWare quality of service profile.
 typedef struct RMW_PUBLIC_TYPE rmw_qos_profile_s

rmw/src/qos_string_conversions.c

@@ -53,6 +53,8 @@ rmw_qos_durability_policy_to_str(enum rmw_qos_durability_policy_e value)
       return "transient_local";
     case RMW_QOS_POLICY_DURABILITY_VOLATILE:
       return "volatile";
+    case RMW_QOS_POLICY_DURABILITY_BEST_AVAILABLE:
+      return "best_available";
     case RMW_QOS_POLICY_DURABILITY_UNKNOWN:  // fallthrough
     default:
       return NULL;
@@ -85,6 +87,8 @@ rmw_qos_liveliness_policy_to_str(enum rmw_qos_liveliness_policy_e value)
       return "automatic";
     case RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC:
       return "manual_by_topic";
+    case RMW_QOS_POLICY_LIVELINESS_BEST_AVAILABLE:
+      return "best_available";
     case RMW_QOS_POLICY_LIVELINESS_UNKNOWN:  // fallthrough
     default:
       return NULL;
@@ -101,6 +105,8 @@ rmw_qos_reliability_policy_to_str(enum rmw_qos_reliability_policy_e value)
       return "reliable";
     case RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT:
       return "best_effort";
+    case RMW_QOS_POLICY_RELIABILITY_BEST_AVAILABLE:
+      return "best_available";
     case RMW_QOS_POLICY_RELIABILITY_UNKNOWN:  // fallthrough
     default:
       return NULL;
@@ -157,6 +163,9 @@ rmw_qos_durability_policy_from_str(const char * str)
   if (RMW_QOS_STREQ_WITH_LITERAL("volatile", str)) {
     return RMW_QOS_POLICY_DURABILITY_VOLATILE;
   }
+  if (RMW_QOS_STREQ_WITH_LITERAL("best_available", str)) {
+    return RMW_QOS_POLICY_DURABILITY_BEST_AVAILABLE;
+  }
   return RMW_QOS_POLICY_DURABILITY_UNKNOWN;
 }
 
@@ -189,6 +198,9 @@ rmw_qos_liveliness_policy_from_str(const char * str)
   if (RMW_QOS_STREQ_WITH_LITERAL("manual_by_topic", str)) {
     return RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC;
   }
+  if (RMW_QOS_STREQ_WITH_LITERAL("best_available", str)) {
+    return RMW_QOS_POLICY_LIVELINESS_BEST_AVAILABLE;
+  }
   return RMW_QOS_POLICY_LIVELINESS_UNKNOWN;
 }
 
@@ -205,5 +217,8 @@ rmw_qos_reliability_policy_from_str(const char * str)
   if (RMW_QOS_STREQ_WITH_LITERAL("best_effort", str)) {
     return RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT;
   }
+  if (RMW_QOS_STREQ_WITH_LITERAL("best_available", str)) {
+    return RMW_QOS_POLICY_RELIABILITY_BEST_AVAILABLE;
+  }
   return RMW_QOS_POLICY_RELIABILITY_UNKNOWN;
 }

rmw/test/test_qos_string_conversions.cpp

@@ -41,15 +41,18 @@ TEST(test_qos_policy_stringify, test_policy_values) {
   TEST_QOS_POLICY_VALUE_STRINGIFY(durability, RMW_QOS_POLICY_DURABILITY_SYSTEM_DEFAULT);
   TEST_QOS_POLICY_VALUE_STRINGIFY(durability, RMW_QOS_POLICY_DURABILITY_TRANSIENT_LOCAL);
   TEST_QOS_POLICY_VALUE_STRINGIFY(durability, RMW_QOS_POLICY_DURABILITY_VOLATILE);
+  TEST_QOS_POLICY_VALUE_STRINGIFY(durability, RMW_QOS_POLICY_DURABILITY_BEST_AVAILABLE);
   TEST_QOS_POLICY_VALUE_STRINGIFY(history, RMW_QOS_POLICY_HISTORY_KEEP_LAST);
   TEST_QOS_POLICY_VALUE_STRINGIFY(history, RMW_QOS_POLICY_HISTORY_KEEP_ALL);
   TEST_QOS_POLICY_VALUE_STRINGIFY(history, RMW_QOS_POLICY_HISTORY_SYSTEM_DEFAULT);
   TEST_QOS_POLICY_VALUE_STRINGIFY(liveliness, RMW_QOS_POLICY_LIVELINESS_AUTOMATIC);
   TEST_QOS_POLICY_VALUE_STRINGIFY(liveliness, RMW_QOS_POLICY_LIVELINESS_MANUAL_BY_TOPIC);
   TEST_QOS_POLICY_VALUE_STRINGIFY(liveliness, RMW_QOS_POLICY_LIVELINESS_SYSTEM_DEFAULT);
+  TEST_QOS_POLICY_VALUE_STRINGIFY(liveliness, RMW_QOS_POLICY_LIVELINESS_BEST_AVAILABLE);
   TEST_QOS_POLICY_VALUE_STRINGIFY(reliability, RMW_QOS_POLICY_RELIABILITY_BEST_EFFORT);
   TEST_QOS_POLICY_VALUE_STRINGIFY(reliability, RMW_QOS_POLICY_RELIABILITY_RELIABLE);
   TEST_QOS_POLICY_VALUE_STRINGIFY(reliability, RMW_QOS_POLICY_RELIABILITY_SYSTEM_DEFAULT);
+  TEST_QOS_POLICY_VALUE_STRINGIFY(reliability, RMW_QOS_POLICY_RELIABILITY_BEST_AVAILABLE);
 
   TEST_QOS_POLICY_STRINGIFY_CORNER_CASES(durability, DURABILITY);
   TEST_QOS_POLICY_STRINGIFY_CORNER_CASES(history, HISTORY);