Add message about available components to AgentDetails (#201)

This PR adds a new ComponentDetails type that allows agents to communicate metadata relating to the components available in the agent.
open-telemetry · Oct 31, 2024 · 75aa498 · 75aa498
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diff --git a/proto/opamp.proto b/proto/opamp.proto
@@ -91,6 +91,10 @@ message AgentToServer {
     // A custom message sent from an Agent to the Server.
     // Status: [Development]
     CustomMessage custom_message = 13;
+
+    // A message indicating the components that are available for configuration on the agent.
+    // Status: [Development]
+    AvailableComponents available_components = 14;
 }
 
 enum AgentToServerFlags {
@@ -145,6 +149,41 @@ message CertificateRequest {
     bytes csr = 1;
 }
 
+// AvailableComponents contains metadata relating to the components included
+// within the agent.
+// status: [Development]
+message AvailableComponents {
+    // A map of a unique component ID to details about the component.
+    // This may be omitted from the message if the server has not
+    // explicitly requested it be sent by setting the ReportAvailableComponents
+    // flag in the previous ServerToAgent message.
+    map<string, ComponentDetails> components = 1;
+
+    // Agent-calculated hash of the components.
+    // This hash should be included in every AvailableComponents message.
+    bytes hash = 2;
+ }
+
+message ComponentDetails {
+    // Extra key/value pairs that may be used to describe the component.
+    // The key/value pairs are according to semantic conventions, see:
+    // https://opentelemetry.io/docs/specs/semconv/
+    //
+    // For example, you may use the "code" semantic conventions to
+    // report the location of the code for a specific component:
+    // https://opentelemetry.io/docs/specs/semconv/attributes-registry/code/
+    //
+    // Or you may use the "vcs" semantic conventions to report the
+    // repository the component may be a part of:
+    // https://opentelemetry.io/docs/specs/semconv/attributes-registry/vcs/
+    repeated KeyValue metadata = 1;
+
+    // A map of component ID to sub components details. It can nest as deeply as needed to
+    // describe the underlying system.
+    map<string, ComponentDetails> sub_component_map = 2;
+}
+
+
 message ServerToAgent {
     // Agent instance uid. MUST match the instance_uid field in AgentToServer message.
     // Used for multiplexing messages from/to multiple agents using one message stream.
@@ -212,6 +251,13 @@ enum ServerToAgentFlags {
     // AgentToServer.sequence_num values.
     // The Server asks the Agent to report full status.
     ServerToAgentFlags_ReportFullState = 0x00000001;
+
+    // ReportAvailableComponents flag can be used by the server if the Agent did
+    // not include the full AvailableComponents message, but only the hash.
+    // If this flag is specified, the agent will populate available_components.components
+    // with a full description of the agent's components.
+    // Status: [Development]
+    ServerToAgentFlags_ReportAvailableComponents = 0x00000002;
 }
 
 enum ServerCapabilities {
@@ -663,6 +709,9 @@ enum AgentCapabilities {
     // know the configured interval and should not make assumptions about it.
     // Status: [Development]
     AgentCapabilities_ReportsHeartbeat               = 0x00002000;
+    // The agent will report AvailableComponents via the AgentToServer.available_components field.
+    // Status: [Development]
+    AgentCapabilities_ReportsAvailableComponents     = 0x00004000;
     // Add new capabilities here, continuing with the least significant unused bit.
 }
 

diff --git a/specification.md b/specification.md
@@ -40,6 +40,7 @@ Status: [Beta]
       - [AgentToServer.connection_settings_request](#agenttoserverconnection_settings_request)
       - [AgentToServer.custom_capabilities](#agenttoservercustom_capabilities)
       - [AgentToServer.custom_message](#agenttoservercustom_message)
+      - [AgentToServer.available_components](#agenttoserveravailable_components)
     + [ServerToAgent Message](#servertoagent-message)
       - [ServerToAgent.instance_uid](#servertoagentinstance_uid)
       - [ServerToAgent.error_response](#servertoagenterror_response)
@@ -173,6 +174,16 @@ Status: [Beta]
         * [Agent Connection](#agent-connection-1)
         * [FindServices](#findservices)
         * [FindServicesResponse](#findservicesresponse)
+  * [AvailableComponents Message](#availablecomponents-message)
+    + [AvailableComponents.components](#availablecomponentscomponents)
+      - [Examples](#examples-1)
+        * [OpenTelemetry Collector](#opentelemetry-collector)
+        * [Fluent Bit](#fluent-bit)
+    + [AvailableComponents.hash](#availablecomponentshash)
+    + [Initial Handshake](#initial-handshake)
+    + [ComponentDetails Message](#componentdetails-message)
+      - [ComponentDetails.metadata](#componentdetailsmetadata)
+      - [ComponentDetails.sub_component_map](#componentdetailssub_component_map)
 - [Connection Management](#connection-management)
   * [Establishing Connection](#establishing-connection)
   * [Closing Connection](#closing-connection)
@@ -505,6 +516,7 @@ message AgentToServer {
     ConnectionSettingsRequest connection_settings_request = 11; // Status: [Development]
     CustomCapabilities custom_capabilities = 12; // Status: [Development]
     CustomMessage custom_message = 13; // Status: [Development]
+    AvailableComponents available_components = 14; // Status: [Development]
 }
 ```
 
@@ -683,6 +695,15 @@ A custom message sent from an Agent to the Server.
 
 See [CustomMessage](#custommessage) message for details.
 
+##### AgentToServer.available_components
+
+Status: [Development]
+
+A message listing the components available in the Agent. This field SHOULD be
+reported if and only if the ReportsAvailableComponents capability is set.
+
+See [AvailableComponents](#availablecomponents-message) message for details.
+
 #### ServerToAgent Message
 
 The body of the WebSocket message or HTTP response body is a binary serialized
@@ -2870,6 +2891,166 @@ CustomMessage {
 }
 ```
 
+### AvailableComponents Message
+
+Status: [Development]
+
+Each Agent may be composed of multiple sub-components. These components may have
+their own associated metadata. The AvailableComponents message allows the Agent
+to inform the OpAMP server about which components the Agent contains.
+
+The AvailableComponents message has the following structure:
+
+```protobuf
+message AvailableComponents {
+    map<string, ComponentDetails> components = 1;
+    bytes hash = 2;
+ }
+```
+
+#### AvailableComponents.components
+
+The components field contains a map of a unique ID
+to a [ComponentsDetails](#componentdetails-message) message.
+This field may be omitted from the message if the OpAMP server has not explicitly
+requested it by setting the ReportAvailableComponents flag in the preceding
+ServerToAgent message.
+
+##### Examples
+
+###### OpenTelemetry Collector
+
+Here is an example of how ComponentDetails could hold information regarding the included
+components for a custom build of the [OpenTelemetry Collector](https://github.com/open-telemetry/opentelemetry-collector):
+
+```jsonc
+{
+  "receivers": {
+    "sub_component_map": {
+      "hostmetrics": {
+        "metadata": {
+          "code.namespace": "github.com/open-telemetry/opentelemetry-collector-contrib/receiver/hostmetricsreceiver@v0.107.0",
+        }
+      }
+    }
+  },
+  "processors": {
+    "sub_component_map": {
+      "batch": {
+        "metadata": {
+          "code.namespace": "go.opentelemetry.io/collector/processor/batchprocessor@v0.107.0"
+        }
+      },
+      "transform": {
+        "metadata": {
+          "code.namespace": "github.com/open-telemetry/opentelemetry-collector-contrib/processor/transformprocessor@v0.107.0"
+        }
+      },
+    }
+  },
+  "exporters": {
+    "sub_component_map": {
+      "nop": {
+        "metadata": {
+          "code.namespace": "go.opentelemetry.io/collector/exporter/nopexporter@v0.107.0"
+        }
+      }
+    }
+  }
+  // ... Component list continues for extensions and collectors ...
+}
+```
+
+###### Fluent Bit
+
+Here's an example of how Fluent Bit could report what components it has available.
+
+```jsonc
+{
+  "input": {
+    "sub_component_map": {
+      "tail": {}
+    }
+  },
+  "parser": {
+    "sub_component_map": {
+      "json": {}
+    }
+  },
+  "filter": {
+    "sub_component_map": {
+      "lua": {},
+      "modify": {}
+    }
+  },
+  "output": {
+    "sub_component_map": {
+      "null": {},
+      "file": {},
+    }
+  }
+}
+```
+
+#### AvailableComponents.hash
+
+The agent-calculated hash of the components field. The agent MUST include this hash
+if it has the ability to report the components it has available.
+Its format is determined by the agent.
+The hash SHOULD be the same for any agent that has the same set of components.
+
+#### Initial Handshake
+
+In order to reduce the amount of data transmitted, the AvailableComponents message
+does not initially contain the entire components map. Instead, the AvailableComponents
+message will have the agent computed hash set, with an empty map for components.
+
+The initial AgentToServer message SHOULD contain the AvailableComponents message
+with just the agent computed hash set.
+
+The OpAMP server may use this hash to determine whether it remembers the set of
+AvailableComponents or not. If the hash is not found on the OpAMP server, the server
+may request for the full components map to be reported by setting the ReportAvailableComponents
+flag in the ServerToAgent message. If this flag is specified, then the Agent will
+populate the components field with a full description of the available components.
+
+The server may then optionally persist the components for this hash, so that the
+server does not need to request them again on subsequent connects.
+
+The AvailableComponents message is also subject to [status compression](#agent-status-compression),
+and may be omitted if the hash has not changed from its previous value.
+
+#### ComponentDetails Message
+
+The ComponentDetails messaged describes a component of the Agent.
+
+The structure of ComponentDetails DOES NOT need to be a 1-to-1 match with
+the ComponentHealth structure. ComponentHealth generally refers to currently running instances of
+components, while ComponentDetails refers to the available types of components,
+which may not be necessarily running currently. It is also possible that the same component
+type may have more than one running instance.
+
+The ComponentDetails message has the following structure:
+
+```protobuf
+message ComponentDetails {
+    repeated KeyValue metadata = 1;
+    map<string, ComponentDetails> sub_component_map = 2;
+}
+```
+
+##### ComponentDetails.metadata
+
+Extra key/value pairs that may be used to describe the component.
+
+The key/value pairs are SHOULD conform to semantic conventions where applicable, see
+the [OpenTelemetry Semantic Conventions](https://opentelemetry.io/docs/specs/semconv/) for more information.
+
+##### ComponentDetails.sub_component_map
+
+A map of unique component ID to sub component details. It can nest as deeply as needed to
+describe the underlying system.
+
 ## Connection Management
 
 ### Establishing Connection