message SegmentObject {
    // A string id represents the whole trace.
    string traceId = 1;
    // A unique id represents this segment.
    string traceSegmentId = 2;
    // Span collections included in this segment.
    repeated SpanObject spans = 3;
    // The logic name represents the service.
    string service = 4;
    // The logic name represents the service instance.
    string serviceInstance = 5;
    // Whether the segment includes all tracked spans.
    bool isSizeLimited = 6;
}

message SpanObject {
    // The number id of the span.
    int32 spanId = 1;
    // The number id of the parent span in the whole segment.
    int32 parentSpanId = 2;
    // Start timestamp in milliseconds of this span,
    int64 startTime = 3;
    // End timestamp in milliseconds of this span,
    int64 endTime = 4;
    // In the across thread and across process, these references targeting the parent segments.
    repeated SegmentReference refs = 5;
    // A logic name represents this span.
    string operationName = 6;
    // Remote address of the peer in RPC/MQ case.This is required when spanType = Exit
    string peer = 7;
    // Span type represents the role in the RPC context.
    SpanType spanType = 8;
    // Span layer represent the component tech stack, related to the network tech.
    SpanLayer spanLayer = 9;
    // Component id is a predefinited number id in the SkyWalking.
    int32 componentId = 10;
    // The status of the span.
    bool isError = 11;
    // String key, String value pair.
    repeated KeyStringValuePair tags = 12;
    // String key, String value pair with an accurate timestamp.
    repeated Log logs = 13;
    // Force the backend don't do analysis, if the value is TRUE.
    bool skipAnalysis = 14;
}

message SegmentReference {
    // Represent the reference type.
    // Typically, refType == CrossProcess means SpanObject#spanType = entry.
    RefType refType = 1;
    // A string id represents the whole trace.
    string traceId = 2;
    // Another segment id as the parent.
    string parentTraceSegmentId = 3;
    // The span id in the parent trace segment.
    int32 parentSpanId = 4;
    // The service logic name of the parent segment.
    string parentService = 5;
    // The service logic name instance of the parent segment.
    string parentServiceInstance = 6;
    // The endpoint name of the parent segment.
    string parentEndpoint = 7;
    // The network address, including ip/hostname and port, which is used in the client side.
    // Such as Client --> use 127.0.11.8:913 -> Server
    // then, in the reference of entry span reported by Server, the value of this field is 127.0.11.8:913.
    string networkAddressUsedAtPeer = 8;
}

message Log {
    // The timestamp in milliseconds of this event.,
    int64 time = 1;
    // String key, String value pair.
    repeated KeyStringValuePair data = 2;
}

enum SpanType {
    // Server side of RPC. Consumer side of MQ.
    Entry = 0;
    // Client side of RPC. Producer side of MQ.
    Exit = 1;
    // A common local code execution.
    Local = 2;
}

// A ID could be represented by multiple string sections.
message ID {
    repeated string id = 1;
}

// Type of the reference
enum RefType {
    // Map to the reference targeting the segment in another OS process.
    CrossProcess = 0;
    // Map to the reference targeting the segment in the same process of the current one, just across thread.
    CrossThread = 1;
}

// Map to the layer of span
enum SpanLayer {
    // Unknown layer. Could be anything.
    Unknown = 0;
    // A database layer, used in tracing the database client component.
    Database = 1;
    // A RPC layer, used in both client and server sides of RPC component.
    RPCFramework = 2;
    // HTTP is a more specific RPCFramework.
    Http = 3;
    // A MQ layer, used in both producer and consuer sides of the MQ component.
    MQ = 4;
    // A cache layer, used in tracing the cache client component.
    Cache = 5;
}