Add new document of protocol in en. (#898)

docs/README.md

@@ -21,6 +21,7 @@
     * [Plugin development guide](en/Plugin-Development-Guide.md)
     * Protocol
       * [Cross Process Propagation Headers Protocol, v1.0](en/Skywalking-Cross-Process-Propagation-Headers-Protocol-v1.md)
+      * [SkyWalking Trace Data Protocol](en/Trace-Data-Protocol.md)
   * [Roadmap](ROADMAP.md)
   * Resources provided by community
     * [Public speakings](https://github.com/OpenSkywalking/Community#public-speakings)

docs/cn/Trace-Data-Protocol-CN.md

@@ -40,11 +40,8 @@ JSON数组，数组的每个元素，为一个有效的gRPC服务地址。
 ### 协议内容
 [gRPC service define](../..apm-protocol/apm-network/src/main/proto/ApplicationRegisterService.proto)
 
-- 首次调用时，applicationCode为客户端设置的应用名（显示在拓扑图和应用列表上的名字）。之后随着追踪过程，会上报此应用相关的周边服务的`ip:port`地址列表
-- KeyWithIntegerValue 返回，key为上报的applicationCode或ip:port地址，value为对应的id。applicationCode对应的返回id,在后续协议中，被称为applicationId。
-- 此服务按需调用，本地无法找到ip:port对应的id时，可异步发起调用。
-- 获取applicationId的操作是必选。后续追踪数据依赖此id
-- 获取ip:port对应的id是可选，使用id，会有效提高collector处理效率，降低网络消耗。
+- applicationCode为客户端设置的应用名.
+- applicationCode对应的返回id,在后续协议中，被称为applicationId。
 
 ## 应用实例发现服务
 ### 简介

docs/en/Trace-Data-Protocol.md

+# Trace Data Protocol 
+Trace Data Protocol describes the data format between SkyWalking agent/sniffer and backend. 
+
+## Abstract
+This protocol includes the downstream and upstream data format. Other languages agents/SDKs can use this protocol to 
+uplink data to the SkyWalking backend.
+
+- Discovery service provided by HTTP only
+- Other services, includes Register, Trace, etc., provided by HTTP/JSON and gRPC both. 
+
+### Version
+v1.1
+
+#### gRPC proto files
+[gRPC proto files](../../apm-protocol/apm-network/src/main/proto)
+
+## Collector discovery service
+### Abstract
+**Collector discovery service should be the first service after agent started** 
+Through this service, get the gRPC service list. The agent can choose any one of them for uplink data. Recommend to 
+acquire the list periodically.
+
+### HTTP GET
+- Input
+GET：http://collectorIp:port/agent/grpc 
+
+- Output
+JSON Array. Each element in the array ia a valid gRPC service address.
+```json
+["ip address1:port1","ip address2:port2","ip address3:port3"]
+```
+
+## Application Register Service
+### Abstract
+Register Application Code to the backend, and receive an integer represents the application.
+
+[gRPC service define](../..apm-protocol/apm-network/src/main/proto/ApplicationRegisterService.proto)
+
+- applicationCode is the config in your `agent.config`.
+- The return id is **ApplicationId** as the value in `KeyWithIntegerValue`, which will be used in further data uplink.
+
+## Discovery Service
+
+### Register Instance Service
+[gRPC service define](../../apm-protocol/apm-network/src/main/proto/DiscoveryService.proto#L11-L12)
+
+- agentUUID generated by agent, should be unique. Stay same before reboot, at least.
+- **ApplicationInstanceId** will be used in further data uplink.
+
+### Heart beat service
+[gRPC service define](../../apm-protocol/apm-network/src/main/proto/DiscoveryService.proto#L14-L15)
+
+- Recommend to report heart beat every 20-60 seconds.
+- Java agent don't use this, because JVM metrics upstream replace the capabilities of this. 
+
+## Service Name Discovery Service
+### Abstract
+Replace the literal String service(operation) name by an id(integer)
+
+[gRPC service define](../../apm-protocol/apm-network/src/main/proto/DiscoveryService.proto#L53-L74)
+
+- Optional service, reduce the network cost but use more memory as a buffer mapping.
+
+## Network Address Register Service
+### Abstract
+Network Address includes all remove service address, includes ip, port, hostname, etc., which used in RPC framework, MQ, DB, etc.
+
+[gRPC service define](../../apm-protocol/apm-network/src/main/proto/NetworkAddressRegisterService.proto)
+
+- Optional service, reduce the network cost but use more memory as a buffer mapping.
+
+## JVM Metrics Service
+### Abstract
+Uplink the JVM metrics, including PermSize, HeapSize, CPU, Memory, etc., every second.
+
+[gRPC service define](../../apm-protocol/apm-network/src/main/proto/JVMMetricsService.proto)
+
+## Trace Segment Service
+[gRPC service define](../../apm-protocol/apm-network/src/main/proto/TraceSegmentService.proto)
+
+- UniqueId represents segmentId and globalTraceId. It have 3 parts(Longs), 1) applicationInstanceId, 2) ThreadId, 3) Timestamp + 10000 + seq(seq is in [0, 100000) )
+- Span data please refs to [Plugin Development Guide](Plugin-Development-Guide.md)
+- Id and name both exist, please use id if possible.
+  - operationNameId/operationName 
+  - networkAddress/networkAddressId
+  - entryServiceName/entryServiceId
+  - parentServiceName/parentServiceId
+  - peerId/peer
+- componentIds are defined in backend, [here](../../apm-protocol/apm-network/src/main/java/org/apache/skywalking/apm/network/trace/component/ComponentsDefine.java)
+
+# HTTP JSON Services
+All HTTP Services match the gRPC services, just adjust use short keys.
+
+## Instance Register Service
+- http://ip:port/instance/register(default: localhost:12800) 
+
+Input:
+```
+{
+    ai: x, #applicationId
+    au: "", #agentUUID
+    rt: x, #registerTime
+    oi: "", #osinfo
+}
+```
+
+Output:
+```
+{
+    ai: x, #applicationId
+    ii: x, #applicationInstanceId
+}
+```
+
+## Heart beat service
+- http://ip:port/instance/heartbeat(default: localhost:12800) 
+
+Input:
+```
+{
+    "ii": x, #applicationInstanceId
+    "ht": x #heartbeatTime, java timestamp format
+}
+```
+
+Output: empty
+
+## Service Name Discovery 
+- http://ip:port/servicename/discovery(default: localhost:12800) 
+
+Input：
+```
+{
+    ai: x, #applicationId
+    sn: "", #serviceName
+    st: x, #srcSpanType
+}
+```
+
+Output：
+```
+{
+    si: x, #osinfo
+    el: { #element
+        ai: x, #applicationId
+        sn: "", #serviceName
+        st: x, #srcSpanType
+    }
+}
+```
+
+## Trace Segment Service
+Input：
+```
+[
+  {
+    "gt": [[230150, 185809, 24040000]], 
+    "sg": { //TraceSegmentObject 
+      "ts": [137150, 185809, 48780000], 
+      "ai": 2, //applicationId
+      "ii": 3, //applicationInstanceId
+      "ss": [ //SpanObject
+        {
+          "si": 0, //spanId
+          "tv": 0, //SpanType
+          "lv": 2, //SpanLayer
+          "ps": -1, //parentSpanId
+          "st": 1501858094726, //startTime
+          "et": 1501858096804, //endTime
+          "ci": 3, //componentId
+          "cn": "", //component
+          "oi": 0, //operationNameId
+          "on": "org.skywaking.apm.testcase.dubbo.services.GreetService.doBusiness()", //operationName
+          "pi": 0, //peerId
+          "pn": "", //peer
+          "ie": false, //isError
+          "rs": [ //TraceSegmentReference
+            {
+              "pts": [230150, 185809, 24040000], //parentTraceSegmentId
+              "pii": 2, //parentApplicationInstanceId
+              "psp": 1, //parentSpanId
+              "psi": 0, //parentServiceId
+              "psn": "/dubbox-case/case/dubbox-rest", //parentServiceName
+              "ni": 0,  //networkAddressId
+              "nn": "172.25.0.4:20880", //networkAddress
+              "eii": 2, //entryApplicationInstanceId
+              "esi": 0, //entryServiceId
+              "esn": "/dubbox-case/case/dubbox-rest", //entryServiceName
+              "rn": 0 //RefType
+            }
+          ],
+          "to": [ //KeyWithStringValue
+            {
+              "k": "url", //key
+              "v": "rest://172.25.0.4:20880/org.skywaking.apm.testcase.dubbo.services.GreetService.doBusiness()" //value
+            },
+            {
+              "k": "http.method",
+              "v": "GET"
+            }
+          ],
+          "lo": { //LogMessage
+            "t": 1501858094726,
+            "d": [
+                "k": "NullPointException",
+                "v": "Error Stack"
+            }
+          }
+        },
+        {
+          "si": 1,
+          "tv": 1,
+          "lv": 1,
+          "ps": 0,
+          "st": 1501858094726,
+          "et": 1501858095804,
+          "ci": 9,
+          "cn": "",
+          "oi": 0,
+          "on": "mongodb://[username:password@]host1[:port1][,host2[:port2],...[,hostN[:portN]]][/[database][?options]]",
+          "pi": 0,
+          "pn": "localhost:27017",
+          "ie": false,
+          "to": [],
+          "lo": []
+        }
+      ]
+    }
+  }
+]
+```