Add v8 upgrade document and fix some tiny doc issues. (#4787)

* Add v8 upgrade document and fix some tiny doc issues.

* Add link to STAM paper.

README.md

@@ -42,10 +42,13 @@ including
 1. Metrics system, including Prometheus, Spring Sleuth(Micrometer).
 1. Zipkin v1/v2 and Jaeger gRPC format with limited topology and metrics analysis.(Experimental).
 
+SkyWalking OAP is using the STAM(Streaming Topology Analysis Method) to analysis topology in the tracing based agent scenario 
+for better performance. Read [the paper of STAM](https://wu-sheng.github.io/STAM/) for more details.
+
 # Document
 [8.x dev](docs/README.md) | [7.0](https://github.com/apache/skywalking/blob/v7.0.0/docs/README.md) | [6.6](https://github.com/apache/skywalking/blob/v6.6.0/docs/README.md), [6.5](https://github.com/apache/skywalking/blob/v6.5.0/docs/README.md).
 
-NOTICE, SkyWalking 8.0+ uses [v3 protocols](docs/en/protocols/README.md). They are incompatible with previous released.
+NOTICE, SkyWalking 8.0+ uses [v3 protocols](docs/en/protocols/README.md). They are incompatible with previous releases.
 
 # Downloads
 Please head to the [releases page](http://skywalking.apache.org/downloads/) to download a release of Apache SkyWalking.

docs/en/FAQ/README.md

@@ -10,6 +10,7 @@ These are known and common FAQs. We welcome you to contribute yours.
 * [Maven compilation failure with `python2 not found` error](maven-compile-npm-failure.md)
 
 ## Runtime
+* [8.x+ upgrade](v8-version-upgrade.md)
 * [Why metrics indexes(ElasticSearch) in Hour and Day precisions stop update after upgrade to 7.x?](Hour-Day-Metrics-Stopping.md)
 * [6.x version upgrade](v6-version-upgrade.md)
 * [Why only traces in UI?](Why-have-traces-no-others.md)

docs/en/FAQ/v8-version-upgrade.md

+# V8 upgrade
+SkyWalking v8 begins to use [v3 protocol](../protocols/README.md), so, it is incompatible with previous releases.
+Users who intend to upgrade in v8 series releases could follow this guidance.
+
+
+Register in v6 and v7 has been removed in v8 for better scaling out performance, please upgrade in the following ways.
+1. Use a different storage or a new namespace. Also, could consider erasing the whole storage index/table(s) related to SkyWalking.
+1. Deploy the whole SkyWalking cluster, and expose in a new network address.
+1. If you are using the language agents, upgrade the new agents too, meanwhile, make sure the agent has supported the different language.
+And set up the backend address to the new SkyWalking OAP cluster.
\ No newline at end of file

docs/en/protocols/README.md

@@ -10,12 +10,8 @@ There are two types of protocols list here.
 They also related to the probe group, for understand that, look [Concepts and Designs](../concepts-and-designs/README.md) document.
 These groups are **Language based native agent protocol**, **Service Mesh protocol** and **3rd-party instrument protocol**.
 
-### Register Protocol
-Register protocol is shared in `Language based native agent protocol`[Required] and `Service Mesh probe protocol`[Optional]. 
-Service, Service Instance, Network address and Endpoint could do register to get an unique integer ID to replace the literal string name and attributes. The probe could use IDs to reduce the cost of memory and network bandwidth. Service and Instance register are required in the language agent. All other cases, register are optional.
-
 ### Language based native agent protocol
-There is two types of protocols to make language agents work in distributed environments.
+There are two types of protocols to make language agents work in distributed environments.
 1. **Cross Process Propagation Headers Protocol** and **Cross Process Correlation Headers Protocol** are in wire data format, 
 agent/SDK usually uses HTTP/MQ/HTTP2 headers
 to carry the data with rpc request. The remote agent will receive this in the request handler, and bind the context 
@@ -33,7 +29,6 @@ SkyWalking javaagent begins to support this since 8.0.0.
 
 [SkyWalking Trace Data Protocol v3](Trace-Data-Protocol-v3.md) defines the communication way and format between agent and backend.
 
-
 ### Service Mesh probe protocol
 The probe in sidecar or proxy could use this protocol to send data to backendEnd. This service provided by gRPC, requires 
 the following key info:

docs/en/setup/backend/backend-receivers.md

@@ -89,6 +89,8 @@ receiver_zipkin:
     needAnalysis: true
 ```
 
+NOTICE, Zipkin receiver is only provided in `apache-skywalking-apm-x.y.z.tar.gz` tar.
+
 ## Jaeger receiver
 Jaeger receiver right now only works in `Tracing Mode`, and no analysis.
 Jaeger receiver provides extra gRPC host/port, if absent, sharing-server host/port will be used, then core gRPC host/port.
@@ -105,4 +107,6 @@ receiver_jaeger:
   default:
     gRPCHost: ${SW_RECEIVER_JAEGER_HOST:0.0.0.0}
     gRPCPort: ${SW_RECEIVER_JAEGER_PORT:14250}
-``` 
\ No newline at end of file
+``` 
+
+NOTICE, Jaeger receiver is only provided in `apache-skywalking-apm-x.y.z.tar.gz` tar.
\ No newline at end of file