docs: add some oracle service doc, fix #1846

README.md

@@ -25,6 +25,7 @@ A complete toolkit for the NEO blockchain, including:
 - [Smart contract compiler](docs/compiler.md)
 - [NEO virtual machine](docs/vm.md)
 - [Smart contract examples](examples/README.md)
+- [Oracle service](docs/oracle.md)
 
 This branch (**master**) is under active development now (read: won't work
 out of the box) and aims to be compatible with Neo 3. For the current stable

docs/oracle.md

@@ -0,0 +1,71 @@
+# NeoGo Oracle service
+
+NeoGo node can act as oracle service node for https and neofs protocols. It
+has to have a wallet with key belonging to one of network's designated oracle
+nodes (stored in `RoleManagement` native contract).
+
+It needs [RPC service](rpc.md) to be enabled and configured properly because
+RPC is used by oracle nodes to exchange signatures of the resulting
+transaction.
+
+## Configuration
+
+To enable oracle service add `Oracle` subsection to `ApplicationConfiguration`
+section of your node config.
+
+Parameters:
+ * `Enabled`: boolean value, enables/disables the service, `true` for service
+   to be enabled
+ * `AllowPrivateHost`: boolean value, enables/disables private IPs (like
+   127.0.0.1 or 192.168.0.1) for https requests, it defaults to false and it's
+   false on public networks, but you can enable it for private ones.
+ * `Nodes`: list of oracle node RPC endpoints, it's used for oracle node
+   communication. All oracle nodes should be specified there.
+ * `NeoFS`: a subsection of its own for NeoFS configuration with two
+   parameters:
+     - `Timeout`: request timeout, like "5s"
+     - `Nodes`: list of NeoFS nodes (their gRPC interfaces) to get data from,
+       one node is enough to operate, but they're used in round-robin fashion,
+       so you can spread the load by specifying multiple nodes
+ * `MaxTaskTimeout`: maximum time a request can be active (retried to
+   process), defaults to 1 hour if not specified.
+ * `RefreshInterval`: retry period for requests that aren't yet processed,
+   defaults to 3 minutes.
+ * `MaxConcurrentRequests`: maximum number of requests processed in parallel,
+   defaults to 10.
+ * `RequestTimeout`: https request timeout, default is 5 seconds.
+ * `ResponseTimeout`: RPC communication timeout for inter-oracle exchange,
+   default is 4 seconds.
+ * `UnlockWallet`: oracle wallet configuration:
+     - `Path`: path to NEP-6 wallet.
+     - `Password`: password for the account to be used by oracle node.
+
+### Example
+
+```
+  Oracle:
+    Enabled: true
+    AllowPrivateHost: false
+    MaxTaskTimeout: 432000000
+    Nodes:
+      - http://oracle1.example.com:20332
+      - http://oracle2.example.com:20332
+      - http://oracle3.example.com:20332
+      - http://oracle4.example.com:20332
+    NeoFS:
+      Nodes:
+        - st1.storage.fs.neo.org:8080
+        - st2.storage.fs.neo.org:8080
+        - st3.storage.fs.neo.org:8080
+        - st4.storage.fs.neo.org:8080
+    UnlockWallet:
+      Path: "/path/to/oracle-wallet.json"
+      Password: "dontworryaboutthevase"
+```
+
+## Operation
+
+To run oracle service on your network you need to:
+ * set oracle node keys in `RoleManagement` contract
+ * configure and run appropriate number of oracle nodes with keys specified in
+   `RoleManagement` contract