solution: describe available methods per chain

src/main/kotlin/io/emeraldpay/dshackle/rpc/Describe.kt

@@ -26,12 +26,13 @@ class Describe(
                     chainUpstreams.getAll().let { ups ->
                         if (ups.isNotEmpty()) {
                             val status = subscribeStatus.chainStatus(chain, ups)
-                            resp.addChains(
-                                    BlockchainOuterClass.DescribeChain.newBuilder()
-                                            .setChain(Common.ChainRef.forNumber(chain.id))
-                                            .setStatus(status)
-                                            .build()
-                            )
+                            val targets = chainUpstreams.getSupportedTargets()
+                            val chainDescription = BlockchainOuterClass.DescribeChain.newBuilder()
+                                    .setChain(Common.ChainRef.forNumber(chain.id))
+                                    .addAllSupportedTargets(targets)
+                                    .setStatus(status)
+                                    .build()
+                            resp.addChains(chainDescription)
                         }
                     }
                 }

src/main/kotlin/io/emeraldpay/dshackle/rpc/NativeCall.kt

@@ -32,6 +32,7 @@ class NativeCall(
             if (chain == Chain.UNSPECIFIED) {
                 throw Exception("Invalid chain id: ${request.chain.number}")
             }
+            // TODO send error to all requests?
             val upstream = upstreams.getUpstream(chain)?.getApi() ?: throw Exception("Chain ${chain.id} is unavailable")
             request.itemsList.toFlux().map {
                 val method = it.target

src/main/kotlin/io/emeraldpay/dshackle/upstream/AggregatedUpstreams.kt

@@ -20,6 +20,14 @@ abstract class AggregatedUpstreams: Upstream {
                 .map { it.status }
     }
 
+    override fun getSupportedTargets(): Set<String> {
+        val list = HashSet<String>()
+        getAll().forEach {
+            list.addAll(it.getSupportedTargets())
+        }
+        return list
+    }
+
     override fun isAvailable(): Boolean {
         return getAll().any { it.isAvailable() }
     }

src/main/kotlin/io/emeraldpay/dshackle/upstream/EthereumApi.kt

@@ -167,4 +167,8 @@ open class EthereumApi(
         }
         throw RpcException(-32601, "Method not found")
     }
+
+    fun getSupportedMethods(): Set<String> {
+        return allowedMethods.plus(hardcodedMethods).toSortedSet()
+    }
 }

src/main/kotlin/io/emeraldpay/dshackle/upstream/EthereumUpstream.kt

@@ -16,6 +16,10 @@ class EthereumUpstream(
         private val options: UpstreamsConfig.Options
 ): Upstream {
 
+    override fun getSupportedTargets(): Set<String> {
+        return api.getSupportedMethods()
+    }
+
     private val log = LoggerFactory.getLogger(EthereumUpstream::class.java)
 
     private val head: EthereumHead = if (ethereumWs != null) {

src/main/kotlin/io/emeraldpay/dshackle/upstream/GrpcUpstream.kt

@@ -20,8 +20,10 @@ import reactor.core.publisher.toMono
 import java.lang.Exception
 import java.math.BigInteger
 import java.time.Duration
+import java.util.*
 import java.util.concurrent.atomic.AtomicReference
 import java.util.function.Function
+import kotlin.collections.ArrayList
 
 open class GrpcUpstream(
         private val chain: Chain,
@@ -41,6 +43,7 @@ open class GrpcUpstream(
     private val head = Head(this)
     private val api: EthereumApi
     private val statusStream: TopicProcessor<UpstreamAvailability> = TopicProcessor.create()
+    private val supportedMethods = HashSet<String>()
 
     init {
         val grpcTransport = EthereumGrpcTransport(chain, client, objectMapper)
@@ -93,6 +96,7 @@ open class GrpcUpstream(
     }
 
     fun init(conf: BlockchainOuterClass.DescribeChain) {
+        supportedMethods.addAll(conf.supportedTargetsList)
         conf.status?.let { status -> onStatus(status) }
     }
 
@@ -110,6 +114,9 @@ open class GrpcUpstream(
     }
     // ------------------------------------------------------------------------------------------
 
+    override fun getSupportedTargets(): Set<String> {
+        return supportedMethods
+    }
 
     override fun isAvailable(): Boolean {
         return headBlock.get() != null

src/main/kotlin/io/emeraldpay/dshackle/upstream/GrpcUpstreams.kt

@@ -56,6 +56,9 @@ class GrpcUpstreams(
                     }
                     chains as List<Chain>
                 }
+                .doOnError { t ->
+                    log.error("Failed to get description from $host:$port", t)
+                }
         //TODO subscribe only after receiving details
         client.subscribeStatus(BlockchainOuterClass.StatusRequest.newBuilder().build())
                 .subscribe { value ->

src/main/kotlin/io/emeraldpay/dshackle/upstream/Upstream.kt

@@ -10,4 +10,5 @@ interface Upstream {
     fun getHead(): EthereumHead
     fun getApi(): EthereumApi
     fun getOptions(): UpstreamsConfig.Options
+    fun getSupportedTargets(): Set<String>
 }