problem: service may miss available chain if initialized after

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

@@ -19,12 +19,18 @@ class AvailableChains(
     private val callTargets = HashMap<Chain, EthereumTargets>()
 
     fun add(chain: Chain) {
+        if (all.contains(chain)) {
+            return
+        }
         all.add(chain)
         bus.onNext(chain)
     }
 
     fun observe(): Flux<Chain> {
-        return Flux.from(bus)
+        return Flux.merge(
+                Flux.fromIterable(all),
+                Flux.from(bus)
+        )
     }
 
     fun supports(chain: Chain): Boolean {

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

@@ -159,9 +159,9 @@ open class ConfiguredUpstreams(
     override fun getOrCreateUpstream(chain: Chain): ChainUpstreams {
         val current = chainMapping[chain]
         if (current == null) {
+            availableChains.add(chain)
             val created = ChainUpstreams(chain, ArrayList<Upstream>(), availableChains.targetFor(chain))
             chainMapping[chain] = created
-            availableChains.add(chain)
             return created
         }
         return current