solution: config option to disable an upstream

src/main/kotlin/io/emeraldpay/dshackle/config/UpstreamsConfigReader.kt

@@ -194,6 +194,9 @@ class UpstreamsConfigReader(
         upstream.id = getValueAsString(upNode, "id")
         upstream.options = tryReadOptions(upNode)
         upstream.methods = tryReadMethods(upNode)
+        getValueAsBool(upNode, "enabled")?.let {
+            upstream.isEnabled = it
+        }
     }
 
     internal fun readUpstreamGrpc(

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

@@ -63,6 +63,10 @@ open class ConfiguredUpstreams(
         log.debug("Starting upstreams")
         val defaultOptions = buildDefaultOptions(config)
         config.upstreams.forEach { up ->
+            if (!up.isEnabled) {
+                log.debug("Upstream ${up.id} is disabled")
+                return@forEach
+            }
             log.debug("Start upstream ${up.id}")
             if (up.connection is UpstreamsConfig.GrpcConnection) {
                 val options = up.options ?: UpstreamsConfig.Options()