NO-TICK Cap the default size of the external operation thread pool (#5878)

Cap the default size of the external operation thread pool to 10 or
the maximum number of available processors, whichever is smaller.

Set the minimum size of the thread pool to 1. Meaning that only a
single thread is used unless the node actually starts to use
`FlowExternalOperation` which consumes threads from this pool.

docs/source/corda-configuration-file.rst

@@ -314,10 +314,10 @@ extraNetworkMapKeys
 .. _corda_configuration_flow_external_operation_thread_pool_size:
 
 flowExternalOperationThreadPoolSize
-  The number of threads available to execute external operations called from flows. See the documentation on
+  The number of threads available to execute external operations that have been called from flows. See the documentation on
-  :ref:`calling external systems inside of flows <api_flows_external_operations>` for more information.
+  :ref:`calling external systems inside flows <api_flows_external_operations>` for more information.
 
-  *Default:* Set to the number of available cores on the machine the node is running on
+*Default:* Set to the lesser of either the maximum number of cores allocated to the node, or 10.
 
 flowMonitorPeriodMillis
   Duration of the period suspended flows waiting for IO are logged.

node/src/main/kotlin/net/corda/node/internal/AbstractNode.kt

@@ -49,10 +49,10 @@ import net.corda.core.node.ServiceHub
 import net.corda.core.node.ServicesForResolution
 import net.corda.core.node.services.ContractUpgradeService
 import net.corda.core.node.services.CordaService
-import net.corda.core.node.services.diagnostics.DiagnosticsService
 import net.corda.core.node.services.IdentityService
 import net.corda.core.node.services.KeyManagementService
 import net.corda.core.node.services.TransactionVerifierService
+import net.corda.core.node.services.diagnostics.DiagnosticsService
 import net.corda.core.schemas.MappedSchema
 import net.corda.core.serialization.SerializationWhitelist
 import net.corda.core.serialization.SerializeAsToken
@@ -61,11 +61,9 @@ import net.corda.core.transactions.LedgerTransaction
 import net.corda.core.utilities.NetworkHostAndPort
 import net.corda.core.utilities.days
 import net.corda.core.utilities.minutes
-import net.corda.nodeapi.internal.lifecycle.NodeServicesContext
 import net.corda.djvm.source.ApiSource
 import net.corda.djvm.source.EmptyApi
 import net.corda.djvm.source.UserSource
-import net.corda.nodeapi.internal.lifecycle.NodeLifecycleEvent
 import net.corda.node.CordaClock
 import net.corda.node.VersionInfo
 import net.corda.node.internal.classloading.requireAnnotation
@@ -85,7 +83,6 @@ import net.corda.node.services.api.FlowStarter
 import net.corda.node.services.api.MonitoringService
 import net.corda.node.services.api.NetworkMapCacheInternal
 import net.corda.node.services.api.NodePropertiesStore
-import net.corda.nodeapi.internal.lifecycle.NodeLifecycleEventsDistributor
 import net.corda.node.services.api.SchemaService
 import net.corda.node.services.api.ServiceHubInternal
 import net.corda.node.services.api.VaultServiceInternal
@@ -155,8 +152,11 @@ import net.corda.nodeapi.internal.crypto.X509Utilities.NODE_IDENTITY_KEY_ALIAS
 import net.corda.nodeapi.internal.cryptoservice.CryptoServiceFactory
 import net.corda.nodeapi.internal.cryptoservice.SupportedCryptoServices
 import net.corda.nodeapi.internal.cryptoservice.bouncycastle.BCCryptoService
-import net.corda.nodeapi.internal.persistence.CordaTransactionSupportImpl
+import net.corda.nodeapi.internal.lifecycle.NodeLifecycleEvent
+import net.corda.nodeapi.internal.lifecycle.NodeLifecycleEventsDistributor
+import net.corda.nodeapi.internal.lifecycle.NodeServicesContext
 import net.corda.nodeapi.internal.persistence.CordaPersistence
+import net.corda.nodeapi.internal.persistence.CordaTransactionSupportImpl
 import net.corda.nodeapi.internal.persistence.CouldNotCreateDataSourceException
 import net.corda.nodeapi.internal.persistence.DatabaseConfig
 import net.corda.nodeapi.internal.persistence.DatabaseIncompatibleException
@@ -178,9 +178,12 @@ import java.sql.Connection
 import java.time.Clock
 import java.time.Duration
 import java.time.format.DateTimeParseException
-import java.util.Properties
+import java.util.*
 import java.util.concurrent.ExecutorService
 import java.util.concurrent.Executors
+import java.util.concurrent.LinkedBlockingQueue
+import java.util.concurrent.ThreadPoolExecutor
+import java.util.concurrent.TimeUnit
 import java.util.concurrent.TimeUnit.MINUTES
 import java.util.concurrent.TimeUnit.SECONDS
 import java.util.function.Consumer
@@ -737,11 +740,17 @@ abstract class AbstractNode<S>(val configuration: NodeConfiguration,
     private fun createExternalOperationExecutor(numberOfThreads: Int): ExecutorService {
         when (numberOfThreads) {
             1 -> log.info("Flow external operation executor has $numberOfThreads thread")
-            else -> log.info("Flow external operation executor has $numberOfThreads threads")
+            else -> log.info("Flow external operation executor has a max of $numberOfThreads threads")
         }
-        return Executors.newFixedThreadPool(
+        // Start with 1 thread and scale up to the configured thread pool size if needed
+        // Parameters of [ThreadPoolExecutor] based on [Executors.newFixedThreadPool]
+        return ThreadPoolExecutor(
+            1,
             numberOfThreads,
-            ThreadFactoryBuilder().setNameFormat("flow-external-operation-thread").build()
+            0L,
+            TimeUnit.MILLISECONDS,
+            LinkedBlockingQueue<Runnable>(),
+            ThreadFactoryBuilder().setNameFormat("flow-external-operation-thread").setDaemon(true).build()
         )
     }
 

node/src/main/kotlin/net/corda/node/services/config/ConfigUtilities.kt

@@ -23,12 +23,15 @@ import net.corda.nodeapi.internal.loadDevCaTrustStore
 import net.corda.nodeapi.internal.registerDevP2pCertificates
 import org.slf4j.LoggerFactory
 import java.nio.file.Path
+import kotlin.math.min
 
 fun configOf(vararg pairs: Pair<String, Any?>): Config = ConfigFactory.parseMap(mapOf(*pairs))
 operator fun Config.plus(overrides: Map<String, Any?>): Config = ConfigFactory.parseMap(overrides).withFallback(this)
 
 object ConfigHelper {
 
+    private const val FLOW_EXTERNAL_OPERATION_THREAD_POOL_SIZE_MAX = 10
+
     private const val CORDA_PROPERTY_PREFIX = "corda."
     private const val UPPERCASE_PROPERTY_PREFIX = "CORDA."
 
@@ -47,7 +50,9 @@ object ConfigHelper {
 
         // Detect the number of cores
         val coreCount = Runtime.getRuntime().availableProcessors()
-        val multiThreadingConfig = configOf("flowExternalOperationThreadPoolSize" to coreCount.toString())
+        val multiThreadingConfig = configOf(
+                "flowExternalOperationThreadPoolSize" to min(coreCount, FLOW_EXTERNAL_OPERATION_THREAD_POOL_SIZE_MAX).toString()
+        )
 
         val systemOverrides = ConfigFactory.systemProperties().cordaEntriesOnly()
         val environmentOverrides = ConfigFactory.systemEnvironment().cordaEntriesOnly()