Update block forging configuration on SIGHUP

Block Forging can be enabled/disabled through SIGHUP signal. Sending
such a signal will trigger the node to read the block forging credential
files. Since the credential files are passed via CLI flags one can not
remove them without restarting the node. For this effect, in order for
one to be able to disable block forging, moving/renaming/deleting the
file at the specified path (for the credential flags) and then sending
the SIGHUP signal is what needs to be done. The code will detect that
the specified files do not exist and it will disable block forging,
while tracing the appropriate log messages.

In case one wants to start a block producing node (i.e. passing the
credentials in the respective flags) but doesn't want it to actually
behave as a BP, there's a new `--start-as-non-producing-node` flag that
will run the node with credentials as a normal node. However on SIGHUP
it will read the credential files and start forging.

Refactor code to accomodate the changes

Added EnabledBlockForging type

Co-authored-by: Marcin Szamotulski <coot@coot.me>

cardano-node/src/Cardano/Node/Configuration/POM.hs

@@ -87,6 +87,8 @@ data NodeConfiguration
        , ncValidateDB      :: !Bool
        , ncShutdownConfig  :: !ShutdownConfig
 
+       , ncStartAsNonProducingNode :: !Bool
+
         -- Protocol-specific parameters:
        , ncProtocolConfig :: !NodeProtocolConfiguration
 
@@ -159,6 +161,8 @@ data PartialNodeConfiguration
        , pncValidateDB      :: !(Last Bool)
        , pncShutdownConfig  :: !(Last ShutdownConfig)
 
+       , pncStartAsNonProducingNode :: !(Last Bool)
+
          -- Protocol-specific parameters:
        , pncProtocolConfig :: !(Last NodeProtocolConfiguration)
 
@@ -309,6 +313,7 @@ instance FromJSON PartialNodeConfiguration where
            , pncProtocolFiles = mempty
            , pncValidateDB = mempty
            , pncShutdownConfig = mempty
+           , pncStartAsNonProducingNode = Last $ Just False
            , pncMaybeMempoolCapacityOverride
            , pncProtocolIdleTimeout
            , pncTimeWaitTimeout
@@ -466,6 +471,7 @@ defaultPartialNodeConfiguration =
     , pncProtocolFiles = mempty
     , pncValidateDB = Last $ Just False
     , pncShutdownConfig = Last . Just $ ShutdownConfig Nothing Nothing
+    , pncStartAsNonProducingNode = Last $ Just False
     , pncProtocolConfig = mempty
     , pncMaxConcurrencyBulkSync = mempty
     , pncMaxConcurrencyDeadline = mempty
@@ -500,6 +506,7 @@ makeNodeConfiguration pnc = do
   topologyFile <- lastToEither "Missing TopologyFile" $ pncTopologyFile pnc
   databaseFile <- lastToEither "Missing DatabaseFile" $ pncDatabaseFile pnc
   validateDB <- lastToEither "Missing ValidateDB" $ pncValidateDB pnc
+  startAsNonProducingNode <- lastToEither "Missing StartAsNonProducingNode" $ pncStartAsNonProducingNode pnc
   protocolConfig <- lastToEither "Missing ProtocolConfig" $ pncProtocolConfig pnc
   loggingSwitch <- lastToEither "Missing LoggingSwitch" $ pncLoggingSwitch pnc
   logMetrics <- lastToEither "Missing LogMetrics" $ pncLogMetrics pnc
@@ -555,6 +562,7 @@ makeNodeConfiguration pnc = do
                    Nothing -> ProtocolFilepaths Nothing Nothing Nothing Nothing Nothing Nothing
              , ncValidateDB = validateDB
              , ncShutdownConfig = shutdownConfig
+             , ncStartAsNonProducingNode = startAsNonProducingNode
              , ncProtocolConfig = protocolConfig
              , ncSocketConfig = socketConfig
              , ncDiffusionMode = diffusionMode

cardano-node/src/Cardano/Node/Parsers.hs

@@ -62,6 +62,7 @@ nodeRunParser = do
   shelleyVRFFile  <- optional parseVrfKeyFilePath
   shelleyCertFile <- optional parseOperationalCertFilePath
   shelleyBulkCredsFile <- optional parseBulkCredsFilePath
+  startAsNonProducingNode <- lastOption parseStartAsNonProducingNode
 
   -- Node Address
   nIPv4Address <- lastOption parseHostIPv4Addr
@@ -102,6 +103,7 @@ nodeRunParser = do
            , pncValidateDB = validate
            , pncShutdownConfig =
                Last . Just $ ShutdownConfig (getLast shutdownIPC) (getLast shutdownOnLimit)
+           , pncStartAsNonProducingNode = startAsNonProducingNode
            , pncProtocolConfig = mempty
            , pncMaxConcurrencyBulkSync = mempty
            , pncMaxConcurrencyDeadline = mempty
@@ -313,6 +315,14 @@ parseVrfKeyFilePath =
         <> completer (bashCompleter "file")
     )
 
+parseStartAsNonProducingNode :: Parser Bool
+parseStartAsNonProducingNode =
+  switch (
+    long "start-as-non-producing-node"
+      <> help ("Start the node as a non block producing node even if "
+            ++ "credentials are specified.")
+  )
+
 -- TODO revisit because it sucks
 parseSnapshotInterval :: Parser SnapshotInterval
 parseSnapshotInterval = fmap (RequestedSnapshotInterval . secondsToDiffTime) parseDifftime