Refactor MIB state machine into asynchronous operations (#210)

Convert to async MIB instrumentation API (#210)

MIB instrumentation API changed to allow for asynchronous
managed objects access. The MIB instrumentation methods
called by the state machine now return immediately and
resume once the callback is called.

The built-in SNMPv2-SMI objects are still synchronous.

This change is a prerequisite for fully asynchronous managed objects
implementation.

CHANGES.txt

@@ -25,15 +25,17 @@ Revision 5.0.0, released 2018-10-??
     just var-binds (as var-arg), the rest of the parameters packed
     into opaque kwargs
 
+  * The `readVars`, `readNextVars` and `writeVars` methods of MIB
+    instrumentation controller return immediately and deliver their
+    results via a call back.
+
   * CommandResponder application passes `snmpEngine` and optionally
     user-supplied `cbCtx` object throughout the MIB instrumentation
     methods. The goal is to let MIB objects access/modify whatever
     custom Python objects they need while being called back.
 
   * CommandResponder refactored to facilitate asynchronous
-    MIB instrumentation routines. The `readVars`, `readNextVars` and
+    MIB instrumentation routines.
-    `writeVars` MIB controller methods return immediately and
-    deliver their results via a call back.
 
 - The high-level API (`hlapi`) extended to cover lightweight SNMP v1arch
   in hope to ease the use of packet-level SNMP API.

examples/v3arch/asyncore/agent/cmdrsp/implementing-scalar-mib-objects.py

@@ -56,7 +56,7 @@ MibScalar, MibScalarInstance = mibBuilder.importSymbols(
 
 class MyStaticMibScalarInstance(MibScalarInstance):
     # noinspection PyUnusedLocal,PyUnusedLocal
-    def getValue(self, name, idx):
+    def getValue(self, name, idx, **context):
         return self.getSyntax().clone(
             'Python %s running on a %s platform' % (sys.version, sys.platform)
         )

examples/v3arch/asyncore/proxy/command/ipv6-to-ipv4-conversion.py

@@ -96,7 +96,7 @@ class CommandResponder(cmdrsp.CommandResponderBase):
         v2c.GetNextRequestPDU.tagSet: cmdgen.NextCommandGeneratorSingleRun(),
         v2c.GetBulkRequestPDU.tagSet: cmdgen.BulkCommandGeneratorSingleRun()
     }
-    pduTypes = cmdGenMap.keys()  # This app will handle these PDUs
+    SUPPORTED_PDU_TYPES = cmdGenMap.keys()  # This app will handle these PDUs
 
     # SNMP request relay
     def handleMgmtOperation(self, snmpEngine, stateReference, contextName,

examples/v3arch/asyncore/proxy/command/v2c-to-v1-conversion.py

@@ -95,7 +95,7 @@ class CommandResponder(cmdrsp.CommandResponderBase):
         v2c.GetNextRequestPDU.tagSet: cmdgen.NextCommandGeneratorSingleRun(),
         v2c.GetBulkRequestPDU.tagSet: cmdgen.BulkCommandGeneratorSingleRun()
     }
-    pduTypes = cmdGenMap.keys()  # This app will handle these PDUs
+    SUPPORTED_PDU_TYPES = cmdGenMap.keys()  # This app will handle these PDUs
 
     # SNMP request relay
     def handleMgmtOperation(self, snmpEngine, stateReference, contextName,

examples/v3arch/asyncore/proxy/command/v2c-to-v3-conversion.py

@@ -95,7 +95,7 @@ class CommandResponder(cmdrsp.CommandResponderBase):
         v2c.GetNextRequestPDU.tagSet: cmdgen.NextCommandGeneratorSingleRun(),
         v2c.GetBulkRequestPDU.tagSet: cmdgen.BulkCommandGeneratorSingleRun()
     }
-    pduTypes = cmdGenMap.keys()  # This app will handle these PDUs
+    SUPPORTED_PDU_TYPES = cmdGenMap.keys()  # This app will handle these PDUs
 
     # SNMP request relay
     def handleMgmtOperation(self, snmpEngine, stateReference, contextName,

examples/v3arch/asyncore/proxy/command/v3-to-v2c-conversion.py

@@ -98,7 +98,7 @@ class CommandResponder(cmdrsp.CommandResponderBase):
         v2c.GetNextRequestPDU.tagSet: cmdgen.NextCommandGeneratorSingleRun(),
         v2c.GetBulkRequestPDU.tagSet: cmdgen.BulkCommandGeneratorSingleRun()
     }
-    pduTypes = cmdGenMap.keys()  # This app will handle these PDUs
+    SUPPORTED_PDU_TYPES = cmdGenMap.keys()  # This app will handle these PDUs
 
     # SNMP request relay
     def handleMgmtOperation(self, snmpEngine, stateReference, contextName,

pysnmp/entity/rfc3413/cmdrsp.py

@@ -15,25 +15,41 @@ from pysnmp import debug
 # 3.2
 class CommandResponderBase(object):
     acmID = 3  # default MIB access control method to use
-    pduTypes = ()
+    SUPPORTED_PDU_TYPES = ()
+    SMI_ERROR_MAP = {
+        pysnmp.smi.error.NoAccessError: 'noAccess',
+        pysnmp.smi.error.WrongTypeError: 'wrongType',
+        pysnmp.smi.error.WrongLengthError: 'wrongLength',
+        pysnmp.smi.error.WrongEncodingError: 'wrongEncoding',
+        pysnmp.smi.error.WrongValueError: 'wrongValue',
+        pysnmp.smi.error.NoCreationError: 'noCreation',
+        pysnmp.smi.error.InconsistentValueError: 'inconsistentValue',
+        pysnmp.smi.error.ResourceUnavailableError: 'resourceUnavailable',
+        pysnmp.smi.error.CommitFailedError: 'commitFailed',
+        pysnmp.smi.error.UndoFailedError: 'undoFailed',
+        pysnmp.smi.error.AuthorizationError: 'authorizationError',
+        pysnmp.smi.error.NotWritableError: 'notWritable',
+        pysnmp.smi.error.InconsistentNameError: 'inconsistentName'
+    }
 
     def __init__(self, snmpEngine, snmpContext, cbCtx=None):
         snmpEngine.msgAndPduDsp.registerContextEngineId(
-            snmpContext.contextEngineId, self.pduTypes, self.processPdu
+            snmpContext.contextEngineId, self.SUPPORTED_PDU_TYPES, self.processPdu
         )
         self.snmpContext = snmpContext
         self.cbCtx = cbCtx
         self.__pendingReqs = {}
 
-    def initiateMgmtOperation(self, snmpEngine, stateReference, contextName, PDU):
-        pass
-
     def close(self, snmpEngine):
         snmpEngine.msgAndPduDsp.unregisterContextEngineId(
-            self.snmpContext.contextEngineId, self.pduTypes
+            self.snmpContext.contextEngineId, self.SUPPORTED_PDU_TYPES
         )
         self.snmpContext = self.__pendingReqs = None
 
+    def releaseStateInformation(self, stateReference):
+        if stateReference in self.__pendingReqs:
+            del self.__pendingReqs[stateReference]
+
     def sendVarBinds(self, snmpEngine, stateReference,
                      errorStatus, errorIndex, varBinds):
         (messageProcessingModel,
@@ -105,10 +121,6 @@ class CommandResponderBase(object):
     _setRequestType = rfc1905.SetRequestPDU.tagSet
     _counter64Type = rfc1902.Counter64.tagSet
 
-    def releaseStateInformation(self, stateReference):
-        if stateReference in self.__pendingReqs:
-            del self.__pendingReqs[stateReference]
-
     def processPdu(self, snmpEngine, messageProcessingModel, securityModel,
                    securityName, securityLevel, contextEngineId, contextName,
                    pduVersion, PDU, maxSizeResponseScopedPDU, stateReference):
@@ -140,63 +152,11 @@ class CommandResponderBase(object):
 
         # 3.2.5
         varBinds = v2c.apiPDU.getVarBinds(PDU)
-        errorStatus, errorIndex = 'noError', 0
 
         debug.logger & debug.flagApp and debug.logger(
             'processPdu: stateReference %s, varBinds %s' % (stateReference, varBinds))
 
-        try:
+        self.initiateMgmtOperation(snmpEngine, stateReference, contextName, PDU)
-            self.initiateMgmtOperation(snmpEngine, stateReference, contextName, PDU)
-
-        # SNMPv2 SMI exceptions
-        except pysnmp.smi.error.GenError:
-            errorIndication = sys.exc_info()[1]
-            debug.logger & debug.flagApp and debug.logger(
-                'processPdu: stateReference %s, errorIndication %s' % (stateReference, errorIndication))
-            if 'oid' in errorIndication:
-                # Request REPORT generation
-                statusInformation['oid'] = errorIndication['oid']
-                statusInformation['val'] = errorIndication['val']
-
-        # PDU-level SMI errors
-        except pysnmp.smi.error.NoAccessError:
-            errorStatus, errorIndex = 'noAccess', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.WrongTypeError:
-            errorStatus, errorIndex = 'wrongType', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.WrongLengthError:
-            errorStatus, errorIndex = 'wrongLength', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.WrongEncodingError:
-            errorStatus, errorIndex = 'wrongEncoding', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.WrongValueError:
-            errorStatus, errorIndex = 'wrongValue', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.NoCreationError:
-            errorStatus, errorIndex = 'noCreation', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.InconsistentValueError:
-            errorStatus, errorIndex = 'inconsistentValue', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.ResourceUnavailableError:
-            errorStatus, errorIndex = 'resourceUnavailable', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.CommitFailedError:
-            errorStatus, errorIndex = 'commitFailed', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.UndoFailedError:
-            errorStatus, errorIndex = 'undoFailed', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.AuthorizationError:
-            errorStatus, errorIndex = 'authorizationError', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.NotWritableError:
-            errorStatus, errorIndex = 'notWritable', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.InconsistentNameError:
-            errorStatus, errorIndex = 'inconsistentName', sys.exc_info()[1]['idx'] + 1
-        except pysnmp.smi.error.SmiError:
-            errorStatus, errorIndex = 'genErr', len(varBinds) and 1 or 0
-        except pysnmp.error.PySnmpError:
-            self.releaseStateInformation(stateReference)
-            return
-        else:  # successful request processor must release state info
-            return
-
-        self.sendVarBinds(snmpEngine, stateReference, errorStatus,
-                          errorIndex, varBinds)
-
-        self.releaseStateInformation(stateReference)
 
     @classmethod
     def verifyAccess(cls, viewType, varBind, **context):
@@ -258,21 +218,86 @@ class CommandResponderBase(object):
                 # This will cause MibTree to skip this OID-value
                 raise pysnmp.smi.error.NoAccessError(name=name, idx=context.get('idx'))
 
+    def _getMgmtFun(self, contextName):
+        return lambda *args, **kwargs: None
 
-class GetCommandResponder(CommandResponderBase):
+    def _checkSmiErrors(self, varBinds):
-    pduTypes = (rfc1905.GetRequestPDU.tagSet,)
+        errorIndication = None
+        errorStatus = errorIndex = 0
+
+        exception = None
+
+        for idx, varBind in enumerate(varBinds):
+            name, value = varBind
+            if isinstance(value, tuple):  # expect exception tuple
+                debug.logger & debug.flagApp and debug.logger(
+                    '_checkSmiErrors: exception reported for OID %s exception %s' % (name, value))
+
+                if not exception:
+                    exception = value
+
+                # reset exception object
+                varBinds[idx] = name, v2c.null
+
+        try:
+            # TODO: perhaps chain exceptions
+            if exception:
+                debug.logger & debug.flagApp and debug.logger(
+                    '_checkSmiErrors: re-raising exception %s' % (exception,))
+                raise exception[1].with_traceback(exception[2])
+
+        # SNMPv2 SMI exceptions
+        except pysnmp.smi.error.GenError:
+            errorIndication = sys.exc_info()[1]
+            debug.logger & debug.flagApp and debug.logger(
+                '_checkSmiErrors: errorIndication %s' % (errorIndication,))
+
+        except pysnmp.smi.error.SmiError:
+            exc_type, exc_obj, trb = sys.exc_info()
+
+            errorStatus = self.SMI_ERROR_MAP.get(exc_type, 'genErr')
+
+            try:
+                errorIndex = exc_obj['idx'] + 1
+
+            except IndexError:
+                errorIndex = len(varBinds) and 1 or 0
+
+        return errorIndication, errorStatus, errorIndex
 
     def completeMgmtOperation(self, varBinds, **context):
-        self.sendVarBinds(context['snmpEngine'], context['stateReference'],
-                          0, 0, varBinds)
-        self.releaseStateInformation(context['stateReference'])
 
-    # rfc1905: 4.2.1
+        try:
+            (errorIndication,
+             errorStatus, errorIndex) = self._checkSmiErrors(varBinds)
+
+        except pysnmp.error.PySnmpError:
+            self.releaseStateInformation(context['stateReference'])
+            return
+
+        stateReference = context['stateReference']
+
+        if errorIndication:
+            statusInformation = self.__pendingReqs[stateReference]['statusInformation']
+
+            try:
+                # Request REPORT generation
+                statusInformation['oid'] = errorIndication['oid']
+                statusInformation['val'] = errorIndication['val']
+
+            except KeyError:
+                pass
+
+        self.sendVarBinds(context['snmpEngine'], stateReference,
+                          errorStatus, errorIndex, varBinds)
+
+        self.releaseStateInformation(stateReference)
+
     def initiateMgmtOperation(self, snmpEngine, stateReference, contextName, PDU):
-        # rfc1905: 4.2.1.1
-        mgmtFun = self.snmpContext.getMibInstrum(contextName).readVars
         varBinds = v2c.apiPDU.getVarBinds(PDU)
 
+        mgmtFun = self._getMgmtFun(contextName)
+
         context = dict(snmpEngine=snmpEngine,
                        stateReference=stateReference,
                        acFun=self.verifyAccess,
@@ -282,56 +307,54 @@ class GetCommandResponder(CommandResponderBase):
         mgmtFun(*varBinds, **context)
 
 
+class GetCommandResponder(CommandResponderBase):
+    SUPPORTED_PDU_TYPES = (rfc1905.GetRequestPDU.tagSet,)
+
+    # rfc1905: 4.2.1
+    def _getMgmtFun(self, contextName):
+        return self.snmpContext.getMibInstrum(contextName).readVars
+
+
 class NextCommandResponder(CommandResponderBase):
-    pduTypes = (rfc1905.GetNextRequestPDU.tagSet,)
+    SUPPORTED_PDU_TYPES = (rfc1905.GetNextRequestPDU.tagSet,)
-
-    def completeMgmtOperation(self, varBinds, **context):
-        self.sendVarBinds(context['snmpEngine'], context['stateReference'],
-                          0, 0, varBinds)
-        self.releaseStateInformation(context['stateReference'])
 
     # rfc1905: 4.2.2
-    def initiateMgmtOperation(self, snmpEngine, stateReference, contextName, PDU):
+    def _getMgmtFun(self, contextName):
-        # rfc1905: 4.2.2.1
+        return self.snmpContext.getMibInstrum(contextName).readNextVars
-        mgmtFun = self.snmpContext.getMibInstrum(contextName).readNextVars
-
-        varBinds = v2c.apiPDU.getVarBinds(PDU)
-
-        context = dict(snmpEngine=snmpEngine,
-                       stateReference=stateReference,
-                       acFun=self.verifyAccess,
-                       cbFun=self.completeMgmtOperation,
-                       cbCtx=self.cbCtx)
-
-        mgmtFun(*varBinds, **context)
 
 
 class BulkCommandResponder(CommandResponderBase):
-    pduTypes = (rfc1905.GetBulkRequestPDU.tagSet,)
+    SUPPORTED_PDU_TYPES = (rfc1905.GetBulkRequestPDU.tagSet,)
     maxVarBinds = 64
 
+    def _getMgmtFun(self, contextName):
+        return self.snmpContext.getMibInstrum(contextName).readNextVars
+
     def _completeNonRepeaters(self, varBinds, **context):
         context['rspVarBinds'][:] = varBinds
-        context['cbFun'] = self.completeMgmtOperation
 
-        mgmtFun = self.snmpContext.getMibInstrum(context['contextName']).readNextVars
+        if context['counters']['M'] and context['counters']['R']:
+            context['cbFun'] = self.completeMgmtOperation
 
-        mgmtFun(*context['varBinds'], **context)
+            mgmtFun = self._getMgmtFun(context['contextName'])
+
+            mgmtFun(*context['reqVarBinds'], **context)
+
+        else:
+            CommandResponderBase.completeMgmtOperation(self, context['rspVarBinds'], **context)
 
     def completeMgmtOperation(self, varBinds, **context):
         context['rspVarBinds'].extend(varBinds)
         context['counters']['M'] -= 1
 
         if context['counters']['M'] and context['counters']['R']:
-            mgmtFun = self.snmpContext.getMibInstrum(context['contextName']).readNextVars
+            mgmtFun = self._getMgmtFun(context['contextName'])
 
             context['cbFun'] = self.completeMgmtOperation
             mgmtFun(*varBinds[-context['counters']['R']:], **context)
 
         else:
-            self.sendVarBinds(context['snmpEngine'], context['stateReference'],
+            CommandResponderBase.completeMgmtOperation(self, context['rspVarBinds'], **context)
-                              0, 0, varBinds)
-            self.releaseStateInformation(context['stateReference'])
 
     # rfc1905: 4.2.3
     def initiateMgmtOperation(self, snmpEngine, stateReference, contextName, PDU):
@@ -355,7 +378,7 @@ class BulkCommandResponder(CommandResponderBase):
         debug.logger & debug.flagApp and debug.logger(
             'initiateMgmtOperation: N %d, M %d, R %d' % (N, M, R))
 
-        mgmtFun = self.snmpContext.getMibInstrum(contextName).readNextVars
+        mgmtFun = self._getMgmtFun(contextName)
 
         context = dict(snmpEngine=snmpEngine,
                        stateReference=stateReference,
@@ -363,7 +386,7 @@ class BulkCommandResponder(CommandResponderBase):
                        acFun=self.verifyAccess,
                        cbFun=self._completeNonRepeaters,
                        cbCtx=self.cbCtx,
-                       varBinds=varBinds[-R:],
+                       reqVarBinds=varBinds[N:],
                        counters={'M': M, 'R': R},
                        rspVarBinds=[])
 
@@ -371,32 +394,14 @@ class BulkCommandResponder(CommandResponderBase):
 
 
 class SetCommandResponder(CommandResponderBase):
-    pduTypes = (rfc1905.SetRequestPDU.tagSet,)
+    SUPPORTED_PDU_TYPES = (rfc1905.SetRequestPDU.tagSet,)
 
-    def completeMgmtOperation(self, varBinds, **context):
+    SMI_ERROR_MAP = CommandResponderBase.SMI_ERROR_MAP.copy()
-        self.sendVarBinds(context['snmpEngine'], context['stateReference'],
-                          0, 0, varBinds)
-        self.releaseStateInformation(context['stateReference'])
 
-    # rfc1905: 4.2.5
+    # turn missing OIDs into access denial
-    def initiateMgmtOperation(self, snmpEngine, stateReference, contextName, PDU):
+    SMI_ERROR_MAP[pysnmp.smi.error.NoSuchObjectError] = 'notWritable'
-        mgmtFun = self.snmpContext.getMibInstrum(contextName).writeVars
+    SMI_ERROR_MAP[pysnmp.smi.error.NoSuchInstanceError] = 'notWritable'
 
-        varBinds = v2c.apiPDU.getVarBinds(PDU)
+    # rfc1905: 4.2.5.1-13
-
+    def _getMgmtFun(self, contextName):
-        context = dict(snmpEngine=snmpEngine,
+        return self.snmpContext.getMibInstrum(contextName).writeVars
-                       stateReference=stateReference,
-                       acFun=self.verifyAccess,
-                       cbFun=self.completeMgmtOperation,
-                       cbCtx=self.cbCtx)
-
-        # rfc1905: 4.2.5.1-13
-        try:
-            mgmtFun(*varBinds, **context)
-
-        except (pysnmp.smi.error.NoSuchObjectError,
-                pysnmp.smi.error.NoSuchInstanceError):
-            instrumError = pysnmp.smi.error.NotWritableError()
-            instrumError.update(sys.exc_info()[1])
-            self.releaseStateInformation(stateReference)
-            raise instrumError

pysnmp/entity/rfc3413/ntfrcv.py

@@ -14,12 +14,12 @@ from pysnmp import debug
 
 # 3.4
 class NotificationReceiver(object):
-    pduTypes = (v1.TrapPDU.tagSet, v2c.SNMPv2TrapPDU.tagSet,
+    SUPPORTED_PDU_TYPES = (v1.TrapPDU.tagSet, v2c.SNMPv2TrapPDU.tagSet,
-                v2c.InformRequestPDU.tagSet)
+                           v2c.InformRequestPDU.tagSet)
 
     def __init__(self, snmpEngine, cbFun, cbCtx=None):
         snmpEngine.msgAndPduDsp.registerContextEngineId(
-            null, self.pduTypes, self.processPdu  # '' is a wildcard
+            null, self.SUPPORTED_PDU_TYPES, self.processPdu  # '' is a wildcard
         )
 
         self.__snmpTrapCommunity = ''
@@ -33,7 +33,7 @@ class NotificationReceiver(object):
 
     def close(self, snmpEngine):
         snmpEngine.msgAndPduDsp.unregisterContextEngineId(
-            null, self.pduTypes
+            null, self.SUPPORTED_PDU_TYPES
         )
         self.__cbFun = self.__cbCtx = None
 

pysnmp/smi/instrum.py

@@ -6,6 +6,8 @@
 #
 import sys
 import traceback
+import functools
+from pysnmp import nextid
 from pysnmp.smi import error
 from pysnmp import debug
 
@@ -24,39 +26,59 @@ class AbstractMibInstrumController(object):
 
 
 class MibInstrumController(AbstractMibInstrumController):
+    STATUS_OK = 'ok'
+    STATUS_ERROR = 'err'
+    
+    STATE_START = 'start'
+    STATE_STOP = 'stop'
+    STATE_ANY = '*'
+    # These states are actually methods of the MIB objects
+    STATE_READ_TEST = 'readTest'
+    STATE_READ_GET = 'readGet'
+    STATE_READ_TEST_NEXT = 'readTestNext'
+    STATE_READ_GET_NEXT = 'readGetNext'
+    STATE_WRITE_TEST = 'writeTest'
+    STATE_WRITE_COMMIT = 'writeCommit'
+    STATE_WRITE_CLEANUP = 'writeCleanup'
+    STATE_WRITE_UNDO = 'writeUndo'
+
     fsmReadVar = {
         # ( state, status ) -> newState
-        ('start', 'ok'): 'readTest',
+        (STATE_START, STATUS_OK): STATE_READ_TEST,
-        ('readTest', 'ok'): 'readGet',
+        (STATE_READ_TEST, STATUS_OK): STATE_READ_GET,
-        ('readGet', 'ok'): 'stop',
+        (STATE_READ_GET, STATUS_OK): STATE_STOP,
-        ('*', 'err'): 'stop'
+        (STATE_ANY, STATUS_ERROR): STATE_STOP
     }
     fsmReadNextVar = {
         # ( state, status ) -> newState
-        ('start', 'ok'): 'readTestNext',
+        (STATE_START, STATUS_OK): STATE_READ_TEST_NEXT,
-        ('readTestNext', 'ok'): 'readGetNext',
+        (STATE_READ_TEST_NEXT, STATUS_OK): STATE_READ_GET_NEXT,
-        ('readGetNext', 'ok'): 'stop',
+        (STATE_READ_GET_NEXT, STATUS_OK): STATE_STOP,
-        ('*', 'err'): 'stop'
+        (STATE_ANY, STATUS_ERROR): STATE_STOP
     }
     fsmWriteVar = {
         # ( state, status ) -> newState
-        ('start', 'ok'): 'writeTest',
+        (STATE_START, STATUS_OK): STATE_WRITE_TEST,
-        ('writeTest', 'ok'): 'writeCommit',
+        (STATE_WRITE_TEST, STATUS_OK): STATE_WRITE_COMMIT,
-        ('writeCommit', 'ok'): 'writeCleanup',
+        (STATE_WRITE_COMMIT, STATUS_OK): STATE_WRITE_CLEANUP,
-        ('writeCleanup', 'ok'): 'readTest',
+        (STATE_WRITE_CLEANUP, STATUS_OK): STATE_READ_TEST,
         # Do read after successful write
-        ('readTest', 'ok'): 'readGet',
+        (STATE_READ_TEST, STATUS_OK): STATE_READ_GET,
-        ('readGet', 'ok'): 'stop',
+        (STATE_READ_GET, STATUS_OK): STATE_STOP,
         # Error handling
-        ('writeTest', 'err'): 'writeCleanup',
+        (STATE_WRITE_TEST, STATUS_ERROR): STATE_WRITE_CLEANUP,
-        ('writeCommit', 'err'): 'writeUndo',
+        (STATE_WRITE_COMMIT, STATUS_ERROR): STATE_WRITE_UNDO,
-        ('writeUndo', 'ok'): 'readTest',
+        (STATE_WRITE_UNDO, STATUS_OK): STATE_READ_TEST,
         # Ignore read errors (removed columns)
-        ('readTest', 'err'): 'stop',
+        (STATE_READ_TEST, STATUS_ERROR): STATE_STOP,
-        ('readGet', 'err'): 'stop',
+        (STATE_READ_GET, STATUS_ERROR): STATE_STOP,
-        ('*', 'err'): 'stop'
+        (STATE_ANY, STATUS_ERROR): STATE_STOP
     }
 
+    FSM_CONTEXT = '_fsmContext'
+
+    FSM_SESSION_ID = nextid.Integer(0xffffffff)
+
     def __init__(self, mibBuilder):
         self.mibBuilder = mibBuilder
         self.lastBuildId = -1
@@ -183,88 +205,115 @@ class MibInstrumController(AbstractMibInstrumController):
 
     # MIB instrumentation
 
-    def flipFlopFsm(self, fsmTable, *varBinds, **context):
+    def _flipFlopFsmCb(self, varBind, **context):
+        fsmContext = context[self.FSM_CONTEXT]
 
+        varBinds = fsmContext['varBinds']
+
+        idx = context.pop('idx')
+
+        if idx >= 0:
+            fsmContext['count'] += 1
+
+            varBinds[idx] = varBind
+
+            debug.logger & debug.flagIns and debug.logger(
+                '_flipFlopFsmCb: var-bind %d, processed %d, expected %d' % (idx, fsmContext['count'], len(varBinds)))
+
+            if fsmContext['count'] < len(varBinds):
+                return
+
+        debug.logger & debug.flagIns and debug.logger(
+            '_flipFlopFsmCb: finished, output %r' % (varBinds,))
+
+        fsmCallable = fsmContext['fsmCallable']
+
+        fsmCallable(**context)
+
+    def flipFlopFsm(self, fsmTable, *varBinds, **context):
         try:
-            fsmContext = context['fsmState']
+            fsmContext = context[self.FSM_CONTEXT]
 
         except KeyError:
             self.__indexMib()
 
-            fsmContext = context['fsmState'] = dict(varBinds=[], state='start', status='ok')
+            fsmContext = context[self.FSM_CONTEXT] = dict(
+                sessionId=self.FSM_SESSION_ID(),
+                varBinds=list(varBinds[:]),
+                fsmCallable=functools.partial(self.flipFlopFsm, fsmTable, *varBinds),
+                state=self.STATE_START, status=self.STATUS_OK
+            )
 
             debug.logger & debug.flagIns and debug.logger('flipFlopFsm: input var-binds %r' % (varBinds,))
 
         mibTree, = self.mibBuilder.importSymbols('SNMPv2-SMI', 'iso')
 
-        outputVarBinds = fsmContext['varBinds']
         state = fsmContext['state']
         status = fsmContext['status']
 
-        origExc = origTraceback = None
+        debug.logger & debug.flagIns and debug.logger(
+            'flipFlopFsm: current state %s, status %s' % (state, status))
+
+        try:
+            newState = fsmTable[(state, status)]
+
+        except KeyError:
+            try:
+                newState = fsmTable[(self.STATE_ANY, status)]
+
+            except KeyError:
+                raise error.SmiError('Unresolved FSM state %s, %s' % (state, status))
+
+        debug.logger & debug.flagIns and debug.logger(
+            'flipFlopFsm: state %s status %s -> new state %s' % (state, status, newState))
+
+        state = newState
+
+        if state == self.STATE_STOP:
+            context.pop(self.FSM_CONTEXT, None)
+
+            cbFun = context.get('cbFun')
+            if cbFun:
+                varBinds = fsmContext['varBinds']
+                cbFun(varBinds, **context)
+
+            return
+
+        fsmContext.update(state=state, count=0)
+
+        # the case of no var-binds
+        if not varBinds:
+            return self._flipFlopFsmCb(None, idx=-1, **context)
+
+        mgmtFun = getattr(mibTree, state, None)
+        if not mgmtFun:
+            raise error.SmiError(
+                'Unsupported state handler %s at %s' % (state, self)
+            )
+
+        for idx, varBind in enumerate(varBinds):
+            try:
+                # TODO: managed objects to run asynchronously
+                #mgmtFun(varBind, idx=idx, **context)
+                self._flipFlopFsmCb(mgmtFun(varBind, idx=idx, **context), idx=idx, **context)
+
+            except error.SmiError:
+                exc = sys.exc_info()
+                debug.logger & debug.flagIns and debug.logger(
+                    'flipFlopFsm: fun %s exception %s for %r with traceback: %s' % (
+                        mgmtFun, exc[0], varBind, traceback.format_exception(*exc)))
+
+                varBind = varBind[0], exc
+
+                fsmContext['status'] = self.STATUS_ERROR
+
+                self._flipFlopFsmCb(varBind, idx=idx, **context)
+
+                return
 
-        while True:
-            k = state, status
-            if k in fsmTable:
-                fsmState = fsmTable[k]
             else:
-                k = '*', status
+                debug.logger & debug.flagIns and debug.logger(
-                if k in fsmTable:
+                    'flipFlopFsm: func %s initiated for %r' % (mgmtFun, varBind))
-                    fsmState = fsmTable[k]
-                else:
-                    raise error.SmiError(
-                        'Unresolved FSM state %s, %s' % (state, status)
-                    )
-            debug.logger & debug.flagIns and debug.logger(
-                'flipFlopFsm: state %s status %s -> fsmState %s' % (state, status, fsmState))
-            state = fsmState
-            status = 'ok'
-            if state == 'stop':
-                break
-
-            for idx, (name, val) in enumerate(varBinds):
-                mgmtFun = getattr(mibTree, state, None)
-                if not mgmtFun:
-                    raise error.SmiError(
-                        'Unsupported state handler %s at %s' % (state, self)
-                    )
-
-                context['idx'] = idx
-
-                try:
-                    # Convert to tuple to avoid ObjectName instantiation
-                    # on subscription
-                    rval = mgmtFun((tuple(name), val), **context)
-
-                except error.SmiError:
-                    exc_t, exc_v, exc_tb = sys.exc_info()
-                    debug.logger & debug.flagIns and debug.logger(
-                        'flipFlopFsm: fun %s exception %s for %s=%r with traceback: %s' % (
-                            mgmtFun, exc_t, name, val, traceback.format_exception(exc_t, exc_v, exc_tb)))
-                    if origExc is None:  # Take the first exception
-                        origExc, origTraceback = exc_v, exc_tb
-                    status = 'err'
-                    break
-                else:
-                    debug.logger & debug.flagIns and debug.logger(
-                        'flipFlopFsm: fun %s succeeded for %s=%r' % (mgmtFun, name, val))
-                    if rval is not None:
-                        outputVarBinds.append((rval[0], rval[1]))
-
-        if origExc:
-            if sys.version_info[0] <= 2:
-                raise origExc
-            else:
-                try:
-                    raise origExc.with_traceback(origTraceback)
-                finally:
-                    # Break cycle between locals and traceback object
-                    # (seems to be irrelevant on Py3 but just in case)
-                    del origTraceback
-
-        cbFun = context.get('cbFun')
-        if cbFun:
-            cbFun(outputVarBinds, **context)
 
     def readVars(self, *varBinds, **context):
         self.flipFlopFsm(self.fsmReadVar, *varBinds, **context)