common code extended with task decorator require_exec and generaliz…

…ation of default targets

src/netrics/measurement/common/__init__.py

@@ -6,3 +6,5 @@
 )
 
 from .dns import AddressLookups  # noqa: F401
+
+from .executable import require_exec  # noqa: F401

src/netrics/measurement/common/connectivity/decorator.py

@@ -159,7 +159,7 @@ def main():
 
     """
     schema = ConfSchema({
-        Optional('destinations', default=default.PING_DESTINATIONS):
+        Optional('destinations', default=default.DESTINATIONS):
             task.schema.DestinationList(),
 
         Optional('attempts', default=command.DEFAULT_ATTEMPTS):

src/netrics/measurement/common/connectivity/default.py

@@ -1,3 +1,3 @@
-PING_DESTINATIONS = ('google.com',
-                     'facebook.com',
-                     'nytimes.com')
+DESTINATIONS = ('google.com',
+                'facebook.com',
+                'nytimes.com')

src/netrics/measurement/common/executable.py

@@ -0,0 +1,43 @@
+"""Common helpers requiring system executables"""
+import functools
+import shutil
+
+import netrics.task
+
+
+class ExecTask:
+    """Wrapped callable requiring a named system executable."""
+
+    def __init__(self, name, func):
+        self._executable_name_ = name
+
+        # assign func's __module__, __name__, etc.
+        # (but DON'T update __dict__)
+        #
+        # (also assigns __wrapped__)
+        functools.update_wrapper(self, func, updated=())
+
+    def __repr__(self):
+        return repr(self.__wrapped__)
+
+    def __call__(self, *args, **kwargs):
+        # ensure executable on PATH
+        executable_path = shutil.which(self._executable_name_)
+
+        if executable_path is None:
+            netrics.task.log.critical(f"{self._executable_name_} executable not found")
+            return netrics.task.status.file_missing
+
+        return self.__wrapped__(executable_path, *args, **kwargs)
+
+
+class require_exec:
+    """Decorator constructor to wrap a callable such that it first
+    checks that the named system executable is accessible via `PATH`.
+
+    """
+    def __init__(self, name):
+        self.executable_name = name
+
+    def __call__(self, func):
+        return ExecTask(self.executable_name, func)

src/netrics/measurement/lml.py

@@ -1,7 +1,6 @@
 """Measure latency to the "last mile" host via scamper."""
 import json
 import random
-import shutil
 import statistics
 import subprocess
 from ipaddress import ip_address
@@ -11,7 +10,11 @@
 
 from netrics import task
 
-from .common import AddressLookups, require_net
+from .common import (
+    AddressLookups,
+    require_exec,
+    require_net,
+)
 
 
 #
@@ -45,8 +48,9 @@
 
 
 @task.param.require(PARAMS)
+@require_exec('scamper')
 @require_net
-def main(params):
+def main(scamper, params):
     """Measure latency to the "last mile" host via scamper.
 
     The local network, and then internet hosts (as configured in global
@@ -67,12 +71,6 @@ def main(params):
     parsed and written out according to configuration.
 
     """
-    # ensure scamper on PATH
-    scamper_path = shutil.which('scamper')
-    if scamper_path is None:
-        task.log.critical("scamper executable not found")
-        return task.status.file_missing
-
     # resolve destination(s) given by domain to IP
     address_lookups = AddressLookups(params.destinations)
 
@@ -97,7 +95,7 @@ def main(params):
         try:
             process = subprocess.run(
                 (
-                    scamper_path,
+                    scamper,
                     '-O', 'json',
                     '-c', trace_cmd,
                     '-i', target_ip,

src/netrics/measurement/lml_traceroute.py

@@ -1,7 +1,6 @@
 """Measure latency to the "last mile" host via traceroute & ping."""
 import random
 import re
-import shutil
 import subprocess
 import typing
 from ipaddress import ip_address
@@ -10,7 +9,11 @@
 
 from netrics import task
 
-from .common import output, require_net
+from .common import (
+    output,
+    require_exec,
+    require_net,
+)
 
 
 #
@@ -39,8 +42,9 @@
 
 
 @task.param.require(PARAMS)
+@require_exec('traceroute')
 @require_net
-def main(params):
+def main(traceroute, params):
     """Measure latency to the "last mile" host via traceroute and ping.
 
     The local network, and then internet hosts (as configured in global
@@ -62,13 +66,6 @@ def main(params):
     written as well.
 
     """
-    # ensure traceroute on PATH
-    # (ping is used by require_net)
-    traceroute_path = shutil.which('traceroute')
-    if traceroute_path is None:
-        task.log.critical("traceroute executable not found")
-        return task.status.file_missing
-
     # randomize target from configured destination(s)
     target_hosts = list(params.destinations)
     random.shuffle(target_hosts)
@@ -77,9 +74,9 @@ def main(params):
     for target_host in target_hosts:
         # trace target
         try:
-            traceroute = subprocess.run(
+            traceroute_process = subprocess.run(
                 (
-                    traceroute_path,
+                    traceroute,
                     target_host,
                 ),
                 capture_output=True,
@@ -99,37 +96,37 @@ def main(params):
         # extract "last mile" host from trace
         try:
             last_mile = LastMileResult.extract(target_host,
-                                               traceroute.stdout,
-                                               traceroute.stderr)
+                                               traceroute_process.stdout,
+                                               traceroute_process.stderr)
         except TracerouteAddressError as exc:
             task.log.error(
                 dest=target_host,
-                stdout=traceroute.stdout,
-                stderr=traceroute.stderr,
+                stdout=traceroute_process.stdout,
+                stderr=traceroute_process.stderr,
                 line=exc.line,
                 msg='failed to parse traceroute hop ip address from output line',
             )
             continue
         except TracerouteParseError as exc:
             task.log.error(
                 dest=target_host,
-                stdout=traceroute.stdout,
-                stderr=traceroute.stderr,
+                stdout=traceroute_process.stdout,
+                stderr=traceroute_process.stderr,
                 line=exc.line,
                 msg='unexpected traceroute output line or parse failure',
             )
             continue
         except TracerouteOutputError:
             task.log.error(
                 dest=target_host,
-                stdout=traceroute.stdout,
-                stderr=traceroute.stderr,
+                stdout=traceroute_process.stdout,
+                stderr=traceroute_process.stderr,
                 msg='failed to extract last mile ip from traceroute output',
             )
             continue
 
         # ping last mile host
-        ping = subprocess.run(
+        ping_process = subprocess.run(
             (
                 'ping',
                 '-c', params.count,
@@ -141,18 +138,18 @@ def main(params):
             text=True,
         )
 
-        if ping.returncode > 1:
+        if ping_process.returncode > 1:
             task.log.critical(
                 dest=last_mile.ip_address,
-                status=f'Error ({ping.returncode})',
-                stdout=ping.stdout,
-                stderr=ping.stderr,
+                status=f'Error ({ping_process.returncode})',
+                stdout=ping_process.stdout,
+                stderr=ping_process.stderr,
                 msg='last mile ping failure',
             )
             return task.status.no_host
 
         # parse ping results
-        ping_stats = output.parse_ping(ping.stdout)
+        ping_stats = output.parse_ping(ping_process.stdout)
 
         break  # we're done!
     else:

src/netrics/measurement/ping.py

@@ -36,7 +36,7 @@
     # destinations: (ping): list of hosts
     #                       OR mapping of hosts to their labels (for results)
     Optional('destinations',
-             default=default.PING_DESTINATIONS): task.schema.DestinationCollection(),
+             default=default.DESTINATIONS): task.schema.DestinationCollection(),
 
     # count: (ping): natural number
     Optional('count', default='10'): task.schema.NaturalStr('count'),