[PATCH-next v3 12/21] add lnst.Tests.CPUStatMonitor

From: Ondrej Lichtner <olichtne(a)redhat.com&gt;

This test module can be used to periodically sample the /proc/stat file
for statistics and report back a list of differences between the
individual samples as well as the raw data.

Can be used to calculate per-cpu and system wide cpu utilization.

Currently the test module samples until interrupted, so it should be run
in the background and stopped with a job.kill(signal.SIGINT) call.

v2:
    * added a comment explaining the interval parameter
    * added a default value for the old_handler variable. In case the
      signal.signal call fails this will be used to avoid a NameError
      exception in the finally block
v3:
    * improved sample parsing based on comment from jtluka, removing the
      useless condition from the loop

Signed-off-by: Ondrej Lichtner <olichtne(a)redhat.com&gt;
---
 lnst/Tests/CPUStatMonitor.py | 115 +++++++++++++++++++++++++++++++++++
 1 file changed, 115 insertions(+)
 create mode 100644 lnst/Tests/CPUStatMonitor.py

diff --git a/lnst/Tests/CPUStatMonitor.py b/lnst/Tests/CPUStatMonitor.py
new file mode 100644
index 0000000..6e317ea
--- /dev/null
+++ b/lnst/Tests/CPUStatMonitor.py
@@ -0,0 +1,115 @@
+import re
+import time
+import signal
+from time import sleep
+from lnst.Common.Parameters import IntParam
+from lnst.Tests.BaseTestModule import BaseTestModule, TestModuleError,
InterruptException
+
+def sigint_handler(signum, frame):
+    raise InterruptException()
+
+class CPUStatMonitor(BaseTestModule):
+    #number of miliseconds to sleep between each sample
+    interval = IntParam(default=1000)
+
+    def run(self):
+        self._res_data = {}
+
+        raw_samples = []
+        old_handler = None
+        try:
+            old_handler = signal.signal(signal.SIGINT, sigint_handler)
+            with open("/proc/stat") as stat:
+                while True:
+                    stat.seek(0)
+                    timestamp = time.time()
+                    stat_lines = "".join(stat.readlines())
+                    raw_samples.append({
+                        "timestamp": timestamp,
+                        "stat": stat_lines
+                        })
+                    sleep(self.params.interval / float(1000))
+        except InterruptException:
+            pass
+        finally:
+            if old_handler is not None:
+                signal.signal(signal.SIGINT, old_handler)
+
+        self._res_data["raw_data"] = raw_samples
+        self._res_data["data"] = self._process_samples(raw_samples)
+
+        return True
+
+    def _process_samples(self, samples):
+        result = []
+        prev_sample = samples[0]
+        for sample in samples[1:]:
+            parsed_prev = self._parse_stat_lines(prev_sample["stat"])
+            parsed_cur = self._parse_stat_lines(sample["stat"])
+
+            interval = self._subtract_nested_dicts(parsed_cur, parsed_prev)
+            interval["duration"] = (sample["timestamp"] -
+                                    prev_sample["timestamp"])
+
+            result.append(interval)
+
+            prev_sample = sample
+        return result
+
+    def _subtract_nested_dicts(self, first, second):
+        result = {}
+        for key, val in first.items():
+            if isinstance(val, dict):
+                result[key] = self._subtract_nested_dicts(val, second[key])
+            else:
+                result[key] = val - second[key]
+        return result
+
+    def _parse_stat_lines(self, stat):
+        result = {}
+        for line in stat.split("\n"):
+            cpu_data = self._parse_cpu_stats(line)
+            if cpu_data:
+                result[cpu_data[0]] = cpu_data[1]
+                continue
+
+            intr_data = self._parse_intr_stats(line)
+            if intr_data:
+                result[intr_data[0]] = intr_data[1]
+                continue
+
+            m = re.match(r"^(.*?) (\d+)$", line)
+            if m:
+                result[m.group(1)] = int(m.group(2))
+        return result
+
+    def _parse_cpu_stats(self, stat_line):
+        result = {}
+        m = re.match(r"^(cpu\d*)\s+(\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+) (\d+)
(\d+) (\d+)$",
+                     stat_line)
+        if m:
+            cpu = m.group(1)
+            result["user"] = int(m.group(2))
+            result["nice"] = int(m.group(3))
+            result["system"] = int(m.group(4))
+            result["idle"] = int(m.group(5))
+            result["iowait"] = int(m.group(6))
+            result["irq"] = int(m.group(7))
+            result["softirq"] = int(m.group(8))
+            result["steal"] = int(m.group(9))
+            result["guest"] = int(m.group(10))
+            result["guest_nice"] = int(m.group(11))
+            return cpu, result
+        else:
+            return None
+
+    def _parse_intr_stats(self, stat_line):
+        result = {}
+        m = re.match(r"^(intr|softirq) (\d+) (.*)$", stat_line)
+        if m:
+            result["total"] = int(m.group(2))
+            for i, irq in enumerate(m.group(3).split(" ")):
+                result[i] = int(irq)
+            return m.group(1), result
+        else:
+            return None
-- 
2.19.1