stat.py

import sqlitedict
import psutil
from uuid import uuid4

class ResourceTracker(object):
	def __init__(self, cpu_usage_total=0, memory_usage_total=0, runtime_total=0, pid=None):
		self.cpu_total = cpu_usage_total
		self.memory_total = memory_usage_total
		self.runtime_total = runtime_total
		self.pid = pid
	
	def update(self, ps_process, time_elapsed):
		self.cpu_total += ps_process.cpu_percent()
		self.memory_used += ps_process.memory_info()[0]
		self.runtime_total += time_elapsed

metrics_store = sqlitedict.open("metrics_store.db")
interval = 30
# In process status update loop
for process in processes:
	tracker = metrics_store.get(process.pid, None) # Deserialize existing record or return None
	if tracker is None:
		tracker = ResourceTracker() # Make fresh record because no reference was present
		process.cpu_percent() # Clear the first dummy value returned by cpu_percent
	tracker.update(process, interval) # Mutate record in memory
	metrics_store[process.pid] = tracker # Serialize record onto disk

	if process.is_complete(): # However you decide the process terminated successfully
		tracker = metrics_store.get(process.pid)
		metrics_store[process.pid] = None # Clear the pid in case it is re-used
		metrics_store[str(process.pid) + '-' + uuid4().hex] = tracker # Set up unique storage for this completed process

metrics_store.commit() # At the end of a status update loop for all currently running processes

# Later, after the run, re-open the database created by a given run and tally up the runtime
# statistics