extract fields from fio JSON output

Closes ceph#8

Author: bengland2

tools/fio-parse-json.py

@@ -0,0 +1,93 @@
+#!/usr/bin/python
+#
+# fio-json-prs.py - example script to parse distributed workload generation result 
+# produced by fio in JSON format
+#
+# input parameters:
+#  1 - JSON file - file containing fio JSON output
+#  2 - JSON path - path through JSON tree to a leaf node
+#
+# assumption: json output of non-leaf nodes consists of either
+# - dictionary - key field selects sub-value
+# - sequence - key field syntax is name=value, where
+#              name is a dictionary key of sequence elements, and
+#              value is the desired value to select a sequence element
+# example:
+# python fio-parse-json.py r.fiojob.json.log 'jobs/jobname=randread/read/iops'
+# 
+
+import os, sys
+from pprint import pprint
+import json
+
+NOTOK=1
+
+if len(sys.argv) < 3:
+  print('usage: fio-parse-json.py fio-json.log path-to-leaf')
+  print('path-to-leaf is a slash-separated list of key names in JSON tree')
+  print('see instructions at top of this script')
+  sys.exit(NOTOK)
+
+
+def filter_json_node(next_branch, node_list_in):
+  #print next_branch, json.dumps(node, indent=4)
+  #print ''
+  #sys.stdout.flush()
+  next_node_list = []
+  for n in node_list_in:
+	dotlist = next_branch.split('=')
+	if len(dotlist) > 2:
+		print('unrecognized syntax at %s'%str(node))
+		sys.exit(NOTOK)
+	elif len(dotlist) == 1:
+		next_node_list.append(n[next_branch])
+		assert(isinstance(n, dict))
+	else: # must be a sequence, take any element with key matching value
+		select_key = dotlist[0]
+		select_value = dotlist[1]
+		for e in n:  # node is a seq
+			#print 'select with key %s value %s sequence element %s'%(select_key, select_value, e)
+			if select_value == '*':
+				next_node_list.append(e)
+			else:
+				v = e[select_key]
+				if v == select_value:
+					next_node_list.append(e)
+			
+		if len(next_node_list) == 0:
+			print('no list member in %s has key %s value %s'%(str(node), select_key, select_value))
+			sys.exit(NOTOK)
+  return next_node_list
+
+
+fn = sys.argv[1]
+json_tree_path = sys.argv[2].split('/')
+with open(fn, 'r') as json_data:
+
+  # check for empty file
+
+  f_info = os.fstat(json_data.fileno())
+  if f_info.st_size == 0:
+    print('JSON input file %s is empty'%fn)
+    sys.exit(NOTOK)
+
+  # find start of JSON object and position file handle right before that
+
+  lines = json_data.readlines()
+  start_of_json_data=0
+  for l in lines:
+    if l[0] == '{': break
+    start_of_json_data += 1
+  json_data.seek(0, os.SEEK_SET)
+  for j in range(0,start_of_json_data):
+    l = json_data.readline()
+
+  # parse the JSON object
+
+  node = json.load(json_data)
+  current_branch = None
+  next_node_list = [node]
+  for next_branch in json_tree_path:
+	next_node_list = filter_json_node(next_branch, next_node_list)
+  for n in next_node_list: print(n)
+