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# to you under the Apache License, Version 2.0 (the
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#
#   http://www.apache.org/licenses/LICENSE-2.0
#
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#
# Verifier for memtracker usage values (Total, Peak, etc).

import re

SIZE_FACTORS = {"b": 1, "kb": 1 << 10, "mb": 1 << 20, "gb": 1 << 30}

def parse_mem_value(value):
  """Parses a memory value with an optional unit like "123", "10 B", or "1.5 KB" into an
  number of bytes.
  """
  elements = value.split()
  result = float(elements[0])
  if len(elements) > 1:
    result *= SIZE_FACTORS[elements[1].lower()]
  return result

class MemUsageVerifier(object):
  """MemUsageVerifier objects can be used to verify values in the debug output of memory
  trackers.
  """

  def __init__(self, impalad_service):
    """Initialize module given an ImpalaService object"""
    self.impalad_service = impalad_service

  def get_mem_usage_values(self, name):
    """Returns a dictionary of all key=value pairs of the memtracker specified by 'name'
    by reading the '/memz' debug webpage. It also parses and converts memory values
    including optional units like "10 B" or "1.5 KB". All strings are converted to
    lowercase. Only the first line starting with 'name' is considered.

    For example, for the line "Data Stream Service: Total=0 Peak=108.00 B" this will
    return "dict(total=0, peak=108.0)".
    """
    memz = self.impalad_service.get_debug_webpage_json("memz")
    details = memz.get("detailed", "")
    for line in details.splitlines():
      line = line.strip()
      prefix = name + ":"
      if line.startswith(prefix):
        line = line[len(prefix):]
        result = {}
        # The value regex matches either '0' or any number including a decimal dot,
        # followed by a required unit.
        for k, v in re.findall(r"(\S+)=(0|[\d\.]+ [KMG]?B)", line):
          result[k.lower()] = parse_mem_value(v)
        return result
    return {}