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289 lines
7.6 KiB
289 lines
7.6 KiB
#!/usr/bin/env python
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"""ROS has a parameter server, we have files.
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The parameter store is a persistent key value store, implemented as a directory with a writer lock.
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On Android, we store params under params_dir = /data/params. The writer lock is a file
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"<params_dir>/.lock" taken using flock(), and data is stored in a directory symlinked to by
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"<params_dir>/d".
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Each key, value pair is stored as a file with named <key> with contents <value>, located in
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<params_dir>/d/<key>
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Readers of a single key can just open("<params_dir>/d/<key>") and read the file contents.
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Readers who want a consistent snapshot of multiple keys should take the lock.
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Writers should take the lock before modifying anything. Writers should also leave the DB in a
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consistent state after a crash. The implementation below does this by copying all params to a temp
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directory <params_dir>/<tmp>, then atomically symlinking <params_dir>/<d> to <params_dir>/<tmp>
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before deleting the old <params_dir>/<d> directory.
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Writers that only modify a single key can simply take the lock, then swap the corresponding value
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file in place without messing with <params_dir>/d.
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"""
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import time
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import os
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import errno
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import sys
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import shutil
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import fcntl
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import tempfile
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from enum import Enum
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def mkdirs_exists_ok(path):
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try:
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os.makedirs(path)
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except OSError:
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if not os.path.isdir(path):
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raise
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class TxType(Enum):
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PERSISTANT = 1
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CLEAR_ON_MANAGER_START = 2
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CLEAR_ON_CAR_START = 3
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class UnknownKeyName(Exception):
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pass
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keys = {
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# written: manager
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# read: loggerd, uploaderd, baseui
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"DongleId": TxType.PERSISTANT,
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"AccessToken": TxType.PERSISTANT,
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"Version": TxType.PERSISTANT,
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"GitCommit": TxType.PERSISTANT,
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"GitBranch": TxType.PERSISTANT,
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# written: baseui
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# read: ui, controls
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"IsMetric": TxType.PERSISTANT,
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"IsRearViewMirror": TxType.PERSISTANT,
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# written: visiond
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# read: visiond
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"CalibrationParams": TxType.PERSISTANT,
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# written: visiond
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# read: visiond, ui
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"CloudCalibration": TxType.PERSISTANT,
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# written: controlsd
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# read: radard
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"CarParams": TxType.CLEAR_ON_CAR_START}
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class FileLock(object):
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def __init__(self, path, create):
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self._path = path
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self._create = create
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self._fd = None
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def acquire(self):
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self._fd = os.open(self._path, os.O_CREAT if self._create else 0)
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fcntl.flock(self._fd, fcntl.LOCK_EX)
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def release(self):
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if self._fd is not None:
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os.close(self._fd)
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self._fd = None
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class DBAccessor(object):
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def __init__(self, path):
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self._path = path
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self._vals = None
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def keys(self):
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self._check_entered()
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return self._vals.keys()
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def get(self, key):
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self._check_entered()
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try:
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return self._vals[key]
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except KeyError:
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return None
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def _get_lock(self, create):
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lock = FileLock(os.path.join(self._path, ".lock"), create)
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lock.acquire()
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return lock
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def _read_values_locked(self):
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"""Callers should hold a lock while calling this method."""
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vals = {}
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try:
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data_path = self._data_path()
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keys = os.listdir(data_path)
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for key in keys:
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with open(os.path.join(data_path, key), "rb") as f:
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vals[key] = f.read()
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except (OSError, IOError) as e:
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# Either the DB hasn't been created yet, or somebody wrote a bug and left the DB in an
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# inconsistent state. Either way, return empty.
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if e.errno == errno.ENOENT:
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return {}
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return vals
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def _data_path(self):
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return os.path.join(self._path, "d")
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def _check_entered(self):
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if self._vals is None:
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raise Exception("Must call __enter__ before using DB")
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class DBReader(DBAccessor):
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def __enter__(self):
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try:
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lock = self._get_lock(False)
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except OSError as e:
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# Do not create lock if it does not exist.
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if e.errno == errno.ENOENT:
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self._vals = {}
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return self
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try:
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# Read everything.
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self._vals = self._read_values_locked()
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return self
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finally:
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lock.release()
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def __exit__(self, type, value, traceback): pass
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class DBWriter(DBAccessor):
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def __init__(self, path):
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super(DBWriter, self).__init__(path)
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self._lock = None
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self._prev_umask = None
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def put(self, key, value):
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self._vals[key] = value
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def delete(self, key):
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self._vals.pop(key, None)
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def __enter__(self):
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mkdirs_exists_ok(self._path)
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# Make sure we can write and that permissions are correct.
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self._prev_umask = os.umask(0)
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try:
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os.chmod(self._path, 0o777)
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self._lock = self._get_lock(True)
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self._vals = self._read_values_locked()
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except:
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os.umask(self._prev_umask)
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self._prev_umask = None
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raise
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return self
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def __exit__(self, type, value, traceback):
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self._check_entered()
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try:
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old_data_path = None
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new_data_path = None
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tempdir_path = tempfile.mkdtemp(prefix=".tmp", dir=self._path)
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try:
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# Write back all keys.
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os.chmod(tempdir_path, 0o777)
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for k, v in self._vals.items():
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with open(os.path.join(tempdir_path, k), "wb") as f:
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f.write(v)
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data_path = self._data_path()
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try:
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old_data_path = os.path.join(self._path, os.readlink(data_path))
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except (OSError, IOError) as e:
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# NOTE(mgraczyk): If other DB implementations have bugs, this could cause
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# copies to be left behind, but we still want to overwrite.
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pass
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new_data_path = "{}.link".format(tempdir_path)
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os.symlink(os.path.basename(tempdir_path), new_data_path)
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os.rename(new_data_path, data_path)
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# TODO(mgraczyk): raise useful error when values are bad.
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except:
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shutil.rmtree(tempdir_path)
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if new_data_path is not None:
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os.remove(new_data_path)
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raise
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# Keep holding the lock while we clean up the old data.
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if old_data_path is not None:
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shutil.rmtree(old_data_path)
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finally:
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os.umask(self._prev_umask)
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self._prev_umask = None
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# Always release the lock.
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self._lock.release()
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self._lock = None
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class JSDB(object):
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def __init__(self, fn):
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self._fn = fn
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def begin(self, write=False):
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if write:
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return DBWriter(self._fn)
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else:
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return DBReader(self._fn)
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class Params(object):
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def __init__(self, db='/data/params'):
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self.env = JSDB(db)
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def _clear_keys_with_type(self, tx_type):
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with self.env.begin(write=True) as txn:
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for key in keys:
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if keys[key] == tx_type:
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txn.delete(key)
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def manager_start(self):
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self._clear_keys_with_type(TxType.CLEAR_ON_MANAGER_START)
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def car_start(self):
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self._clear_keys_with_type(TxType.CLEAR_ON_CAR_START)
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def get(self, key, block=False):
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if key not in keys:
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raise UnknownKeyName(key)
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while 1:
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with self.env.begin() as txn:
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ret = txn.get(key)
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if not block or ret is not None:
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break
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# is polling really the best we can do?
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time.sleep(0.05)
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return ret
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def put(self, key, dat):
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if key not in keys:
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raise UnknownKeyName(key)
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with self.env.begin(write=True) as txn:
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txn.put(key, dat)
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print "set", key
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if __name__ == "__main__":
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params = Params()
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if len(sys.argv) > 2:
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params.put(sys.argv[1], sys.argv[2])
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else:
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for k in keys:
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pp = params.get(k)
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if pp is None:
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print k, "is None"
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elif all(ord(c) < 128 and ord(c) >= 32 for c in pp):
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print k, pp
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else:
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print k, pp.encode("hex")
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# Test multiprocess:
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# seq 0 100000 | xargs -P20 -I{} python common/params.py DongleId {} && sleep 0.05
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# while python common/params.py DongleId; do sleep 0.05; done
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