Add histogram, add hdfs. (#657)

* Add histogram, add hdfs.

demo/components/histogram_test.py

+# Copyright (c) 2020 VisualDL Authors. All Rights Reserve.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+# =======================================================================
+# coding=utf-8
+from visualdl import LogWriter
+import numpy as np
+
+
+if __name__ == '__main__':
+    values = np.arange(0, 1000)
+    with LogWriter(logdir="./log/histogram_test/train") as writer:
+        for index in range(5):
+            writer.add_histogram(tag='default1',
+                                 values=values+index,
+                                 step=index,
+                                 buckets=10)

requirements.txt

@@ -8,3 +8,4 @@ Flask-Babel >= 1.0.0
 six >= 1.14.0
 protobuf >= 3.1.0
 opencv-python
+hdfs

visualdl/component/__init__.py

@@ -24,5 +24,11 @@ components = {
     },
     "audio": {
         "enabled": False
+    },
+    "histogram": {
+        "enabled": False
+    },
+    "graph": {
+        "enabled": False
     }
 }

visualdl/component/base_component.py

@@ -131,3 +131,11 @@ def audio(tag, audio_array, sample_rate, step, walltime):
     return Record(values=[
         Record.Value(id=step, tag=tag, timestamp=walltime, audio=audio_data)
     ])
+
+
+def histogram(tag, hist, bin_edges, step, walltime):
+    histogram = Record.Histogram(hist=hist, bin_edges=bin_edges)
+    return Record(values=[
+        Record.Value(
+            id=step, tag=tag, timestamp=walltime, histogram=histogram)
+    ])

visualdl/io/bfile.py

@@ -15,6 +15,7 @@
 
 import os
 import tempfile
+import hdfs
 
 # Note: Some codes here refer to TensorBoardX.
 # A good default block size depends on the system in question.
@@ -90,6 +91,51 @@ class LocalFileSystem(object):
 default_file_factory.register_filesystem("", LocalFileSystem())
 
 
+class HDFileSystem(object):
+    def __init__(self):
+        self.cli = hdfs.config.Config().get_client('dev')
+
+    def exists(self, path):
+        if self.cli.status(hdfs_path=path[7:], strict=False) is None:
+            return False
+        else:
+            return True
+
+    def makedirs(self, path):
+        self.cli.makedirs(hdfs_path=path[7:])
+
+    @staticmethod
+    def join(path, *paths):
+        return os.path.join(path, *paths)
+
+    def read(self, filename, binary_mode=False, size=0, continue_from=None):
+        offset = 0
+        if continue_from is not None:
+            offset = continue_from.get("last_offset", 0)
+
+        encoding = None if binary_mode else "utf-8"
+        with self.cli.read(hdfs_path=filename[7:], offset=offset, encoding=encoding) as reader:
+            data = reader.read()
+            continue_from_token = {"last_offset": offset + len(data)}
+            return data, continue_from_token
+
+    def append(self, filename, file_content, binary_mode=False):
+        self.cli.write(hdfs_path=filename[7:], data=file_content, append=True)
+
+    def write(self, filename, file_content, binary_mode=False):
+        self.cli.write(hdfs_path=filename[7:], data=file_content)
+
+    def walk(self, dir):
+        walks = self.cli.walk(hdfs_path=dir[7:])
+        return (['hdfs://'+root, dirs, files] for root, dirs, files in walks)
+
+
+try:
+    default_file_factory.register_filesystem("hdfs", HDFileSystem())
+except hdfs.util.HdfsError:
+    print("HDFS initialization failed, please check if .hdfscli，cfg exists.")
+
+
 class BFile(object):
     def __init__(self, filename, mode):
         if mode not in ('r', 'rb', 'br', 'w', 'wb', 'bw'):

visualdl/proto/record.proto

@@ -29,6 +29,11 @@ message Record {
     bytes encoded_vectors = 2;
   }
 
+message Histogram {
+  repeated double hist = 1 [packed = true];
+  repeated double bin_edges = 2 [packed = true];
+};
+
   message Value {
     int64 id = 1;
     string tag = 2;
@@ -38,6 +43,7 @@ message Record {
       Image image = 5;
       Audio audio = 6;
       Embeddings embeddings = 7;
+      Histogram histogram = 8;
     }
   }
 

visualdl/proto/record_pb2.py

@@ -18,7 +18,7 @@ DESCRIPTOR = _descriptor.FileDescriptor(
   package='visualdl',
   syntax='proto3',
   serialized_options=None,
-  serialized_pb=b'\n\x0crecord.proto\x12\x08visualdl\"\xdf\x04\n\x06Record\x12&\n\x06values\x18\x01 \x03(\x0b\x32\x16.visualdl.Record.Value\x1a%\n\x05Image\x12\x1c\n\x14\x65ncoded_image_string\x18\x04 \x01(\x0c\x1a}\n\x05\x41udio\x12\x13\n\x0bsample_rate\x18\x01 \x01(\x02\x12\x14\n\x0cnum_channels\x18\x02 \x01(\x03\x12\x15\n\rlength_frames\x18\x03 \x01(\x03\x12\x1c\n\x14\x65ncoded_audio_string\x18\x04 \x01(\x0c\x12\x14\n\x0c\x63ontent_type\x18\x05 \x01(\t\x1a+\n\tEmbedding\x12\r\n\x05label\x18\x01 \x01(\t\x12\x0f\n\x07vectors\x18\x02 \x03(\x02\x1a<\n\nEmbeddings\x12.\n\nembeddings\x18\x01 \x03(\x0b\x32\x1a.visualdl.Record.Embedding\x1a\x43\n\x10\x62ytes_embeddings\x12\x16\n\x0e\x65ncoded_labels\x18\x01 \x01(\x0c\x12\x17\n\x0f\x65ncoded_vectors\x18\x02 \x01(\x0c\x1a\xd6\x01\n\x05Value\x12\n\n\x02id\x18\x01 \x01(\x03\x12\x0b\n\x03tag\x18\x02 \x01(\t\x12\x11\n\ttimestamp\x18\x03 \x01(\x03\x12\x0f\n\x05value\x18\x04 \x01(\x02H\x00\x12\'\n\x05image\x18\x05 \x01(\x0b\x32\x16.visualdl.Record.ImageH\x00\x12\'\n\x05\x61udio\x18\x06 \x01(\x0b\x32\x16.visualdl.Record.AudioH\x00\x12\x31\n\nembeddings\x18\x07 \x01(\x0b\x32\x1b.visualdl.Record.EmbeddingsH\x00\x42\x0b\n\tone_valueb\x06proto3'
+  serialized_pb=b'\n\x0crecord.proto\x12\x08visualdl\"\xc6\x05\n\x06Record\x12&\n\x06values\x18\x01 \x03(\x0b\x32\x16.visualdl.Record.Value\x1a%\n\x05Image\x12\x1c\n\x14\x65ncoded_image_string\x18\x04 \x01(\x0c\x1a}\n\x05\x41udio\x12\x13\n\x0bsample_rate\x18\x01 \x01(\x02\x12\x14\n\x0cnum_channels\x18\x02 \x01(\x03\x12\x15\n\rlength_frames\x18\x03 \x01(\x03\x12\x1c\n\x14\x65ncoded_audio_string\x18\x04 \x01(\x0c\x12\x14\n\x0c\x63ontent_type\x18\x05 \x01(\t\x1a+\n\tEmbedding\x12\r\n\x05label\x18\x01 \x01(\t\x12\x0f\n\x07vectors\x18\x02 \x03(\x02\x1a<\n\nEmbeddings\x12.\n\nembeddings\x18\x01 \x03(\x0b\x32\x1a.visualdl.Record.Embedding\x1a\x43\n\x10\x62ytes_embeddings\x12\x16\n\x0e\x65ncoded_labels\x18\x01 \x01(\x0c\x12\x17\n\x0f\x65ncoded_vectors\x18\x02 \x01(\x0c\x1a\x34\n\tHistogram\x12\x10\n\x04hist\x18\x01 \x03(\x01\x42\x02\x10\x01\x12\x15\n\tbin_edges\x18\x02 \x03(\x01\x42\x02\x10\x01\x1a\x87\x02\n\x05Value\x12\n\n\x02id\x18\x01 \x01(\x03\x12\x0b\n\x03tag\x18\x02 \x01(\t\x12\x11\n\ttimestamp\x18\x03 \x01(\x03\x12\x0f\n\x05value\x18\x04 \x01(\x02H\x00\x12\'\n\x05image\x18\x05 \x01(\x0b\x32\x16.visualdl.Record.ImageH\x00\x12\'\n\x05\x61udio\x18\x06 \x01(\x0b\x32\x16.visualdl.Record.AudioH\x00\x12\x31\n\nembeddings\x18\x07 \x01(\x0b\x32\x1b.visualdl.Record.EmbeddingsH\x00\x12/\n\thistogram\x18\x08 \x01(\x0b\x32\x1a.visualdl.Record.HistogramH\x00\x42\x0b\n\tone_valueb\x06proto3'
 )
 
 
@@ -216,6 +216,43 @@ _RECORD_BYTES_EMBEDDINGS = _descriptor.Descriptor(
   serialized_end=417,
 )
 
+_RECORD_HISTOGRAM = _descriptor.Descriptor(
+  name='Histogram',
+  full_name='visualdl.Record.Histogram',
+  filename=None,
+  file=DESCRIPTOR,
+  containing_type=None,
+  fields=[
+    _descriptor.FieldDescriptor(
+      name='hist', full_name='visualdl.Record.Histogram.hist', index=0,
+      number=1, type=1, cpp_type=5, label=3,
+      has_default_value=False, default_value=[],
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=b'\020\001', file=DESCRIPTOR),
+    _descriptor.FieldDescriptor(
+      name='bin_edges', full_name='visualdl.Record.Histogram.bin_edges', index=1,
+      number=2, type=1, cpp_type=5, label=3,
+      has_default_value=False, default_value=[],
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=b'\020\001', file=DESCRIPTOR),
+  ],
+  extensions=[
+  ],
+  nested_types=[],
+  enum_types=[
+  ],
+  serialized_options=None,
+  is_extendable=False,
+  syntax='proto3',
+  extension_ranges=[],
+  oneofs=[
+  ],
+  serialized_start=419,
+  serialized_end=471,
+)
+
 _RECORD_VALUE = _descriptor.Descriptor(
   name='Value',
   full_name='visualdl.Record.Value',
@@ -272,6 +309,13 @@ _RECORD_VALUE = _descriptor.Descriptor(
       message_type=None, enum_type=None, containing_type=None,
       is_extension=False, extension_scope=None,
       serialized_options=None, file=DESCRIPTOR),
+    _descriptor.FieldDescriptor(
+      name='histogram', full_name='visualdl.Record.Value.histogram', index=7,
+      number=8, type=11, cpp_type=10, label=1,
+      has_default_value=False, default_value=None,
+      message_type=None, enum_type=None, containing_type=None,
+      is_extension=False, extension_scope=None,
+      serialized_options=None, file=DESCRIPTOR),
   ],
   extensions=[
   ],
@@ -287,8 +331,8 @@ _RECORD_VALUE = _descriptor.Descriptor(
       name='one_value', full_name='visualdl.Record.Value.one_value',
       index=0, containing_type=None, fields=[]),
   ],
-  serialized_start=420,
-  serialized_end=634,
+  serialized_start=474,
+  serialized_end=737,
 )
 
 _RECORD = _descriptor.Descriptor(
@@ -308,7 +352,7 @@ _RECORD = _descriptor.Descriptor(
   ],
   extensions=[
   ],
-  nested_types=[_RECORD_IMAGE, _RECORD_AUDIO, _RECORD_EMBEDDING, _RECORD_EMBEDDINGS, _RECORD_BYTES_EMBEDDINGS, _RECORD_VALUE, ],
+  nested_types=[_RECORD_IMAGE, _RECORD_AUDIO, _RECORD_EMBEDDING, _RECORD_EMBEDDINGS, _RECORD_BYTES_EMBEDDINGS, _RECORD_HISTOGRAM, _RECORD_VALUE, ],
   enum_types=[
   ],
   serialized_options=None,
@@ -318,7 +362,7 @@ _RECORD = _descriptor.Descriptor(
   oneofs=[
   ],
   serialized_start=27,
-  serialized_end=634,
+  serialized_end=737,
 )
 
 _RECORD_IMAGE.containing_type = _RECORD
@@ -327,9 +371,11 @@ _RECORD_EMBEDDING.containing_type = _RECORD
 _RECORD_EMBEDDINGS.fields_by_name['embeddings'].message_type = _RECORD_EMBEDDING
 _RECORD_EMBEDDINGS.containing_type = _RECORD
 _RECORD_BYTES_EMBEDDINGS.containing_type = _RECORD
+_RECORD_HISTOGRAM.containing_type = _RECORD
 _RECORD_VALUE.fields_by_name['image'].message_type = _RECORD_IMAGE
 _RECORD_VALUE.fields_by_name['audio'].message_type = _RECORD_AUDIO
 _RECORD_VALUE.fields_by_name['embeddings'].message_type = _RECORD_EMBEDDINGS
+_RECORD_VALUE.fields_by_name['histogram'].message_type = _RECORD_HISTOGRAM
 _RECORD_VALUE.containing_type = _RECORD
 _RECORD_VALUE.oneofs_by_name['one_value'].fields.append(
   _RECORD_VALUE.fields_by_name['value'])
@@ -343,6 +389,9 @@ _RECORD_VALUE.fields_by_name['audio'].containing_oneof = _RECORD_VALUE.oneofs_by
 _RECORD_VALUE.oneofs_by_name['one_value'].fields.append(
   _RECORD_VALUE.fields_by_name['embeddings'])
 _RECORD_VALUE.fields_by_name['embeddings'].containing_oneof = _RECORD_VALUE.oneofs_by_name['one_value']
+_RECORD_VALUE.oneofs_by_name['one_value'].fields.append(
+  _RECORD_VALUE.fields_by_name['histogram'])
+_RECORD_VALUE.fields_by_name['histogram'].containing_oneof = _RECORD_VALUE.oneofs_by_name['one_value']
 _RECORD.fields_by_name['values'].message_type = _RECORD_VALUE
 DESCRIPTOR.message_types_by_name['Record'] = _RECORD
 _sym_db.RegisterFileDescriptor(DESCRIPTOR)
@@ -384,6 +433,13 @@ Record = _reflection.GeneratedProtocolMessageType('Record', (_message.Message,),
     })
   ,
 
+  'Histogram' : _reflection.GeneratedProtocolMessageType('Histogram', (_message.Message,), {
+    'DESCRIPTOR' : _RECORD_HISTOGRAM,
+    '__module__' : 'record_pb2'
+    # @@protoc_insertion_point(class_scope:visualdl.Record.Histogram)
+    })
+  ,
+
   'Value' : _reflection.GeneratedProtocolMessageType('Value', (_message.Message,), {
     'DESCRIPTOR' : _RECORD_VALUE,
     '__module__' : 'record_pb2'
@@ -400,7 +456,10 @@ _sym_db.RegisterMessage(Record.Audio)
 _sym_db.RegisterMessage(Record.Embedding)
 _sym_db.RegisterMessage(Record.Embeddings)
 _sym_db.RegisterMessage(Record.bytes_embeddings)
+_sym_db.RegisterMessage(Record.Histogram)
 _sym_db.RegisterMessage(Record.Value)
 
 
+_RECORD_HISTOGRAM.fields_by_name['hist']._options = None
+_RECORD_HISTOGRAM.fields_by_name['bin_edges']._options = None
 # @@protoc_insertion_point(module_scope)

visualdl/reader/reader.py

@@ -61,6 +61,10 @@ class LogReader(object):
         self.load_new_data(update=True)
         self._a_tags = {}
 
+    @property
+    def logdir(self):
+        return self.dir
+
     def parse_from_bin(self, record_bin):
         """Register to self._tags by component type.
 
@@ -83,6 +87,8 @@ class LogReader(object):
                 component = "embeddings"
             elif "audio" == value_type:
                 component = "audio"
+            elif "histogram" == value_type:
+                component = "histogram"
             else:
                 raise TypeError("Invalid value type `%s`." % value_type)
             self._tags[path] = component
@@ -202,9 +208,14 @@ class LogReader(object):
     def components(self, update=False):
         """Get components type used by vdl.
         """
+        if self.logdir is None:
+            return set()
         if update is True:
             self.load_new_data(update=update)
-        return list(set(self._tags.values()))
+        components_set = set(self._tags.values())
+        if 0 == len(components_set):
+            return {'scalar'}
+        return components_set
 
     def load_new_data(self, update=True):
         """Load remain data.
@@ -212,5 +223,6 @@ class LogReader(object):
         Make sure all readers for every vdl log file are registered, load all
         remain data.
         """
+        if self.logdir is not None:
             self.register_readers(update=update)
             self.add_remain()

visualdl/reader/record_reader.py

@@ -14,6 +14,7 @@
 # =======================================================================
 from visualdl.io import bfile
 import struct
+from hdfs.util import HdfsError
 
 
 class _RecordReader(object):
@@ -30,10 +31,13 @@ class _RecordReader(object):
     def get_next(self):
         # Read the header
         self._curr_event = None
+        try:
             header_str = self.file_handle.read(8)
+        except HdfsError:
+            raise EOFError('No more events to read on HDFS.')
         if len(header_str) != 8:
             # Hit EOF so raise and exit
-            raise EOFError('No more events to read')
+            raise EOFError('No more events to read on LFS.')
         header = struct.unpack('Q', header_str)
         header_len = int(header[0])
         event_str = self.file_handle.read(header_len)

visualdl/server/api.py

@@ -123,6 +123,7 @@ class Api(object):
         key = os.path.join('data/plugin/audio/audio', run, tag)
         return self._get_with_retry(key, lib.get_audio_tag_steps, run, tag)
 
+    @result()
     def audio_audio(self, run, tag, index=0):
         index = int(index)
         key = os.path.join('data/plugin/audio/individualAudio', run, tag, str(index))
@@ -134,6 +135,15 @@ class Api(object):
         key = os.path.join('data/plugin/embeddings/embeddings', run, str(dimension), reduction)
         return self._get_with_retry(key, lib.get_embeddings, run, tag, reduction, dimension)
 
+    @result()
+    def histogram_tags(self):
+        return self._get_with_retry('data/plugin/histogram/tags', lib.get_histogram_tags)
+
+    @result()
+    def histogram_histogram(self, run, tag):
+        key = os.path.join('data/plugin/embeddings/embeddings', run, tag)
+        return self._get_with_retry(key, lib.get_embeddings, run, tag)
+
 
 def create_api_call(logdir, cache_timeout):
     api = Api(logdir, cache_timeout)
@@ -146,12 +156,14 @@ def create_api_call(logdir, cache_timeout):
         'images/tags': (api.images_tags, []),
         'audio/tags': (api.audio_tags, []),
         'embeddings/tags': (api.embeddings_tags, []),
+        'histogram/tags': (api.histogram_tags, []),
         'scalars/list': (api.scalars_list, ['run', 'tag']),
         'images/list': (api.images_list, ['run', 'tag']),
         'images/image': (api.images_image, ['run', 'tag', 'index']),
         'audio/list': (api.audio_list, ['run', 'tag']),
         'audio/audio': (api.audio_audio, ['run', 'tag', 'index']),
-        'embeddings/embedding': (api.embeddings_embedding, ['run', 'tag', 'reduction', 'dimension'])
+        'embeddings/embedding': (api.embeddings_embedding, ['run', 'tag', 'reduction', 'dimension']),
+        'histogram/histogram': (api.histogram_histogram, ['run', 'tag'])
     }
 
     def call(path: str, args):

visualdl/server/app.py

@@ -89,6 +89,7 @@ def create_app(args):
             lang = get_locale()
             if lang == default_language:
                 return redirect(public_path + '/index', code=302)
+            lang = support_language[0] if lang is None else lang
             return redirect(public_path + '/' + lang + '/index', code=302)
 
         @app.route(public_path + '/<path:filename>')

visualdl/server/args.py

@@ -38,11 +38,6 @@ class DefaultArgs(object):
 
 
 def validate_args(args):
-    # exit if no logdir specified
-    if not args.logdir or args.logdir is None:
-        logger.error('Log directory is not specified.')
-        sys.exit(-1)
-
     # if not in API mode, public path cannot be set to root path
     if not args.api_only and args.public_path == '/':
         logger.error('Public path cannot be set to root path.')
@@ -91,7 +86,6 @@ def parse_args():
     parser = ArgumentParser(description="VisualDL, a tool to visualize deep learning.")
     parser.add_argument(
         "--logdir",
-        required=True,
         action="store",
         dest="logdir",
         nargs="+",
@@ -142,8 +136,5 @@ def parse_args():
     )
 
     args = parser.parse_args()
-    # print help if no logdir specified
-    if not args.logdir:
-        parser.print_help()
 
     return format_args(args)

visualdl/server/lib.py

@@ -22,7 +22,9 @@ from visualdl.utils.string_util import encode_tag, decode_tag
 
 
 def get_components(log_reader):
-    return log_reader.components(update=True)
+    components = log_reader.components(update=True)
+    components.add('graph')
+    return list(components)
 
 
 def get_runs(log_reader):
@@ -108,6 +110,10 @@ def get_embeddings_tags(log_reader):
     return get_logs(log_reader, "embeddings")
 
 
+def get_histogram_tags(log_reader):
+    return get_logs(log_reader, "histogram")
+
+
 def get_embeddings(log_reader, run, tag, reduction, dimension=2):
     log_reader.load_new_data()
     records = log_reader.data_manager.get_reservoir("embeddings").get_items(
@@ -131,6 +137,24 @@ def get_embeddings(log_reader, run, tag, reduction, dimension=2):
     return {"embedding": low_dim_embs.tolist(), "labels": labels}
 
 
+def get_histogram(log_reader, run, tag):
+    log_reader.load_new_data()
+    records = log_reader.data_manager.get_reservoir("histogram").get_items(
+        run, decode_tag(tag))
+
+    results = []
+    for item in records:
+        histogram = item.histogram
+        hist = histogram.hist
+        bin_edges = histogram.bin_edges
+        histogram_data = []
+        for index in range(len(hist)):
+            histogram_data.append([bin_edges[index], bin_edges[index+1], hist[index]])
+        results.append([item.timestamp, item.id, histogram_data])
+
+    return results
+
+
 def retry(ntimes, function, time2sleep, *args, **kwargs):
     '''
     try to execute `function` `ntimes`, if exception catched, the thread will

visualdl/writer/writer.py

@@ -15,7 +15,7 @@
 import os
 import time
 from visualdl.writer.record_writer import RecordFileWriter
-from visualdl.component.base_component import scalar, image, embedding, audio
+from visualdl.component.base_component import scalar, image, embedding, audio, histogram
 import numpy as np
 
 
@@ -99,6 +99,10 @@ class LogWriter(object):
         self._get_file_writer()
         self.loggers = {}
 
+    @property
+    def logdir(self):
+        return self._logdir
+
     def _get_file_writer(self):
         if not self._write_to_disk:
             self._file_writer = DummyFileWriter(logdir=self._logdir)
@@ -242,6 +246,41 @@ class LogWriter(object):
                 step=step,
                 walltime=walltime))
 
+    def add_histogram(self,
+                      tag,
+                      values,
+                      step,
+                      walltime=None,
+                      buckets=10):
+        """Add an histogram to vdl record file.
+
+        Args:
+            tag (string): Data identifier
+            value (numpy.ndarray or list): value represented by a numpy.array or list
+            step (int): Step of histogram
+            walltime (int): Wall time of audio
+            buckets (int): Number of buckets, default is 10
+
+        Example:
+            values = np.arange(0, 1000)
+            with LogWriter(logdir="./log/histogram_test/train") as writer:
+                for index in range(5):
+                    writer.add_histogram(tag='default',
+                                         values=values+index,
+                                         step=index)
+        """
+        if '%' in tag:
+            raise RuntimeError("% can't appear in tag!")
+        hist, bin_edges = np.histogram(values, bins=buckets)
+        walltime = round(time.time()) if walltime is None else walltime
+        self._get_file_writer().add_record(
+            histogram(
+                tag=tag,
+                hist=hist,
+                bin_edges=bin_edges,
+                step=step,
+                walltime=walltime))
+
     def flush(self):
         """Flush all data in cache to disk.
         """