// Licensed to the Apache Software Foundation (ASF) under one
// or more contributor license agreements.  See the NOTICE file
// distributed with this work for additional information
// regarding copyright ownership.  The ASF licenses this file
// to you 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.
syntax = "proto2";
package kudu.log;

option java_package = "org.apache.kudu.log";

import "kudu/common/common.proto";
import "kudu/consensus/consensus.proto";
import "kudu/consensus/metadata.proto";
import "kudu/util/compression/compression.proto";

// ===========================================================================
//  Log Entries - Log specific messages + single node messages
// ===========================================================================

// Types of log entries.
enum LogEntryTypePB {
  UNKNOWN = 0;
  REPLICATE = 1;
  COMMIT = 2;
  // Marker entry for dummy log messages. These will never end up in the log,
  // just serve the purpose of making sure that all entries up to the FLUSH_MARKER
  // entry are flushed.
  FLUSH_MARKER = 999;
};

// An entry in the WAL/state machine log.
message LogEntryPB {
  required LogEntryTypePB type = 1;
  optional consensus.ReplicateMsg replicate = 2;
  optional consensus.CommitMsg commit = 3;
}

// A batch of entries in the WAL.
message LogEntryBatchPB {
  repeated LogEntryPB entry = 1;
}

// A header for a log segment.
message LogSegmentHeaderPB {
  // Log format major/minor version. These were written by Kudu 1.2 and
  // earlier, and marked as required in those versions, but unfortunately
  // they were never verified on read. So, in order to make the logs written
  // by newer versions give a reasonable error if an old version tries to
  // read them, we no longer write these fields.
  optional uint32 DEPRECATED_major_version = 1;
  optional uint32 DEPRECATED_minor_version = 2;

  enum FeatureFlag {
    UNKNOWN = 999;
  }
  // Set of features used in this log segment which would make the segment
  // unreadable by earlier versions that do not implement them. If a reader
  // sees a value in this list that doesn't correspond to a known value of
  // the above enum, then it should avoid opening the WAL segment.
  //
  // See KUDU-1850 for details on why we can't just use the FeatureFlag type
  // directly.
  repeated int32 incompatible_features = 10;

  // The ID of the tablet this WAL segment stores entries for.
  required bytes tablet_id = 5;

  // The tablet-specific sequence number of this WAL segment.
  required uint64 sequence_number = 6;

  // Schema used when appending entries to this log, and its version.
  required SchemaPB schema = 7;
  optional uint32 schema_version = 8;

  // Compression codec used for log entries.
  optional CompressionType compression_codec = 9 [ default = NO_COMPRESSION ];
}

// A footer for a log segment.
//
// Log segment footers might not be present (e.g. if the server
// crashed) so they should contain no information that cannot
// be obtained by actually reading the entries in the log.
//
// We use the footer to keep sparse index entries mapping
// op_id->offset (right now we just keep the first entry with an
// id in the log)
message LogSegmentFooterPB {
  // the total number of operations inside this segment
  required int64 num_entries = 1;

  // The minimum and maximum index of a REPLICATE message in this segment.
  // NOTE: because of log truncation, the min/max are not necessarily the first/last!
  // For example, a log segment may contain entries "1.5, 1.6, 3.3, 2.3" due to multiple
  // term changes.
  //
  // Because it's possible for a segment to have no replicate messages in it,
  // these are optional. We set the default to -1 to avoid accidentally reading
  // 0, which might look like a real log index.
  optional int64 min_replicate_index = 2 [ default = -1 ];
  optional int64 max_replicate_index = 3 [ default = -1 ];

  // The time (microseconds since epoch) when this segment was closed.
  // NOTE: since log segments are rewritten during bootstrap, these will all
  // be reset to the time of the bootstrap on a newly-restarted server, rather
  // than copied over from the old log segments.
  optional int64 close_timestamp_micros = 4;
}