cursor

Documentation

Overview

Copyright 2018-2019 The logrange Authors

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.

Index

• type Cursor
• type JournalsProvider
• type Provider
  • func NewProvider() Provider
• type State
  • func (s State) String() string

Types

type Cursor

type Cursor interface {
	model.Iterator
	Id() uint64

	// Offset moves the cursor position to backward (negative offset) of forward(positive offset)
	// from the current cursor position
	Offset(ctx context.Context, offs int)
	ApplyState(state State) error
	State(context.Context) State
	WaitNewData(ctx context.Context) error
}

type JournalsProvider

type JournalsProvider interface {
	// GetJournals returns map of journals by tags:partition.Journal or an error, if any. The returned journals
	// must be released after usage by Release() function
	GetJournals(ctx context.Context, tagsCond *lql.Source, maxLimit int) (map[tag.Line]journal.Journal, error)

	// Release releases the partition. Journal must not be used after the call
	Release(jn string)
}

JournalsProvider interface is used for creating new cursors. partition.Service most probably implements it.

type Provider

type Provider interface {
	// GetOrCreate creates a new, or returns already exist cursor by its state (which contains cursor Id)
	GetOrCreate(ctx context.Context, state State, cache bool) (Cursor, error)

	// Release allows to release a cursor
	Release(ctx context.Context, curs Cursor) State
}

Provider interface provides interface for managing cursors

func NewProvider

func NewProvider() Provider

type State

type State struct {
	// Id the cursor state Id
	Id uint64

	// The Query contains the initial query for the cursor.
	Query string

	// Pos indicates the position of the record which must be read next. If it is not empty, it
	// will be applied to the Query
	Pos string
}

State describes state of a cursor. This structure is used for creating new ones and for providing current state of a cursor

func (State) String

func (s State) String() string