path: root/swarm/storage/memstore.go

// Copyright 2018 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

// memory storage layer for the package blockhash

package storage

import (
    "context"
    "sync"

    lru "github.com/hashicorp/golang-lru"
)

type MemStore struct {
    cache    *lru.Cache
    requests *lru.Cache
    mu       sync.RWMutex
    disabled bool
}

//NewMemStore is instantiating a MemStore cache. We are keeping a record of all outgoing requests for chunks, that
//should later be delivered by peer nodes, in the `requests` LRU cache. We are also keeping all frequently requested
//chunks in the `cache` LRU cache.
//
//`requests` LRU cache capacity should ideally never be reached, this is why for the time being it should be initialised
//with the same value as the LDBStore capacity.
func NewMemStore(params *StoreParams, _ *LDBStore) (m *MemStore) {
    if params.CacheCapacity == 0 {
        return &MemStore{
            disabled: true,
        }
    }

    onEvicted := func(key interface{}, value interface{}) {
        v := value.(*Chunk)
        <-v.dbStoredC
    }
    c, err := lru.NewWithEvict(int(params.CacheCapacity), onEvicted)
    if err != nil {
        panic(err)
    }

    requestEvicted := func(key interface{}, value interface{}) {
        // temporary remove of the error log, until we figure out the problem, as it is too spamy
        //log.Error("evict called on outgoing request")
    }
    r, err := lru.NewWithEvict(int(params.ChunkRequestsCacheCapacity), requestEvicted)
    if err != nil {
        panic(err)
    }

    return &MemStore{
        cache:    c,
        requests: r,
    }
}

func (m *MemStore) Get(ctx context.Context, addr Address) (*Chunk, error) {
    if m.disabled {
        return nil, ErrChunkNotFound
    }

    m.mu.RLock()
    defer m.mu.RUnlock()

    r, ok := m.requests.Get(string(addr))
    // it is a request
    if ok {
        return r.(*Chunk), nil
    }

    // it is not a request
    c, ok := m.cache.Get(string(addr))
    if !ok {
        return nil, ErrChunkNotFound
    }
    return c.(*Chunk), nil
}

func (m *MemStore) Put(ctx context.Context, c *Chunk) {
    if m.disabled {
        return
    }

    m.mu.Lock()
    defer m.mu.Unlock()

    // it is a request
    if c.ReqC != nil {
        select {
        case <-c.ReqC:
            if c.GetErrored() != nil {
                m.requests.Remove(string(c.Addr))
                return
            }
            m.cache.Add(string(c.Addr), c)
            m.requests.Remove(string(c.Addr))
        default:
            m.requests.Add(string(c.Addr), c)
        }
        return
    }

    // it is not a request
    m.cache.Add(string(c.Addr), c)
    m.requests.Remove(string(c.Addr))
}

func (m *MemStore) setCapacity(n int) {
    if n <= 0 {
        m.disabled = true
    } else {
        onEvicted := func(key interface{}, value interface{}) {
            v := value.(*Chunk)
            <-v.dbStoredC
        }
        c, err := lru.NewWithEvict(n, onEvicted)
        if err != nil {
            panic(err)
        }

        r, err := lru.New(defaultChunkRequestsCacheCapacity)
        if err != nil {
            panic(err)
        }

        m = &MemStore{
            cache:    c,
            requests: r,
        }
    }
}

func (s *MemStore) Close() {}