url_cache.go

Documentation: github.com/google/certificate-transparency-go/fixchain

     1  // Copyright 2016 Google LLC. All Rights Reserved.
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     http://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package fixchain
    16  
    17  import (
    18  	"fmt"
    19  	"io"
    20  	"log"
    21  	"net/http"
    22  	"sync"
    23  	"sync/atomic"
    24  	"time"
    25  )
    26  
    27  type lockedCache struct {
    28  	m map[string][]byte
    29  	sync.RWMutex
    30  }
    31  
    32  func (c *lockedCache) get(str string) ([]byte, bool) {
    33  	c.RLock()
    34  	defer c.RUnlock()
    35  	b, ok := c.m[str]
    36  	return b, ok
    37  }
    38  
    39  func (c *lockedCache) set(str string, b []byte) {
    40  	c.Lock()
    41  	defer c.Unlock()
    42  	c.m[str] = b
    43  }
    44  
    45  func newLockedCache() *lockedCache {
    46  	return &lockedCache{m: make(map[string][]byte)}
    47  }
    48  
    49  type urlCache struct {
    50  	client *http.Client
    51  	cache  *lockedCache
    52  
    53  	hit       uint32
    54  	miss      uint32
    55  	errors    uint32
    56  	badStatus uint32
    57  	readFail  uint32
    58  }
    59  
    60  func (u *urlCache) getURL(url string) ([]byte, error) {
    61  	r, ok := u.cache.get(url)
    62  	if ok {
    63  		atomic.AddUint32(&u.hit, 1)
    64  		return r, nil
    65  	}
    66  	c, err := u.client.Get(url)
    67  	if err != nil {
    68  		atomic.AddUint32(&u.errors, 1)
    69  		return nil, err
    70  	}
    71  	defer c.Body.Close()
    72  	// TODO(katjoyce): Add caching of permanent errors.
    73  	if c.StatusCode != 200 {
    74  		atomic.AddUint32(&u.badStatus, 1)
    75  		return nil, fmt.Errorf("can't deal with status %d", c.StatusCode)
    76  	}
    77  	r, err = io.ReadAll(c.Body)
    78  	if err != nil {
    79  		atomic.AddUint32(&u.readFail, 1)
    80  		return nil, err
    81  	}
    82  	atomic.AddUint32(&u.miss, 1)
    83  	u.cache.set(url, r)
    84  	return r, nil
    85  }
    86  
    87  func newURLCache(c *http.Client, logStats bool) *urlCache {
    88  	u := &urlCache{cache: newLockedCache(), client: c}
    89  
    90  	if logStats {
    91  		t := time.NewTicker(time.Second)
    92  		go func() {
    93  			for range t.C {
    94  				log.Printf("url cache: %d hits, %d misses, %d errors, "+
    95  					"%d bad status, %d read fail, %d cached", u.hit,
    96  					u.miss, u.errors, u.badStatus, u.readFail,
    97  					len(u.cache.m))
    98  			}
    99  		}()
   100  	}
   101  
   102  	return u
   103  }
   104
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