github.com/niedbalski/juju@v0.0.0-20190215020005-8ff100488e47/api/crossmodelrelations/macarooncache.go (about)

     1  // Copyright 2017 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package crossmodelrelations
     5  
     6  import (
     7  	"runtime"
     8  	"sync"
     9  	"time"
    10  
    11  	"github.com/juju/clock"
    12  	"gopkg.in/macaroon-bakery.v2-unstable/bakery/checkers"
    13  	"gopkg.in/macaroon.v2-unstable"
    14  )
    15  
    16  // MacaroonCache contains macaroons which are removed at a specified interval.
    17  type MacaroonCache struct {
    18  	// We use a separate struct for the actual cache and a wrapper to export to the
    19  	// user so that the expiry worker which references the internal cache doesn't
    20  	// prevent the exported cache from being garbage collected.
    21  	*cacheInternal
    22  }
    23  
    24  // NewMacaroonCache returns a cache containing macaroons which are removed
    25  // after the macaroons' expiry time.
    26  func NewMacaroonCache(clock clock.Clock) *MacaroonCache {
    27  	c := &cacheInternal{clock: clock, macaroons: make(map[string]*macaroonEntry)}
    28  	cache := &MacaroonCache{c}
    29  	// The interval to run the expiry worker is somewhat arbitrary.
    30  	// Expired macaroons will be re-issued as needed; we just want to ensure
    31  	// that those which fall out of use are eventually cleaned up.
    32  	c.runExpiryWorker(10 * time.Minute)
    33  	runtime.SetFinalizer(cache, stopMacaroonCacheExpiryWorker)
    34  	return cache
    35  }
    36  
    37  type expiryWorker struct {
    38  	clock    clock.Clock
    39  	interval time.Duration
    40  	stop     chan bool
    41  }
    42  
    43  func (w *expiryWorker) loop(c *cacheInternal) {
    44  	for {
    45  		select {
    46  		case <-w.clock.After(w.interval):
    47  			c.deleteExpired()
    48  		case <-w.stop:
    49  			return
    50  		}
    51  	}
    52  }
    53  
    54  type macaroonEntry struct {
    55  	ms         macaroon.Slice
    56  	expiryTime *time.Time
    57  }
    58  
    59  func (i *macaroonEntry) expired(clock clock.Clock) bool {
    60  	return i.expiryTime != nil && i.expiryTime.Before(clock.Now())
    61  }
    62  
    63  type cacheInternal struct {
    64  	sync.Mutex
    65  	clock clock.Clock
    66  
    67  	macaroons    map[string]*macaroonEntry
    68  	expiryWorker *expiryWorker
    69  }
    70  
    71  // Upsert inserts or updates a macaroon slice in the cache.
    72  func (c *cacheInternal) Upsert(token string, ms macaroon.Slice) {
    73  	c.Lock()
    74  	defer c.Unlock()
    75  
    76  	var et *time.Time
    77  	if expiryTime, ok := checkers.MacaroonsExpiryTime(ms); ok {
    78  		et = &expiryTime
    79  	}
    80  	c.macaroons[token] = &macaroonEntry{
    81  		ms:         ms,
    82  		expiryTime: et,
    83  	}
    84  }
    85  
    86  // Get returns a macaroon slice from the cache, and a bool indicating
    87  // if the slice for the key was found.
    88  func (c *cacheInternal) Get(k string) (macaroon.Slice, bool) {
    89  	c.Lock()
    90  	defer c.Unlock()
    91  
    92  	entry, found := c.macaroons[k]
    93  	if !found {
    94  		return nil, false
    95  	}
    96  	if entry.expired(c.clock) {
    97  		delete(c.macaroons, k)
    98  		return nil, false
    99  	}
   100  	return entry.ms, true
   101  }
   102  
   103  func (c *cacheInternal) deleteExpired() {
   104  	c.Lock()
   105  	defer c.Unlock()
   106  
   107  	for k, v := range c.macaroons {
   108  		if v.expired(c.clock) {
   109  			delete(c.macaroons, k)
   110  		}
   111  	}
   112  }
   113  
   114  func stopMacaroonCacheExpiryWorker(mc *MacaroonCache) {
   115  	mc.expiryWorker.stop <- true
   116  }
   117  
   118  func (c *cacheInternal) runExpiryWorker(interval time.Duration) {
   119  	w := &expiryWorker{
   120  		interval: interval,
   121  		clock:    c.clock,
   122  		stop:     make(chan bool),
   123  	}
   124  	c.expiryWorker = w
   125  	go w.loop(c)
   126  }