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Introduce cache chain for the http handler (#12)
* Introduce cache chain for the http handler * Fix e2e test * Replace map[string]models.GeoIPRepository in Chain type by Cache type * Fix random failures in TestNewChecks() unit test due to random iteration over maps * Fix e2e failing tests by running e2e-curl after e2e-go
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,8 @@ | ||
| apiVersion: skaffold/v2beta28 | ||
| kind: Config | ||
| metadata: | ||
| name: e2e | ||
| deploy: | ||
| kubectl: | ||
| manifests: | ||
| - .e2e/curl/e2e.yaml |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,164 @@ | ||
| package chain | ||
|
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| import ( | ||
| "context" | ||
| "errors" | ||
| "sync" | ||
|
|
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| "github.com/lescactus/geolocation-go/internal/models" | ||
| "github.com/rs/zerolog" | ||
| "github.com/rs/zerolog/hlog" | ||
| ) | ||
|
|
||
| // Cache is a models.GeoIPRepository and is used within a | ||
| // Chain. | ||
| type Cache struct { | ||
| name string | ||
| repository models.GeoIPRepository | ||
| } | ||
|
|
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| // Chain acts as a list of GeoIPRepository. | ||
| // It's goal is to provide a cache to read and write models.GeoIP | ||
| // in a chained way: when requesting a read, the first GeoIPRepository | ||
| // will be queried and in case of cache miss, the second GeoIPRepository will be queried, | ||
| // then in case of cache miss, the third GeoIPRepository will be queried and so on... | ||
| // When one of the cache is a hit, all the other caches will be updated if necessary. | ||
| // | ||
| // | ||
| // Typically, the chain would be composed of several caches stores, starting from the fastest to | ||
| // the slowest. | ||
| // | ||
| // Ex: | ||
| // | ||
| // 1. In memory cache - very fast | ||
| // | | ||
| // V | ||
| // 2. Redis - fast but slower than in memory cache | ||
| // | | ||
| // V | ||
| // 3. MySQL - fast but slower than redis | ||
| // | ||
| type Chain struct { | ||
| caches []Cache | ||
| l *zerolog.Logger | ||
| } | ||
|
|
||
| // New will return a new empty chain. | ||
| // It is then up to the caller to use the Add() | ||
| // method to add GeoIPRepository to the chain. | ||
| func New(l *zerolog.Logger) *Chain { | ||
| return &Chain{ | ||
| l: l, | ||
| caches: make([]Cache, 0), | ||
| } | ||
| } | ||
|
|
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| // Add will add a models.GeoIPRepository to the chain. | ||
| // Return an error if the GeoIPRepository is already present. | ||
| func (c *Chain) Add(name string, g models.GeoIPRepository) error { | ||
| if g == nil { | ||
| return errors.New("error: GeoIPRepository cannot be nil") | ||
| } | ||
|
|
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| if len(c.caches) == 0 { | ||
| c.caches = append(c.caches, Cache{ | ||
| name: name, | ||
| repository: g, | ||
| }) | ||
| return nil | ||
| } | ||
|
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| for _, cache := range c.caches { | ||
| if cache.name == name { | ||
| return errors.New("error: GeoIPRepository already present in chain") | ||
| } | ||
| } | ||
|
|
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| c.caches = append(c.caches, Cache{name: name, repository: g}) | ||
|
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| return nil | ||
| } | ||
|
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| // Get will attempt to retrieve the *models.GeoIP corresponding to the given ip. | ||
| // | ||
| // It will lookup each GeoIPRepository in the chain and return the first *models.GeoIP | ||
| // found. | ||
| // Each GeoIPRepository which doesn't have the *models.GeoIP will be updated accordingly. | ||
| // | ||
| // If no *models.GeoIP is found, an error will be returned. | ||
| func (c *Chain) Get(ctx context.Context, ip string) (*models.GeoIP, error) { | ||
| var g *models.GeoIP | ||
| var err error | ||
| var cacheMiss []string | ||
|
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| req_id := reqIDFromContext(ctx) | ||
|
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| for _, cache := range c.caches { | ||
| c.l.Trace().Str("req_id", req_id).Msgf("looking for %s in %s database from cache chain", ip, cache.name) | ||
|
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| g, err = cache.repository.Get(ctx, ip) | ||
| if err != nil { | ||
| c.l.Debug().Str("req_id", req_id).Err(err).Msgf("cache miss from %s database", cache.name) | ||
| cacheMiss = append(cacheMiss, cache.name) | ||
| } else { | ||
| c.l.Debug().Str("req_id", req_id).Msgf("cache hit from %s database", cache.name) | ||
|
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| // Update all caches with g if needed | ||
| if len(cacheMiss) > 0 { | ||
| go c.SaveInAllCaches(ctx, g) | ||
| } | ||
| return g, nil | ||
| } | ||
| } | ||
|
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| return nil, errors.New("couldn't find entry in cache chain") | ||
| } | ||
|
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| // Statuses will call each GeoIPRepository Status() function concurrently | ||
| // and return errors if any. | ||
| func (c *Chain) Statuses(ctx context.Context) map[string]error { | ||
| var wg sync.WaitGroup | ||
|
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| errors := make(map[string]error) | ||
|
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| for _, cache := range c.caches { | ||
| c := make(chan error, 1) | ||
| wg.Add(1) | ||
| go cache.repository.Status(ctx, &wg, c) | ||
|
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| errors[cache.name] = <-c | ||
| } | ||
| wg.Wait() | ||
|
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| return errors | ||
| } | ||
|
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| // SaveInAllCaches will save geoip asynchronousely in all the caches from the chain. | ||
| func (c *Chain) SaveInAllCaches(ctx context.Context, geoip *models.GeoIP) { | ||
| req_id := reqIDFromContext(ctx) | ||
|
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| var wg sync.WaitGroup | ||
| wg.Add(len(c.caches)) | ||
|
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| for _, cache := range c.caches { | ||
| go func(cache Cache) { | ||
| defer wg.Done() | ||
|
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| c.l.Debug().Str("req_id", req_id).Msgf("updating cache %s with entry %s", cache.name, geoip.IP) | ||
| if err := cache.repository.Save(ctx, geoip); err != nil { | ||
| c.l.Error().Str("req_id", req_id).Msgf("fail to cache in %s database: %s", cache.name, err.Error()) | ||
| } else { | ||
| c.l.Trace().Str("req_id", req_id).Msgf("cache %s updated with entry %s", cache.name, geoip.IP) | ||
| } | ||
| }(cache) | ||
| } | ||
|
|
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| wg.Wait() | ||
| } | ||
|
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| // reqIDFromContext extracts and returns the request id from | ||
| // the given context. | ||
| func reqIDFromContext(ctx context.Context) string { | ||
| req_id, _ := hlog.IDFromCtx(ctx) | ||
| return req_id.String() | ||
| } |
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