Cache debugging

When customizing the Cache module configuration or using an advanced caching strategy, it can be helpful to have some confirmation things are working as intended. By turning on the debugging features of the cache module, you can verify both cache and flush events.

Cache filter

The cache filter is the entry point into cache debugging. To see if an item is being cached, enable DEBUG using the Log Tools app or adjust the log4j2 configuration file. The former is a transient adjustment (resets on restart), while the latter is permanent (survives the restart). Usually, using the app is the preferred approach.

Enable filter debugging

  1. Open the Log Tools app.

  2. Go to the Log Levels tab.

  3. At the bottom of the page, enter the Logger name: info.magnolia.module.cache.filter.CacheFilter

  4. Click Add logger config and check the entry is added to the list above at DEBUG level.

Debug requests

With debug enabled, you can begin making some test requests.

Using the travel demo as an example:

The cache behaves differently for author and public instances. For testing purposes, a public instance typically makes the most sense.

  1. Request the page http://localhost:8080/magnoliaPublic/travel.html.

  2. First request: behaviour=store

    2021-04-07 06:40:09,806 DEBUG info.magnolia.module.cache.filter.CacheFilter :
Cache policy result: CachePolicyResult{behaviour=store, cacheName=defaultPageCache,
cacheKey=DefaultCacheKey{uri='/travel.html', serverName='localhost', locale='en', channel='all', params={}', secure='false', method='get', additionalAttributes='{cookiesConsent=dismiss}'},
cachedEntry=null}

  3. Second request: behaviour=useCache

    2021-04-07 06:44:22,511 DEBUG info.magnolia.module.cache.filter.CacheFilter :
Cache policy result: CachePolicyResult{behaviour=useCache, cacheName=defaultPageCache,
cacheKey=DefaultCacheKey{uri='/travel.html', serverName='localhost', locale='en', channel='all', params={}', secure='false', method='get', additionalAttributes='{cookiesConsent=dismiss}'},
cachedEntry=info.magnolia.module.cache.filter.InMemoryCachedEntry@bb8bd81[gzippedContent=5712 bytes,plainContent=25141 bytes,characterEncoding=UTF-8,contentType=text/html,lastModificationTime=1617792009808,originalUrl=http://localhost:8080/dx-core-webapp/travel.html,serializableHeadersBackingList=<null>,statusCode=200,timeToLiveInSeconds=-1]}

Cache policy result

With DEBUG enabled, the CachePolicyResult is printed to the log.

Parameter Description

behaviour

One of three values:

  • bypass: Skips caching. This is useful for content that can’t or shouldn’t be cached.

  • useCache: Retrieves the cached item from the cache and streams it to the client.

  • store: Stores the response in the cache for future use.

cacheName

The name of the cache being used to store the result. The defaultPageCache is essentially the fallback cache store for requests that don’t use site-aware caching.

cacheKey

The default cache key implementation is based on the URI, server name, parameters, and request headers.

Since the server name is likely to change from server to server, copying cached items around doesn’t prevent generating cache entries.
Parameter Description

uri

The URI of the requested resource. This is the key used by the cache for storage and retrieval of the value stored by the cache. The value is the HTML generated during rendering or the binary data of the requested resource.

serverName

The requested server.

locale

The requested locale.

channel

The requested channel. Typical values are all, desktop, and mobile. Sometimes, it can be "unresolved" if the MultiChannelFilter can’t determine the channel.

params

Any parameters passed as part of the request.

secure

Indicates if the request was made over a secure connection.

method

The request method. POST, GET, PUT, DELETE, and so on.

additionalAttributes

Any other attributes passed as part of the request.

cachedEntry

Cache entry keeping the content in memory. Stores a gzipped and non-gzipped version.

Parameter Description

gzippedContent

Length of the gzipped content.

plainContent

Length of the plain content.

characterEncoding

Character encoding for the stored content.

contentType

Type of content being stored.

lastModificationTime

Last time the content was modified.

originalUrl

Original requesting URL.

serializableHeadersBackingList

List of serializable headers associated with the request.

statusCode

HTTP status code.

timeToLiveInSeconds

Time for how long the content should be valid. -1 means forever.

Flush events

Cache flush events happen when content is updated. When debugging a custom cache configuration, it can be helpful to have these flushes indicated in the log file. This is especially helpful when using advance caching strategies like serve old content while recaching or eager recaching.

To enable the TRACE level logging for flush events use the Log Tools app or adjust the log4j2 configuration file.

Enable flush debugging

With flush debugging enabled, you see the flush event indicated in the log. This also provides the name of the cache being flushed if you use multiple caches.

  1. Open the Log Tools app.

  2. Go to the Log Levels tab.

  3. At the bottom of the page, enter the Logger name: info.magnolia.module.cache

  4. Click Add logger config and check the entry is added to the list above at ALL level.

Site aware

Using the Advanced Cache module it’s possible to configure workspaces to be site-aware. For site-ware caching to work properly, two configurations are required.

  • The site aware flush configuration. Set in the Advanced Cache app.

  • The mapping configuration of the site definition. Set in the Site app. To enable the TRACE level logging for flush events use the Log Tools app or adjust the log4j2 configuration file.

Enable flush debugging

With flush debugging enabled, you’ll see the flush event indicated in the log. This will also provide the name of the cache being flushed in the case you use multiple caches.

  1. Open the Log Tools app.

  2. Select the subApp Log Levels.

  3. At the bottom of the subApp enter the Logger name: info.magnolia.module.advancedcache

  4. Click "Add logger config" and confirm the entry is added to the list above at ALL level.

    2021-06-08 12:48:43,164 INFO  ing.receiver.operation.jcr.JcrPublicationOperation: About to update content under path [/travel].
2021-06-08 12:48:43,387 INFO  r.operation.jcr.JcrTransactionPublicationOperation: 364 User superuser successfully published website:/travel on magnoliaPublic.
2021-06-08 12:48:48,413 TRACE ule.advancedcache.SiteAwareFlushAllListeningPolicy: Cache flushed: sportstation
2021-06-08 12:48:48,427 TRACE ule.advancedcache.SiteAwareFlushAllListeningPolicy: Cache flushed: travel
2021-06-08 12:48:48,431 TRACE info.magnolia.module.cache.FlushAllListeningPolicy: Cache flushed: uuid-key-mapping
2021-06-08 12:48:48,434 TRACE ule.advancedcache.SiteAwareFlushAllListeningPolicy: Cache flushed: defaultPageCache

2021-06-08 12:56:17,172 INFO  ing.receiver.operation.jcr.JcrPublicationOperation: About to update content under path [/travel/tour-type].
2021-06-08 12:56:17,253 INFO  r.operation.jcr.JcrTransactionPublicationOperation: 360 User superuser successfully published website:/travel/tour-type on magnoliaPublic.
2021-06-08 12:56:22,410 TRACE ule.advancedcache.SiteAwareFlushAllListeningPolicy: Cache flushed: travel
2021-06-08 12:56:22,410 TRACE ule.advancedcache.SiteAwareFlushAllListeningPolicy: Cache flushed: defaultPageCache
2021-06-08 12:56:22,410 TRACE info.magnolia.module.cache.FlushAllListeningPolicy: Cache flushed: uuid-key-mapping
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