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ConfigurationCaching

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mrogalski edited this page Aug 8, 2018 · 2 revisions

Overview

The service maintains the following runtime caches:

Cache name Description
gists holds responses returned by /gists/{gistid} and /{gistId}/{commitId} GET endpoints
comments holds responses returned by /gists/{gistId}/comments and /gists/{gistId}/comments/{commentId} GET endpoints
commentstore cache for a comment store
metadatastore cache for a metadata store
historystore caches commits extracted from gist (git) repository
filecontentcache caches content of files stored in gist (git) repository
sessionkeys caches authenticated session keys

Default Configuration

Default configuration of caches is located in application.yml and it looks like this:

caches:
  - 
    name: 'sessionkeys'
    evictionPolicy: LRU
    ttl: 60
    maxSize: 100
    maxIdleSeconds: 60
  - 
    name: 'gists'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'comments'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'commentstore'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'metadatatore'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'historystore'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'filecontentcache'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300

Cache Properties

Each cache has the following properties:

Property Description Accepted Values
evictionPolicy which entries should be deleted if eviction of elements is requested NONE (no eviction), LRU (Least Recently Used), LFU (Least Frequently Used)
ttl (time to live) Maximum number of seconds for each entry to stay in the cache. Entries that are older than ttl value and not updated for ttl will get automatically evicted Integer between 0 and Integer.MAX_VALUE. Zero means infinite.
maxSize Maximum number of elements in the cache. When maxSize is reached, elements are evicted using the evictionPolicy Integer between 0 and Integer.MAX_VALUE. Zero means Integer.MAX_VALUE.
maxIdleSeconds Maximum number of seconds for each entry to stay idle in the map. Entries that are not touched (idle) for more than the specified amount of time will get evicted Integer between 0 and Integer.MAX_VALUE. Zero means infinite.

Configuration

To change the cache configuration add the caches element to /opt/rcloud-gist-service/application.yml with all caches configurations, and modify properties of the caches that you wish to override.

Note - you need to include all caches configuration, even if you just want to change settings of a single element. If not, the changes won't take an effect.

Example

To change default settings of filecontentcache, so maxIdleSeconds and ttl is 300000 seconds, add the following section to /opt/rcloud-gist-service/application.yml file:

caches:
  - 
    name: 'sessionkeys'
    evictionPolicy: LRU
    ttl: 60
    maxSize: 100
    maxIdleSeconds: 60
  - 
    name: 'gists'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'comments'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'commentstore'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'metadatatore'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'historystore'
    evictionPolicy: LRU
    ttl: 300
    maxSize: 200
    maxIdleSeconds: 300
  - 
    name: 'filecontentcache'
    evictionPolicy: LFU
    ttl: 30000
    maxSize: 2000
    maxIdleSeconds: 30000

You need to restart the service for the changes to take an effect.

Advanced Configuration

The service uses Hazelcast as cache implementation. Hazelcast configuration is located at hazelcast.xml

The configuration results in a standalone hazelcast instance with a default map configuration, which all caches used by the service extend:

    <map name="default">
        <!--
           Data type that will be used for storing recordMap.
           Possible values:
           BINARY (default): keys and values will be stored as binary data
           OBJECT : values will be stored in their object forms
           NATIVE : values will be stored in non-heap region of JVM
        -->
        <in-memory-format>BINARY</in-memory-format>

        <!--
            Number of backups. If 1 is set as the backup-count for example,
            then all entries of the map will be copied to another JVM for
            fail-safety. 0 means no backup.
        -->
        <backup-count>1</backup-count>
        <!--
            Number of async backups. 0 means no backup.
        -->
        <async-backup-count>0</async-backup-count>
        <!--
			Maximum number of seconds for each entry to stay in the map. Entries that are
			older than <time-to-live-seconds> and not updated for <time-to-live-seconds>
			will get automatically evicted from the map.
			Any integer between 0 and Integer.MAX_VALUE. 0 means infinite. Default is 0.
		-->
        <time-to-live-seconds>300</time-to-live-seconds>
        <!--
			Maximum number of seconds for each entry to stay idle in the map. Entries that are
			idle(not touched) for more than <max-idle-seconds> will get
			automatically evicted from the map. Entry is touched if get, put or containsKey is called.
			Any integer between 0 and Integer.MAX_VALUE. 0 means infinite. Default is 0.
		-->
        <max-idle-seconds>300</max-idle-seconds>
        <!--
            Valid values are:
            NONE (no eviction),
            LRU (Least Recently Used),
            LFU (Least Frequently Used).
            NONE is the default.
        -->
        <eviction-policy>LFU</eviction-policy>
        <!--
            Maximum size of the map. When max size is reached,
            map is evicted based on the policy defined.
            Any integer between 0 and Integer.MAX_VALUE. 0 means
            Integer.MAX_VALUE. Default is 0.
        -->
        <max-size policy="PER_NODE">1000</max-size>
        <!--
            When max. size is reached, specified percentage of
            the map will be evicted. Any integer between 0 and 100.
            If 25 is set for example, 25% of the entries will
            get evicted.
        -->
        <eviction-percentage>25</eviction-percentage>
        <!--
            Minimum time in milliseconds which should pass before checking
            if a partition of this map is evictable or not.
            Default value is 100 millis.
        -->
        <min-eviction-check-millis>100</min-eviction-check-millis>
        <!--
            While recovering from split-brain (network partitioning),
            map entries in the small cluster will merge into the bigger cluster
            based on the policy set here. When an entry merge into the
            cluster, there might an existing entry with the same key already.
            Values of these entries might be different for that same key.
            Which value should be set for the key? Conflict is resolved by
            the policy set here. Default policy is PutIfAbsentMapMergePolicy

            There are built-in merge policies such as
            com.hazelcast.map.merge.PassThroughMergePolicy; entry will be overwritten if merging entry exists for the key.
            com.hazelcast.map.merge.PutIfAbsentMapMergePolicy ; entry will be added if the merging entry doesn't exist in the cluster.
            com.hazelcast.map.merge.HigherHitsMapMergePolicy ; entry with the higher hits wins.
            com.hazelcast.map.merge.LatestUpdateMapMergePolicy ; entry with the latest update wins.
        -->
        <merge-policy>com.hazelcast.map.merge.PutIfAbsentMapMergePolicy</merge-policy>

        <!--
           Control caching of de-serialized values. Caching makes query evaluation faster, but it cost memory.
           Possible Values:
                        NEVER: Never cache deserialized object
                        INDEX-ONLY: Caches values only when they are inserted into an index.
                        ALWAYS: Always cache deserialized values.
        -->
        <cache-deserialized-values>INDEX-ONLY</cache-deserialized-values>

    </map>

The map configuration specifies a PER_NODE policy for controlling the maximum size of caches. This policy results in the maxSize property to specify the maximum number of elements allowed in each cache.

In case the PER_NODE policy does not suite the service usage scheme, there are other policies available MaxSizeConfig.MaxSizePolicy

Changing maxSize Policy

Note, changing policy affects all caches used by the service. Controlling the policy on per-cache basis is not currently supported.

In order to change the maxSize policy of caches used by the service, the following actions need to be performed:

  • hazelcast.xml configuration needs to be placed in /opt/rcloud-gist-service
  • the policy attribute of the max-size element in the map element needs to be updated to required policy, e.g.:
<map>
[...]
<max-size policy="FREE_HEAP_PERCENTAGE">20</max-size>
[...]
</map>
  • Caches configuration in /opt/rcloud-gist-service/application.yml need to be customized, so their maxSize property values are valid for the new policy, e.g.:
[...]
caches:
  -
    name: 'sessionkeys'
    evictionPolicy: LRU
    ttl: 60
    maxSize: 10
    maxIdleSeconds: 60
  -
    name: 'gists'
    evictionPolicy: LRU
    ttl: 10
    maxSize: 20
    maxIdleSeconds: 10
  -
    name: 'comments'
    evictionPolicy: LRU
    ttl: 10
    maxSize: 20
    maxIdleSeconds: 10
  -
    name: 'commentstore'
    evictionPolicy: LRU
    ttl: 10
    maxSize: 20
    maxIdleSeconds: 10
  -
    name: 'metadatatore'
    evictionPolicy: LRU
    ttl: 10
    maxSize: 20
    maxIdleSeconds: 10
  -
    name: 'historystore'
    evictionPolicy: LRU
    ttl: 10
    maxSize: 20
    maxIdleSeconds: 10
  -
    name: 'filecontentcache'
    evictionPolicy: LRU
    ttl: 300000
    maxSize: 20
    maxIdleSeconds: 300000
[...]
  • restart the service

The example above, will result in caches which elements are evicted when the available free heap memory of the service drops to 20%.

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