geode-docs/developing/partitioned_regions/fixed_custom_partitioning.html.md.erb

---
title:  Fixed Custom Partitioning
---

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By default, <%=vars.product_name%> partitions each data entry
into a bucket using a hashing policy on the key.
Additionally, the physical location of the key-value pair is
abstracted away from the application.
You can change these policies for a partitioned region
by providing a fixed custom partition resolver that not only maps entries
to a set of buckets called a partition,
but also specifies which members host which data buckets.  

<a id="custom_partition_region_data__section_CF05CE974C9C4AF78430DA55601D2158"></a>
**Note:**
If you are both colocating region data and custom partitioning,
all colocated regions must use the same custom partitioning mechanism.
See [Colocate Data from Different Partitioned Regions](colocating_partitioned_region_data.html#colocating_partitioned_region_data).

To custom-partition your region data, follow two steps:

- implement the interface
- configure the regions

These steps differ based on which partition resolver is used.

**Implementing Fixed Custom Partitioning**

-   Implement the `org.apache.geode.cache.FixedPartitionResolver`
interface within one of the following locations,
listed here in the search order used by <%=vars.product_name%>:
    -   **Custom class**. Specify this class as the partition resolver during region creation.
    -   **Entry key**. For keys implemented as objects, define the interface for the key's class.
    -   **Within the cache callback class**. Implement the interface
within a cache callback's class. When using this implementation,
any and all `Region` operations must be those that specify the callback
as a parameter.

-   Implement the resolver's `getName`, `init`, and `close` methods.

    A simple implementation of `getName` is

    ``` pre
    return getClass().getName();
    ```

    The `init` method does any initialization steps upon cache
    start that relate to the partition resolver's task. 

    The `close` method accomplishes any clean up that must be accomplished
    before a cache close completes. For example, `close` might close
    files or connections that the partition resolver opened. 

-   Implement the resolver's `getRoutingObject` method to return 
the routing object for each entry.
A hash of that returned routing object determines the bucket
within a partition.
   
    This method can be empty for fixed partitioning where there is
only one bucket per partition.
That implementation assigns partitions to servers
such that the application has full control of grouping entries
on servers.

    **Note:**
    Only fields on the key should be used when creating the routing object. Do not use the value or additional metadata for this purpose.

-   Implement the `getPartitionName` method 
to return the name of the partition for each entry,
based on where you want the entries to reside.
All entries within a partition will be on a single server.

    This example places the data based on date, with a different partition name for each quarter-year and a different routing object for each month.

    ``` pre
    /**
     * Returns one of four different partition names
     * (Q1, Q2, Q3, Q4) depending on the entry's date
     */
    class QuarterFixedPartitionResolver implements
        FixedPartitionResolver<String, String> {

      @Override
      public String getPartitionName(EntryOperation<String, String> opDetails,
          Set<String> targetPartitions) {

         Date date = (Date)opDetails.getKey();
         Calendar cal = Calendar.getInstance();
         cal.setTime(date);
         int month = cal.get(Calendar.MONTH);
         if (month >= 0 && month < 3) {
            if (targetPartitions.contains("Q1")) return "Q1";
         }
         else if (month >= 3 && month < 6) {
            if (targetPartitions.contains("Q2")) return "Q2";
         }
         else if (month >= 6 && month < 9) {
            if (targetPartitions.contains("Q3")) return "Q3";
         }
         else if (month >= 9 && month < 12) {
            if (targetPartitions.contains("Q4")) return "Q4";
         }
         return "Invalid Quarter";
      }

      @Override
      public String getName() {
         return "QuarterFixedPartitionResolver";
      }

      @Override
      public Serializable getRoutingObject(EntryOperation<String, String> opDetails) {
         Date date = (Date)opDetails.getKey();
         Calendar cal = Calendar.getInstance();
         cal.setTime(date);
         int month = cal.get(Calendar.MONTH);
         return month;
      }

      @Override
      public void close() {
      }
    }
    ```

**Configuring Fixed Custom Partitioning**

-  Set the fixed-partition attributes for each member.

    These attributes define the data stored for the region by the member and must be different for different members. See `org.apache.geode.cache.FixedPartitionAttributes` for definitions of the attributes. Define each `partition-name` in your data-host members for the region. For each partition name, in the member you want to host the primary copy, define it with `is-primary` set to `true`. In every member you want to host the secondary copy, define it with `is-primary` set to `false` (the default). The number of secondaries must match the number of redundant copies you have defined for the region. See [Configure High Availability for a Partitioned Region](configuring_ha_for_pr.html).

    **Note:**
    Buckets for a partition are hosted only by the members that have defined the partition name in their `FixedPartitionAttributes`.

    These examples set the partition attributes for a member to be the primary host for the "Q1" partition data and a secondary host for "Q3" partition data.
    -   XML:

        ``` pre
        <cache>
           <region name="Trades">
              <region-attributes>
                 <partition-attributes redundant-copies="1">
                   <partition-resolver>
                      <class-name>myPackage.QuarterFixedPartitionResolver</class-name>
                   </partition-resolver>
                   <fixed-partition-attributes partition-name="Q1" is-primary="true"/>
                   <fixed-partition-attributes partition-name="Q3" is-primary="false"
                        num-buckets="6"/>
                 </partition-attributes> 
              </region-attributes>
           </region>
        </cache>
        ```
    -   Java:


        ``` pre
        FixedPartitionAttribute fpa1 = FixedPartitionAttributes
             .createFixedPartition("Q1", true);
        FixedPartitionAttribute fpa3 = FixedPartitionAttributes
             .createFixedPartition("Q3", false, 6);

        PartitionAttributesFactory paf = new PartitionAttributesFactory()
             .setPartitionResolver(new QuarterFixedPartitionResolver())
             .setTotalNumBuckets(12)
             .setRedundantCopies(2)
             .addFixedPartitionAttribute(fpa1)
             .addFixedPartitionAttribute(fpa3);

        Cache c = new CacheFactory().create();

        Region r = c.createRegionFactory()
            .setPartitionAttributes(paf.create())
            .create("Trades");
        ```
    -   gfsh:

        You cannot specify a fixed partition resolver using gfsh.

-   If your colocated data is in a server system,
add the class that implements the `FixedPartitionResolver` interface
to the `CLASSPATH` of your Java clients.
For Java single-hop access to work,
the resolver class needs to have a zero-argument constructor,
and the resolver class must not have any state;
the `init` method is included in this restriction.