Search Server Clustering

Elastic Path Search Server provides product discovery (searching and browsing) for Cortex and catalog management for Commerce Manager. This section provides advice for how to scale a Search Server deployment in a production environment. For staging environments, it is usually sufficient to have a single search primary server and no replicas.

Topology

Search Server is implemented using a primary-replica topology. Only a single primary can run at a time, otherwise database conflicts occur updating the TINDEXBUILDSTATUS table.

Two common deployment topologies:

Small Deployment Topology

The simplest topology suitable for small deployments is to deploy a Search replica on every Cortex node. Then access Search Server through the http://localhost:8082/searchserver URL.
Large Deployment Topology

Large deployments typically have a separate cluster of Search replicas behind a stateless load balancer. The cluster is accessed through the load balancer URL.

As a starting point, Elastic Path recommends deploying one Search replica for every three Cortex servers to support catalog searching and browsing. This ratio may vary depending on the searching and browsing patterns for the store and customizations that change search server usage. A large deployment example is shown below:

Cluster Configuration

The Search primary and replica servers are deployed using the same WAR file. By default, the WAR is configured to run as a primary node with replication disabled. The steps below configure both primary and the replica.

Externalize solrHome directory (primary & replica)

Move the solrHome directory from the Search WAR to an external location. Elastic Path recommends to include the solrHome in the deployment package as a separate artifact and then deploy the artifact to the desired location on the server. The benefits of this method are:
- You can add replication configuration without invading the WAR
- Search indexes are not deleted when a new WAR is deployed
After solrHome is deployed to the desired location, add the following JVM (Java Virtual Machine) parameters to the appserver startup script:
```
-Dsolr.index.dir.category=/home/ep/solrHome/data/index-category
-Dsolr.index.dir.cmuser=/home/ep/solrHome/data/index-cmuser
-Dsolr.index.dir.customer=/home/ep/solrHome/data/index-customer
-Dsolr.index.dir.product=/home/ep/solrHome/data/index-product
-Dsolr.index.dir.promotion=/home/ep/solrHome/data/index-promotion
-Dsolr.index.dir.shippingservicelevel=/home/ep/solrHome/data/index-shippingservicelevel
-Dsolr.index.dir.sku=/home/ep/solrHome/data/index-sku
```

Configure primary replication

Each config file in solrHome/conf has an <xi:include> tag that points to a corresponding replication configuration file.

<!-- include primary/replica replication settings -->
<xi:include href="file:/etc/ep/product.solr.replication.config.xml" xmlns:xi="http://www.w3.org/2001/XInclude">
<xi:fallback>
    <!-- Currently this reference is relative to the CWD. As of SOLR 3.1 it will be relative to the current XML file's directory -->
    <xi:include href="../replication/product.solr.replication.config.xml" xmlns:xi="http://www.w3.org/2001/XInclude">
    <!-- Silent fallback if no external configuration found -->
    <xi:fallback />
    </xi:include>
</xi:fallback>
</xi:include>

In this case, Solr first looks for product.solr.replication.config.xml in /etc/ep and then in the ../replication relative path.The relative path is relative to where the Search server shell script is run.

If necessary, you can change the <xi:include> block in the Solr config files if /etc/ep is not an acceptable location.

Here is an example of the product.solr.replication.config.xml file.

<requestHandler name="/replication" class="solr.ReplicationHandler">
    <lst name="master">

        <!--Replicate on 'startup' and 'commit'. 'optimize' is also a valid value for replicateAfter. -->
        <str name="replicateAfter">startup</str>
        <str name="replicateAfter">commit</str>
        <!-- <str name="replicateAfter">optimize</str> -->

        <!--Create a backup after 'optimize'. Other values can be 'commit', 'startup'. It is
        possible to have multiple entries of this config string. Note that this is just for backup,
        replication does not require this. -->
        <!-- <str name="backupAfter">optimize</str> -->

        <!--If configuration files need to be replicated give the names here, separated by comma -->
        <str name="confFiles">schema.xml,stopwords.txt,elevate.xml</str>

        <!--The default value of reservation is 10 secs.See the documentation below . Normally , you
        should not need to specify this -->
        <str name="commitReserveDuration">00:00:10</str>
    </lst>
</requestHandler>

Create separate config files for each index you want replicated. You don’t have to replicate all indexes; just the ones that are actually needed. Here is the full list of config files:

Index	Replication Config File	Index Used By
Category	`category.solr.replication.config.xml`	Cortex, CM
CM User	`cmuser.solr.replication.config.xml`	CM
Customer	`customer.solr.replication.config.xml`	CM
Product	`product.solr.replication.config.xml`	Cortex, CM
Promotion	`promotion.solr.replication.config.xml`	CM
SKU	`sku.solr.replication.config.xml`	CM

For each replication configuration file on the primary, create a corresponding configuration file on the replica. Here is an example of the product.solr.replication.config.xml file:

<requestHandler name="/replication"  class="solr.ReplicationHandler" >
    <lst name="slave">
        <str name="enable">true</str>

        <!--fully qualified url for the replication handler of primary. It is possible to pass on this
        as a request param for the fetchindex command-->
        <str name="masterUrl">http://venus.elasticpath.net:8080/searchserver/product/replication</str>

        <!--Interval in which the replica should poll primary. Format is HH:mm:ss . If this is absent replica does
        not poll automatically.
        But a fetchindex can be triggered from the admin or the http API -->
        <str name="pollInterval">00:00:20</str>

        <!-- THE FOLLOWING PARAMETERS ARE USUALLY NOT REQUIRED-->
        <!--to use compression while transferring the index files. The possible values are internal|external
        if the value is 'external' make sure that your primary Solr has the settings to honour the
        accept-encoding header.
        see here for details http://wiki.apache.org/solr/SolrHttpCompression
        If it is 'internal' everything will be taken care of automatically.
        USE THIS ONLY IF YOUR BANDWIDTH IS LOW . THIS CAN ACTUALLY SLOWDOWN REPLICATION IN A LAN-->
        <str name="compression">internal</str>

        <!--The following values are used when the replica connects to the primary to download the index files.
        Default values implicitly set as 5000ms and 10000ms respectively. The user DOES NOT need to specify
        these unless the bandwidth is extremely low or if there is an extremely high latency-->
        <str name="httpConnTimeout">5000</str>
        <str name="httpReadTimeout">10000</str>

        <!-- If HTTP Basic authentication is enabled on the primary, then the replica can be configured
        with the following
        <str name="httpBasicAuthUser">username</str>
        <str name="httpBasicAuthPassword">password</str>
        -->

    </lst>
</requestHandler>

Disable indexing on replicas

Add the following line to the ep.properties file on each replica server to stop the replicas from indexing themselves.
```
ep.search.triggers=disabled
```
Enable the Search Primary

Add the following line to ep.properties on the server containing the search primary to identify which server contains the Search primary.
```
ep.search.requires.master=true
```
Configure searchHost setting

Configure the search server URLs through the system configuration setting COMMERCE/SYSTEM/SEARCH/searchHost. You can also use the -Dep.search.default.url and -Dep.search.master.url Java system properties. The URLs you set depends on your deployment topology.
- Simple topology
  
  In a simple deployment topology, you only need to configure the default value to point to http://localhost:<port>/<contextPath>/.
- Replica cluster topology
  
  If the search replicas are clustered behind a load balancer, then you need two setting values or Java system properties. The default value identifies the replica cluster and an additional value identifies the search primary.
  
  Setting Context Path Java System Property Value
  
  -Dep.search.default.url URL of the load balancer for the replica cluster
  
  master -Dep.search.master.url URL of the search primary

Setting Context Path	Java System Property	Value
	`-Dep.search.default.url`	URL of the load balancer for the replica cluster
master	`-Dep.search.master.url`	URL of the search primary

Updating Search Server Cluster

Halt any user updates to the system and ensure no changes are in progress through Commerce Manager, the Import/Export tool, or the Data Sync tool.
In Commerce Manager, ensure the indexing activity is complete for all indexes. You can find the index status in the Configuration section under Search Indexes.

Back up all existing indexes by calling the following links. These links will call the Solr replication API:

http://master_host:port/searchserver/category/replication?command=backup
http://master_host:port/searchserver/cmuser/replication?command=backup
http://master_host:port/searchserver/customer/replication?command=backup
http://master_host:port/searchserver/dynamicContentDelivery/replication?command=backup
http://master_host:port/searchserver/product/replication?command=backup
http://master_host:port/searchserver/promotion/replication?command=backup
http://master_host:port/searchserver/shippingservicelevel/replication?command=backup
http://master_host:port/searchserver/sku/replication?command=backup

Disable replication on the replica servers by calling the following links. Make sure this is done for all replicas.

http://slave_host:port/searchserver/category/replication?command=disablepoll
http://slave_host:port/searchserver/cmuser/replication?command=disablepoll
http://slave_host:port/searchserver/customer/replication?command=disablepoll
http://slave_host:port/searchserver/dynamicContentDelivery/replication?command=disablepoll
http://slave_host:port/searchserver/product/replication?command=disablepoll
http://slave_host:port/searchserver/promotion/replication?command=disablepoll
http://slave_host:port/searchserver/shippingservicelevel/replication?command=disablepoll
http://slave_host:port/searchserver/sku/replication?command=disablepoll

Shut down, update, and restart the primary search server:
1. Shut down the application server
2. Redeploy the updated search server war
3. Restart the application server.
If your search indexes are normally located within the searchserver/WEB-INF folder, you may need to restore them from your back up location or do a full rebuild
Using Commerce Manager, rebuild any indexes that would be affected by the update.

For step-by-step instructions on how to do this, see Requesting Search Index Rebuilds.
Verify the primary indexes.

Since the primary server is a full search instance, you can check its state by doing one of the following:
1. Issuing manual Solr queries.
2. By redirecting Cortex server instance to point to the primary instead of a replica.

Do one of the following:

If you are applying code updates to the replica servers, do the following for all replicas:
1. Remove the replica from the search cluster
2. Shutdown the server.
3. Redeploy the updated search server war.
4. Restart the server.
  
  The restarted replica will immediately begin polling the primary for index updates on startup.
5. Restore the replica to the search cluster.
If you are not updating the replica servers, resume index replication by calling the following links for all replicas:

http://slave_host:port/searchserver/category/replication?command=enablepoll
http://slave_host:port/searchserver/cmuser/replication?command=enablepoll
http://slave_host:port/searchserver/customer/replication?command=enablepoll
http://slave_host:port/searchserver/dynamicContentDelivery/replication?command=enablepoll
http://slave_host:port/searchserver/product/replication?command=enablepoll
http://slave_host:port/searchserver/promotion/replication?command=enablepoll
http://slave_host:port/searchserver/shippingservicelevel/replication?command=enablepoll
http://slave_host:port/searchserver/sku/replication?command=enablepoll

Search Server Cluster Checklist

To verify if your search server cluster is running properly:

Check if the indexes are being replicated to the replica server
Ensure requests are being redirected to the replica
Make sure the update requests are only redirected to the primary server
Trace requests in the Apache HTTP server’s log and Tomcat server’s access logs
See if requests are redirected to another server if a server is unavailable

Commerce

7.6.x

Search Server Deployment

Configuration

Performance & Monitoring

Search Server Clustering

Topology

Cluster Configuration

Updating Search Server Cluster

Search Server Cluster Checklist