The collections API supports the following operations, which can be used to create, remove, or reload collections:

There are more operations available, and they can be found on the Solr Wiki. In this chapter, we'll just see how we can use the collections API to manage a Solr configuration.

Let's go ahead and create a new collection with the number of shards as 2. To do this, we'll execute the following command:

curl "http://localhost:8983/solr/admin/collections?action=CREATE&name=sampleCatalog&replicationFactor=2&numShards=2&collection.configName=default&maxShardsPerNode=2&wt=json&indent=2"

We'll get the output as follows after running this command:

{
  "responseHeader":{
    "status":0,
    "QTime":10346},
  "success":{
    "":{
      "responseHeader":{
        "status":0,
        "QTime":9381},
      "core":"sampleCatalog_shard1_replica1"},
    "":{
      "responseHeader":{
        "status":0,
        "QTime":9565},
      "core":"sampleCatalog_shard1_replica2"},
    "":{
      "responseHeader":{
        "status":0,
        "QTime":9689},
      "core":"sampleCatalog_shard2_replica1"},
    "":{
      "responseHeader":{
        "status":0,
        "QTime":9774},
      "core":"sampleCatalog_shard2_replica2"}}}

After creating the new catalog, we can navigate to the Cloud tab in Solr Admin UI. We can see that our new core has been created.

Now, let's use the collections API to delete the newly created collection. We'll use the following command to delete it:

curl "http://localhost:8983/solr/admin/collections?action=DELETE&name=sampleCatalog&wt=json&indent=2"

We'll get this response after running the preceding command:

{
  "responseHeader": {
    "status": 0,
    "QTime": 1272
  },
  "success": {
    "192.168.56.1:8983_solr": {
      "responseHeader": {
        "status": 0,
        "QTime": 182
      }
    },
    "192.168.56.1:8983_solr": {
      "responseHeader": {
        "status": 0,
        "QTime": 209
      }
    },
    "192.168.56.1:8987_solr": {
      "responseHeader": {
        "status": 0,
        "QTime": 200
      }
    },
    "192.168.56.1:8987_solr": {
      "responseHeader": {
        "status": 0,
        "QTime": 216
      }
    }
  }
}

After we have run the delete query, we can run the list command to get the current list of collections.

To do this, we use the following command:

curl "http://localhost:8983/solr/admin/collections?action=LIST&wt=json&indent=2"

We'll get this response:

{
  "responseHeader": {
    "status": 0,
    "QTime": 283
  },
  "collections": [
    "collection1",
    "musicCatalogue-solrcloud"
  ]
}

We've seen how we can create and delete collections. Now let's see one more feature of the collections API. We can create an alias using this API.

Let's create an alias for our collection using this command:

curl "http://localhost:8983/solr/admin/collections?action=CREATEALIAS&name=musicCatalogue-alias&collections=musicCatalogue-solrcloud&wt=json&indent=2"

After running it, we should get the following response:

{
  "responseHeader": {
    "status": 0,
    "QTime": 282
  }
}

Now, let's use the alias we've just created and run a query against it:

curl "http://localhost:8983/solr/musicCatalogue-alias/select?q=*%3A*&wt=json&indent=true"

We'll get this response:

{
  "responseHeader": {
    "status": 0,
    "QTime": 32,
    "params": {
      "q": "*:*",
      "indent": "true",
      "wt": "json"
    }
  },
  "response": {
    "numFound": 3,
    "start": 0,
    "maxScore": 1.0,
    "docs": [
      {
        "id": "1",
        "title": [
          "Apache Solr Indexing Data"
        ],
        "_version_": 1516224129180631040
      },
      {
        "id": "2",
        "title": [
          "Apache Solr Cookbook"
        ],
        "_version_": 1516224138192093184
      }
    ]
  }
}

This shows us how we can create an alias for a collection using the Collections API. One of the main benefits of using an alias is that it hides the main collection from the search client application. For example, we can have an alias named onlineArticles; when queried, it can return documents from magazines and blogs collections.

An alias can also be deleted using the following command:

curl "http://localhost:8983/solr/admin/collections?action=DELETEALIAS&name=musicCatalogue-alias&wt=json&indent=2"

There is always a need to update configuration files in Solr. In Solr, while using SolrCloud, we can always maintain the configuration files in SVN, Git, or any other version control tool. Any changes in the configuration file can be pushed to the ZooKeeper instance that will keep all the Solr instances in sync with the latest version of the configuration.

Let's now see how we can update an instance of a file in ZooKeeper. To do this, we'll create a new file in the conf directory, which we'll then push to Zookeeper using the zkcli script.

We create a new file called updateMe.conf in %SOLR_HOME%/example/solr/collection1/conf. After this we run the following command, which will push the file:

$ $SOLR_HOME/example/scripts/cloud-scripts/zkcli.sh -zkhost localhost:9983 -cmd upconfig -confdir %SOLR_HOME%/example/solr/collection1/conf -confname default

After running this command, we can navigate to the Cloud tab and then click on the Tree button, which will show us the files that are available in the Zookeeper instance. We can see in the following screenshot that our newly created file is present in the /configs/default location:

After updating the collection, we should always reload it, which will load up any changes made in the configuration files. We can reload a collection using the Collections API, like this:

curl "http://localhost:8983/solr/admin/collections?action=RELOAD&name=musicCatalogue-solrcloud&wt=json&indent=2"

We've discussed new terms in this chapter such as sharding and replication. Let's see what these terms mean in SolrCloud:

The Solr Cloud view also shows the configuration that was sent to ZooKeeper. The following screenshot shows the Solr Cloud view:

The Cloud tab contains the graph (radial) view, which can be used to see the shards and replicas currently being used in a graphical way. This screenshot shows our collection in a radial view: