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The requestDispatcher element of solrconfig.xml controls the way the Solr HTTP RequestDispatcher implementation responds to requests. Included are parameters for defining if it should handle /select urls (for Solr 1.1 compatibility), if it will support remote streaming, the maximum size of file uploads and how it will respond to HTTP cache headers in requests.

Topics in this section:

handleSelect Element

handleSelect is for legacy back-compatibility; those new to Solr do not need to change anything about the way this is configured by default.

The first configurable item is the handleSelect attribute on the <requestDispatcher> element itself. This attribute can be set to one of two values, either "true" or "false". It governs how Solr responds to requests such as /select?qt=XXX. The default value "false" will ignore requests to /select if a requestHandler is not explicitly registered with the name /select. A value of "true" will route query requests to the parser defined with the qt value.

In recent versions of Solr, a /select requestHandler is defined by default, so a value of "false" will work fine. See the section RequestHandlers and SearchComponents in SolrConfig for more information.

requestParsers Element

The <requestParsers> sub-element controls values related to parsing requests. This is an empty XML element that doesn't have any content, only attributes.

The attribute enableRemoteStreaming controls whether remote streaming of content is allowed. If set to false, streaming will not be allowed. Setting it to true (the default) lets you specify the location of content to be streamed using stream.file or stream.url parameters.

If you enable remote streaming, be sure that you have authentication enabled. Otherwise, someone could potentially gain access to your content by accessing arbitrary URLs. It's also a good idea to place Solr behind a firewall to prevent it being accessed from untrusted clients.

The attribute multipartUploadLimitInKB sets an upper limit in kilobytes on the size of a document that may be submitted in a multi-part HTTP POST request. The value specified is multiplied by 1024 to determine the size in bytes.

The attribute formdataUploadLimitInKB sets a limit in kilobytes on the size of form data (application/x-www-form-urlencoded) submitted in a HTTP POST request, which can be used to pass request parameters that will not fit in a URL.

The attribute addHttpRequestToContext can be used to indicate that the original HttpServletRequest object should be included in the context map of the SolrQueryRequest using the key httpRequest. This HttpServletRequest is not used by any Solr component, but may be useful when developing custom plugins.

httpCaching Element

The <httpCaching> element controls HTTP cache control headers. Do not confuse these settings with Solr's internal cache configuration. This element controls caching of HTTP responses as defined by the W3C HTTP specifications.

This element allows for three attributes and one sub-element. The attributes of the <httpCaching> element control whether a 304 response to a GET request is allowed, and if so, what sort of response it should be. When an HTTP client application issues a GET, it may optionally specify that a 304 response is acceptable if the resource has not been modified since the last time it was fetched.

Parameter

Description

never304

If present with the value true, then a GET request will never respond with a 304 code, even if the requested resource has not been modified. When this attribute is set to true, the next two attributes are ignored. Setting this to true is handy for development, as the 304 response can be confusing when tinkering with Solr responses through a web browser or other client that supports cache headers.

lastModFrom

This attribute may be set to either openTime (the default) or dirLastMod. The value openTime indicates that last modification times, as compared to the If-Modified-Since header sent by the client, should be calculated relative to the time the Searcher started. Use dirLastMod if you want times to exactly correspond to when the index was last updated on disk.

etagSeed

This value of this attribute is sent as the value of the ETag header. Changing this value can be helpful to force clients to re-fetch content even when the indexes have not changed---for example, when you've made some changes to the configuration.

cacheControl Element

In addition to these attributes, <httpCaching> accepts one child element: <cacheControl>. The content of this element will be sent as the value of the Cache-Control header on HTTP responses. This header is used to modify the default caching behavior of the requesting client. The possible values for the Cache-Control header are defined by the HTTP 1.1 specification in Section 14.9.

Setting the max-age field controls how long a client may re-use a cached response before requesting it again from the server. This time interval should be set according to how often you update your index and whether or not it is acceptable for your application to use content that is somewhat out of date. Setting must-revalidate will tell the client to validate with the server that its cached copy is still good before re-using it. This will ensure that the most timely result is used, while avoiding a second fetch of the content if it isn't needed, at the cost of a request to the server to do the check.

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  1. Recently I hit an odd situation related with the formdataUploadLimitInKB configuration param.

    In solrcloud mode, this parameter limit the maximum of data that an internal request can pass to another node. This is relevant when we are doing queries that has a rows value very high (400k or more). It would be nice the wiki notice about this situation because the error that we have in this situation is not very intuitive.