Solr Upgrade Notes

The following notes describe changes to Solr in recent releases that you should be aware of before upgrading.

These notes highlight the biggest changes that may impact the largest number of implementations. It is not a comprehensive list of all changes to Solr in any release.

When planning your Solr upgrade, consider the customizations you have made to your system and review the CHANGES.txt file found in your Solr package. That file includes all the changes and updates that may effect your existing implementation.

Detailed steps for upgrading a Solr cluster are in the section Upgrading a Solr Cluster.

Upgrading to 8.x Releases

If you are upgrading from 7.x, see the section Upgrading from 7.x Releases below.

Solr 8.5

See the 8.5 Release Notes for an overview of the main new features of Solr 8.5.

When upgrading to 8.5.x users should be aware of the following major changes from 8.4.

Note: an index incompatibility warning was retroactively added below to 8.4 for users choosing a non-default postings format (e.g. "FST50").

Considerations for a SolrCloud Upgrade

Solr 8.5 introduces a change in the format used for the elements in the Overseer queues and maps (see SOLR-14095 for technical discussion of the change). This queue is used internally by the Overseer to reliably handle operations, to communicate operation results between the Overseer and the coordinator node, and by the REQUESTSTATUS API for displaying information about async Collection operations.

This change won’t require you to change any client-side code you should see no differences on the client side. However, it does require some care when upgrading an existing SolrCloud cluster depending on your upgrade strategy.

If you are upgrading Solr with an atomic restart strategy:

  • If you don’t use async or REQUESTSTATUS operations, you should be able to restart and not see any issues.
  • If you do use Collection API operations:
    1. Pause Collection API operations.
    2. Cleanup queues (See the section DELETESTATUS for examples) if you use async operations.
    3. Upgrade and restart the nodes.
    4. Resume all normal operations.

If you are upgrading Solr with a rolling restart strategy:

  • If you don’t use Collection API operations, you should be able to do a rolling restart and not see any issues.
  • If you do use Collection API operations, but you can pause their use during the restart the easiest way is to:
    1. Pause Collection API operations.
    2. Upgrade and restart all nodes.
    3. Cleanup queues (See the section DELETESTATUS for examples) if you use async operations.
    4. Resume all normal operations.

If you use Collection API operations and can’t pause them during the upgrade:

  1. Start 8.5 nodes with the system property: -Dsolr.useUnsafeOverseerResponse=deserialization. Ensure the Overseer node is upgraded last.
  2. Once all nodes are in 8.5 and once you don’t need to read old status anymore, restart again removing the system property.

If you prefer to keep the old (but insecure) serialization strategy, you can start your nodes using the system property: -Dsolr.useUnsafeOverseerResponse=true. Keep in mind that this will be removed in future version of Solr.

Security Manager

Solr now has the ability to run with a Java security manager enabled. To enable this, set the property SOLR_SECURITY_MANAGER_ENABLED=true in solr.in.sh or solr.in.cmd. Note that if you are using HDFS to store indexes, you cannot enable the security manager.

In Solr 9.0, this will be the default.

See also the section Enable Security Manager.

Block/Allow Specific IPs

Solr has two new parameters to allow you to restrict access to Solr using IP addresses. Use SOLR_IP_WHITELIST to configure a whitelist, and SOLR_IP_BLACKLIST to configure a blacklist. These properties are defined in solr.in.sh or solr.in.cmd.

See also the section Enable IP Access Control.

BlockJoin Facet Deprecation

The BlockJoinFacetComponent is marked for deprecation and will be removed in 9.0. Users are encouraged to migrate to uniqueBlock() in JSON Facet API. More information about this is available in the section Block Join Domain Changes.

Caching with the Boolean Query Parser

By default, the Boolean Query Parser caches queries in Solr’s filterCache. It’s now possible to disable this with the local param cache=false.

Indexing Log Files

Solr now includes a command line tool, bin/postlogs which will index Solr’s log files into a collection. This provides an easy way to use Solr or visualization tools (such as Zeppelin) to troubleshoot problems with the system.

This tool is not yet officially documented in the Reference Guide, but draft documentation is available in a branch and can be accessed via GitHub.

Highlighting

Solr’s Unified Highlighter now has two parameters to help control passage sizing, hl.fragAlignRatio and hl.fragsizeIsMinimum. See the section The Unified Highlighter for details about these new parameters. Regardless of the settings, the passages may be sized differently than before.

Shared Library System Parameter

Solr’s solr.xml file has long had support for a sharedLib parameter, which allows you to define a common location for .jar files that may need to be in the path for all cores.

This property can now be defined in solr.in.sh or solr.in.cmd as a system property (-Dsolr.sharedLib=/path/to/lib) added to SOLR_OPTS (see solr.in.sh or solr.in.cmd for details).

Solr 8.4

See the 8.4 Release Notes for an overview of the main new features of Solr 8.4.

When upgrading to 8.4.x users should be aware of the following major changes from 8.3.

Reminder: If you set the postingsFormat or docValuesFormat in the schema in order to use a non-default option, you risk preventing yourself from upgrading your Lucene/Solr software at future versions. Multiple non-default postings formats changed in 8.4, thus rendering the index data from a previous index. This includes "FST50" which was recommended by the Solr TaggerHandler for performance reasons. There is now improved documentation to navigate this trade-off choice.

Package Management System

Version 8.4 introduces a package management system to Solr. The goals of the system are to allow hot (live) deployment of plugins, provide packaging guidelines for plugins, and standardize Solr’s approach by following familiar concepts used in other package management systems.

The system is designed to eventually replace use of the <lib ../> directive, the Blob Store, and other methods of deploying plugins and custom components to Solr.

The system is currently considered experimental, so use with caution. It must be enabled with a system parameter passed at start up before it can be used. For details, please see the section Package Management.

With this feature Solr’s Blob Store functionality is now deprecated and will likely be removed in 9.0.

Security

The follow mix of changes were all made with the intention of making Solr more secure out of the box.

  • The solrconfig.xml file in Solr’s _default configset has been trimmed of the following previously pre-configured items:
    • All <lib …​/> directives. This means that Solr Cell (aka Tika), Learning to Rank, Clustering (with Carrot2), language identification, and Velocity (for the /browse sample search interface) are no longer enabled out of the box.
    • The /browse, /tvrh, and /update/extract request handlers.
    • The Term Vector Component.

    • The XSLT and Velocity response writers.

      All of these items can be added to your Solr implementation by manually editing solrconfig.xml to add them back in, or use the Config API.

      The sample_techproducts_configs and the examples found in ./example are unchanged.

  • Configsets that have been uploaded with an unsecured Configset API (i.e., when authentication is not enabled) are considered "Untrusted Configsets".

    In order to bolster Solr’s out-of-the-box security, these untrusted configsets are no longer allowed to use the <lib …​/> directive to implement contribs or custom Jars.

    When upgrading to 8.4, if you are using untrusted configsets that contain <lib ../> directives, their corresponding collections will not load (they will cease to work). You have a few options in this case:

    • You can secure your Solr instance with authentication and re-upload the configset (using the bin/solr zk upconfig …​ Solr CLI command);
    • You can put your custom Jars in Solr’s classpath instead of lib directories;

    • You can try the new package management system to manage your custom Jars.

      See the section Upload a Configset for more details about trusted vs. untrusted configsets.

  • Our default Jetty configuration has been updated to now set a Content-Security-Policy (CSP) by default. See ./server/etc/jetty.xml for details about how it is configured.

    As a result of this change, any custom HTML served by Solr’s HTTP server that contains inline Javascript will no longer execute in modern browsers. The options for you are:

    • Change your JavaScript code to not run inline any longer;
    • Edit jetty.xml to remove CSP (creating weaker security protection);
    • Remove/alter the headers with a reverse proxy.
  • Solr’s Blob Store and runtime libs functionality are now deprecated and are planned to be removed from Solr in version 9.0. It has been replaced with the new package management system.
  • The Velocity response writer is also now deprecated and is planned to be removed from Solr in version 9.0.

Using Collapse with Group Disallowed

Using the CollapsingQueryParser with Result Grouping has never been supported as it causes inconsistent behavior and NullPointerException errors. We have now explicitly disallowed this combination to prevent these errors. If you are using these together, you will need to modify your queries.

SolrJ

  • SolrJ now supports the shards.preference parameter for single-shard scenarios to ensure multi-shard and single-shard request routing works in the same way.

    See Cloud Request Routing and shards.preference Parameter for details.

  • QueryResponse.getExplainMap() type has changed from Map<String, String> to Map<String, Object> in order to support structured explanations.

    This change is expected to be mostly back-compatible. Compiled third-party components will work the same due to type erasure, but source code changes may be required.

  • Replica routing code has been moved to SolrJ, making those classes available to clients if necessary.

Streaming Expressions

  • A new DBSCAN clustering streaming evaluator has been added.
  • The precision stream evaluator can now operate on matrices.
  • The random streaming expression can now create the x-axis.

JSON Facets

  • Two new aggregations have been added: missing and countvals.
  • Several aggregations now support multi-valued fields: min, max, avg, sum, sumsq, stddev, variance, and percentile.

Caches

  • After the addition of CaffeineCache in 8.3, legacy SolrCache implementations are deprecated and likely to be removed in 9.0.

    Users are encouraged to transition their cache configurations to use org.apache.solr.search.CaffeineCache as soon as feasible.

Solr 8.3

See the 8.3 Release Notes for an overview of the main new features of Solr 8.3.

When upgrading to 8.3.x users should be aware of the following major changes from 8.2.

JWT Authentication

JWT Authentication now supports multiple identity providers. To allow this, the parameter jwkUrl has been deprecated and replaced with jwksUrl. Implementations using jwkUrl will continue to work as normal, but users should plan to transition their configurations to use jwksUrl instead as soon as feasible.

Caches

  • Solr has a new cache implementation, CaffeineCache, which is now recommended over other caches. This cache is expected to generally provide most users lower memory footprint, higher hit ratio, and better multi-threaded performance.

    Since caching has a direct impact on the performance of your Solr implementation, before switching to any new cache implementation in production, take care to test for your environment and traffic patterns so you fully understand the ramifications of the change.

  • A new parameter, maxIdleTime, allows automatic eviction of cache items that have not been used in the defined amount of time. This allows the cache to release some memory and should aid those who want or need to fine-tune their caches.

See the section Query Settings in SolrConfig for more details about these and other cache options and parameters.

Solr 8.2

See the 8.2 Release Notes for an overview of the main new features of Solr 8.2.

When upgrading to 8.2.x, users should be aware of the following major changes from v8.1.

ZooKeeper 3.5.5

Solr 8.2 updates the version of ZooKeeper included with Solr to v3.5.5.

It is recommended that external ensembles set up to work with Solr also be updated to ZooKeeper 3.5.5.

This ZooKeeper release includes many new security features. In order for Solr’s Admin UI to work with 3.5.5, the zoo.cfg file must allow access to ZooKeeper’s "four-letter commands". At a minimum, ruok, conf, and mntr must be enabled, but other commands can optionally be enabled if you choose. See the section Configuration for a ZooKeeper Ensemble for details.

Until 8.3, SOLR-13672 causes the ZK Status screen in the Admin UI to not be able to report status. This only impacts the UI, ZooKeeper still operates correctly.

Routed Aliases

  • Routed aliases now use collection properties to identify collections that belong to the alias; prior to 8.2, these aliases used core properties.

    This is backward-compatible and aliases created with prior versions will continue to work. However, new collections will no longer add the routedAliasName property to the core.properties file so any external code depending on this location will need to be updated.

  • Time-routed aliases now include a TRA infix in the collection name, in the pattern <alias>_TRA_<timestamp>.
    Collections created with older versions will continue to work.

Distributed Tracing Support

This release adds support for tracing requests in Solr. Please review the section Distributed Solr Tracing for details on how to configure this feature.

Solr 8.1

See the 8.1 Release Notes for an overview of the main new features of Solr 8.1.

When upgrading to 8.1.x, users should be aware of the following major changes from v8.0.

Global maxBooleanClauses Parameter

  • The behavior of the maxBooleanClauses parameter has changed to reduce the risk of exponential query expansion when dealing with pathological query strings.

    A default upper limit of 1024 clauses is now enforced at the node level. This was the default prior to 7.0, and it can be overridden with a new global parameter in solr.xml. This limit will be enforced for all queries whether explicitly defined by the user (or client), or created by Solr and Lucene internals.

    An identical parameter is available in solrconfig.xml for limiting the size of queries explicitly defined by the user (or client), but this per-collection limit will still be restricted by the global limit set in solr.xml.

    If your use case demands that you a lot of OR or AND clauses in your queries, upon upgrade to 8.1 you may need to adjust the global maxBooleanClauses parameter since between 7.0 and 8.1 the limit was effectively unbounded.

    For more information about the new parameter, see the section Format of solr.xml: maxBooleanClauses.

Security

  • JSON Web Tokens (JWT) are now supported for authentication. These allow Solr to assert a user is already authenticated via an external identity provider, such as an OpenID Connect-enabled IdP. For more information, see the section JWT Authentication Plugin.
  • A new security plugin for audit logging has been added. A default class SolrLogAuditLoggerPlugin is available and configurable in security.json. The base class is also extendable for adding custom audit plugins if needed. See the section Audit Logging for more information.

Collections API

  • The output of the REQUESTSTATUS command in the Collections API will now include internal asynchronous requests (if any) in the "success" or "failed" keys.
  • The CREATE command will now return the appropriate status code (4xx, 5xx, etc.) when the command has failed. Previously, it always returned 0, even in failure.
  • The MODIFYCOLLECTION command now accepts an attribute to set a collection as read-only. This can be used to block a collection from receiving any updates while still allowing queries to be served. See the section MODIFYCOLLECTION for details on how to use it.
  • A new command RENAME allows renaming a collection by setting up a one-to-one alias using the new name. For more information, see the section RENAME.
  • A new command REINDEXCOLLECTION allows indexing existing stored fields from a source collection into a new collection. For more information, please see the section REINDEXCOLLECTION.

Logging

  • The default Log4j2 logging mode has been changed from synchronous to asynchronous. This will improve logging throughput and reduce system contention at the cost of a slight chance that some logging messages may be missed in the event of abnormal Solr termination.

    If even this slight risk is unacceptable, the Log4j configuration file found in server/resources/log4j2.xml has the synchronous logging configuration in a commented section and can be edited to re-enable synchronous logging.

Metrics

  • The SolrGangliaReporter has been removed from Solr. The metrics library used by Solr, Dropwizard Metrics, was updated to version 4, and Ganglia support was removed from it due to a dependency on the LGPL license.

Browse UI (Velocity)

Default Garbage Collector (GC)

  • Solr’s default GC has been changed from CMS to G1. If you prefer to use CMS or any other GC method, you can modify the GC_TUNE section of solr.in.sh (*nix) or solr.in.cmd (Windows).

Upgrading from 7.x Releases

The upgrade from 7.x to Solr 8.0 introduces several major changes that you should be aware of before upgrading. These changes are described in the section Major Changes in Solr 8. It’s strongly recommended that you do a thorough review of that section before starting your upgrade.

If you run in SolrCloud mode, you must be on Solr version 7.3 or higher in order to upgrade to 8.x.

Upgrading from Pre-7.x Versions

Users upgrading from versions of Solr prior to 7.x are strongly encouraged to consult CHANGES.txt for the details of all changes since the version they are upgrading from.

The upgrade from Solr 6.x to Solr 7.0 introduced several major changes that you should be aware of before upgrading. Please do a thorough review of the section Major Changes in Solr 7 before starting your upgrade.

A summary of the significant changes between Solr 5.x and Solr 6.0 is in the section Major Changes from Solr 5 to Solr 6.