Audit Logging

Solr has the ability to log an audit trail of all HTTP requests entering the system. Audit loggers are pluggable to suit any possible format or log destination.

An audit trail (also called audit log) is a security-relevant chronological record, set of records, and/or destination and source of records that provide documentary evidence of the sequence of activities that have affected at any time a specific operation, procedure, event, or device.
— Wikipedia

Configuring Audit Logging

Audit logging is configured in security.json under the auditlogging key.

The example below uses plugin defaults to configure synchronous audit logging to Solr’s default log file.

    "class": "solr.SolrLogAuditLoggerPlugin"

By default any audit logging plugin will log asynchronously in the background to avoid slowing down the requests. To make audit logging happen synchronously, add the parameter async with a value of false.

When using asynchronous logging, you may optionally also configure queue size, number of threads, and whether it should block when the queue is full or discard events:

    "class": "solr.SolrLogAuditLoggerPlugin",
    "async": true,
    "blockAsync" : false,
    "numThreads" : 2,
    "queueSize" : 4096,

Audit Logging Parameters

These parameters are:



Default: none

The audit logging plugin class name. Either solr.SolrLogAuditLoggingPlugin or solr.MultiDestinationAuditLogger (described below in the section Chaining Multiple Loggers).



Default: true

Defines if events are logged asynchronously. This defaults to true to avoid slowing down requests. However, if you are confident in the performance characteristics of your system and need events logged synchronously, you can change this to false.



Default: false

Defines if requests should be blocked if the queue is full. The default of false will discard unlogged events. Only used when async=true.



Default: 2

The number of threads available to audit logging. If the number of CPU-cores available to the server is higher than 4, then the default is modified to CPU-cores / 2. Only used when async=true.



Default: 4096

The size of the queue. Only used when async=true.




The event types to log. See the section Event Types below for type options.



Default: none

Defines the circumstances when events should not be logged (muted). Possible rules can exclude requests from certain users, IPs, paths, or request parameters. See the section Muting Certain Events below for mute rule options.

Event Types

The event types logged can be configured with the eventTypes parameter. By default only the final event types REJECTED, ANONYMOUS_REJECTED, UNAUTHORIZED, COMPLETED and ERROR are logged.

These are the event types triggered by the framework:

EventType Usage


User successfully authenticated


Authentication request rejected


Request proceeds with unknown user


Request from unknown user rejected


Authorization succeeded


Authorization failed


Request completed successfully


Request was not executed due to an error

Muting Certain Events

The configuration parameter muteRules lets you mute logging for certain events. You may specify multiple rules and combination of rules that will cause muting. You can mute by request type, username, collection name, path, request parameters or IP address.

The following example uses muteRules to mute audit logging for three categories of requests: any SEARCH requests, any requests made by user johndoe, and any requests from IP address

    "class": "solr.SolrLogAuditLoggerPlugin",
    "muteRules": [ "type:SEARCH", "user:johndoe", "ip:" ]

A mute rule may also be a list, in which case all items in the list must be true for muting to happen. The configuration below has three mute rules:

    "class": "solr.SolrLogAuditLoggerPlugin",
    "muteRules": [
      "ip:", (1)
      [ "path:/admin/collections", "param:action=LIST" ], (2)
      [ "path:/admin/collections", "param:collection=test" ] (3)
1 This will mute all events from client IP
2 This rule will mute Collection API requests with action=LIST.
3 The final rule will mute Collection API requests for the collection named test.

Note how you can mix single string rules with lists of rules that must all match:

Options for mute rules are:

  • type:<request-type>: A request-type by name: ADMIN, SEARCH, UPDATE, STREAMING, or UNKNOWN.

  • collection:<collection-name>: A collection by name.

  • user:<userid>: A user by userid.

  • path:</path/to/handler>: A request path relative to /solr or for search or update requests relative to collection. Path is prefix matched, i.e., /admin will mute any sub path as well.

  • ip:<ip-address>: An IPv4 address.

  • param:<param>=<value>: A request parameter. This will likely mostly be used in conjunction with the path rule, as shown in the example above.

Chaining Multiple Loggers

Using the MultiDestinationAuditLogger multiple audit logger plugins can be configured in a chain to log to multiple destinations.

    "class" : "solr.MultiDestinationAuditLogger",
    "plugins" : [
      { "class" : "solr.SolrLogAuditLoggerPlugin" },
      { "class" : "solr.MyOtherAuditPlugin",
        "customParam" : "value"

Note that logging to alternate destinations would need to be defined with a custom audit logging plugin. See the javadocs for the base class at AuditLoggerPlugin.


Audit logging plugins record metrics about count and timing of log requests, as well as queue size for async loggers. The metrics keys are all recorded on the SECURITY category, and each metric name are prefixed with a scope of /auditlogging and the class name of the logger, e.g., SolrLogAuditLoggerPlugin. The individual metrics are:

  • count: (meter) Records number and rate of audit logs written.

  • errors: (meter) Records number and rate of errors.

  • lost: (meter) Records number and rate of events lost if the queue is full and blockAsync=false.

  • requestTimes: (timer) Records latency and percentiles for audit logging performance.

  • totalTime: (counter) Records total time spent logging.

  • queueCapacity: (gauge) Records the maximum size of the async logging queue.

  • queueSize: (gauge) Records the number of events currently waiting in the queue.

  • queuedTime: (timer) Records the amount of time events waited in queue. Adding this with the requestTimes metric will show the total time from event to logging complete.

  • async: (gauge) Tells whether this logger is in async mode.

If you experience a very high request rate and have a slow audit logger plugin, you may see the queueSize and queuedTime metrics increase, and possibly start dropping events (shown by an increase in lost count). In this case you may want to increase the numThreads setting.