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, or event. (Wikipedia)

Configuration in security.json

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

The example security.json below configures synchronous audit logging to Solr default log file.

    "class": "solr.SolrLogAuditLoggerPlugin"

By default any AuditLogger plugin configured will log asynchronously in the background to avoid slowing down the requests. To make audit logging happen synchronously, add the parameter async: false. For async 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,

The defaults are async: true, blockAsync: false, queueSize: 4096. The default for numThreads is 2, or if the server has more than 4 CPU-cores then we use CPU-cores/2.

Event Types

These are the event types triggered by the framework:

AUTHENTICATEDUser successfully authenticated
REJECTEDAuthentication request rejected
ANONYMOUSRequest proceeds with unknown user
ANONYMOUS_REJECTEDRequest from unknown user rejected
AUTHORIZEDAuthorization succeeded
UNAUTHORIZEDAuthorization failed
COMPLETEDRequest completed successfully
ERRORRequest was not executed due to an error

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

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. We’ll explain through examples:

The below example will mute logging for all SEARCH requests as well as all requests made my user johndoe or from IP address

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

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

    "class": "solr.SolrLogAuditLoggerPlugin"
    "muteRules": [
      [ "path:/admin/collections", "param:action=LIST" ], 
      [ "path:/admin/collections", "param:collection=test" ] 
1The first will mute all events from client IP
2The second rule will mute collection admin requests with action=LIST
3The third rule will mute collection admin requests for the collection named test

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

Valid mute rules are:

  • type:<request-type> (request-type by name: ADMIN, SEARCH, UPDATE, STREAMING, UNKNOWN)
  • collection:<collection-name> (collection by name)
  • user:<userid> (user by userid)
  • path:</path/to/handler> (request path relative to /solr or for search/update requests relative to collection. Path is prefix matched, i.e., /admin will mute any sub path as well.
  • ip:<ip-address> (IPv4-address)
  • param:<param>=<value> (request parameter)

Chaining Multiple Loggers

Using the MultiDestinationAuditLogger you can configure multiple audit logger plugins in a chain, to log to multiple destinations, as follows:

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


AuditLoggerPlugins 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 (type: meter. Records number and rate of audit logs done)
  • errors (type: meter. Records number and rate of errors)
  • lost (type: meter. Records number and rate of events lost due to queue full and blockAsync=false)
  • requestTimes (type: timer. Records latency and perceniles for logging performance)
  • totalTime (type: counter. Records total time spent)
  • queueCapacity (type: gauge. Records the max size of the async logging queue)
  • queueSize (type: gauge. Records the number of events currently waiting in the queue)
  • queuedTime (type: timer. Records the amount of time events waited in queue. Adding this with requestTimes you get total time from event to logging complete)
  • async (type: gauge. Tells whether this logger is in async mode)
If you expect a very high request rate and have a slow audit logger plugin, you may see that the queueSize and queuedTime metrics increase, and in worst case start dropping events and see an increase in lost count. In this case you may want to increas the numThreads setting.