# Configuration

BlackLab and BlackLab Server settings can be configured in configuration files.


These files can be in YAML or JSON format. On this page, we will use the YAML format (as it allows comments and is arguably more readable), but it the two can be easily converted back and forth (for example here (opens new window)). Just be sure to use the .json extension for JSON and .yaml or .yml for YAML.

# BlackLab vs. BlackLab Server config

The configuration files are called blacklab-server.yaml and blacklab.yaml. You most likely only need blacklab-server.yaml, which can contain everything blacklab.yaml can and more.

To be precise: BlackLab programs such as QueryTool, IndexTool and BlackLab Server always look for blacklab.yaml. BlackLab Server also looks for blacklab-server.yaml. So if you're just running BlackLab Server, you probably only need a blacklab-server.yaml file, but if you also want to configure some detail about how IndexTool and QueryTool (or other BlackLab-based applications) run, it can be useful to have a blacklab.yaml file too.

# Config file locations

Where should this file (or files) be located? BlackLab looks for them in the following places:

  • the directory specified in $BLACKLAB_CONFIG_DIR, if this environment variable was defined
  • $HOME/.blacklab
  • /etc/blacklab
  • the Java classpath

In addition, BlackLab Server will also look for blacklab-server.yaml in the directory where the .war file is located, e.g. /usr/share/tomcat/webapps.

# Minimal config file

Here's a minimal configuration file for BlackLab Server. Name it blacklab-server.yaml and place it in the same directory as the blacklab-server.war file or in /etc/blacklab (or configure a different location as just described).

configVersion: 2

# Where indexes can be found
# (list directories whose subdirectories are indexes, or directories containing a single index)
- /data/index

This simply tells BlackLab Server where to find its indexes.

A minimal example of blacklab.yaml would be no file at all, as no setting in blacklab.yaml is required for IndexTool or QueryTool to run.

# Complete config file

Below is a fully populated version of blacklab-server.yaml.


You don't need all these sections! Just use the ones you want to specifically influence, and leave the rest out. See the minimal config file above to get started.


You can also use a file called blacklab.yaml if you want to configure details about running IndexTool and QueryTool as well. It can only contain the log, search, indexing and plugin sections (located at the end of this example config). This file may be useful if you want to increase the number of metadata values stored in the index metadata file, for example. If you're not sure, you probably don't need this.

# BlackLab Server config file
# ===============================================================

# This indicates we're using the new index format.
configVersion: 2

# Where indexes can be found
# (list directories whose subdirectories are indexes, or directories containing a single index)
- /data/index

# Directory containing each users' private indexes
# (only works if you've configured an authentication system, see below)
userIndexes: /data/user-index

# Settings related to BlackLab Server's protocol, i.e. requests and responses

    # If true, omits empty annotation values from XML results.
    omitEmptyProperties: false
    # Default response type (XML or JSON; default XML)
    defaultOutputType: XML
    # Value for the Access-Control-Allow-Origin HTTP header (default: *)
    accessControlAllowOrigin: "*"

# Defaults and maximum values for parameters
# (some values will affect server load)

    # Are searches case/accent-sensitive or -insensitive by default?
    defaultSearchSensitivity: insensitive

    # The maximum number of hits to process (return as results, and 
    # use for sorting, grouping, etc.). -1 means no limit.
    # ("maxretrieve" parameter)
    # (higher values will put more stress on the server)
        default: 1000000
        max: 2000000

    # The maximum number of hits to count. -1 means no limit.
    # ("maxcount" parameter)
    # (higher values will put more stress on the server)
        default: -1
        max: 10000000

    # Number of results per page ("number" parameter). -1 means no limit.
    # (a very high max value might lead to performance problems)
        default: 50
        max: 3000

    # Context around match ("context" parameter)
    # (higher values might cause copyright issues and may stress the server)
    # Set to 0 to omit the left and right context altogether.
        default: 5
        max: 20

    #  Default pattern language to use.
    #  The pattlang URL parameter override this value.
    patternLanguage: bcql

    #  Default filter language to use.
    #  The filterlang URL parameter override this value.
    filterLanguage: luceneql

    # By default, should we include the grouped hits in
    # grouped responses? If false, just include group 
    # identity and size. Defaults to false. Can be overridden 
    # using the "includegroupcontents" URL parameter.
    writeHitsAndDocsInGroupedHits: false

    # If we're capturing part of our matches, should
    # we include empty captures? This can happen when the
    # clause to capture is optional, e.g. A:[]?
    # Defaults to false. Can be overridden using the 
    # "omitemptycaptures" URL parameter.
    omitEmptyCaptures: false

    # What REST API version to attempt compatibility with.
    # Valid values are currently: 3.0, 4.0, current, experimental.
    # Defaults to current.
    api: current

#  Settings for job caching.

    # How much free memory the cache should shoot for (in megabytes) while cleaning up.
    # Because we don't have direct control over the garbage collector, we can't reliably clean up until
    # this exact number is available. Instead we just get rid of a few cached tasks whenever a
    # new task is added and we're under this target number.
    targetFreeMemMegs: 100

    # The minimum amount of free memory required to start a new search task. If this memory is not available,
    # your search will be queued.
    minFreeMemForSearchMegs: 50
    # Maximum number of searches that may be queued. If you try to add another search, this will return an error.
    # Queued searches don't take up memory, but it's no use building up a huge queue that will take a very long time
    # to get through. Better to ask users to return when server load is lower.
    maxQueuedSearches: 20,

    # How long after it was last accessed will a completed search task be removed from 
    # the cache? (in seconds)
    # (don't set this too low; instead, set targetFreeMemMegs, the target amount of free memory)
    # If you want to disable the cache altogether, set this to 0.
    maxJobAgeSec: 3600

    # If a search is aborted, how long should we keep the search in the cache to prevent
    # the client from resubmitting right away? A sort of "deny list" if you will.
    denyAbortedSearchSec: 600

    # After how much time should a running search be aborted?
    # (larger values put stress on the server, but allow complicated searches to complete)
    maxSearchTimeSec: 300

    # How long the client may keep results we give them in their local (browser) cache.
    # This is used to write HTTP cache headers. Low values mean clients might re-request
    # the same information, making clients less responsive and consuming more network resources.
    # Higher values make clients more responsive but could cause problems if the data (or worse,
    # the protocol) changes after an update. A value of an hour or so seems reasonable.
    clientCacheTimeSec: 3600

    # Maximum number of cache entries to keep.
    # Please note that memory use per cache entry may vary wildly,
    # so you may prefer to use targetFreeMemMegs to set a "free memory goal"
    # and/or maxJobAgeSec to set a maximum age for cache entries.
    maxNumberOfJobs: 100
    # The cache implementation to use.
    # (FQDN or class name (in package nl.inl.blacklab.server.search) of
    # SearchCache subclass to instantiate)
    # The default is BlsCache. An alternative is ResultsCache, which is more
    # efficient if you have a large number of small, short-lived indexes.
    implementation: BlsCache

# Settings related to tuning server load and client responsiveness

    # How many search tasks should be able to run simultaneously
    # (set this to take advantage of the cores/threads available to the machine;
    # probably don't set it any larger, as this won't help and might hurt)
    # Note that this is a rough guideline, not an absolute maximum number of threads
    # that will ever be running. New searches are only started (unqueued) if there's 
    # fewer than this number of threads running.
    # (-1 to autodetect)
    maxConcurrentSearches: 6

    # How many threads may a single search task use at most?
    # (lower values will allow more simultaneous searches to run;
    # higher values improve search performance, but will crowd out other searches.
    # e.g. if you set this to the same number as maxConcurrentSearches, a single 
    # search may queue all other searches until it's done)
    maxThreadsPerSearch: 3

    # Abhort a count if the client hasn't asked about it for 30s
    # (lower values are easier on the server, but might abort a count too soon)
    abandonedCountAbortTimeSec: 30

# Settings for diagnosing problems
    #  A list of IPs that will run in debug mode.
    #  In debug mode, ...
    #  - the /cache-info resource show the contents of the job cache
    #    (other debug information resources may be added in the future)
    #  - output is prettyprinted by default (can be overriden with the prettyprint
    #    GET parameter)
    -       #  IPv4 localhost
    - 0:0:0:0:0:0:0:1 #  IPv6 localhost

# How to determine current user
# (you only need this if you want per-user private indices or authorization)
        class: AuthDebugFixed
        userId: jan.niestadt@ivdnt.org
        # For CLARIN (Shibboleth), use the following authentication config:
        #class: AuthClarinEppn

    #  Clients from these IPs may choose their own user id and send it along in a GET parameter userid.
    #  This setting exists for web applications that contact the webservice (partly) through the
    #  server component. They would get the same session id for each user, making them likely 
    #  to hit the maxRunningJobsPerUser setting. Instead, they should assign session IDs for each of
    #  their clients and send them along with any request to the webservice.
    -       #  IPv4 localhost
    - 0:0:0:0:0:0:0:1 #  IPv6 localhost
    # This is an insecure way of authenticating to BlackLab Server by sending
    # two HTTP headers. It is only intended for testing purposes.
    # Choose a 'secret' password here. Then send your requests to BlackLab Server 
    # with the extra HTTP headers X-BlackLabAccessToken (the 'secret' password) and
    # X-BlackLabUserId (the user you wish to authenticate as).
    # Needless to say this method is insecure because it allows full access to
    # all users' corpora, and the access token could potentially leak to an
    # attacker.
    #debugHttpHeaderAuthToken: secret

# ---------------------------------------------------------------------------
# What follows are general BlackLab settings that can apply to different 
# BlackLab applications, not just to BlackLab Server.
# (These can go in a separate file named blacklab.yaml, which is read by all
# BlackLab applications. Make sure to include configVersion as well)
# (you generally don't need to change these if you're running BlackLab Server,
# unless you're using some of the advanced features such as indexing/plugins,
# or you're trying to diagnose problems)

# Settings related to logging

    # What subjects to log messages for
        # BL trace settings
        indexOpening: false
        optimization: true
        queryExecution: true

        # BLS trace settings
        cache: true

# Defaults for searching
# NOTE: these are BlackLab defaults, not the defaults for the BlackLab Server parameters;
# see the parameters section for those.

    # Collator to use for sorting, grouping, etc.
        language: nl   # required
        country: NL    # optional
        #variant: x     # optional

    # Default number of words around hit.
    contextSize: 5

    # The default maximum number of hits to retrieve (and use for sorting, grouping, etc.).
    # -1 means no limit, but be careful, this may stress your server.
    maxHitsToRetrieve: 1000000
    # The default maximum number of hits to count.
    # -1 means no limit, but be careful, this may stress your server.
    maxHitsToCount: -1

    # How eagerly to apply "forward index matching" to certain queries
    # [advanced technical setting; don't worry about this unless you want to experiment]
    # [if you want to disable forward index matching, which may be beneficial
    #  if you indexes are small and your query volume is high, set this to 0]
    fiMatchFactor: 900
    # Enable result sets larger than 2^31?
    # If you don't need this, you can disable it for slightly better performance.
    # (defaults to true)
    enableHugeResultSets: true

# Options for indexing operations, if enabled
# (right now, in BLS, they're only enabled for logged-in users in
#  their own private area)

    # (By default, http downloads of e.g. metadata are not allowed)
    downloadAllowed: false

    # Where to store cached files
    downloadCacheDir: /tmp/bls-download-cache

    # Max. size of entire cache in MB
    downloadCacheSizeMegs: 100

    # Max. size of single download in MB
    downloadCacheMaxFileSizeMegs: 1

    # Max. number of zip files to keep opened
    zipFilesMaxOpen: 10
    # Number of threads to use for indexing operations
    # (more threads is faster, but uses more memory)
    numberOfThreads: 2
    # Max. number of values to store per metadata field
    maxMetadataValuesToStore: 100
    # Max. number of indices per user
    # (only relevant if you've configured private indices and authorization)
    maxNumberOfIndicesPerUser: 10

# Plugin options. Plugins allow you to automatically convert files (e.g. .html, .docx) or 
# apply linguistic tagging before indexing via BLS (experimental functionality).

    # Should we initialize plugins when they are first used?
    # (plugin initialization can take a while; during development, delayed initialization is
    # often convenient, but during production, you usually want to initialize right away)
    delayInitialization: false

    # # Individual plugin configurations

        # Conversion plugin
            jarPath: "/home/jan/projects/openconvert_en_tagger/OpenConvertMaven/target/OpenConvert-0.2.0.jar"

        # Tagging plugin
            jarPath: "/home/jan/projects/openconvert_en_tagger/DutchTagger/target/DutchTagger-0.2.0.jar"
            vectorFile:  "/home/jan/projects/openconvert_en_tagger/tagger-data/sonar.vectors.bin"
            modelFile:   "/home/jan/projects/openconvert_en_tagger/tagger-data/withMoreVectorrs"
            lexiconFile: "/home/jan/projects/openconvert_en_tagger/tagger-data/spelling.tab"