240 lines
10 KiB
Plaintext
240 lines
10 KiB
Plaintext
[role="xpack"]
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[testenv="platinum"]
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[[ml-configuring-categories]]
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= Detecting anomalous categories of data
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Categorization is a {ml} process that tokenizes a text field, clusters similar
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data together, and classifies it into categories. It works best on
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machine-written messages and application output that typically consist of
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repeated elements. For example, it works well on logs that contain a finite set
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of possible messages:
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//Obtained from it_ops_new_app_logs.json
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[source,js]
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----------------------------------
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{"@timestamp":1549596476000,
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"message":"org.jdbi.v2.exceptions.UnableToExecuteStatementException: com.mysql.jdbc.exceptions.MySQLTimeoutException: Statement cancelled due to timeout or client request [statement:\"SELECT id, customer_id, name, force_disabled, enabled FROM customers\"]",
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"type":"logs"}
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----------------------------------
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//NOTCONSOLE
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Categorization is tuned to work best on data like log messages by taking token
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order into account, including stop words, and not considering synonyms in its
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analysis. Complete sentences in human communication or literary text (for
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example email, wiki pages, prose, or other human-generated content) can be
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extremely diverse in structure. Since categorization is tuned for machine data,
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it gives poor results for human-generated data. It would create so many
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categories that they couldn't be handled effectively. Categorization is _not_
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natural language processing (NLP).
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When you create a categorization {anomaly-job}, the {ml} model learns what
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volume and pattern is normal for each category over time. You can then detect
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anomalies and surface rare events or unusual types of messages by using
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<<ml-count-functions,count>> or <<ml-rare-functions,rare>> functions.
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In {kib}, there is a categorization wizard to help you create this type of
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{anomaly-job}. For example, the following job generates categories from the
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contents of the `message` field and uses the count function to determine when
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certain categories are occurring at anomalous rates:
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[role="screenshot"]
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image::images/ml-category-wizard.jpg["Creating a categorization job in Kibana"]
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[%collapsible]
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.API example
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====
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[source,console]
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----------------------------------
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PUT _ml/anomaly_detectors/it_ops_app_logs
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{
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"description" : "IT ops application logs",
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"analysis_config" : {
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"categorization_field_name": "message",<1>
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"bucket_span":"30m",
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"detectors" :[{
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"function":"count",
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"by_field_name": "mlcategory"<2>
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}]
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},
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"data_description" : {
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"time_field":"@timestamp"
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}
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}
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----------------------------------
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// TEST[skip:needs-licence]
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<1> This field is used to derive categories.
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<2> The categories are used in a detector by setting `by_field_name`,
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`over_field_name`, or `partition_field_name` to the keyword `mlcategory`. If you
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do not specify this keyword in one of those properties, the API request fails.
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====
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You can use the **Anomaly Explorer** in {kib} to view the analysis results:
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[role="screenshot"]
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image::images/ml-category-anomalies.jpg["Categorization results in the Anomaly Explorer"]
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For this type of job, the results contain extra information for each anomaly:
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the name of the category (for example, `mlcategory 2`) and examples of the
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messages in that category. You can use these details to investigate occurrences
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of unusually high message counts.
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If you use the advanced {anomaly-job} wizard in {kib} or the
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{ref}/ml-put-job.html[create {anomaly-jobs} API], there are additional
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configuration options. For example, the optional `categorization_examples_limit`
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property specifies the maximum number of examples that are stored in memory and
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in the results data store for each category. The default value is `4`. Note that
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this setting does not affect the categorization; it just affects the list of
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visible examples. If you increase this value, more examples are available, but
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you must have more storage available. If you set this value to `0`, no examples
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are stored.
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Another advanced option is the `categorization_filters` property, which can
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contain an array of regular expressions. If a categorization field value matches
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the regular expression, the portion of the field that is matched is not taken
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into consideration when defining categories. The categorization filters are
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applied in the order they are listed in the job configuration, which enables you
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to disregard multiple sections of the categorization field value. In this
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example, you might create a filter like `[ "\\[statement:.*\\]"]` to remove the
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SQL statement from the categorization algorithm.
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[discrete]
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[[ml-configuring-analyzer]]
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== Customizing the categorization analyzer
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Categorization uses English dictionary words to identify log message categories.
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By default, it also uses English tokenization rules. For this reason, if you use
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the default categorization analyzer, only English language log messages are
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supported, as described in the <<ml-limitations>>.
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If you use the categorization wizard in {kib}, you can see which categorization
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analyzer it uses and highlighted examples of the tokens that it identifies. You
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can also change the tokenization rules by customizing the way the categorization
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field values are interpreted:
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[role="screenshot"]
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image::images/ml-category-analyzer.jpg["Editing the categorization analyzer in Kibana"]
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The categorization analyzer can refer to a built-in {es} analyzer or a
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combination of zero or more character filters, a tokenizer, and zero or more
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token filters. In this example, adding a
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{ref}/analysis-pattern-replace-charfilter.html[`pattern_replace` character filter]
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achieves exactly the same behavior as the `categorization_filters` job
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configuration option described earlier. For more details about these properties,
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see the
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{ref}/ml-put-job.html#ml-put-job-request-body[`categorization_analyzer` API object].
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If you use the default categorization analyzer in {kib} or omit the
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`categorization_analyzer` property from the API, the following default values
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are used:
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[source,console]
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--------------------------------------------------
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POST _ml/anomaly_detectors/_validate
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{
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"analysis_config" : {
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"categorization_analyzer" : {
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"tokenizer" : "ml_classic",
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"filter" : [
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{ "type" : "stop", "stopwords": [
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"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday",
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"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun",
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"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December",
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"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
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"GMT", "UTC"
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] }
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]
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},
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"categorization_field_name": "message",
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"detectors" :[{
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"function":"count",
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"by_field_name": "mlcategory"
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}]
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},
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"data_description" : {
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}
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}
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--------------------------------------------------
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If you specify any part of the `categorization_analyzer`, however, any omitted
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sub-properties are _not_ set to default values.
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The `ml_classic` tokenizer and the day and month stopword filter are more or
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less equivalent to the following analyzer, which is defined using only built-in
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{es} {ref}/analysis-tokenizers.html[tokenizers] and
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{ref}/analysis-tokenfilters.html[token filters]:
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[source,console]
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----------------------------------
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PUT _ml/anomaly_detectors/it_ops_new_logs3
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{
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"description" : "IT Ops Application Logs",
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"analysis_config" : {
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"categorization_field_name": "message",
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"bucket_span":"30m",
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"detectors" :[{
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"function":"count",
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"by_field_name": "mlcategory",
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"detector_description": "Unusual message counts"
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}],
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"categorization_analyzer":{
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"tokenizer": {
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"type" : "simple_pattern_split",
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"pattern" : "[^-0-9A-Za-z_.]+" <1>
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},
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"filter": [
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{ "type" : "pattern_replace", "pattern": "^[0-9].*" }, <2>
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{ "type" : "pattern_replace", "pattern": "^[-0-9A-Fa-f.]+$" }, <3>
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{ "type" : "pattern_replace", "pattern": "^[^0-9A-Za-z]+" }, <4>
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{ "type" : "pattern_replace", "pattern": "[^0-9A-Za-z]+$" }, <5>
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{ "type" : "stop", "stopwords": [
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"",
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"Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday",
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"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun",
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"January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December",
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"Jan", "Feb", "Mar", "Apr", "May", "Jun", "Jul", "Aug", "Sep", "Oct", "Nov", "Dec",
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"GMT", "UTC"
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] }
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]
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}
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},
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"analysis_limits":{
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"categorization_examples_limit": 5
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},
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"data_description" : {
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"time_field":"time",
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"time_format": "epoch_ms"
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}
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}
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----------------------------------
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// TEST[skip:needs-licence]
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<1> Tokens basically consist of hyphens, digits, letters, underscores and dots.
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<2> By default, categorization ignores tokens that begin with a digit.
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<3> By default, categorization also ignores tokens that are hexadecimal numbers.
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<4> Underscores, hyphens, and dots are removed from the beginning of tokens.
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<5> Underscores, hyphens, and dots are also removed from the end of tokens.
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The key difference between the default `categorization_analyzer` and this
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example analyzer is that using the `ml_classic` tokenizer is several times
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faster. The difference in behavior is that this custom analyzer does not include
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accented letters in tokens whereas the `ml_classic` tokenizer does, although
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that could be fixed by using more complex regular expressions.
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If you are categorizing non-English messages in a language where words are
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separated by spaces, you might get better results if you change the day or month
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words in the stop token filter to the appropriate words in your language. If you
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are categorizing messages in a language where words are not separated by spaces,
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you must use a different tokenizer as well in order to get sensible
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categorization results.
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It is important to be aware that analyzing for categorization of machine
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generated log messages is a little different from tokenizing for search.
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Features that work well for search, such as stemming, synonym substitution, and
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lowercasing are likely to make the results of categorization worse. However, in
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order for drill down from {ml} results to work correctly, the tokens that the
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categorization analyzer produces must be similar to those produced by the search
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analyzer. If they are sufficiently similar, when you search for the tokens that
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the categorization analyzer produces then you find the original document that
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the categorization field value came from.
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