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Configuration

The configuration language consists of two distinct entities: collectors and rules.

The collectors declare where metrics come from, while the rules decide how the metrics are processed.

Configuration statements always end with either a semi-colon (statement ;) or a body delimited by curly braces (statement { ... }).

Since the configuration languages deals very much with operations on metrics/TSData, it is recommended to read up on the datamodel first.

Comments

Anything starting at the # character, until the end of the line, is treated as a comment. Comments are skipped during rule evaluation.

Collectors

In general, the import statement looks like:

collect collector_name ...;
collect collector_name { ... }

Please refer to the documentation on each collector for details.

Rules

Rules take action on data gathered by the importers. The end goal of rules is to allow transformations on metrics and to generate alerts.

  • alert Describes how to process alerts.
  • alias Refer to a group by a convenient (and shorter) identifier.
  • constant Describes simple constants that are to be added to existing groups.
  • define Define new metrics, based on expressions from other metrics.
  • match Describes how to apply a group of statements onto a wildcard of groups. Think of it as a foreach body applied to a select (as in SQL select) of groups.
  • tag Describes how to assign extra tags to a group, by evaluating an expression.

Expressions

Rules make use of expressions. Most simple arithmatic and boolean logic has been implemented.

  • metric Describes how to read a metric.
  • group selector Describes how to select groups using a pattern.
  • operators Describes the operators that are implemented.
  • count function Describes the counting function.
  • sum function Describes the summation function.
  • avg function Describes the average function.
  • min/max functions Describes the min and max functions.
  • percentile_agg function Describes the percentile aggregate.
  • str function Describes the string concatenation function.
  • name function Describes the name function, that takes (part of) a (group/metric) name and returns it as a metric value.
  • rate function Describes the rate function, which is used to convert a monotonic increasing counter into a rate per second value.
  • [regexp function(expressions/regexp.md) Describes how to reformat a string, using a regular expression and back-references.
  • tag function Describes the tag extraction function.

Example

This is an example of a configuration for a java application written using spring-boot. Comments to explain how it works are inline.

# Declare which raw metrics to gether.
#
collect jmx_listener "java.lang:*",      # Gather all MXBeans in java.lang
                     "java.lang.*:*",    # and all MXBeans in subpackages.
                     "metrics:name=*",   # Gather Codahale metrics.
                     "java.nio:*";       # Also gather java NIO data.

# Add a latency_critical constant to each of the request handlers.
# These are later tested with alerts.
#
# If someone introduces a new handler, but forgets to add monitoring,
# this rule will allow for a default latency measurement.
#
match com.groupon.lex.controller.*.* as handler {
  constant handler latency_critical 20000;
}

# Specify better constants for selected request handlers.
#
# Note that the constants inside the match statement above are overriden
# using these values.
#
constant com.groupon.lex.controller.MerchantController.listDeals latency_critical 2500;
constant com.groupon.lex.controller.MerchantController.uploadAsset latency_critical 5000;

# Declare an alert for each handler, based on the 50thPercentile as it was
# measured by the application, compared against the corresponding
# critical value declared as a constant above.
#
# The syntax ${handler} allows us to get the name of the handler,
# so the alert will have a meaningful name that is related to its metrics.
#
match com.groupon.lex.controller.*.* as handler {
  alert ${handler} if handler '50thPercentile' > handler latency_critical;
}

# Declare an alert for the rate of queries.
# Spring-boot exposes a QPS metric for each endpoint,
# so we have to sum them together for the entire application.
#
# By comparing it against a value derived from the number of cores
# of the machine, we can use the same logic regardless of the number
# of CPUs the machine actually has.
#
alert qps_high
if  ( com.groupon.lex.controller.MerchantController.cloneDeal OneMinuteRate
    + com.groupon.lex.controller.MerchantController.createDeal OneMinuteRate
    + com.groupon.lex.controller.MerchantController.deleteDeal OneMinuteRate
    + com.groupon.lex.controller.MerchantController.findDeal OneMinuteRate
    + com.groupon.lex.controller.MerchantController.getCategories OneMinuteRate
    + com.groupon.lex.controller.MerchantController.getMessages OneMinuteRate
    + com.groupon.lex.controller.MerchantController.json2csv OneMinuteRate
    + com.groupon.lex.controller.MerchantController.listDeals OneMinuteRate
    + com.groupon.lex.controller.MerchantController.csv2json OneMinuteRate
    + com.groupon.lex.controller.MerchantController.setMessages OneMinuteRate
    + com.groupon.lex.controller.MerchantController.updateDeal OneMinuteRate
    + com.groupon.lex.controller.MerchantController.uploadAsset OneMinuteRate)
  > 10 * java.lang.OperatingSystem AvailableProcessors;  # 10 qps per core

# Furthermore, we measure the response codes from the webserver.
# The application has a very low QPS rate (see above).
# The purpose of these alerts is not to alert if the service is overloaded
# (that is the role of the 'qps_high' alert).
# Instead, it is to alert if the service seems to be misbehaving.
#
# As the application never responds with 100 and 300 status codes,
# we set their threshold to zero.
#
alert com.groupon.lex.dealcentre.http_1xx_rate
if com.groupon.lex.dealcentre.http_1xx_rate OneMinuteRate > 0;
alert com.groupon.lex.dealcentre.http_2xx_rate
if com.groupon.lex.dealcentre.http_2xx_rate OneMinuteRate > 50;
alert com.groupon.lex.dealcentre.http_3xx_rate
if com.groupon.lex.dealcentre.http_3xx_rate OneMinuteRate > 0;
alert com.groupon.lex.dealcentre.http_4xx_rate
if com.groupon.lex.dealcentre.http_4xx_rate OneMinuteRate > 10;
alert com.groupon.lex.dealcentre.http_5xx_rate
if com.groupon.lex.dealcentre.http_5xx_rate OneMinuteRate > 10;