- Elasticsearch
- ISO8601 or Unix timestamped data
- Python 2.7
- pip, see requirements.txt
- Packages on Ubuntu 14.x: python-pip python-dev libffi-dev libssl-dev
You can either install the latest released version of ElastAlert using pip:
$ pip install elastalert
or you can clone the ElastAlert repository for the most recent changes:
$ git clone https://github.com/Yelp/elastalert.git
Install the module:
$ pip install "setuptools>=11.3" $ python setup.py install
Depending on the version of Elasticsearch, you may need to manually install the correct version of elasticsearch-py.
Elasticsearch 5.0+:
$ pip install "elasticsearch>=5.0.0"
Elasticsearch 2.X:
$ pip install "elasticsearch<3.0.0"
Next, open up config.yaml.example. In it, you will find several configuration options. ElastAlert may be run without changing any of these settings.
rules_folder
is where ElastAlert will load rule configuration files from. It will attempt to load every .yaml file in the folder. Without any valid rules, ElastAlert will not start. ElastAlert will also load new rules, stop running missing rules, and restart modified rules as the files in this folder change. For this tutorial, we will use the example_rules folder.
run_every
is how often ElastAlert will query Elasticsearch.
buffer_time
is the size of the query window, stretching backwards from the time each query is run. This value is ignored for rules where use_count_query
or use_terms_query
is set to true.
es_host
is the address of an Elasticsearch cluster where ElastAlert will store data about its state, queries run, alerts, and errors. Each rule may also use a different Elasticsearch host to query against.
es_port
is the port corresponding to es_host
.
use_ssl
: Optional; whether or not to connect to es_host
using TLS; set to True
or False
.
verify_certs
: Optional; whether or not to verify TLS certificates; set to True
or False
. The default is True
client_cert
: Optional; path to a PEM certificate to use as the client certificate
client_key
: Optional; path to a private key file to use as the client key
ca_certs
: Optional; path to a CA cert bundle to use to verify SSL connections
es_username
: Optional; basic-auth username for connecting to es_host
.
es_password
: Optional; basic-auth password for connecting to es_host
.
es_url_prefix
: Optional; URL prefix for the Elasticsearch endpoint.
es_send_get_body_as
: Optional; Method for querying Elasticsearch - GET
, POST
or source
. The default is GET
writeback_index
is the name of the index in which ElastAlert will store data. We will create this index later.
alert_time_limit
is the retry window for failed alerts.
Save the file as config.yaml
ElastAlert saves information and metadata about its queries and its alerts back to Elasticsearch. This is useful for auditing, debugging, and it allows ElastAlert to restart and resume exactly where it left off. This is not required for ElastAlert to run, but highly recommended.
First, we need to create an index for ElastAlert to write to by running elastalert-create-index
and following the instructions:
$ elastalert-create-index New index name (Default elastalert_status) Name of existing index to copy (Default None) New index elastalert_status created Done!
For information about what data will go here, see :ref:`ElastAlert Metadata Index <metadata>`.
Each rule defines a query to perform, parameters on what triggers a match, and a list of alerts to fire for each match. We are going to use example_rules/example_frequency.yaml
as a template:
# From example_rules/example_frequency.yaml es_host: elasticsearch.example.com es_port: 14900 name: Example rule type: frequency index: logstash-* num_events: 50 timeframe: hours: 4 filter: - term: some_field: "some_value" alert: - "email" email: - "elastalert@example.com"
es_host
and es_port
should point to the Elasticsearch cluster we want to query.
name
is the unique name for this rule. ElastAlert will not start if two rules share the same name.
type
: Each rule has a different type which may take different parameters. The frequency
type means "Alert when more than num_events
occur within timeframe
." For information other types, see :ref:`Rule types <ruletypes>`.
index
: The name of the index(es) to query. If you are using Logstash, by default the indexes will match "logstash-*"
.
num_events
: This parameter is specific to frequency
type and is the threshold for when an alert is triggered.
timeframe
is the time period in which num_events
must occur.
filter
is a list of Elasticsearch filters that are used to filter results. Here we have a single term filter for documents with some_field
matching some_value
. See :ref:`Writing Filters For Rules <writingfilters>` for more information. If no filters are desired, it should be specified as an empty list: filter: []
alert
is a list of alerts to run on each match. For more information on alert types, see :ref:`Alerts <alerts>`. The email alert requires an SMTP server for sending mail. By default, it will attempt to use localhost. This can be changed with the smtp_host
option.
email
is a list of addresses to which alerts will be sent.
There are many other optional configuration options, see :ref:`Common configuration options <commonconfig>`.
All documents must have a timestamp field. ElastAlert will try to use @timestamp
by default, but this can be changed with the timestamp_field
option. By default, ElastAlert uses ISO8601 timestamps, though unix timestamps are supported by setting timestamp_type
.
As is, this rule means "Send an email to elastalert@example.com when there are more than 50 documents with some_field == some_value
within a 4 hour period."
Running the elastalert-test-rule
tool will test that your config file successfully loads and run it in debug mode over the last 24 hours:
$ elastalert-test-rule example_rules/example_frequency.yaml
If you want to specify a configuration file to use, you can run it with the config flag.
$ elastalert-test-rule --config <path-to-config-file> example_rules/example_frequency.yaml.
- The configuration preferences will be loaded as follows:
- Configurations specified in the yaml file.
- Configurations specified in the config file, if specified.
- Default configurations, for the tool to run.
See :ref:`the testing section for more details <testing>`
There are two ways of invoking ElastAlert. As a daemon, through Supervisor (http://supervisord.org/), or directly with Python. For easier debugging purposes in this tutorial, we will invoke it directly:
$ python -m elastalert.elastalert --verbose --rule example_frequency.yaml # or use the entry point: elastalert --verbose --rule ... No handlers could be found for logger "Elasticsearch" INFO:root:Queried rule Example rule from 1-15 14:22 PST to 1-15 15:07 PST: 5 hits INFO:Elasticsearch:POST http://elasticsearch.example.com:14900/elastalert_status/elastalert_status?op_type=create [status:201 request:0.025s] INFO:root:Ran Example rule from 1-15 14:22 PST to 1-15 15:07 PST: 5 query hits (0 already seen), 0 matches, 0 alerts sent INFO:root:Sleeping for 297 seconds
ElastAlert uses the python logging system and --verbose
sets it to display INFO level messages. --rule example_frequency.yaml
specifies the rule to run, otherwise ElastAlert will attempt to load the other rules in the example_rules folder.
Let's break down the response to see what's happening.
Queried rule Example rule from 1-15 14:22 PST to 1-15 15:07 PST: 5 hits
ElastAlert periodically queries the most recent buffer_time
(default 45 minutes) for data matching the filters. Here we see that it matched 5 hits.
POST http://elasticsearch.example.com:14900/elastalert_status/elastalert_status?op_type=create [status:201 request:0.025s]
This line showing that ElastAlert uploaded a document to the elastalert_status index with information about the query it just made.
Ran Example rule from 1-15 14:22 PST to 1-15 15:07 PST: 5 query hits (0 already seen), 0 matches, 0 alerts sent
The line means ElastAlert has finished processing the rule. For large time periods, sometimes multiple queries may be run, but their data will be processed together. query hits
is the number of documents that are downloaded from Elasticsearch, already seen
refers to documents that were already counted in a previous overlapping query and will be ignored, matches
is the number of matches the rule type outputted, and alerts sent
is the number of alerts actually sent. This may differ from matches
because of options like realert
and aggregation
or because of an error.
Sleeping for 297 seconds
The default run_every
is 5 minutes, meaning ElastAlert will sleep until 5 minutes have elapsed from the last cycle before running queries for each rule again with time ranges shifted forward 5 minutes.
Say, over the next 297 seconds, 46 more matching documents were added to Elasticsearch:
INFO:root:Queried rule Example rule from 1-15 14:27 PST to 1-15 15:12 PST: 51 hits ... INFO:root:Sent email to ['elastalert@example.com'] ... INFO:root:Ran Example rule from 1-15 14:27 PST to 1-15 15:12 PST: 51 query hits, 1 matches, 1 alerts sent
The body of the email will contain something like:
Example rule At least 50 events occurred between 1-15 11:12 PST and 1-15 15:12 PST @timestamp: 2015-01-15T15:12:00-08:00
If an error occurred, such as an unreachable SMTP server, you may see:
ERROR:root:Error while running alert email: Error connecting to SMTP host: [Errno 61] Connection refused
Note that if you stop ElastAlert and then run it again later, it will look up elastalert_status
and begin querying
at the end time of the last query. This is to prevent duplication or skipping of alerts if ElastAlert is restarted.
By using the --debug
flag instead of --verbose
, the body of email will instead be logged and the email will not be sent. In addition, the queries will not be saved to elastalert_status
.