Running ElastAlert for the First Time¶
- ISO8601 or Unix timestamped data
- Python 2.6 or 2.7
- pip, see requirements.txt
Downloading and Configuring¶
First, clone the ElastAlert repository:
$ git clone https://github.com/Yelp/elastalert.git
Install the module:
$ python setup.py install $ pip install -r requirements.txt
Depending on the version of Elasticsearch, you may need to manually install the correct version of elasticsearch-py.
$ pip install "elasticsearch>=5.0.0"
$ 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_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
use_ssl: Optional; whether or not to connect to
es_host using TLS; set to
verify_certs: Optional; whether or not to verify TLS certificates; set to
False. The default is
es_username: Optional; basic-auth username for connecting to
es_password: Optional; basic-auth password for connecting to
es_url_prefix: Optional; URL prefix for the Elasticsearch endpoint.
es_send_get_body_as: Optional; Method for querying Elasticsearch -
source. The default is
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
Setting Up Elasticsearch¶
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 ElastAlert Metadata Index.
Creating a Rule¶
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: - "firstname.lastname@example.org"
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 Rule types.
index: The name of the index(es) to query. If you are using Logstash, by default the indexes will match
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_value. See Writing Filters For Rules for more information. If no filters are desired, it should be specified as an empty list:
alert is a list of alerts to run on each match. For more information on alert types, see 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
There are many other optional configuration options, see Common configuration options.
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
As is, this rule means “Send an email to email@example.com when there are more than 50 documents with
some_field == some_value within a 4 hour period.”
Testing Your Rule¶
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.
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
aggregation or because of an error.
Sleeping for 297 seconds
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 ['firstname.lastname@example.org'] ... 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