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Send Structured Logs with Honeytail

Table of Contents

We have written a lightweight tool called honeytail. Honeytail will tail your existing log files, parse the content, and send it up to Honeycomb.

If you already have structured data in an existing log, this is the easiest method to get that data in to Honeycomb.

The quality of your dataset within Honeycomb depends entirely upon the quality of the data going into the log file. To get the most useful insight out of Honeycomb, you must provide high quality data in your log file. In addition to as much detail about each event as you can include, it is best to always include some host-level information to give each event in the log context. For example, the host on which the log exists.

Honeytail is designed to run as a daemon so that it can continuously consume new content as it appears in the log files as well as detect when a log file rotates. It must be configured with your team API key and the name of the Dataset to which you want to write data. You specify one of the available parser modules depending on how your log data is structured. Once running, honeytail will take care of uploading all the data in your log file and picking up new data as it comes in.

Honeytail is open source—we encourage auditing the software you will run on your servers. We also happily consider pull requests with new log format parsers and other improvements.

To see an example of Honeytail in action, try out our Honeytail Example.

Installation 

honeytail will tail existing log files, parse the content, and send it up to Honeycomb. You can view its source here.

Download and install the latest honeytail by running:

wget -q https://honeycomb.io/download/honeytail/v1.9.0/honeytail_1.9.0_amd64.deb

echo '16bd171d495f73a2dc2c0d2a7eaaa36fc2c57446c9f8e5c5dfe10c1a8442241f  honeytail_1.9.0_amd64.deb' | sha256sum -c

sudo dpkg -i honeytail_1.9.0_amd64.deb

wget -q https://honeycomb.io/download/honeytail/v1.9.0/honeytail_1.9.0_arm64.deb

echo '70b3ec1a0a748556ef5f1d8decc83d47160ae30f5df55bd3ab666009d4f6dc4b  honeytail_1.9.0_arm64.deb' | sha256sum -c

sudo dpkg -i honeytail_1.9.0_arm64.deb

wget -q https://honeycomb.io/download/honeytail/v1.9.0/honeytail-1.9.0-1.x86_64.rpm

echo 'f4bc1a5c87e240d641c090f014793098b2e92e0fc58c0c0d0e592ab9e71f717a  honeytail-1.9.0-1.x86_64.rpm' | sha256sum -c

sudo rpm -i honeytail-1.9.0-1.x86_64.rpm

wget -q -O honeytail https://honeycomb.io/download/honeytail/v1.9.0/honeytail-linux-amd64

echo 'bc26b2dc4ae003e18e600c4157121f626f9292201d0b96280c9298df81df1852  honeytail' | shasum -a 256 -c

chmod 755 ./honeytail

wget -q -O honeytail https://honeycomb.io/download/honeytail/v1.9.0/honeytail-linux-arm64

echo '36d21063e656b380d6435003a56b21007289ab047b157c5618d2b94b6962a0fd  honeytail' | shasum -a 256 -c

chmod 755 ./honeytail

wget -q -O honeytail https://honeycomb.io/download/honeytail/v1.9.0/honeytail-darwin-amd64

echo '04de45c55bb340a4c3e54e45b68b2b95ef8cae3fbc0c70d86db75d13d0aaeb2c  honeytail' | shasum -a 256 -c

chmod 755 ./honeytail

git clone https://github.com/honeycombio/honeytail

cd honeytail; go install

An example Dockerfile is also available on GitHub.

Then, modify the configuration file. Uncomment and set the following variables:

• ParserName to the appropriate one of json, nginx, mysql, arangodb, regex
• WriteKey to your API key
• LogFiles to the path for the log file you want to ingest, or - for stdin
• Dataset to the name of the dataset you wish to create with this log file.

The docs pages for JSON, NGINX, MySQL, PostgreSQL and regex have more detail on additional options to set for each parser. The other available options are all described in the configuration file and below.

Launch honeytail by hand with honeytail -c /etc/honeytail/honeytail.conf or using the standard sudo initctl start honeytail (upstart) or sudo systemctl start honeytail (systemd) commands.

honeytail will automatically start back up after rebooting your system. To disable this, put the word manual in /etc/init/honeytail.override (upstart) or run systemctl disable honeytail (systemd).

Launch the Agent 

Start up a honeytail process using upstart or systemd, or by launching the process by hand. This will tail the log file specified in the configuration and leave the process running as a daemon.

sudo initctl start honeytail

sudo systemctl start honeytail

honeytail -c /etc/honeytail/honeytail.conf

In order to start successfully sending data, you will need to update the configuration file included with these packages to specify the parser (for example, nginx), its associated options, such as where the log files are found, and the API key.

Data Formats 

Honeytail has predefined formats for many different use cases. It has built-in support for many existing log formats, including popular services like:

• MySQL
• PostgresSQL
• Nginx
• Mongo
• ArangoDB

It also has support for common data formats that many services and applications use or can be configured to use:

• JSON
• Regex
• CSV
• KeyVal
• Syslog

Reading from Standard Input (stdin) 

Honeytail can read directly from standard input (stdin) by setting the file as -. In this example, the honeytail invocation uses standard input as the data source:

honeytail \
    -c /etc/honeytail/honeytail.conf \
    --file=-

Backfilling Existing Data 

If you have events in older log files that you would like to load into Honeycomb, use honeytail with the --backfill option.

Here is an example honeytail invocation to pull in multiple existing logs and as much as the current log as possible.

honeytail \
    -c /etc/honeytail/honeytail.conf \
    --file=/var/log/app/myapp.log.* \
    --file=/var/log/app/myapp.log \
    --backfill

Let us break down the various parts of this command:

• --parser=json: For the purposes of this example, all logs are already JSON formatted. Take a look at the timestamp section of the JSON connector to make sure your historical logs have their times interpreted correctly.
• --file=/var/log/app/myapp.log.*: Honeycomb understands file globs and will ingest all of the files in series.
• --file=/var/log/app/myapp.log: Specify the --file (or its short form, -f) as many times as necessary to include additional files that do not match a glob. Ingest as much of the current file as exists.
• --backfill: This flag tells honeytail to read the specified files in their entirety, stop when finished reading, and to respond to rate limited responses (HTTP 429) by slowing down the rate at which it sends events.

Honeytail will read all the content in all the old logs and then stop. When it finishes, you are ready to send new log lines. By default, honeytail will keep track of its progress through a file, and if interrupted, will pick back up where it left off. By launching honeytail pointing at the main app log, it will find the state file it created while reading in the backlog and start up where it left off.

Here is the second honeytail invocation, where it will tail the current log file and send in recent entries:

honeytail \
    --writekey=YOUR_API_KEY \
    --parser=json \
    --dataset='My App' \
    --file=/var/log/app/myapp.log

Globs with Same File Names 

If using a glob that returns files with the same name in different directories, such as log files within multiple websites, use the tail.hash_statefile_paths option to ensure each tailed file gets its own state file. This option prevents a single state file from being used for multiple files, and avoids unnecessary file write contentions and load.

honeytail \
    --writekey=YOUR_API_KEY \
    --parser=json \
    --dataset='My App' \
    --file=/var/www/*/log/daily/app.log
    --tail.hash_statefile_paths

Sampling High Volume Data 

Let us say you have an incredible volume of log content and your website gets hit frequently enough that you will still get excellent data quality even if you are only looking at 1/20th the traffic. Honeytail can sample the log file and for each 20 lines, only send one of them. It does so randomly, so you will not see every 20th line being sent - instead each line will have a 5% chance of being sent.

When these log lines reach Honeycomb, they will include metadata indicating that each one represents 20 similar lines, so all your graphs will show accurate total counts.

honeytail \
    --writekey=YOUR_API_KEY \
    --dataset='Webtier' \
    --parser=nginx \
    --file=/var/log/nginx/access.log \
    --samplerate 20 \
    --nginx.conf /etc/nginx/nginx.conf \
    --nginx.format main

Adjusting the sample rate based on the content of your events can allow you to keep important infrequent events while discarding less important higher volume traffic. Honeytail has a dynamic sampler that will vary the sample rate based on the contents of the fields of your choice - more frequent occurrences of the content of the field will be sampled more heavily.

For example, suppose that successful web traffic (HTTP status codes in the 200 range) is much more frequent than errored traffic (status codes in the 500s) - you might want to discard more of the successful traffic and keep more of the errored traffic. Applying the dynamic sampler to the status field in your nginx traffic will have this effect. The actual sample rate applied will vary based on the cardinality of the chosen field and the frequency of each value, but it will be in the ballpark of the samplerate specified.

honeytail \
    --writekey=YOUR_API_KEY \
    --dataset='Webtier' \
    --parser=nginx \
    --file=/var/log/nginx/access.log \
    --samplerate 20 \
    --nginx.conf /etc/nginx/nginx.conf \
    --nginx.format main \
    --dynsampling status

You can specify the dynsampling flag multiple times and it will sample traffic based on the frequency and uniqueness of concatenating all the values of the fields you specify.

Sampling Deterministically 

In addition to static and dynamic sampling support, Honeytail also has support for sampling data deterministically based on the value of a field. This is useful for making sampling decisions based on properties like a request ID or trace ID. Approximately 1/N events will be sampled (where N is the sample rate), and any events, which have the same value for the field passed to the --deterministic_sampling flag, will be sampled consistently. This flag must be used with --samplerate to specify the sampling rate.

honeytail \
    --writekey=YOUR_API_KEY \
    --dataset='Deterministically Sampled Nginx Logs' \
    --parser=nginx \
    --file=/var/log/nginx/access.log \
    --deterministic_sampling request_id \
    --samplerate 2

For instance, in the above example, about half of the requests would be sampled and if another Honeytail instance were running elsewhere with the same settings for --samplerate and --deterministic_sampling, it would sample the same subset of requests.

Adding Extra Information into Your Events 

It is not unusual for a log to omit interesting information like the name of the machine on which the process is running. After all, you are on that machine, right? Why would you add the hostname? Log transports like rsyslog will prepend logs with the hostname sending them, but if you are sending logs from each host, this data may not exist. Honeytail lets you add in extra fields to each event sent up to Honeycomb with the --add_field flag.

For this example, let us assume that you have nginx running as a web server in both your production and staging environments. Your shell sets $ENV with the environment (prod or staging). Here is how to run honeytail to consume your nginx log and insert the hostname and environment along with each log line:

honeytail \
    --writekey=YOUR_API_KEY \
    --dataset='Webtier' \
    --parser=nginx \
    --file=/var/log/nginx/access.log \
    --nginx.conf /etc/nginx/nginx.conf \
    --nginx.format main \
    --add_field hostname=$(hostname) \
    --add_field env=$ENV

When it comes time to add additional fields based on the content of your log file, it is time to invoke the data augmentation flag, --da_map_file. As an example, your log file might contain the IP address of the host connecting to this service, but you would really like to include the hostname in your events. Or your log file contains user ID and you would like to add user name and group. If you can build a map of source values to new fields, then you can use the --da_map_file flag to augment your data.

As our example, let us add hostname and AWS availability zone to a log file that contains a IP addresses. The IP address is stored in a field called ip_addr in the events we are processing.

The first step is to build a JSON file containing the name of the source column (ip_addr), and a map of values to new fields (10.0.0.6 should add a field hostname with the value app21 and aws_az of c, 10.0.0.7 has different fields).

{
  "ip_addr": {
    "10.0.0.6": { "hostname": "app21", "aws_az": "c" },
    "10.0.0.7": { "hostname": "app32", "aws_az": "b" }
  }
}

When the log parser comes across an event that has "ip_addr":"10.0.0.6", it will add the two additional fields "hostname":"app21","aws_az":"c". Note that additional source column names may be specified (each with their own translation map) by extending the content of the JSON map file.

The recommended method to deploy this is to generate a map of all the values to the new fields that should be added and distribute it to all the hosts that will be running Honeytail. Example use cases:

• a mysql slow query log includes the IP address of the client; translate those IP addresses to names and host groups to identify unexpected servers connecting to your database
• ssh can log the fingerprint of the key used to authenticate; distribute a mapping of key fingerprint to key owners to make it easier to see who is logging in to what servers
• different users are sharded to different backend clusters; use the authenticated user ID to add information about which shard they are on, making it easier to spot problems that are localized to individual shards

Dropping or Scrubbing Fields 

Sometimes you will have fields in your log file that you do not want to send to Honeycomb or that you want to obscure before letting them leave your servers. For this example, let us say that you have in your log a large text field with the contents of an email. It is large enough that you do not want it sent up to Honeycomb. Also in this log you have a some sensitive information like a person’s birthday. You want to be able to ask questions about the most common birthdays, but you do not want to expose the actual birthdays outside your infrastructure.

Honeytail has two flags that will help you accomplish these goals. --drop_field will remove a field before sending the event to Honeycomb and --scrub_field will subject the value of a field to a SHA256 hash before sending it along. You will still be able to do inclusion and frequency analysis on the hashed fields (as there will be a 1-1 mapping of value to hashed value) but the actual value will be obscured.

Here is your honeytail invocation:

honeytail \
    --writekey=YOUR_API_KEY \
    --dataset='My App' \
    --parser=json \
    --file=/var/log/app/myapp.log \
    --drop_field email_content \
    --scrub_field birthday

Versioning honeytail Configuration 

Convert Command Lines to YAML Configuration 

The honeytail binary supports reading its configuration from a YAML configuration file, as well as command line arguments. To get started, if you have already been using a few command line arguments, add an additional flag: --write_current_yaml. This flag will write your command line configuration as YAML to STDOUT so you can use it as a starting point.

honeytail \
    -p mysql \
    -k YOUR_API_KEY \
    -d YOUR_DATASET \
    -f ./mysql-slow.log \
    --mysql.host=my.fake.host.com \
    --write_current_yaml  > ./scrubbed_mysql.yaml

Display the output captured in scrubbed_mysql.yaml.

cat ./scrubbed_mysql.yaml
apihost: https://api.honeycomb.io/
# or if on our EU instance, https://api.eu1.honeycomb.io
samplerate: 1
poolsize: 80
send_frequency_ms: 100
send_batch_size: 50
status_interval: 60
request_parse_query: whitelist
dynsample_window: 30
dynsample_minimum: 1
required_options:
    parsername: mysql
    writekey: YOUR_API_KEY
    logfiles:
        - ./mysql-slow.log
    dataset: YOUR_DATASET
mysql:
    host: my.fake.host.com
    user: ""
    pass: ""
    queryinterval: 0

This flag can be particularly useful for versioning or productionizing honeytail use, or for providing additional configuration when using advanced honeytail features, like scrubbing sensitive fields or parsing custom URL structures.

Convert from an INI configuration to YAML 

Previous versions of honeytail used the INI file format (.ini) for configuration, but this is now deprecated. To create a YAML configuration file that is equivalent to an existing INI configuration, use this command with your .ini configuration file name:

honeytail --config EXISTING_CONFIG_FILENAME --write_current_yaml

This command will write the YAML for your current configuration file to STDOUT.

Using a Configuration File 

Once the configuration file is created, run honeytail with a --config_yaml argument in lieu of all of the other flags:

honeytail --config_yaml ./scrubbed_mysql.yaml

Notes on Using YAML Configuration 

• When using YAML configuration, any configuration flags specified on the command line are ignored.
• The names of fields in the YAML file are the same “long” names you see in the Honeytail help file. For example, honeytail -h
• Any field with help that notes “May have multiple values” is specified in YAML as an array. For example:

scrub_field:
    - field_name_1
    - field_name_2

• Any values with dotted names in help are specified as YAML objects, with appropriate indentation. For example, --mysql.host=my.fake.host.com becomes:

mysql:
    host: my.fake.host.com
    user: ""
    pass: ""
    queryinterval: 0

Parsing URL Patterns 

honeytail can break URLs up into their component parts, storing extra information in additional columns. This behavior is turned on by default for the request field on nginx datasets, but can become more useful with a little bit of guidance from you.

There are several flags that adjust the behavior of honeytail as it breaks apart URLs.

Identifying the URL Field 

When using the nginx parser, honeytail looks for a field named request. When using a different parser (such as the JSON parser), you should specify the name of the field that contains the URL with the --request_shape flag.

Using this flag creates a few generated fields. Given a request field containing a value like:

GET /alpha/beta/gamma?foo=1&bar=2 HTTP/1.1

… will produce nginx events for Honeycomb that look like:

(The generated fields will all be prefixed by the field name specified by --request_shape— in the above example request. Use the --shape_prefix field to prepend an additional string to these generated fields.)

If the URL field contains just the URL, the request_method and request_protocol_version fields will be omitted.

URL Normalization 

The path portion of the URL (from the beginning / up to the ? that separates the path from the query) can be grouped by common patterns, as is common for REST interfaces.

For example, given a URL fragments like:

/books/978-0812536362
/books/978-9995788940

We can break the fragments into a field containing the generic endpoint (/books/:isbn) and a separate field for the ISBN number itself by specifying a --request_pattern flag:

honeytail ... \ # other arguments
    --parser=nginx \
    --request_pattern=/books/:isbn

This will produce, among other fields:

You can specify multiple --request_pattern flags and they will be considered in order. The first one to match a URL will be used. Patterns should represent the entire path portion of the URL - include a “*” at the end to match arbitrary additional segments.

For example, if we have a wider variety of URL fragments, like:

/books/978-0812536362
/books/978-3161484100/borrow
/books/978-9995788940
/books/978-9995788940/borrow

We can provide our additional --request_pattern flags and track a wider variety of request_shapes:

honeytail ... \ # other arguments
    --parser=nginx \
    --request_pattern=/books/:isbn/borrow --request_pattern=/books/:isbn

We will see our request_path_isbn populated as before, as the :isbn parameter is respected in both patterns:

A URL’s query string can be broken apart similarly, with the --request_query_keys flag, with generated fields named like <field>_query_<keyname>.

If, on top of our previous examples, our URL fragments had query strings like:

/books/978-0812536362?borrower_id=23597

Providing --request_query_keys=borrower_id would return us a Honeycomb event with a request_query_borrower_id field with a value of 23597.

If you would like to automatically create a field for every key in the query string, you can use the flag --request_parse_query=all. This will automatically create a new field <field>_query_<key> for every query parameter encountered in the query string. For any publicly accessible web server, it is likely that this will quickly create many useless columns because of all the random traffic on the internet.

For more detail and examples, see our urlshaper package on GitHub.

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