Set up prospectors

Filebeat uses prospectors to locate and process files. To configure Filebeat, you specify a list of prospectors in the filebeat.prospectors section of the filebeat.yml config file.

Each item in the list begins with a dash (-) and specifies prospector-specific configuration options, including the list of paths that are crawled to locate the files.

Here is a sample configuration:

filebeat.prospectors:
- type: log
  paths:
    - /var/log/apache/httpd-*.log

- type: log
  paths:
    - /var/log/messages
    - /var/log/*.log

One of the following input types:

The value that you specify here is used as the type for each event published to Logstash and Elasticsearch.

A list of glob-based paths that should be crawled and fetched. All patterns supported by Golang Glob are also supported here. For example, to fetch all files from a predefined level of subdirectories, the following pattern can be used: /var/log/*/*.log. This fetches all .log files from the subfolders of /var/log. It does not fetch log files from the /var/log folder itself. It is possible to recursively fetch all files in all subdirectories of a directory using the optional recursive_glob settings.

Filebeat starts a harvester for each file that it finds under the specified paths. You can specify one path per line. Each line begins with a dash (-).

Enable expanding ** into recursive glob patterns. With this feature enabled, the rightmost ** in each path is expanded into a fixed number of glob patterns. For example: /foo/** expands to /foo, /foo/*, /foo/*/*, and so on. If enabled it expands a single ** into a 8-level deep * pattern.

This feature is enabled by default, set to recursive_glob.enabled to false to disable it.

The file encoding to use for reading files that contain international characters. See the encoding names recommended by the W3C for use in HTML5.

Here are some sample encodings from W3C recommendation:

The plain encoding is special, because it does not validate or transform any input.

A list of regular expressions to match the lines that you want Filebeat to exclude. Filebeat drops any lines that match a regular expression in the list. By default, no lines are dropped.

If multiline is also specified, each multiline message is combined into a single line before the lines are filtered by exclude_lines.

The following example configures Filebeat to drop any lines that start with "DBG".

filebeat.prospectors:
- paths:
    - /var/log/myapp/*.log
  exclude_lines: ['^DBG']

See Regular expression support for a list of supported regexp patterns.

A list of regular expressions to match the lines that you want Filebeat to include. Filebeat exports only the lines that match a regular expression in the list. By default, all lines are exported.

If multiline is also specified, each multiline message is combined into a single line before the lines are filtered by include_lines.

The following example configures Filebeat to export any lines that start with "ERR" or "WARN":

filebeat.prospectors:
- paths:
    - /var/log/myapp/*.log
  include_lines: ['^ERR', '^WARN']

The following example exports all Apache log lines except the debugging messages (DBGs):

 include_lines: ['apache']
 exclude_lines: ['^DBG']

See Regular expression support for a list of supported regexp patterns.

A list of regular expressions to match the files that you want Filebeat to ignore. By default no files are excluded.

The following example configures Filebeat to ignore all the files that have a gz extension:

  exclude_files: ['\.gz$']

See Regular expression support for a list of supported regexp patterns.

A list of tags that the Beat includes in the tags field of each published event. Tags make it easy to select specific events in Kibana or apply conditional filtering in Logstash. These tags will be appended to the list of tags specified in the general configuration.

Example:

filebeat.prospectors:
- paths: ["/var/log/app/*.json"]
  tags: ["json"]

Optional fields that you can specify to add additional information to the output. For example, you might add fields that you can use for filtering log data. Fields can be scalar values, arrays, dictionaries, or any nested combination of these. By default, the fields that you specify here will be grouped under a fields sub-dictionary in the output document. To store the custom fields as top-level fields, set the fields_under_root option to true. If a duplicate field is declared in the general configuration, then its value will be overwritten by the value declared here.

filebeat.prospectors:
- paths: ["/var/log/app/*.log"]
  fields:
    app_id: query_engine_12

If this option is set to true, the custom fields are stored as top-level fields in the output document instead of being grouped under a fields sub-dictionary. If the custom field names conflict with other field names added by Filebeat, then the custom fields overwrite the other fields.

A list of processors to apply to the data generated by the prospector.

See Filter and enhance the exported data for information about specifying processors in your config.

If this option is enabled, Filebeat ignores any files that were modified before the specified timespan. Configuring ignore_older can be especially useful if you keep log files for a long time. For example, if you want to start Filebeat, but only want to send the newest files and files from last week, you can configure this option.

You can use time strings like 2h (2 hours) and 5m (5 minutes). The default is 0, which disables the setting. Commenting out the config has the same effect as setting it to 0.

The files affected by this setting fall into two categories:

For files which were never seen before, the offset state is set to the end of the file. If a state already exist, the offset is not changed. In case a file is updated again later, reading continues at the set offset position.

The ignore_older setting relies on the modification time of the file to determine if a file is ignored. If the modification time of the file is not updated when lines are written to a file (which can happen on Windows), the ignore_older setting may cause Filebeat to ignore files even though content was added at a later time.

To remove the state of previously harvested files from the registry file, use the clean_inactive configuration option.

Before a file can be ignored by the prospector, it must be closed. To ensure a file is no longer being harvested when it is ignored, you must set ignore_older to a longer duration than close_inactive.

If a file that’s currently being harvested falls under ignore_older, the harvester will first finish reading the file and close it after close_inactive is reached. Then, after that, the file will be ignored.

The close_* configuration options are used to close the harvester after a certain criteria or time. Closing the harvester means closing the file handler. If a file is updated after the harvester is closed, the file will be picked up again after scan_frequency has elapsed. However, if the file is moved or deleted while the harvester is closed, Filebeat will not be able to pick up the file again, and any data that the harvester hasn’t read will be lost.

When this option is enabled, Filebeat closes the file handle if a file has not been harvested for the specified duration. The counter for the defined period starts when the last log line was read by the harvester. It is not based on the modification time of the file. If the closed file changes again, a new harvester is started and the latest changes will be picked up after scan_frequency has elapsed.

We recommended that you set close_inactive to a value that is larger than the least frequent updates to your log files. For example, if your log files get updated every few seconds, you can safely set close_inactive to 1m. If there are log files with very different update rates, you can use multiple prospector configurations with different values.

Setting close_inactive to a lower value means that file handles are closed sooner. However this has the side effect that new log lines are not sent in near real time if the harvester is closed.

The timestamp for closing a file does not depend on the modification time of the file. Instead, Filebeat uses an internal timestamp that reflects when the file was last harvested. For example, if close_inactive is set to 5 minutes, the countdown for the 5 minutes starts after the harvester reads the last line of the file.

You can use time strings like 2h (2 hours) and 5m (5 minutes). The default is 5m.

When this option is enabled, Filebeat closes the file handler when a file is renamed. This happens, for example, when rotating files. By default, the harvester stays open and keeps reading the file because the file handler does not depend on the file name. If the close_renamed option is enabled and the file is renamed or moved in such a way that it’s no longer matched by the file patterns specified for the prospector, the file will not be picked up again. Filebeat will not finish reading the file.

WINDOWS: If your Windows log rotation system shows errors because it can’t rotate the files, you should enable this option.

When this option is enabled, Filebeat closes the harvester when a file is removed. Normally a file should only be removed after it’s inactive for the duration specified by close_inactive. However, if a file is removed early and you don’t enable close_removed, Filebeat keeps the file open to make sure the harvester has completed. If this setting results in files that are not completely read because they are removed from disk too early, disable this option.

This option is enabled by default. If you disable this option, you must also disable clean_removed.

WINDOWS: If your Windows log rotation system shows errors because it can’t rotate files, make sure this option is enabled.

When this option is enabled, Filebeat closes a file as soon as the end of a file is reached. This is useful when your files are only written once and not updated from time to time. For example, this happens when you are writing every single log event to a new file. This option is disabled by default.

When this option is enabled, Filebeat gives every harvester a predefined lifetime. Regardless of where the reader is in the file, reading will stop after the close_timeout period has elapsed. This option can be useful for older log files when you want to spend only a predefined amount of time on the files. While close_timeout will close the file after the predefined timeout, if the file is still being updated, the prospector will start a new harvester again per the defined scan_frequency. And the close_timeout for this harvester will start again with the countdown for the timeout.

This option is particularly useful in case the output is blocked, which makes Filebeat keep open file handlers even for files that were deleted from the disk. Setting close_timeout to 5m ensures that the files are periodically closed so they can be freed up by the operating system.

If you set close_timeout to equal ignore_older, the file will not be picked up if it’s modified while the harvester is closed. This combination of settings normally leads to data loss, and the complete file is not sent.

When you use close_timeout for logs that contain multiline events, the harvester might stop in the middle of a multiline event, which means that only parts of the event will be sent. If the harvester is started again and the file still exists, only the second part of the event will be sent.

This option is set to 0 by default which means it is disabled.

The clean_* options are used to clean up the state entries in the registry file. These settings help to reduce the size of the registry file and can prevent a potential inode reuse issue.

When this option is enabled, Filebeat removes the state of a file after the specified period of inactivity has elapsed. The state can only be removed if the file is already ignored by Filebeat (the file is older than ignore_older). The clean_inactive setting must be greater than ignore_older + scan_frequency to make sure that no states are removed while a file is still being harvested. Otherwise, the setting could result in Filebeat resending the full content constantly because clean_inactive removes state for files that are still detected by the prospector. If a file is updated or appears again, the file is read from the beginning.

The clean_inactive configuration option is useful to reduce the size of the registry file, especially if a large amount of new files are generated every day.

This config option is also useful to prevent Filebeat problems resulting from inode reuse on Linux. For more information, see Inode reuse causes Filebeat to skip lines?.

When this option is enabled, Filebeat cleans files from the registry if they cannot be found on disk anymore under the last known name. This means also files which were renamed after the harvester was finished will be removed. This option is enabled by default.

If a shared drive disappears for a short period and appears again, all files will be read again from the beginning because the states were removed from the registry file. In such cases, we recommend that you disable the clean_removed option.

You must disable this option if you also disable close_removed.

How often the prospector checks for new files in the paths that are specified for harvesting. For example, if you specify a glob like /var/log/*, the directory is scanned for files using the frequency specified by scan_frequency. Specify 1s to scan the directory as frequently as possible without causing Filebeat to scan too frequently. We do not recommend to set this value <1s.

If you require log lines to be sent in near real time do not use a very low scan_frequency but adjust close_inactive so the file handler stays open and constantly polls your files.

The default setting is 10s.

If you specify a value other than the empty string for this setting you can determine whether to use ascending or descending order using scan.order. Possible values are modtime and filename. To sort by file modification time, use modtime, otherwise use filename. Leave this option empty to disable it.

If you specify a value for this setting, you can use scan.order to configure whether files are scanned in ascending or descending order.

The default setting is disabled.

Specifies whether to use ascending or descending order when scan.sort is set to a value other than none. Possible values are asc or desc.

The default setting is asc.

The size in bytes of the buffer that each harvester uses when fetching a file. The default is 16384.

The maximum number of bytes that a single log message can have. All bytes after max_bytes are discarded and not sent. This setting is especially useful for multiline log messages, which can get large. The default is 10MB (10485760).

These options make it possible for Filebeat to decode logs structured as JSON messages. Filebeat processes the logs line by line, so the JSON decoding only works if there is one JSON object per line.

The decoding happens before line filtering and multiline. You can combine JSON decoding with filtering and multiline if you set the message_key option. This can be helpful in situations where the application logs are wrapped in JSON objects, like it happens for example with Docker.

Example configuration:

json.keys_under_root: true
json.add_error_key: true
json.message_key: log

You must specify at least one of the following settings to enable JSON parsing mode:

Options that control how Filebeat deals with log messages that span multiple lines. See Manage multiline messages for more information about configuring multiline options.

If this option is set to true, Filebeat starts reading new files at the end of each file instead of the beginning. When this option is used in combination with log rotation, it’s possible that the first log entries in a new file might be skipped. The default setting is false.

This option applies to files that Filebeat has not already processed. If you ran Filebeat previously and the state of the file was already persisted, tail_files will not apply. Harvesting will continue at the previous offset. To apply tail_files to all files, you must stop Filebeat and remove the registry file. Be aware that doing this removes ALL previous states.

The Ingest Node pipeline ID to set for the events generated by this prospector.

The symlinks option allows Filebeat to harvest symlinks in addition to regular files. When harvesting symlinks, Filebeat opens and reads the original file even though it reports the path of the symlink.

When you configure a symlink for harvesting, make sure the original path is excluded. If a single prospector is configured to harvest both the symlink and the original file, the prospector will detect the problem and only process the first file it finds. However, if two different prospectors are configured (one to read the symlink and the other the original path), both paths will be harvested, causing Filebeat to send duplicate data and the prospectors to overwrite each other’s state.

The symlinks option can be useful if symlinks to the log files have additional metadata in the file name, and you want to process the metadata in Logstash. This is, for example, the case for Kubernetes log files.

Because this option may lead to data loss, it is disabled by default.

The backoff options specify how aggressively Filebeat crawls open files for updates. You can use the default values in most cases.

The backoff option defines how long Filebeat waits before checking a file again after EOF is reached. The default is 1s, which means the file is checked every second if new lines were added. This enables near real-time crawling. Every time a new line appears in the file, the backoff value is reset to the initial value. The default is 1s.

The maximum time for Filebeat to wait before checking a file again after EOF is reached. After having backed off multiple times from checking the file, the wait time will never exceed max_backoff regardless of what is specified for backoff_factor. Because it takes a maximum of 10s to read a new line, specifying 10s for max_backoff means that, at the worst, a new line could be added to the log file if Filebeat has backed off multiple times. The default is 10s.

Requirement: max_backoff should always be set to max_backoff <= scan_frequency. In case max_backoff should be bigger, it is recommended to close the file handler instead let the prospector pick up the file again.

This option specifies how fast the waiting time is increased. The bigger the backoff factor, the faster the max_backoff value is reached. The backoff factor increments exponentially. The minimum value allowed is 1. If this value is set to 1, the backoff algorithm is disabled, and the backoff value is used for waiting for new lines. The backoff value will be multiplied each time with the backoff_factor until max_backoff is reached. The default is 2.

The harvester_limit option limits the number of harvesters that are started in parallel for one prospector. This directly relates to the maximum number of file handlers that are opened. The default for harvester_limit is 0, which means there is no limit. This configuration is useful if the number of files to be harvested exceeds the open file handler limit of the operating system.

Setting a limit on the number of harvesters means that potentially not all files are opened in parallel. Therefore we recommended that you use this option in combination with the close_* options to make sure harvesters are stopped more often so that new files can be picked up.

Currently if a new harvester can be started again, the harvester is picked randomly. This means it’s possible that the harvester for a file that was just closed and then updated again might be started instead of the harvester for a file that hasn’t been harvested for a longer period of time.

This configuration option applies per prospector. You can use this option to indirectly set higher priorities on certain prospectors by assigning a higher limit of harvesters.

The enabled option can be used with each prospector to define if a prospector is enabled or not. By default, enabled is set to true.

When used with type: udp, specifies the maximum size of the message received over UDP. The default is 10240.

These options are only available when using docker prospector type. They allow to configure the list of containers to read logs from.

Docker prospector will search for container logs under its path, and parse them into common message lines, extracting timestamps too. Everything happens before line filtering, multiline and JSON decoding, so it can be used in combination with them.

Example configuration:

containers.ids:
  - '8b6fe7dc9e067b58476dc57d6986dd96d7100430c5de3b109a99cd56ac655347'

When using docker prospector type you must define containers.ids, these are all available settings: