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Syslog Input Plugin

The syslog plugin listens for syslog messages transmitted over a Unix Domain socket, UDP, TCP, or TLS; with or without the octet counting framing.

Syslog messages should be formatted according to RFC 5424 (syslog protocol) or RFC 3164 (BSD syslog protocol).

Service Input

This plugin is a service input. Normal plugins gather metrics determined by the interval setting. Service plugins start a service to listens and waits for metrics or events to occur. Service plugins have two key differences from normal plugins:

  1. The global or plugin specific interval setting may not apply
  2. The CLI options of --test, --test-wait, and --once may not produce output for this plugin

Global configuration options

In addition to the plugin-specific configuration settings, plugins support additional global and plugin configuration settings. These settings are used to modify metrics, tags, and field or create aliases and configure ordering, etc. See the CONFIGURATION.md for more details.

Configuration

[[inputs.syslog]]
  ## Protocol, address and port to host the syslog receiver.
  ## If no host is specified, then localhost is used.
  ## If no port is specified, 6514 is used (RFC5425#section-4.1).
  ##   ex: server = "tcp://localhost:6514"
  ##       server = "udp://:6514"
  ##       server = "unix:///var/run/telegraf-syslog.sock"
  ## When using tcp, consider using 'tcp4' or 'tcp6' to force the usage of IPv4
  ## or IPV6 respectively. There are cases, where when not specified, a system
  ## may force an IPv4 mapped IPv6 address.
  server = "tcp://127.0.0.1:6514"

  ## Permission for unix sockets (only available on unix sockets)
  ## This setting may not be respected by some platforms. To safely restrict
  ## permissions it is recommended to place the socket into a previously
  ## created directory with the desired permissions.
  ##   ex: socket_mode = "777"
  # socket_mode = ""

  ## Maximum number of concurrent connections (only available on stream sockets like TCP)
  ## Zero means unlimited.
  # max_connections = 0

  ## Read timeout (only available on stream sockets like TCP)
  ## Zero means unlimited.
  # read_timeout = "0s"

  ## Optional TLS configuration (only available on stream sockets like TCP)
  # tls_cert = "/etc/telegraf/cert.pem"
  # tls_key  = "/etc/telegraf/key.pem"
  ## Enables client authentication if set.
  # tls_allowed_cacerts = ["/etc/telegraf/clientca.pem"]

  ## Maximum socket buffer size (in bytes when no unit specified)
  ## For stream sockets, once the buffer fills up, the sender will start
  ## backing up. For datagram sockets, once the buffer fills up, metrics will
  ## start dropping. Defaults to the OS default.
  # read_buffer_size = "64KiB"

  ## Period between keep alive probes (only applies to TCP sockets)
  ## Zero disables keep alive probes. Defaults to the OS configuration.
  # keep_alive_period = "5m"

  ## Content encoding for message payloads
  ## Can be set to "gzip" for compressed payloads or "identity" for no encoding.
  # content_encoding = "identity"

  ## Maximum size of decoded packet (in bytes when no unit specified)
  # max_decompression_size = "500MB"

  ## Framing technique used for messages transport
  ## Available settings are:
  ##   octet-counting  -- see RFC5425#section-4.3.1 and RFC6587#section-3.4.1
  ##   non-transparent -- see RFC6587#section-3.4.2
  # framing = "octet-counting"

  ## The trailer to be expected in case of non-transparent framing (default = "LF").
  ## Must be one of "LF", or "NUL".
  # trailer = "LF"

  ## Whether to parse in best effort mode or not (default = false).
  ## By default best effort parsing is off.
  # best_effort = false

  ## The RFC standard to use for message parsing
  ## By default RFC5424 is used. RFC3164 only supports UDP transport (no streaming support)
  ## Must be one of "RFC5424", or "RFC3164".
  # syslog_standard = "RFC5424"

  ## Character to prepend to SD-PARAMs (default = "_").
  ## A syslog message can contain multiple parameters and multiple identifiers within structured data section.
  ## Eg., [id1 name1="val1" name2="val2"][id2 name1="val1" nameA="valA"]
  ## For each combination a field is created.
  ## Its name is created concatenating identifier, sdparam_separator, and parameter name.
  # sdparam_separator = "_"

Message transport

The framing option only applies to streams. It governs the way we expect to receive messages within the stream. Namely, with the "octet counting" technique (default) or with the "non-transparent" framing.

The trailer option only applies when framing option is "non-transparent". It must have one of the following values: "LF" (default), or "NUL".

Best effort

The best_effort option instructs the parser to extract partial but valid info from syslog messages. If unset only full messages will be collected.

Rsyslog Integration

Rsyslog can be configured to forward logging messages to Telegraf by configuring remote logging.

Most system are setup with a configuration split between /etc/rsyslog.conf and the files in the /etc/rsyslog.d/ directory, it is recommended to add the new configuration into the config directory to simplify updates to the main config file.

Add the following lines to /etc/rsyslog.d/50-telegraf.conf making adjustments to the target address as needed:

$ActionQueueType LinkedList # use asynchronous processing
$ActionQueueFileName srvrfwd # set file name, also enables disk mode
$ActionResumeRetryCount -1 # infinite retries on insert failure
$ActionQueueSaveOnShutdown on # save in-memory data if rsyslog shuts down

# forward over tcp with octet framing according to RFC 5425
*.* @@(o)127.0.0.1:6514;RSYSLOG_SyslogProtocol23Format

# uncomment to use udp according to RFC 5424
#*.* @127.0.0.1:6514;RSYSLOG_SyslogProtocol23Format

You can alternately use advanced format (aka RainerScript):

# forward over tcp with octet framing according to RFC 5425
action(type="omfwd" Protocol="tcp" TCP_Framing="octet-counted" Target="127.0.0.1" Port="6514" Template="RSYSLOG_SyslogProtocol23Format")

# uncomment to use udp according to RFC 5424
#action(type="omfwd" Protocol="udp" Target="127.0.0.1" Port="6514" Template="RSYSLOG_SyslogProtocol23Format")

To complete TLS setup please refer to rsyslog docs.

Metrics

  • syslog
    • tags
      • severity (string)
      • facility (string)
      • hostname (string)
      • appname (string)
      • source (string)
    • fields
      • version (integer)
      • severity_code (integer)
      • facility_code (integer)
      • timestamp (integer): the time recorded in the syslog message
      • procid (string)
      • msgid (string)
      • sdid (bool)
      • Structured Data (string)
    • timestamp: the time the messages was received

Structured Data

Structured data produces field keys by combining the SD_ID with the PARAM_NAME combined using the sdparam_separator as in the following example:

170 <165>1 2018-10-01:14:15.000Z mymachine.example.com evntslog - ID47 [exampleSDID@32473 iut="3" eventSource="Application" eventID="1011"] An application event log entry...
syslog,appname=evntslog,facility=local4,hostname=mymachine.example.com,severity=notice exampleSDID@32473_eventID="1011",exampleSDID@32473_eventSource="Application",exampleSDID@32473_iut="3",facility_code=20i,message="An application event log entry...",msgid="ID47",severity_code=5i,timestamp=1065910455003000000i,version=1i 1538421339749472344

Troubleshooting

# TCP with octet framing
echo "57 <13>1 2018-10-01T12:00:00.0Z example.org root - - - test" | nc 127.0.0.1 6514

# UDP
echo "<13>1 2018-10-01T12:00:00.0Z example.org root - - - test" | nc -u 127.0.0.1 6514

Resolving Source IPs

The source tag stores the remote IP address of the syslog sender. To resolve these IPs to DNS names, use the reverse_dns processor.

You can send debugging messages directly to the input plugin using netcat:

RFC3164

RFC3164 encoded messages are supported for UDP only, but not all vendors output valid RFC3164 messages by default

  • E.g. Cisco IOS

If you see the following error, it is due to a message encoded in this format:

E! Error in plugin [inputs.syslog]: expecting a version value in the range 1-999 [col 5]

Users can use rsyslog to translate RFC3164 syslog messages into RFC5424 format. Add the following lines to the rsyslog configuration file (e.g. /etc/rsyslog.d/50-telegraf.conf):

# This makes rsyslog listen on 127.0.0.1:514 to receive RFC3164 udp
# messages which can them be forwarded to telegraf as RFC5424
$ModLoad imudp #loads the udp module
$UDPServerAddress 127.0.0.1
$UDPServerRun 514

Make adjustments to the target address as needed and sent your RFC3164 messages to port 514.

Example Output

Here is example output of this plugin:

syslog,appname=docker-compose,facility=daemon,host=bb8,hostname=droplet,location=home,severity=info,source=10.0.0.12 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643706396113000i,version=1i 1624643706400667198
syslog,appname=tailscaled,facility=daemon,host=bb8,hostname=dev,location=home,severity=info,source=10.0.0.15 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643706403394000i,version=1i 1624643706407850408
syslog,appname=docker-compose,facility=daemon,host=bb8,hostname=droplet,location=home,severity=info,source=10.0.0.12 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643706675853000i,version=1i 1624643706679251683
syslog,appname=telegraf,facility=daemon,host=bb8,hostname=droplet,location=home,severity=info,source=10.0.0.12 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643710005006000i,version=1i 1624643710008285426
syslog,appname=telegraf,facility=daemon,host=bb8,hostname=droplet,location=home,severity=info,source=10.0.0.12 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643710005696000i,version=1i 1624643710010754050
syslog,appname=docker-compose,facility=daemon,host=bb8,hostname=droplet,location=home,severity=info,source=10.0.0.12 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643715777813000i,version=1i 1624643715782158154
syslog,appname=docker-compose,facility=daemon,host=bb8,hostname=droplet,location=home,severity=info,source=10.0.0.12 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643716396547000i,version=1i 1624643716400395788
syslog,appname=tailscaled,facility=daemon,host=bb8,hostname=dev,location=home,severity=info,source=10.0.0.15 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643716404931000i,version=1i 1624643716416947058
syslog,appname=docker-compose,facility=daemon,host=bb8,hostname=droplet,location=home,severity=info,source=10.0.0.12 facility_code=3i,message="<redacted>",severity_code=6i,timestamp=1624643716676633000i,version=1i 1624643716680157558