Socket Listener

Overview

The Socket Listener is a service input plugin that listens for messages from streaming (tcp, unix) or datagram (udp, unixgram) protocols.

The plugin expects messages in the Input Data Formats.

Prerequisites

This plugin uses the snmptranslate programs from the net-snmp project. These tools will need to be installed into the PATH in order to be located. Other utilities from the net-snmp project may be useful for troubleshooting, but are not directly used by the plugin.

These programs will load available MIBs on the system. Typically the default directory for MIBs is /usr/share/snmp/mibs, but if your MIBs are in a different location you may need to make the paths known to net-snmp. The location of these files can be configured in the snmp.conf or via the MIBDIRS environment variable. See man 1 snmpcmd for more information.

Configuration

This is a sample configuration for the plugin.

# Generic socket listener capable of handling multiple socket types.
[[inputs.socket_listener]]
  ## URL to listen on
  # service_address = "tcp://:8094"
  # service_address = "tcp://127.0.0.1:http"
  # service_address = "tcp4://:8094"
  # service_address = "tcp6://:8094"
  # service_address = "tcp6://[2001:db8::1]:8094"
  # service_address = "udp://:8094"
  # service_address = "udp4://:8094"
  # service_address = "udp6://:8094"
  # service_address = "unix:///tmp/circonus-unified-agent.sock"
  # service_address = "unixgram:///tmp/circonus-unified-agent.sock"

  ## Change the file mode bits on unix sockets.  These permissions may not be
  ## respected by some platforms, to safely restrict write permissions it is best
  ## to place the socket into a directory that has previously been created
  ## with the desired permissions.
  ##   ex: socket_mode = "777"
  # socket_mode = ""

  ## Maximum number of concurrent connections.
  ## Only applies to stream sockets (e.g. TCP).
  ## 0 (default) is unlimited.
  # max_connections = 1024

  ## Read timeout.
  ## Only applies to stream sockets (e.g. TCP).
  ## 0 (default) is unlimited.
  # read_timeout = "30s"

  ## Optional TLS configuration.
  ## Only applies to stream sockets (e.g. TCP).
  # tls_cert = "/etc/circonus-unified-agent/cert.pem"
  # tls_key  = "/etc/circonus-unified-agent/key.pem"
  ## Enables client authentication if set.
  # tls_allowed_cacerts = ["/etc/circonus-unified-agent/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.
  ## 0 disables keep alive probes.
  ## Defaults to the OS configuration.
  # keep_alive_period = "5m"

  ## Data format to consume.
  ## Each data format has its own unique set of configuration options, read
  ## more about them here:
  ## https://github.com/circonus-labs/circonus-unified-agent/blob/master/docs/DATA_FORMATS_INPUT.md
  # data_format = "influx"

  ## Content encoding for message payloads, can be set to "gzip" to or
  ## "identity" to apply no encoding.
  # content_encoding = "identity"

A Note on UDP OS Buffer Sizes

The read_buffer_size config option can be used to adjust the size of the socket buffer, but this number is limited by OS settings. On Linux, read_buffer_size will default to rmem_default and will be capped by rmem_max. On BSD systems, read_buffer_size is capped by maxsockbuf, and there is no OS default setting.

Instructions on how to adjust these OS settings are available below.

Some OSes (most notably, Linux) place very restrictive limits on the performance of UDP protocols. It is highly recommended that you increase these OS limits to at least 8MB before trying to run large amounts of UDP traffic to your instance. 8MB is just a recommendation, and can be adjusted higher.

Linux

Check the current UDP/IP receive buffer limit & default by typing the following commands:

sysctl net.core.rmem_max
sysctl net.core.rmem_default

If the values are less than 8388608 bytes you should add the following lines to the /etc/sysctl.conf file:

net.core.rmem_max=8388608
net.core.rmem_default=8388608

Changes to /etc/sysctl.conf do not take effect until reboot. To update the values immediately, type the following commands as root:

sysctl -w net.core.rmem_max=8388608
sysctl -w net.core.rmem_default=8388608

BSD/Darwin

On BSD/Darwin systems you need to add about a 15% padding to the kernel limit socket buffer. Meaning if you want an 8MB buffer (8388608 bytes) you need to set the kernel limit to 8388608*1.15 = 9646900. This is not documented anywhere but happens in the kernel here.

Check the current UDP/IP buffer limit by typing the following command:

sysctl kern.ipc.maxsockbuf

If the value is less than 9646900 bytes you should add the following lines to the /etc/sysctl.conf file (create it if necessary):

kern.ipc.maxsockbuf=9646900

Changes to /etc/sysctl.conf do not take effect until reboot. To update the values immediately, type the following command as root:

sysctl -w kern.ipc.maxsockbuf=9646900