SNMP

Overview

The snmp input plugin uses polling to gather metrics from SNMP agents. Support for gathering individual OIDs as well as complete SNMP tables is included.

This plugin sends metrics directly to Circonus - it bypasses aggregators, processors, parsers, and outputs. The intended use-case is for sitations where a large number of SNMP collector instances is required. In such cases optimizations and efficiencies can be gained by sending metrics directly.

The snmp input plugin introduces a new capability to send metrics directly to Circonus direct_metrics. Useful when there are a large number of snmp plugin instances.

Prerequisites

This plugin uses the snmptable and 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

[[inputs.snmp]]
  ## Instance ID is required
  instance_id = ""
  ## Direct metrics
  # direct_metrics = false

  ## example of collecting hundreds of devices on a 5m cadence
  # collection interval
  interval = "5m"
  # flush interval, so cua does not log warning about input 
  # taking too long w/flush delay
  flush_interval = "5m"
  # spread flushing submissions over a two minute window
  flush_delay = "2m"

  ## Agent addresses to retrieve values from.
  ##   example: agents = ["udp://127.0.0.1:161"]
  ##            agents = ["tcp://127.0.0.1:161"]
  agents = ["udp://127.0.0.1:161"]

  ## Timeout for each request.
  # timeout = "5s"

  ## SNMP version; can be 1, 2, or 3.
  # version = 2

  ## SNMP community string.
  # community = "public"

  ## Agent host tag
  # agent_host_tag = "agent_host"

  ## Number of retries to attempt.
  # retries = 3

  ## The GETBULK max-repetitions parameter.
  # max_repetitions = 10

  ## SNMPv3 authentication and encryption options.
  ##
  ## Security Name.
  # sec_name = "myuser"
  ## Authentication protocol; one of "MD5", "SHA", or "".
  # auth_protocol = "MD5"
  ## Authentication password.
  # auth_password = "pass"
  ## Security Level; one of "noAuthNoPriv", "authNoPriv", or "authPriv".
  # sec_level = "authNoPriv"
  ## Context Name.
  # context_name = ""
  ## Privacy protocol used for encrypted messages; one of "DES", "AES" or "".
  # priv_protocol = ""
  ## Privacy password used for encrypted messages.
  # priv_password = ""

  ## Add fields and tables defining the variables you wish to collect.  This
  ## example collects the system uptime and interface variables.  Reference the
  ## full plugin documentation for configuration details.
  [[inputs.snmp.field]]
    oid = "RFC1213-MIB::sysUpTime.0"
    name = "uptime"

  [[inputs.snmp.field]]
    oid = "RFC1213-MIB::sysName.0"
    name = "source"
    is_tag = true

  [[inputs.snmp.table]]
    oid = "IF-MIB::ifTable"
    name = "interface"
    inherit_tags = ["source"]

    [[inputs.snmp.table.field]]
      oid = "IF-MIB::ifDescr"
      name = "ifDescr"
      is_tag = true

Configure SNMP Requests

This plugin provides two methods for configuring the SNMP requests: fields and tables. Use the field option to gather single ad-hoc variables. To collect SNMP tables, use the table option.

Field

Use a field to collect a variable by OID. Requests specified with this option operate similar to the snmpget utility.

[[inputs.snmp]]
  # ... snip ...

  [[inputs.snmp.field]]
    ## Object identifier of the variable as a numeric or textual OID.
    oid = "RFC1213-MIB::sysName.0"

    ## Name of the field or tag to create.  If not specified, it defaults to
    ## the value of 'oid'. If 'oid' is numeric, an attempt to translate the
    ## numeric OID into a textual OID will be made.
    # name = ""

    ## If true the variable will be added as a tag, otherwise a field will be
    ## created.
    # is_tag = false

    ## Apply one of the following conversions to the variable value:
    ##   float(X) Convert the input value into a float and divides by the
    ##            Xth power of 10. Effectively just moves the decimal left
    ##            X places. For example a value of `123` with `float(2)`
    ##            will result in `1.23`.
    ##   float:   Convert the value into a float with no adjustment. Same
    ##            as `float(0)`.
    ##   int:     Convert the value into an integer.
    ##   hwaddr:  Convert the value to a MAC address.
    ##   ipaddr:  Convert the value to an IP address.
    # conversion = ""

Table

Use a table to configure the collection of a SNMP table. SNMP requests formed with this option operate similarly way to the snmptable command.

Control the handling of specific table columns using a nested field. These nested fields are specified similarly to a top-level field.

By default all columns of the SNMP table will be collected - it is not required to add a nested field for each column, only those which you wish to modify. To only collect certain columns, omit the oid from the table section and only include oid settings in field sections. For more complex include/exclude cases for columns use metric filtering.

One metric is created for each row of the SNMP table.

[[inputs.snmp]]
  # ... snip ...

  [[inputs.snmp.table]]
    ## Object identifier of the SNMP table as a numeric or textual OID.
    oid = "IF-MIB::ifTable"

    ## Name of the field or tag to create.  If not specified, it defaults to
    ## the value of 'oid'.  If 'oid' is numeric an attempt to translate the
    ## numeric OID into a textual OID will be made.
    # name = ""

    ## Which tags to inherit from the top-level config and to use in the output
    ## of this table's measurement.
    ## example: inherit_tags = ["source"]
    # inherit_tags = []

    ## Add an 'index' tag with the table row number.  Use this if the table has
    ## no indexes or if you are excluding them.  This option is normally not
    ## required as any index columns are automatically added as tags.
    # index_as_tag = false

    [[inputs.snmp.table.field]]
      ## OID to get. May be a numeric or textual module-qualified OID.
      oid = "IF-MIB::ifDescr"

      ## Name of the field or tag to create.  If not specified, it defaults to
      ## the value of 'oid'. If 'oid' is numeric an attempt to translate the
      ## numeric OID into a textual OID will be made.
      # name = ""

      ## Output this field as a tag.
      # is_tag = false

      ## The OID sub-identifier to strip off so that the index can be matched
      ## against other fields in the table.
      # oid_index_suffix = ""

      ## Specifies the length of the index after the supplied table OID (in OID
      ## path segments). Truncates the index after this point to remove non-fixed
      ## value or length index suffixes.
      # oid_index_length = 0

      ## Specifies if the value of given field should be snmptranslated
      ## by default no field values are translated
      # translate = true

Troubleshooting

Check that a numeric field can be translated to a textual field:

snmptranslate .1.3.6.1.2.1.1.3.0
DISMAN-EVENT-MIB::sysUpTimeInstance

Request a top-level field:

snmpget -v2c -c public 127.0.0.1 sysUpTime.0

Request a table:

snmptable -v2c -c public 127.0.0.1 ifTable

To collect a packet capture, run this command in the background while running agent or one of the above commands. Adjust the interface, host and port as needed:

sudo tcpdump -s 0 -i eth0 -w circonus-unified-agent-snmp.pcap host 127.0.0.1 and port 161