weewx-snmp

WeeWX service to fetch data by SNMP

There are sensors that offer their readings by SNMP. Fortunately there is a powerful Python module available to speak SNMP. This extension makes it available to WeeWX.

Prerequisites

Install PySNMP if it is not already there.

sudo apt-get install python3-pysnmp

In newer releases of Ubuntu you have to enter:

sudo apt-get install python3-pysnmp4

Installation instructions

1. download

   wget -O weewx-snmp.zip https://github.com/roe-dl/weewx-snmp/archive/master.zip
   

2. run the installer

   WeeWX up to version 4.X

   sudo wee_extension --install weewx-snmp.zip
   

   WeeWX from version 5.0 on

   sudo weectl extension install weewx-snmp.zip
   

3. edit configuration in weewx.conf

   Before using this extension you have to set up which devices to be queried and which variables to be fetched. See section "Configuration" for details.

   Caution! If you want to save the readings to a separate database and have it created properly, you have to edit the configuration file before you first start WeeWX after installing the extension.

   If you want to add additional variables afterwards you have to extend the database schema manually by using the wee_database utility (weectl database in WeeWX 5). This is not done automatically.

4. restart weewx

   for SysVinit systems:

   sudo /etc/init.d/weewx stop
   sudo /etc/init.d/weewx start
   

   for systemd systems:

   sudo systemctl stop weewx
   sudo systemctl start weewx
   

Configuration

This extension can query several devices simultaneously. It creates a separate thread for each of them. In section [SNMP] of weewx.conf each device has its own subsection. You can name that subsection as you want. The name is used to name the thread, only.

Each subsection contains of the following information:

• connection data
• authentication data
• subsubsection(s) containing the description of the variables (observation types) to fetch, their names in WeeWX, unit and unit group, and - if necessary - some conversion formula.

General options

• enable: If True or omitted, retrieve data from that device. If False, that subsection is not used. (optional)
• log_success: If True, log successful operation. If omitted, global options apply. (optional)
• log_failure: If True, log unsuccessful operation. If omitted, global options apply. (optional)
• data_binding: data binding to use for storage (or None if no extra data binding is to be used)

Connection configuration

• host: host name or IP address of the device to get data from (mandatory)
• port: port number (mandatory, standard 161)
• timeout: request timeout (optional, default is 0.5s)
• retries: request retries (0 is no retries) (optional, default is no retries)
• query_interval: query interval (optional, default 5s)

Authentication configuration

There are different authentication methods for SNMP version 1 and 2c on one hand and 3 on the other hand.

configuration entries for SNMP version 1 and 2c:

• protocol_version: Protocol version to use. Possible values are 1 or 2c
• community: Community name for receiving data. Often it is public.

configuration entries for SNMP version 3:

• protocol_version: Protocol version to use. In this case 3.
• username: User name
• password: Password (optional)
• password_protocol: Authentication protocol, see below for possible values (optional)
• encryption: Encryption passphrase (optional)
• encryption_protocol: Privacy protocol (means: encryption protocol), see below for possible values (optional)

Possible values for password_protocol:

• usmNoAuthProtocol
• usmHMACMD5AuthProtocol
• usmHMACSHAAuthProtocol
• usmHMAC128SHA224AuthProtocol
• usmHMAC192SHA256AuthProtocol
• usmHMAC256SHA384AuthProtocol
• usmHMAC384SHA512AuthProtocol

Possible values for encryption_protocol:

• usmNoPrivProtocol
• usmDESPrivProtocol
• usm3DESEDEPrivProtocol
• usmAesCfb128Protocol
• usmAesCfb192Protocol
• usmAesCfb256Protocol
• usmAesBlumenthalCfb192Protocol
• usmAesBlumenthalCfb256Protocol

Variables configuration

There are two possible subsubsections, [[[once]]] and [[[loop]]], the former is used once at program start and logged to syslog, the latter is performed continuously and included in the LOOP packets. If no [[[once]]] subsubsection is present, defaults are used, fetching some general device information. For the [[[loop]]] subsubsection, there are no defaults.

• oid: OID of the variable. If omitted, the section name is used for OID.
• conversion: optional conversion formula
• name: Observation type name used inside WeeWX
• unit: The unit the reading is provided by the device. That is not the unit the readings are to be saved to database or displayed in skins. For those purposes the values are converted automatically by WeeWX. The unit here is the source unit.
• group: Unit group, used by WeeWX to choose the right unit to save to database and to display in skins. If omitted, the extension tries to determine the unit group by the unit.
• sql_datatype: If specified, this datatype is used when creating the database table. Default is REAL if omitted. This entry can be used for string data especially. An example for a string datatype is VARCHAR(30).

See WeeWX Customization Guide for a list of predefined units and unit groups.

The observation types are automatically registered with WeeWX.

The standardized OID for sensor readings is iso.3.6.1.2.1.99.1.1.1.4, followed by an index of the sensor, starting with .1.

Accumulators

Accumulators define how to aggregate the readings during the archive interval. This extension tries to set up reasonable accumulators for the observation types defined in the [[[loop]]] subsubsection. If they do not work for you, you can set up accumulators manually in the [Accumulator] section of weewx.conf. See WeeWX Accumulators wiki page for how to set up accumulators in WeeWX.

The accumulator firstlast does not work for numeric values of this extension. The reason is that the database schema within this extension includes all numeric values in the list of daily summeries tables. But WeeWX let you have an observation type either with a daily summeries table or the firstlast accumulator, not both.

Example configuration

...

[DataBindings]
    ...
    # additional section for an extra database to store the SNMP data
    # optional!
    [[snmp_binding]]
        database = snmp_sqlite
        table_name = archive
        manager = weewx.manager.DaySummaryManager
        schema = user.snmp.schema

[Databases]
    ...
    # additional section for an extra database to store SNMP data
    # optional!
    [[snmp_sqlite]]
        database_name = snmp.sdb
        database_type = SQLite

[Engine]
    [[Services]]
        data_services = ..., user.snmp.SNMPservice
        archive_services = ..., user.snmp.SNMParchive

...

[SNMP]

    # extra database
    # optional!
    # to switch off set data_binding = None
    data_binding = snmp_binding

    # Each subsection represents one device to be connected. There
    # can be several such sections. The section name can be freely 
    # chosen. It is only used for the thread name. 
    [[UPS]]

        # host and port to be connected
        host = replace_me
        port = 161
        # optional
        #query_interval = 5

        # authentication data
        protocol_version = 2c # possible values '1', '2c', '3'
        # for version 1 and 2c
        community = replace_me
        # for version 3
        #username = replace_me
        #password = replace_me
        #password_protocol = usmNoAuthProtocol

        # data to fetch
        [[[loop]]]
            # UPS data
            [[[[iso.3.6.1.2.1.33.1.3.3.1.2.1]]]]
                name = 'upsInputFrequency'
                conversion = lambda x:float(x)/10.0
                unit = 'hertz'
                group = 'group_frequency'
            [[[[iso.3.6.1.2.1.33.1.3.3.1.3.1]]]]
                name = 'upsInputVoltage'
                unit = 'volt'
                group = 'group_volt'
            [[[[iso.3.6.1.2.1.33.1.4.1.0]]]]
                name = 'upsOutputSource'
            [[[[iso.3.6.1.2.1.33.1.4.2.0]]]]
                name = 'upsOutputFrequency'
                conversion = lambda x:float(x)/10.0
                unit = 'hertz'
                group = 'group_frequency'
            [[[[iso.3.6.1.2.1.33.1.4.4.1.2.1]]]]
                name = 'upsOutputVoltage'
                conversion = lambda x:float(x)
                unit = 'volt'
                group = 'group_volt'
            [[[[iso.3.6.1.2.1.33.1.4.4.1.3.1]]]]
                name = 'upsOutputCurrent'
                conversion = lambda x:float(x)/10.0
                unit = 'amp'
                group = 'group_amp'
            [[[[iso.3.6.1.2.1.33.1.4.4.1.4.1]]]]
                name = 'upsOutputPower'
                conversion = None
                unit = 'watt'
                group ='group_power'
            [[[[iso.3.6.1.2.1.33.1.4.4.1.5.1]]]]
                name = 'upsOutputPercentLoad'
                unit = 'percent'
                group = 'group_percent'
            # extra sensor data
            [[[[iso.3.6.1.2.1.99.1.1.1.4.1]]]]
                # cabinet temperature
                name = 'cabTemp'
                conversion = lambda x: float(x)/10.0
                unit = 'degree_C'
                group = 'group_temperature'
            [[[[iso.3.6.1.2.1.99.1.1.1.4.2]]]]
                # cabinet humidity
                name = 'cabHumidity'
                unit = 'percent'
                group = 'group_percent'

Default [[[once]]] section

This is the default [[[once]]] subsubsection that applies if no [[[once]]] subsubsection is present.

        [[[once]]]
            [[[[SNMPv2-MIB::sysDescr.0]]]]
                oid = 'SNMPv2-MIB', 'sysDescr', 0
                name = sysDescr
            [[[[SNMPv2-MIB::sysObjectID.0]]]]
                oid = 'SNMPv2-MIB', 'sysObjectID', 0
                name = sysObjectID
            [[[[SNMPv2-MIB::sysUpTime.0]]]]
                oid = 'SNMPv2-MIB', 'sysUpTime', 0
                name = sysUpTime
            [[[[SNMPv2-MIB::sysContact.0]]]]
                oid = 'SNMPv2-MIB', 'sysContact', 0
                name = sysContact
            [[[[SNMPv2-MIB::sysName.0]]]]
                oid = 'SNMPv2-MIB', 'sysName', 0
                name = sysName
            [[[[SNMPv2-MIB::sysLocation.0]]]]
                oid = 'SNMPv2-MIB', 'sysLocation', 0
                name = sysLocation
            [[[[SNMPv2-MIB::sysServices.0]]]]
                oid = 'SNMPv2-MIB', 'sysServices', 0
                name = sysServices
            [[[[SNMPv2-MIB::sysORLastChange.0]]]]
                oid = 'SNMPv2-MIB', 'sysORLastChange', 0
                name = sysORLastChange

OIDs

See OIDs wiki page

References

SNMP

• Net-SNMP tools (contains snmpget and snmpwalk command line tool to retrieve data from SNMP agents)
• SNMP tester for Windows

Python modules

• PySNMP documentation
• PySNMP at Github
• PyASN1 at Github
• PySMI at Github

MIBs

• http://www.oidview.com/mibs/0/SNMPv2-MIB.html
• http://www.oidview.com/mibs/0/SNMPv2-SMI.html
• http://www.oidview.com/mibs/0/UPS-MIB.html
• https://www.circitor.fr/Mibs/Html/R/RFC1213-MIB.php
• https://www.circitor.fr/Mibs/Html/E/ENTITY-SENSOR-MIB.php
• Private enterprise numbers

WeeWX

• WeeWX website
• WeeWX information in german
• WeeWX customization guide (See this guide for using the observation types in skins.)
• WeeWX accumulators (This extension tries to set up reasonable accumulators for the observation types, but if you want them different or if they do not work appropriately, you can define them in weewx.conf)
• Calculation in templates
• WeeWX extension to monitor the computer WeeWX is running on (That is not related to SNMP, but to monitoring. It uses Linux tools.)