### Relevant telegraf.conf
```toml
# Configuration for telegraf agent
[agen…t]
## Default data collection interval for all inputs
interval = "10s"
## Rounds collection interval to 'interval'
## ie, if interval="10s" then always collect on :00, :10, :20, etc.
round_interval = true
## Telegraf will send metrics to outputs in batches of at most
## metric_batch_size metrics.
## This controls the size of writes that Telegraf sends to output plugins.
metric_batch_size = 1000
## Maximum number of unwritten metrics per output. Increasing this value
## allows for longer periods of output downtime without dropping metrics at the
## cost of higher maximum memory usage.
metric_buffer_limit = 10000
## Collection jitter is used to jitter the collection by a random amount.
## Each plugin will sleep for a random time within jitter before collecting.
## This can be used to avoid many plugins querying things like sysfs at the
## same time, which can have a measurable effect on the system.
collection_jitter = "0s"
## Default flushing interval for all outputs. Maximum flush_interval will be
## flush_interval + flush_jitter
flush_interval = "10s"
## Jitter the flush interval by a random amount. This is primarily to avoid
## large write spikes for users running a large number of telegraf instances.
## ie, a jitter of 5s and interval 10s means flushes will happen every 10-15s
flush_jitter = "0s"
## By default or when set to "0s", precision will be set to the same
## timestamp order as the collection interval, with the maximum being 1s.
## ie, when interval = "10s", precision will be "1s"
## when interval = "250ms", precision will be "1ms"
## Precision will NOT be used for service inputs. It is up to each individual
## service input to set the timestamp at the appropriate precision.
## Valid time units are "ns", "us" (or "µs"), "ms", "s".
precision = ""
## Log at debug level.
debug = true
## Log only error level messages.
# quiet = false
## Log target controls the destination for logs and can be one of "file",
## "stderr" or, on Windows, "eventlog". When set to "file", the output file
## is determined by the "logfile" setting.
# logtarget = "file"
## Name of the file to be logged to when using the "file" logtarget. If set to
## the empty string then logs are written to stderr.
# logfile = ""
## The logfile will be rotated after the time interval specified. When set
## to 0 no time based rotation is performed. Logs are rotated only when
## written to, if there is no log activity rotation may be delayed.
# logfile_rotation_interval = "0d"
## The logfile will be rotated when it becomes larger than the specified
## size. When set to 0 no size based rotation is performed.
# logfile_rotation_max_size = "0MB"
## Maximum number of rotated archives to keep, any older logs are deleted.
## If set to -1, no archives are removed.
# logfile_rotation_max_archives = 5
## Pick a timezone to use when logging or type 'local' for local time.
## Example: America/Chicago
# log_with_timezone = ""
## Override default hostname, if empty use os.Hostname()
hostname = ""
## If set to true, do no set the "host" tag in the telegraf agent.
omit_hostname = false
[[outputs.influxdb_v2]]
## The URLs of the InfluxDB cluster nodes.
##
## Multiple URLs can be specified for a single cluster, only ONE of the
## urls will be written to each interval.
## ex: urls = ["https://us-west-2-1.aws.cloud2.influxdata.com"]
urls = ["${INFLUXDB_HOST}:${INFLUXDB_PORT}"]
## Token for authentication.
token = "${DOCKER_INFLUXDB_INIT_ADMIN_TOKEN}"
## Organization is the name of the organization you wish to write to; must exist.
organization = "${DOCKER_INFLUXDB_INIT_ORG}"
## Destination bucket to write into.
bucket = "${DOCKER_INFLUXDB_INIT_BUCKET}"
## The value of this tag will be used to determine the bucket. If this
## tag is not set the 'bucket' option is used as the default.
# bucket_tag = ""
## If true, the bucket tag will not be added to the metric.
# exclude_bucket_tag = false
## Timeout for HTTP messages.
# timeout = "5s"
## Additional HTTP headers
# http_headers = {"X-Special-Header" = "Special-Value"}
## HTTP Proxy override, if unset values the standard proxy environment
## variables are consulted to determine which proxy, if any, should be used.
# http_proxy = "http://corporate.proxy:3128"
## HTTP User-Agent
# user_agent = "telegraf"
## Content-Encoding for write request body, can be set to "gzip" to
## compress body or "identity" to apply no encoding.
# content_encoding = "gzip"
## Enable or disable uint support for writing uints influxdb 2.0.
# influx_uint_support = false
## Optional TLS Config for use on HTTP connections.
tls_ca = "${INFLUXD_TLS_CERT}"
tls_cert = "${INFLUXD_TLS_CERT}"
tls_key = "${INFLUXD_TLS_KEY}"
## Use TLS but skip chain & host verification
# insecure_skip_verify = false
[[inputs.cpu]]
## Whether to report per-cpu stats or not
percpu = true
## Whether to report total system cpu stats or not
totalcpu = true
## If true, collect raw CPU time metrics
collect_cpu_time = false
## If true, compute and report the sum of all non-idle CPU states
report_active = false
[[inputs.disk]]
## By default stats will be gathered for all mount points.
## Set mount_points will restrict the stats to only the specified mount points.
# mount_points = ["/"]
## Ignore mount points by filesystem type.
ignore_fs = ["tmpfs", "devtmpfs", "devfs", "iso9660", "overlay", "aufs", "squashfs"]
[[inputs.diskio]]
## By default, telegraf will gather stats for all devices including
## disk partitions.
## Setting devices will restrict the stats to the specified devices.
# devices = ["sda", "sdb", "vd*"]
## Uncomment the following line if you need disk serial numbers.
# skip_serial_number = false
#
## On systems which support it, device metadata can be added in the form of
## tags.
## Currently only Linux is supported via udev properties. You can view
## available properties for a device by running:
## 'udevadm info -q property -n /dev/sda'
## Note: Most, but not all, udev properties can be accessed this way. Properties
## that are currently inaccessible include DEVTYPE, DEVNAME, and DEVPATH.
# device_tags = ["ID_FS_TYPE", "ID_FS_USAGE"]
#
## Using the same metadata source as device_tags, you can also customize the
## name of the device via templates.
## The 'name_templates' parameter is a list of templates to try and apply to
## the device. The template may contain variables in the form of '$PROPERTY' or
## '${PROPERTY}'. The first template which does not contain any variables not
## present for the device is used as the device name tag.
## The typical use case is for LVM volumes, to get the VG/LV name instead of
## the near-meaningless DM-0 name.
# name_templates = ["$ID_FS_LABEL","$DM_VG_NAME/$DM_LV_NAME"]
[[inputs.mem]]
# no configuration
[[inputs.net]]
## By default, telegraf gathers stats from any up interface (excluding loopback)
## Setting interfaces will tell it to gather these explicit interfaces,
## regardless of status.
##
# interfaces = ["eth0"]
##
## On linux systems telegraf also collects protocol stats.
## Setting ignore_protocol_stats to true will skip reporting of protocol metrics.
##
# ignore_protocol_stats = false
##
[[inputs.processes]]
# no configuration
[[inputs.swap]]
# no configuration
[[inputs.system]]
## Uncomment to remove deprecated metrics.
# fielddrop = ["uptime_format"]
# Retrieve data from MODBUS slave devices
[[inputs.modbus]]
## Trace the connection to the modbus device as debug messages
## Note: You have to enable telegraf's debug mode to see those messages!
debug_connection = true
## Define the configuration schema
## |---register -- define fields per register type in the original style (only supports one slave ID)
## |---request -- define fields on a requests base
configuration_type = "register"
## Connection Configuration
##
## The plugin supports connections to PLCs via MODBUS/TCP or
## via serial line communication in binary (RTU) or readable (ASCII) encoding
##
## Device name
name = "SIEMENS SICAM P"
## Slave ID - addresses a MODBUS device on the bus
## Range: 0 - 255 [0 = broadcast; 248 - 255 = reserved]
slave_id = 1
## Timeout for each request
timeout = "1s"
## Maximum number of retries and the time to wait between retries
## when a slave-device is busy.
# busy_retries = 0
# busy_retries_wait = "100ms"
# TCP - connect via Modbus/TCP
controller = "tcp://${MODBUS_HOST}:${MODBUS_PORT}"
## Serial (RS485; RS232)
# controller = "file:///dev/ttyUSB0"
# baud_rate = 9600
# data_bits = 8
# parity = "N"
# stop_bits = 1
# transmission_mode = "RTU"
## Measurements
##
## Digital Variables, Discrete Inputs and Coils
## measurement - the (optional) measurement name, defaults to "modbus"
## name - the variable name
## address - variable address
discrete_inputs = [
]
coils = [
]
## Analog Variables, Input Registers and Holding Registers
## measurement - the (optional) measurement name, defaults to "modbus"
## name - the variable name
## byte_order - the ordering of bytes
## |---AB, ABCD - Big Endian
## |---BA, DCBA - Little Endian
## |---BADC - Mid-Big Endian
## |---CDAB - Mid-Little Endian
## data_type - INT16, UINT16, INT32, UINT32, INT64, UINT64, FLOAT32-IEEE, FLOAT64-IEEE (the IEEE 754 binary representation)
## FLOAT32 (deprecated), FIXED, UFIXED (fixed-point representation on input)
## scale - the final numeric variable representation
## address - variable address
holding_registers = [
{ name = "active_energy_demand", byte_order = "ABCD", data_type = "FLOAT32", scale=1.0, address = [40807, 40808] },
]
input_registers = [
]
```
### Logs from Telegraf
```text
adex-iot-telegraf | 2022-05-13T18:47:40Z D! [inputs.modbus] trying to read holding@40807[2]...
adex-iot-telegraf | 2022-05-13T18:47:40Z D! [inputs.modbus] modbus: send 02 34 00 00 00 06 01 03 9f 67 00 02
adex-iot-telegraf | 2022-05-13T18:47:40Z D! [inputs.modbus] modbus: recv 02 34 00 00 00 08 01 03 04 4d 4b bb a1 2e
adex-iot-telegraf | 2022-05-13T18:47:40Z E! [inputs.modbus] Error in plugin: modbus: response data size '5' does not match count '4'
```
### System info
Telegraf 1.22-alpine, InfluxDB 2.2-alpine, Ubuntu 18.04.5 LTS, Docker version 19.03.12
### Docker
version: '3.7'
services:
influxdb:
image: influxdb:2.2-alpine
container_name: ${CONTAINER_NAME}-influxdb
volumes:
- influxdb-data:/var/lib/influxdb2:rw
- ./influxdb/ssl/influxdb-selfsigned.crt:${INFLUXD_TLS_CERT}:ro
- ./influxdb/ssl/influxdb-selfsigned.key:${INFLUXD_TLS_KEY}:ro
env_file:
- .env
ports:
- 8086:8086
telegraf:
image: telegraf:1.22-alpine
container_name: ${CONTAINER_NAME}-telegraf
volumes:
- ./influxdb/telegraf.conf:/etc/telegraf/telegraf.conf:ro
- ./influxdb/ssl/influxdb-selfsigned.crt:${INFLUXD_TLS_CERT}:ro
- ./influxdb/ssl/influxdb-selfsigned.key:${INFLUXD_TLS_KEY}:ro
env_file:
- .env
depends_on:
- influxdb
volumes:
influxdb-data:
name: ${CONTAINER_NAME}-influxdb-data
### Steps to reproduce
1. Configure all env vars from telegraf.conf on your local environment
2. Lift both InfluxDB & Telegraf containers from the docker-compose.yml file
3. Wait until Telegraf starts reading the MODBUS holding registers and check the debug output
### Expected behavior
The data from the holding registers is read and published to InfluxDB
### Actual behavior
Following error occurs from Telegraf service/container:
```
Error in plugin: modbus: response data size '5' does not match count '4'
```
No data is sent/stored to InfluxDB.
### Additional info
Device is SIEMENS SICAM P with Modbus RTU translated over TCP.
Reading the same holding registers with another tools works perfectly, for example using `modpoll`:
```
modpoll -p ${MODBUS_PORT} -a 1 -f -t 4:float -r 40807 ${MODBUS_HOST}
```
results in:
```
[40807]: 213209248.000000
...
```
