# MQTT Telegraf JSON - trailing NULL character - payload parsing problem **URL:** \ **Category:** Telegraf\ **Created:** [March 18, 2023, 4:27pm UTC](https://community.influxdata.com/t/mqtt-telegraf-json-trailing-null-character-payload-parsing-problem/29111 "2023-03-18T16:27:59Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Tom999](https://avatars.discourse-cdn.com/v4/letter/t/8797f3/32.png) [@Tom999](https://community.influxdata.com/u/Tom999)\ **Post date:** [March 18, 2023, 4:27pm UTC](https://community.influxdata.com/t/mqtt-telegraf-json-trailing-null-character-payload-parsing-problem/29111/1 "2023-03-18T16:27:59Z")
Hello All, following input quasi JSON: ‘{“TimeStamp”:1679156093057,“WorkCenter”:“MyPlant1”,“PlantCode”:“4183”,“LineName”:“Line001”,“MachineName”:“AssemblerNo1”,“StationName”:“10N1”,“DeviceName”:“HardStop”,“TagName”:“ExtCmd\_T”,“Value”:50,“Anomaly”:0,“AvgWindow”:50.0,“StdWindow”:0.0} NULL’ as you can see last character in this string is NULL which is produced by PLC. I can’t get rid of it. Now how can I convert this in fact non-JSON into valid line protocol for InfluxDB ver2.0? How to parse tags and fields from payload (not topic) os this JSON? How to create measurement name as hard-coded name (not parsed from topic or payload) ? I tried many configurations and read all topics in internet. There is no clear documentation with examples how to handle such issue. What I found is: > > > Hi everyone, > > I’m working on some project, where I need to collect data to inf…luxdb using mqtt input plugin in telegraf. But I’m facing strange behaviour of mqtt input. I’m sending data on specific topic using JSON string (i.e. “{value”:15}", but MQTT producer, which I’m using adds, null (’\\x00’) char at the end of message. It looks like below in preview using MQTTBox client: > !\[14eeee37bcfdb5e2943c54c0281cae077d6ebade\](https://user-images.githubusercontent.com/65446967/82209574-c2337c00-990d-11ea-88af-1e5f69277588.png) > > > > First message was sent from MQTT producer and it has lenght of 41 bytes, while second I sent from regular MQTT client - MQTTBox - length of the second message is 40 bytes - null character at the end is missing. First message causes error in telegraf, while second is correctly wrote to database: > > \`\`\` > 2020-05-16T14:03:14Z E! \[inputs.mqtt\_consumer\] Error in plugin: invalid character '\\x00' after top-level value > 2020-05-16T14:03:15Z E! \[inputs.mqtt\_consumer\] Error in plugin: invalid character '\\x00' after top-level value > \`\`\` > My current telegraf config file looks like this (I have to use multiple MQTT inputs to multiple Influx databases, but this not a problem): > > \`\`\` > \[\[outputs.influxdb\]\] > urls = \["http://localhost:8086"\] > database = "telegraf\_metrics\_01" > retention\_policy = "" > write\_consistency = "any" > timeout = "37s" > tagexclude = \["destinationdb"\] > \[outputs.influxdb.tagpass\] > destinationdb = \["db01"\] > > \[\[inputs.mqtt\_consumer\]\] > servers = \["tcp://localhost:1883"\] > qos = 0 > topics = \[ > "test/maszyna1/#" > \] > data\_format = "json" > > \[inputs.mqtt\_consumer.tags\] > destinationdb = "db01" > \`\`\` > Do you have any idea, how to configure telegraf to (maybe) ignore those null characters, or cut this one byte using some processor plugin? I read some about proccessors.string.trim\_right plugin, but as I tested - it only works, when input data are correct, so It won't be helpful in this case. > > It’s also important that, when I’m using “value” data\_format of mqtt input, instead of “json” - telegraf works fine with this mqtt producer, even at the end of simple value also null character appears. > \*\*So maybe plugin (or even parser) should ignore those characters in payload (i.e. whitespaces, nulls) by default?\*\* Anyways - I have to use json format to pass multiple parameters to influx at once. > > I will appreciate any help > Have a good day! So probably parsing the non-Json from string to valid JSON is needed. But I use InfluxDB \>=2.0 I used also docker. Here is my telegraf.conf: ```auto [agent] interval = "1s" round_interval = true metric_batch_size = 1000 metric_buffer_limit = 10000 collection_jitter = "0s" flush_interval = "10s" flush_jitter = "0s" precision = "" hostname = "" omit_hostname = true ############################################################################## [[inputs.mqtt_consumer]] servers = ["tcp://MQTT_Broker:1883"] topics = ["PPS_L1/AssemblerNo1/10N1/HardStop/ExtCmd_T"] username = "mqttbroker" password = "LoopEdge.123" #data_format = "json" ##data_format = "influx" data_format = "value" data_type = "string" #data_format = "json_v2" topic_tag = "" [[inputs.mqtt_consumer.json_v2]] measurement_name = "measurement1" timestamp_path = "TimeStamp" timestamp_format = "unix" [[inputs.mqtt_consumer.json_v2.tag]] path = "LineName" [[inputs.mqtt_consumer.json_v2.field]] path = "Value" type = "float" [[inputs.mqtt_consumer.json_v2.field]] path = "AvgWindow" type = "float" ############################################################################### [[processors.parser]] parse_fields = ["Value", "Anomaly", "AvgWindow"] parse_tags = ["LineName", "MachineName"] merge = "override" data_format = "json" ############################################################################### [[outputs.influxdb_v2]] urls = ["http://InfluxDB:8086"] token = "firToJO9jjn0USZfpmAg5RfU5-R5BCKYjDFHNL8j3oI3VmVAjEQxLmPRq3uGzQw5w6t8PuBGy-A5KRzjv_7EBA==" organization = "Company" namepass = ["measurement1"] bucket = "BUCKET_TEST" ``` So please, please any hint and clear answers with vallid telegraf.conf file are appreciated. Regards Tom ---
**Author:** ![Anaisdg](https://sea1.discourse-cdn.com/flex023/user_avatar/community.influxdata.com/anaisdg/32/6401_2.png) [@Anaisdg](https://community.influxdata.com/u/Anaisdg)\ **Post date:** [March 19, 2023, 9:16pm UTC](https://community.influxdata.com/t/mqtt-telegraf-json-trailing-null-character-payload-parsing-problem/29111/2 "2023-03-19T21:16:32Z")
Hello @Tom999, I like to use the `--test` flag to see what the resulting line protocol looks like and then fix my config based off of that. As well as setting `debug=true` in the agent portion of the config. > **[Telegraf commands and flags | Telegraf 1.21 Documentation](https://docs.influxdata.com/telegraf/v1.21/administration/commands/)** > > The telegraf command starts and runs all the processes necessary for Telegraf to function. Can you please use that and share the output? ---
**Author:** ![Tom999](https://avatars.discourse-cdn.com/v4/letter/t/8797f3/32.png) [@Tom999](https://community.influxdata.com/u/Tom999)\ **Post date:** [March 23, 2023, 10:21am UTC](https://community.influxdata.com/t/mqtt-telegraf-json-trailing-null-character-payload-parsing-problem/29111/3 "2023-03-23T10:21:36Z")
OK, I managed to fix it on the PLC level to send valid JSON. Thank you.