telegraf file output failed to write message - fileoutputstream

Question

This is my /etc/telegraf/telegraf.conf file, section outputs.file:
[[outputs.file]]
files = ["stdout", "/home/zeinab/metrics.out"]
data_format = "influx"
But telegraf log (which are written in /var/log/syslog) shows error continuously:
Jan 15 12:14:33 ZiZi telegraf[19916]: kernel,host=ZiZi context_switches=9275452836i,boot_time=1515496651i,processes_forked=1203986i,interrupts=1381624861i 1516005867000000000
Jan 15 12:14:33 ZiZi telegraf[19916]: 2018-01-15T08:44:33Z E! Error writing to output [file]: failed to write message: kernel,host=ZiZi context_switches=9275452836i,boot_time=1515496651i,processes_forked=1203986i,interrupts=1381624861i 1516005867000000000
Jan 15 12:14:33 ZiZi telegraf[19916]: , invalid argument
EDIT 1:
The whole un-commented configs are:
[global_tags]
[agent]
interval = "10s"
round_interval = true
metric_batch_size = 1000
metric_buffer_limit = 10000
collection_jitter = "0s"
flush_interval = "10s"
flush_jitter = "0s"
precision = ""
debug = false
quiet = false
logfile = ""
hostname = ""
omit_hostname = false
[[outputs.influxdb]]
urls = ["udp://127.0.0.1:8089"] # UDP endpoint example
database = "telegraf" # required
[[outputs.elasticsearch]]
urls = [ "http://127.0.0.1:9200" ] # required.
timeout = "5s"
index_name = "telegraf-%Y.%m.%d" # required.
manage_template = true
template_name = "telegraf"
overwrite_template = false
[[outputs.file]]
files = ["stdout", "/home/zeinab/metrics.out"]
data_format = "influx"
[[inputs.cpu]]
percpu = true
totalcpu = true
collect_cpu_time = false
report_active = false
[[inputs.disk]]
ignore_fs = ["tmpfs", "devtmpfs", "devfs"]
[[inputs.diskio]]
[[inputs.kernel]]
[[inputs.mem]]
[[inputs.processes]]
[[inputs.swap]]
[[inputs.system]]
[[inputs.jolokia2_agent]]
urls = ["http://192.168.100.179:8778/jolokia"]
[[inputs.jolokia2_agent.metric]]
name = "heap_memory_usage"
mbean = "java.lang:type=Memory"
paths = ["HeapMemoryUsage"]
[[inputs.jolokia2_agent.metrics]]
name = "send_success"
mbean = "wr-core:type=monitor,name=execution"
paths = ["MessageSendSuccessCount"]
I start telegraf as a service:
service telegraf start