flume: no configuration found for this host

[#1]

i have configured a .conf file with source type "exec"

i am new to flume, want to set up the configuration and listen to the file in /root/data/data.log

but got the error

configration file:

a1.sources = r1
a1.sinks = k1
a1.channels = c1

# Describe/configure the source
a1.sources.r1.type = exec
a1.sources.r1.command=tail -F /root/data/data.log
a1.sources.r1.shell=/bin/sh -c

# Describe the sink
a1.sinks.k1.type = logger

# Use a channel which buffers events in memory
a1.channels.c1.type = memory

# Bind the source and sink to the channel
a1.sources.r1.channels = c1
a1.sinks.k1.channel = c1

received an error:

[#2]

2020-03-01 03:13:34,655 (conf-file-poller-0) [WARN - org.apache.flume.node.AbstractConfigurationProvider.getConfiguration(AbstractConfigurationProvider.java:138)] No configuration found for this host:$