inputs.tail can't read from named pipe

[phemmer]

Bug report

Relevant telegraf.conf:

[[inputs.tail]]
  files = ["/var/tmp/foo.fifo"]
  from_beginning = true
  data_format = "influx"

System info:

telegraf-1.0.1_7_g00637b3-0
CentOS/7

Steps to reproduce:

1. mkfifo /var/tmp/foo.fifo
2. Launch telegraf with above config

Expected behavior:

To tail the pipe

Actual behavior:

Doesn't tail the pipe

Additional info:

No error output is generated at all. Telegraf silently closes the file descriptor and does nothing.

[pid 27416] openat(AT_FDCWD, "/var/tmp/foo.fifo", O_RDONLY|O_CLOEXEC) = 4
[pid 27416] futex(0xc8200d9108, FUTEX_WAKE, 1) = 1
[pid 27420] <... futex resumed> )       = 0
[pid 27414] <... select resumed> )      = 0 (Timeout)
[pid 27416] futex(0x204db78, FUTEX_WAKE, 1 <unfinished ...>
[pid 27414] select(0, NULL, NULL, NULL, {0, 20} <unfinished ...>
[pid 27416] <... futex resumed> )       = 1
[pid 27420] futex(0xc8200f6108, FUTEX_WAKE, 1 <unfinished ...>
[pid 27418] <... futex resumed> )       = 0
[pid 27416] write(2, "2016/11/26 14:38:31 Input [tail] gathered metrics, (1m0s interval) in 28.988\302\265s\n", 80 <unfinished ...>
2016/11/26 14:38:31 Input [tail] gathered metrics, (1m0s interval) in 28.988µs
[pid 27414] <... select resumed> )      = 0 (Timeout)
[pid 27416] <... write resumed> )       = 80
[pid 27414] select(0, NULL, NULL, NULL, {0, 20} <unfinished ...>
[pid 27416] lseek(4, 0, SEEK_SET)       = -1 ESPIPE (Illegal seek)
[pid 27420] <... futex resumed> )       = 1
[pid 27419] <... futex resumed> )       = 0
[pid 27418] futex(0xc8200d8d08, FUTEX_WAIT, 0, NULL <unfinished ...>
[pid 27419] futex(0xc8200d8d08, FUTEX_WAKE, 1 <unfinished ...>
[pid 27420] futex(0xc8200d9108, FUTEX_WAIT, 0, NULL <unfinished ...>
[pid 27418] <... futex resumed> )       = -1 EAGAIN (Resource temporarily unavailable)
[pid 27419] <... futex resumed> )       = 0
[pid 27419] futex(0x204db78, FUTEX_WAIT, 0, {0, 199933916} <unfinished ...>
[pid 27418] futex(0xc8200d8d08, FUTEX_WAIT, 0, NULL <unfinished ...>
[pid 27416] write(2, "2016/11/26 14:38:31 Seeked /var/tmp/foo.fifo - &{Offset:0 Whence:0}\n", 81 <unfinished ...>
[pid 27414] <... select resumed> )      = 0 (Timeout)
2016/11/26 14:38:31 Seeked /var/tmp/foo.fifo - &{Offset:0 Whence:0}
[pid 27414] select(0, NULL, NULL, NULL, {0, 20} <unfinished ...>
[pid 27416] <... write resumed> )       = 81
[pid 27416] futex(0xc8200d8d08, FUTEX_WAKE, 1) = 0
[pid 27416] close(4)                    = 0

I suspect this can be fixed by not attempting to perform a seek if from_beginning = true.
It seems we also have an issue where the error is silently discarded.