How to troubleshoot "write on backend 0 failed"

Hi All,

We are using pgpool 3.6.1 with two nodes in the cluster. We are seeing
frequent occurrences where one node will be marked as offline.

When this occurs we are seeing the following statements in our logs.

2017-02-09 09:45:38: pid 12125: WARNING: write on backend 0 failed with
error :"Success"
2017-02-09 09:45:38: pid 12125: DETAIL: while trying to write data from
offset: 0 wlen: 5

How do we troubleshoot the issue?

From looking at the source, the message appears to be generated from
pool_stream.c:pool_flush_it().

Based on the fact that the strerr() returns "Success", did anything
actually go wrong? What if the write() function simply returned 0 bytes
written? That's not necessarily an error is it?

Thanks in advance for your help,

Dave