Re: Reliable WAL file shipping over unreliable network

There seem to be 2 fundamental misunderstandings here:

1) That other processes cannot see data written to a file until it is flushed to disk; this is not true; while file data is still in file cache, it is visible to other processes.

2) That rsync writes the file on the destination directly; it does not; it writes into a temporary file and renames that file when it is complete.

> On Feb 28, 2018, at 10:53 AM, Nagy László Zsolt  wrote:
> 
> 
>> 
>> Just use "-ac”;  you want -c option to ensure no data corruption during the transfer.  Do not delete the file; let Postgres manage that.
>> 
>> Here is a snippet from I script I use for archiving.  You also want to make your script returns failure or success correctly.  
>> 
>> # SSH Command and options
>> SSH_CMD="ssh -o ServerAliveInterval=20 $ARCH_SERVER"
>> STS=3
>> 
>> OUTPUT=$(rsync -ac --rsync-path="mkdir -p $ARCH_DIR && rsync" $XLOGFILE $ARCH_SERVER:$ARCH_DIR/$WALFILE)
>> if [ $? == 0 ]; then 
>>    STS=0
>> fi
>> 
>> exit $STS
>> 

--
Scott Ribe
https://www.linkedin.com/in/scottribe/
(303) 722-0567