more tuneables for destinations
these new settings were previously hardcoded (to the values that are now the defaults):
connbuf=<int> connection buffer (how many metrics can be queued, not written into network conn). default 30k
iobuf=<int> buffered io connection buffer in bytes. default: 2M
spoolbuf=<int> num of metrics to buffer across disk-write stalls. practically, tune this to number of metrics in a second. default: 10000
spoolmaxbytesperfile=<int> max filesize for spool files. default: 200MiB (200 * 1024 * 1024)
spoolsyncevery=<int> sync spool to disk every this many metrics. default: 10000
spoolsyncperiod=<int> sync spool to disk every this many milliseconds. default 1000
spoolsleep=<int> sleep this many microseconds(!) in between ingests from bulkdata/redo buffers into spool. default 500
unspoolsleep=<int> sleep this many microseconds(!) in between reads from the spool, when replaying spooled data. default 10