• create a collection with 100 documents of 1 MB each
• begin tcpdump capture
• do a collection scan
• end tcpdump capture
• create playback file from the tcpdump capture using the --gzip option

              mongoreplay record -f $pcap -p $bson
  

The resulting file seems to be truncated:

• mongoreplay monitor --gzip quits early and complains

  2016/10/20 12:05:32 OpChan: ReadDocument Error: unexpected EOF
  

• gunzip reports "unexpected end of file"