buid: Bipartite Unique Identifier

15 November 2017

A BUID is a 128-bit unique ID composed of two 64-bit parts: shard and key.

It is not only a unique ID, but also contains the sharding information, so that the messages with the same BUID could be stored together within the same DB shard.

Also, when a message is stored in a shard, the shard part of the BUID can be trimmed off to save the space, and only the key part needs to be stored as the primary key.

Bigendian is chosen to make each part byte-wise lexicographic sortable.

The string representation uses basex 62 encoding.

How to Measure Response Time with Curl

20 June 2017
curl [args] --write-out "%{time_total}s" --output /dev/null --silent [URL] 

How to Delete a Git Branch

9 June 2017
git fetch       --prune  origin
git branch      --delete [branch-name]
git push origin --delete [branch-name]

A Single Command to Download a Website

9 April 2017
wget --recursive --level=2 --no-parent --no-clobber --convert-links --continue

How to Remove Old Kernels in Ubuntu

10 September 2016
sudo apt install byobu
sudo purge-old-kernels


Making Code Block Wrap in Jira

5 September 2016

It is a hack.

Set Jira Administration -> System -> Announcement Banner -> Announcement:

<style type="text/css">
pre {
    white-space: pre-wrap!important;

One-liner to check MongoDB Connections

2 September 2016
mongo --eval "JSON.stringify(db.currentOp(true))" | \
tail -n +3 | \
jq -r .inprog[].client | \
sed 's/\(.*\):.*/\1/' \
| sort | uniq -c | sort -nr
  • dump connection information in standard JSON format
  • remove MongoDB header
  • extract IP:port as a list
  • trim port
  • sort IPs by freqencies