What is the difference between open-source with closed-source accessories, and crippleware? I think it depends on how people define the core functionality of software. Some might say that backup is core functionality for a database; and others would point to mysqldump and say that InnoDB isn’t crippleware as long as there is some alternative.

I think InnoDB is an interesting case that illustrates what can happen when commercial and GPL play together. Part of that story is the appearance of XtraBackup, an open-source competitor to InnoDB Hot Backup. Everyone’s subject to the rules of the game, unless they restrict the “core,” which would make it non-open-source to begin with.

Further Reading:

• Does MySQL really have an open-source business model?
• Xtrabackup is for InnoDB tables too, not just XtraDB
• Measuring open-source success by jobs
• What does an open source sales model look like?
• Making Maatkit more Open Source one step at a time

A short time ago in a galaxy nearby, Domas Mituzas wrote about contention profiling with GDB stack traces. Mark Callaghan found the technique useful, and contributed an awk script (in the comments) to aggregate stack traces and identify which things are blocking most threads. I’ve used it myself a time or five. But I’ve found myself wanting it to be fancier, for various reasons. So I wrote a little utility that can aggregate and pretty-print backtraces. It can handle unresolved symbols, and aggregate by only the first N lines of the stack trace. Here’s an example of a mysqld instance that’s really, really frozen up:

bt-aggregate -4 samples/backtrace.txt | head -n12
2396 threads with the following stack trace:
        #0  0x00000035e7c0a4b6 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
        #1  0x00000000005f2bd8 in open_table ()
        #2  0x00000000005f3fb4 in open_tables ()
        #3  0x00000000005f4247 in open_and_lock_tables_derived ()

4 threads with the following stack trace:
        #0  0x00000035e7c0a4b6 in pthread_cond_wait@@GLIBC_2.3.2 () from /lib64/libpthread.so.0
        #1  0x0000000000780099 in os_event_wait_low ()
        #2  0x000000000077de42 in os_aio_simulated_handle ()
        #3  0x000000000074a261 in fil_aio_wait ()

Further Reading:

• A script snippet to relative-ize numbers embedded in text
• A tweak to column alignment for the mext script
• GnuCash to MySQL export script
• Using Aspersa to capture diagnostic data
• The unexpected consequences of SELinux

seq 10 20 | xargs -n 1 -P 5 sleep

This will send a sequence of numbers to xargs, which will divide it into chunks of one argument at a time and fork off 5 parallel processes to execute each. You can see it in action:

$ ps -eaf | grep sleep
baron     5830  5482  0 11:12 pts/2    00:00:00 xargs -n 1 -P 5 sleep
baron     5831  5830  0 11:12 pts/2    00:00:00 sleep 10
baron     5832  5830  0 11:12 pts/2    00:00:00 sleep 11
baron     5833  5830  0 11:12 pts/2    00:00:00 sleep 12
baron     5834  5830  0 11:12 pts/2    00:00:00 sleep 13
baron     5835  5830  0 11:12 pts/2    00:00:00 sleep 14

There are basically unlimited uses for this!

Further Reading:

• Introducing MySQL Parallel Dump
• How to check and optimize MySQL tables in parallel
• Introducing MySQL Parallel Restore
• How I keep track of tasks
• How to read Linux’s /proc/diskstats easily