Legacy-.*

In the middle of an otherwise pleaseant conversation recently, the other person suddenly burst out that “Varnish was part of our legacy software.”

That stung a bit.

But fair enough: They have been running varnish since 2009 or so.

Neither Raymond’s “New Hacker’s Dictionary”, nor the legacy publication it tried to replace, Kelly-Bootle’s “The Devils DP Dictionary”, define “legacy software”. The former because the collective “we” did not bother with utter trivialities such as invoicing, the latter because back then people didnt abandon software.

Tomorrow I will be sitting in a small hut in the middle of a field, trying to figure out what somebody could possibly have been thinking about, when 10 years ago they claimed to implement “V.42” while also using their own HDLC frame layout.

“V.42” and “HDLC” are also a legacy at this point, but chances are you have used it: That was the hot way to do error-correction on modems, when dialing into a BBS or ISP in the 1990ies.

I guess I should say “legacy-modems” ?

Big-endianess, storing the bytes the sensible way for hex-dumps, is rapidly becoming legacy, as the final old HP and SUN irons are finally become eWaste.

Objectively there is no difference of merit between little-endian and big-endian, the most successful computers architectures of all time picked equally one or the other, and the consolidation towards little-endian is driven more by “It’s actually not that important” than by anything else.

But we still have a bit of code which cares about endianess in Varnish, in particular in the imported zlib code.

For a while I ran a CI client on a WLAN access point with a big-endian MIPS-processor. But with only 128MB RAM the spurious error rate caused too much noise.

Nothing has been proclaimed “Legacy” more often and with more force, than the IBM mainframe, but they are still around, keeping the books balanced, as they have for half a century.

And because they were born with variable length data types, IBM mainframes are big-endian, and because we in Varnish care about portability, you can also run Varnish Cache on your IBM mainframe: Thanks to Ingvar, there are “s390x” architecture Varnish packages if you need them.

So I reached out to IBM’s FOSS-outreach people and asked if we could borrow a cup of mainframe to run a CI-client, and before I knew it, the Varnish Cache Project had access to a virtual s390x machine somewhere in IBM’s cloud.

For once “In the Cloud” literally means “On somebody’s mainframe” :-)

I’m not up to date on IBM Mainframe technology, the last one I used was a 3090 in 1989, so I have no idea how much performance IBM has allocated to us, on what kind of hardware, or what it might cost.

But it runs a full CI iteration on Varnish Cache in 3 minutes flat, making it one of the fastest CI-clients we have.

Thanks IBM!

Poul-Henning, 2021-05-24