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Sean B. Palmer commented on COUCHDB-2248:
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The OED separates the sense of "mastering" from "master-slave" as follows:
(I) In the sense of mastering: master, n.1. 10. "b. an original (of a sound
recording, film, data file, etc.) from which copies may be made."
(II) In the sense of master-slave: master-slave adj., in master, n.1. "(a) gen.
involving a master and a slave; relating to masters and slaves; (b) chiefly
Electronics and Computing, designating or relating to a system in which one
component controls the behaviour of one or more other components."
CouchDB uses master in sense (I), not in sense (II). In fact, master-slave
should not apply, etymologically speaking, to database replication. As all of
the quotes in the OED show, since the c.1940s when the term was coined, the
meaning of master-slave in the technology sense has been when some component
"controls the behaviour of one or more other components".
The sense has now obviously been extended in colloquial usage at least to cover
database replication, since it is presently used in CouchDB. But the metaphor
makes sense only for the original meaning. A mechanism whose behaviour is
controlled by another mechanism is in a fairly literal "master-slave"
relationship, modulo the emotive elements of the term, whereas a database is
information, and does not actually perform the replication itself.
A better metaphor would be a 3D-printer bashing out copies (something that used
to be confined to the likes of Star Trek: TNG).
But this is mostly background. The main point that I want to draw attention to
here is that senses (I) and (II) are entirely separate. They come from separate
environments, they developed separately, and they have separate meanings.
The oldest dating for sense (I) is 1904. The oldest dating for sense (II) is
1940. So the concept of mastering emerged several decades before the concept of
master-slave. Not only that, but the former emerged in the context of
phonography, whereas the first recorded instance of the latter is made by a
famous horologist, Frank Hope-Jones. (Hope-Jones is also responsible for
inventing the Greenwich radio pips broadcast by the BBC.)
Django have gone with "primary-replica", subsequent to the suggestion of
"leader-follower". Both "primary" and "leader" are inferior to "master" in the
sense of mastering, sense (I), because mastering has the meaning of
inviolability as the version from which all copies are sourced. Neither
"leader" nor "primary" have this meaning.
On the other hand, "slave" is unreasonably senseless, and in master-slave the
term "master" is used in an entirely different sense, sense (II), from that
which is intended for CouchDB, which is sense (I). Therefore, from this point
of view, the term "slave" can be replaced. Programming is a very logical
discipline, but the use of "slave" is not logical.
Since a master database is either cloned or replicated, the nominal forms of
the verbs "clone" or "replicate" are entirely suitable, and a master-clone or
master-replica relationship is certainly more logical.
Earlier in this thread, however, Robert Newson commented that the "suggestion
to use 'replica' instead of slave is misguided. Both the 'master' and 'slave'
are replicas (it would not be an error to talk of a 'master replica' and a
'slave replica' in my opinion)."
This argument is stymied by the unusual tautology.
If "master-slave" is understood here in its etymologically and semantically
suspect sense of database replication, then just saying "master" instead of
"master replica" should be sufficient; and likewise with "slave". If, on the
other hand, the terms "master" and "slave" need to be used only as qualifiers
of "replica", then it is evidence that "master-slave" is not yet suitably
established for referring to databases.
So if you accept this argument, then "replica" is redundant and it can be used
in place of "slave". If you do not accept this argument, then "master-slave" is
even more semantically dubious than I have indicated, and the argument for
finding an alternative, whatever it may be, is furthered. The former of the two
scenarios, that "replica" is available for use as Alexander Shorin suggests, is
most likely.
I have shown that as "mastering" (sense I) is etymologically distinct to
"master" (sense II), there can be no reasonable moral objection to it. I have
also shown that as the meaning of sense I is superior to that of sense II in
the present context, there can be no reasonable nomenclatural objection to it.
The situation is reversed for "slave". It only appears in sense II, which has
contested moral integrity. Moreover, the metaphor does not really make sense,
whereas "replica" or "clone" certainly do. These terms are also compatible with
existing terminology. You should pick from these candidates.
> Replace "master" and "slave" terminology
> ----------------------------------------
>
> Key: COUCHDB-2248
> URL: https://issues.apache.org/jira/browse/COUCHDB-2248
> Project: CouchDB
> Issue Type: Bug
> Security Level: public(Regular issues)
> Components: Documentation
> Reporter: Noah Slater
> Priority: Trivial
>
> Inspired by the comments on this PR:
> https://github.com/django/django/pull/2692
> Summary is: `master` and `slave` are racially charged terms, and it would be
> good to avoid them. Django have gone for `primary` and `replica`. But we also
> have to deal with what we now call multi-master setups. I propose "peer to
> peer" as a replacement, or just "peer" if you're describing one node.
> As far as I can tell, the primary work here is the docs. The wiki and any
> supporting material can be updated after.
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