[Buildbot] #2956: Provide latent Docker build slave

[Buildbot trac]

#2956: Provide latent Docker build slave
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Reporter:  sa2ajj                 |       Owner:  Ben
    Type:  enhancement            |      Status:  assigned
Priority:  patches-accepted       |   Milestone:  0.9.+
 Version:  master                 |  Resolution:
Keywords:  docker, slave, latent  |
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Comment (by sa2ajj):

 I do not think we need to hardcode anything.

 A common Docker approach is to pass parameters via environment variables.
 In case of latent Docker slave, we'd have to pass 4 parameters (names are
 examples):

 * `BUILDBOT_MASTER_HOST`
 * `BUILDBOT_MASTER_PORT`
 * `BUILDBOT_SLAVE_NAME`
 * `BUILDBOT_SLAVE_PASSWORD`

 and modify `buildbot.tac` to use these parameters when they are present.

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Ticket URL: <http://trac.buildbot.net/ticket/2956#comment:10>
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