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Re: Bootstrapping Beam's Job Server

Thanks Henning and Thomas. It looks like

a) we want to keep the Docker Job Server Docker container and rely on
spinning up "sibling" SDK harness containers via the Docker socket. This should require little changes to the Runner code.

b) have the InProcess SDK harness as an alternative way to running user
code. This can be done independently of a).

Thomas, let's sync today on the InProcess SDK harness. I've created a
JIRA issue: https://issues.apache.org/jira/browse/BEAM-5187


On 21.08.18 00:35, Thomas Weise wrote:
The original objective was to make test/development easier (which I think is super important for user experience with portable runner).

From first hand experience I can confirm that dealing with Flink clusters and Docker containers for local setup is a significant hurdle for Python developers.

To simplify using Flink in embedded mode, the (direct) process based SDK harness would be a good option, especially when it can be linked to the same virtualenv that developers have already setup, eliminating extra packaging/deployment steps.

Max, I would be interested to sync up on what your thoughts are regarding that option since you mention you also started to work on it (see previous discussion [1], not sure if there is a JIRA for it yet). Internally we are planning to use a direct SDK harness process instead of Docker containers. For our specific needs it will works equally well for development and production, including future plans to deploy Flink TMs via Kubernetes.


[1] https://lists.apache.org/thread.html/d8b81e9f74f77d74c8b883cda80fa48efdcaf6ac2ad313c4fe68795a@%3Cdev.beam.apache.org%3E

On Mon, Aug 20, 2018 at 3:00 PM Maximilian Michels <mxm@xxxxxxxxxx <mailto:mxm@xxxxxxxxxx>> wrote:

    Thanks for your suggestions. Please see below.

     > Option 3) would be to map in the docker binary and socket to allow
     > the containerized Flink job server to start "sibling" containers on
     > the host.

    Do you mean packaging Docker inside the Job Server container and
    mounting /var/run/docker.sock from the host inside the container? That
    looks like a bit of a hack but for testing it could be fine.

     > notably, if the runner supports auto-scaling or similar non-trivial
     > configurations, that would be difficult to manage from the SDK side.

    You're right, it would be unfortunate if the SDK would have to deal with
    spinning up SDK harness/backend containers. For non-trivial
    configurations it would probably require an extended protocol.

     > Option 4) We are also thinking about adding process based SDKHarness.
     > This will avoid docker in docker scenario.

    Actually, I had started implementing a process-based SDK harness but
    figured it might be impractical because it doubles the execution path
    for UDF code and potentially doesn't work with custom dependencies.

     > Process based SDKHarness also has other applications and might be
     > desirable in some of the production use cases.

    True. Some users might want something more lightweight.