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Change architecture of Workers pool #329

Merged
merged 9 commits into from
Oct 17, 2022
Merged

Change architecture of Workers pool #329

merged 9 commits into from
Oct 17, 2022

Commits on Oct 17, 2022

  1. fix: small performance improvement 

    Do not duplicate in memory the contents of a Wasm module, just to read
its metadata.

Signed-off-by: Flavio Castelli <[email protected]>
    @flavio
    flavio committed Oct 17, 2022
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  2. refactor: remove utils module 

    Small refactoring, consolidate methods and functions inside of the
`settings` module.

Signed-off-by: Flavio Castelli <[email protected]>
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    flavio committed Oct 17, 2022
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  3. fix: update to latest Burrego release 

    The latest Burrego releases breaks some APIs.

Signed-off-by: Flavio Castelli <[email protected]>
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    flavio committed Oct 17, 2022
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  4. fix: optimize policies download 

    The same policy can be instantiated multiple times. Prior to this
commit, the Downloader would download and verify the same WebAssembly module
over and over again.

Now the Download avoids doing that.

Moreover, prior to this commit, the code mutated the list of policies
provided as a parameter. That was done to add the local path to the
WebAssembly module. The new code avoids doing this mutation, which was a
bit ugly.

Signed-off-by: Flavio Castelli <[email protected]>
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    flavio committed Oct 17, 2022
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  5. remove utils from main.rs 

    Signed-off-by: Flavio Castelli <[email protected]>
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  6. together with downloader ref 

    Signed-off-by: Flavio Castelli <[email protected]>
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  7. refactor: update internal communication struct 

    Ensure the worker_pool receives the list of fetched policies.
This is needed because now the `settings::Policy` structs do no
longer have an attribute that holds this information. See previous
commit.

Signed-off-by: Flavio Castelli <[email protected]>
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    flavio committed Oct 17, 2022
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  8. refactor: reorganize workers 

    This is a big refactoring of the WorkerPool and the Worker structs.

The major changes done to WorkerPool:

* Perform the validation of policies settings only once per policy.
Prior to that, each worker validated the settings of all the policies.
* Precompile all the WebAssembly modules once, then give the precompiled
  modules to the workers. This reduces the bootstrap time **a lot**.

About the latter point, creating a `wasmtime::Module` by reading the
contents of the `.wasm` file is an expensive operation. Prior to that,
the same WebAssembly module was compiled by each worker.

Note, we cannot rely on Wasmtime `cache` feature because, given the number of
workers we start, there would be quite some resource contention among
them.

Changes done to the Worker:

* Create one single `wasmtime::Engine` to be shared among all the
  Modules hosted by the Worker. This reduces resource usage and is
  needed to implement the "limit execution time of the policies"
  feature.
* Instantiate the `wasmtime::Module` instances by using the precompiled
  objects prepared by the WorkerPool. This saves an insane amount of
  time at bootstrap time
* Do not perform settings validation anymore. They have already been
  validated prior to the creation of the Worker

Signed-off-by: Flavio Castelli <[email protected]>
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    flavio committed Oct 17, 2022
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  9. Update dependencies 

    Use latest version of policy_evaluator, plus require the rayon crate
which is now being used by the worker pool.

Signed-off-by: Flavio Castelli <[email protected]>
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    flavio committed Oct 17, 2022
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