I was figuring out how to run existing models. Because I am no expert in Machine Learning.
I looked at how others are doing it, Tensorflow Serving, etc. I wished Elixir had something like that.
Lo and behold: Bumblebee. 
Machine learning serving from the comfort of Elixir.
How are people so awesome?!?
Thank you @josevalim.
No surprise, image classification would be a great addition to image but for some reason I can’t fathom, starting up Nx.Serving is failing with:
06:30:13.408 [notice] Application image exited: exited in: Image.Application.start(:normal, [])
** (EXIT) exited in: GenServer.call(EXLA.Client, {:client, :host, [platform: :host]}, :infinity)
** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started
Which suggests there is a failure starting EXLA.Client.
If I don’t configure EXLA then the app starts fine. But no surprise - the binary backend isn’t suited to this kind of work and I lose patience after 5 minutes of a test run 
Any help would be appreciated - I’m pretty sure this is a stupid user error. Here’s the relevant info: (Mac ARM, OTP 25, Elixir 1.14)
# Image.Application
defmodule Image.Application do
@moduledoc false
use Application
def start(_type, _args) do
Supervisor.start_link(
[
{Nx.Serving, serving: Image.Classification.serving(), name: Image.Serving, batch_timeout: 100}
],
strategy: :one_for_one
)
end
end
# Image.Classification
defmodule Image.Classification do
alias Vix.Vips.Image, as: Vimage
def serving(model \\ "microsoft/resnet-50", featurizer \\ "microsoft/resnet-50") do
{:ok, model_info} = Bumblebee.load_model({:hf, model})
{:ok, featurizer} = Bumblebee.load_featurizer({:hf, featurizer})
Bumblebee.Vision.image_classification(model_info, featurizer,
top_k: 1,
compile: [batch_size: 10],
defn_options: [compiler: EXLA]
)
end
def classify(%Vimage{} = image) do
with {:ok, binary} <- Image.to_nx(image) do
Nx.Serving.batched_run(Image.Serving, binary)
end
end
end
# mix.exs
defp deps do
[
...
# For NX interchange and
# Bumblebee for image classification
if(otp_release() >= 24, do: [
{:nx, "~> 0.4.1", optional: true},
{:bumblebee, "~> 0.1.0", optional: true},
{:exla, "~> 0.4.1", optional: true}
]),
...
]
|> List.flatten()
|> Enum.reject(&is_nil/1)
end
# dev.exs
config :nx,
default_backend: EXLA.Backend
It looks like the EXLA client process died, usually this happens when startup fails like when there is a linking error or something in the NIF. Is there any additional error messages before you hit this point?
@seanmor5 thanks for the assist. No other errors. I tried starting it manually from iex and perhaps the following helps a little?
Interactive Elixir (1.14.0) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> Supervisor.start_link([{Nx.Serving, serving: Image.Classification.serving(), name: Image.Serving, batch_timeout: 100}])
** (exit) exited in: GenServer.call(EXLA.Client, {:client, :host, [platform: :host]}, :infinity)
** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started
(elixir 1.14.0) lib/gen_server.ex:1027: GenServer.call/3
(exla 0.4.1) lib/exla/backend.ex:147: EXLA.Backend.client_and_device_id/1
(exla 0.4.1) lib/exla/backend.ex:44: EXLA.Backend.from_binary/3
(bumblebee 0.1.0) lib/bumblebee/conversion/pytorch/loader.ex:71: Bumblebee.Conversion.PyTorch.Loader.object_resolver/1
(unpickler 0.1.0) lib/unpickler.ex:828: Unpickler.resolve_object/2
(unpickler 0.1.0) lib/unpickler.ex:818: anonymous fn/2 in Unpickler.finalize_stack_items/2
(elixir 1.14.0) lib/map.ex:924: Map.get_and_update/3
iex:1: (file)
Just to try to dive one level further I manually started EXLA.Client without error but of course then Nx.Serving won’t start:
iex(2)> Supervisor.start_link([EXLA.Client], strategy: :one_for_one)
{:ok, #PID<0.18669.0>}
iex(3)> Supervisor.start_link([{Nx.Serving, serving: Image.Classification.serving(), name: Image.Serving, batch_timeout: 100}])
2022-12-10 12:58:37.980550: I tensorflow/compiler/xla/pjrt/tfrt_cpu_pjrt_client.cc:214] TfrtCpuClient created.
** (exit) exited in: GenServer.call(EXLA.Defn.LockedCache, {:lock, {#Function<88.82845959/1 in EXLA.Backend.reshape/2>, [{{:f, 32}, {2048000}, [nil]}]}}, :infinity)
** (EXIT) no process: the process is not alive or there's no process currently associated with the given name, possibly because its application isn't started
(elixir 1.14.0) lib/gen_server.ex:1027: GenServer.call/3
Oh I didn’t realize you were starting it up in this way. EXLA spins up a few processes: nx/exla/lib/exla/application.ex at main · elixir-nx/nx · GitHub
That you will need to start to work with it
That was just a test to see if EXLA.Client would start. My configuration is, as best I can tell, exactly the same as that in the demo Phoenix app. It seems EXLA.Client can start (just as a test). But when starting Nx.Servering as a supervised child, the error in the original message occurs. I’m definitely stuck.
Just to make sure I force-compiled exla again and no errors:
kip@Kips-MacBook-Pro image % mix deps.compile exla --force
==> exla
Unpacking /Users/kip/Library/Caches/xla/0.4.1/cache/download/xla_extension-aarch64-darwin-cpu.tar.gz into /Users/kip/Development/image/deps/exla/cache
c++ -fPIC -I/Users/kip/.asdf/installs/erlang/25.1/erts-13.1/include -Icache/xla_extension/include -O3 -Wall -Wno-sign-compare -Wno-unused-parameter -Wno-missing-field-initializers -Wno-comment -shared -std=c++17 -w -DLLVM_ON_UNIX=1 c_src/exla/exla.cc c_src/exla/exla_nif_util.cc c_src/exla/exla_client.cc -o cache/libexla.so -Lcache/xla_extension/lib -lxla_extension -flat_namespace -undefined suppress
install_name_tool -change bazel-out/darwin_arm64-opt/bin/tensorflow/compiler/xla/extension/libxla_extension.so @loader_path/xla_extension/lib/libxla_extension.so -change bazel-out/darwin-opt/bin/tensorflow/compiler/xla/extension/libxla_extension.so @loader_path/xla_extension/lib/libxla_extension.so cache/libexla.so
Compiling 21 files (.ex)
Generated exla app
I noticed you have exla as an optional dep. I don’t remember off the top of my head but optionals may not be automatically started. Try Application.ensure_all_started(:exla) before the call site.
@wojtekmach thank you so much. As I suspected, totally a user error and a pretty silly one! Starts up perfectly fine now. Sorry for the noise. Very excited by what this represents for several of my libraries!
iex> Image.open!("./test/support/images/lamborghini-forsennato-concept.jpg")
...> |> Image.Classification.classify()
%{predictions: [%{label: "sports car, sport car", score: 0.9962735176086426}]}