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#574: add instructions about how to build with Bazel #747

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May 26, 2021
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#574: add instructions about how to build with Bazel #747

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#574: add instructions about how to build with Bazel
iblancasa May 13, 2021
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Merge branch 'main' into feature/574
maxgolov May 13, 2021
83b0044
Merge branch 'main' into feature/574
lalitb May 14, 2021
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Merge branch 'main' into feature/574
maxgolov May 20, 2021
d130452
fix markdown lint
lalitb May 25, 2021
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Merge branch 'main' into feature/574
lalitb May 26, 2021
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53 changes: 52 additions & 1 deletion INSTALL.md
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Expand Up @@ -134,4 +134,55 @@ target_link_libraries(foo PRIVATE ${OPENTELEMETRY_CPP_LIBRARIES})

## Build instructions using Bazel

TBD
### Prerequisites

- A supported platform (e.g. Windows, macOS or Linux).
Refer to [Platforms Supported](./README.md#supported-development-platforms)
for more information.
- A compatible C++ compiler supporting at least C++11.
Major compilers are supported.
Refer to [Supported Compilers](./README.md#supported-c-versions) for more information.
- [Git](https://git-scm.com/) for fetching opentelemetry-cpp source code from repository.
To install Git, consult the [Set up Git](https://help.github.com/articles/set-up-git/)
guide on GitHub.
- [Bazel](https://www.bazel.build/) for building opentelemetry-cpp API,
SDK with their unittests. We use 3.7.2 in our build system.
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@maxgolov maxgolov May 13, 2021 •
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Can we somehow omit 3.7.2. here. It's 10 seconds to follow the guidelines, even if we don't mention the version explicitly. Maybe suggesting to check what version is being used indirectly, by lookup up the file contents here:

opentelemetry-cpp/.bazelversion

Line 1 in 414a731

3.7.2

Something like: Please install the exact version of bazel mentioned in .bazelversion ?

mgolovanov@xps:/mnt/c/work/opentelemetry-cpp.main$ bazel build //...
ERROR: The project you're trying to build requires Bazel 3.7.2 (specified in /mnt/c/work/opentelemetry-cpp.main/.bazelversion), but it wasn't found in /usr/bin.

You can install the required Bazel version via apt:
  sudo apt update && sudo apt install bazel-3.7.2

Even if someone messes it up like I did, it takes 10 seconds to correct it - it even tells how to correct / install the right version. I think we might be upgrading the Bazel soon anyways, so probably not worth it anchoring to specific version in the how-to doc.

@jsuereth

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Yeah, I think we should likely encourage folks to install/use Bazelisk, as it can auto-correct versions on the fly and leads to a much smoother developer experience when you move back/forth between different bazel projects.


To install Bazel, consult the [Installing Bazel](https://docs.bazel.build/versions/3.7.0/install.html) guide.

### Building as Standalone Bazel Project
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Isn't this more useful for contributors, less so installation?

E.g. I'd expect most bazel users to want to do something like pulling in OTel CPP via WORKSPACE definition using http_archive or some other mechanism.

Not that this isn't useful, just not how I'd expect folks to consume.

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e.g. https://github.com/GoogleCloudPlatform/opentelemetry-operations-cpp/blob/main/WORKSPACE#L46

Or you can see:

https://github.com/googleapis/google-cloud-cpp/pull/1230/files for an example usage of OpenCensus C++

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This is a good point. We can have a separate section (say) "Incorporating Into An Existing Project", which includes the above-mentioned steps, similar to how we document for CMake.


1. Getting the opentelementry-cpp source:

```console
# Change to the directory where you want to create the code repository
$ cd ~
$ mkdir source && cd source
$ git clone https://github.com/open-telemetry/opentelemetry-cpp
Cloning into 'opentelemetry-cpp'...
...
Resolving deltas: 100% (3225/3225), done.
$
```

2. Download the dependencies and build the source code:

```console
$ bazel build //...
bazel build -- //... -//exporters/otlp/... -//exporters/prometheus/...
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@maxgolov maxgolov May 13, 2021 •
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Technically the exclusion here -//exporters/otlp/... - isn't right. It all builds in its entirety right now, including otlp - which is going to be the main thing. Helper script for windows:

opentelemetry-cpp/tools/build-bazel.cmd

Line 4 in 414a731

bazel.exe build %* //...

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How about just invoke tools/buildbazel.cmd here which will keep both consistent?

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Maybe we need to add a script for Linux then, like tools/build-bazel.sh . But I actually like this document too.

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Suggested change
bazel build -- //... -//exporters/otlp/... -//exporters/prometheus/...
bazel build //...

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@maxgolov maxgolov May 13, 2021 •
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OTLP-gRPC takes forever to build though 😄 (293s total on my docker container with WSL2)

Extracting Bazel installation...
Starting local Bazel server and connecting to it...
INFO: Analyzed 121 targets (98 packages loaded, 3815 targets configured).
INFO: Found 121 targets...
INFO: From Compiling sdk/src/trace/tracer_context.cc:
...

```

4. Once Bazel tests are built, run them with `bazel test //...` command

```console
$ bazel test //...
```

5. The build artifacts will be located under `bazel-bin`