# opentelemetry_exporter
The OpenTelemetry Protocol exporter for use with the [OpenTelemetry
Collector](https://github.com/open-telemetry/opentelemetry-collector). The
version of this Application does not track the supported version of the
OpenTelemetry Protocol (OTLP). The currently used version of the [OTLP protobufs
is v0.11.0](https://github.com/open-telemetry/opentelemetry-proto/tree/v0.11.0).
Currently only supports the Tracer protocol using either GRPC or Protobuffers over HTTP1.1.
## Configuration
By default the exporter will use HTTP to export protobuf encoded Spans to
`http://localhost:4318/v1/traces`.
Available configuration keys:
- `otlp_endpoint`: The URL to send traces and metrics to, for traces the path `v1/traces` is appended to the path in the URL.
- `otlp_traces_endpoint`: URL to send only traces to. This takes precedence for exporting traces and the path of the URL is kept as is, no suffix is appended.
- `otlp_headers`: List of additional headers (`[{unicode:chardata(), unicode:chardata()}]`) to add to export requests.
- `otlp_traces_headers`: Additional headers (`[{unicode:chardata(), unicode:chardata()}]`) to add to only trace export requests.
- `otlp_protocol`: The transport protocol, supported values: `grpc` and `http_protobuf`. Defaults to `http_protobuf`.
- `otlp_traces_protocol`: The transport protocol to use for exporting traces, supported values: `grpc` and `http_protobuf`. Defaults to `http_protobuf`.
- `otlp_compression`: Compression type to use, supported values: `gzip`. Defaults to no compression.
- `otlp_traces_compression`: Compression type to use for exporting traces, supported values: `gzip`. Defaults to no compression.
- `ssl_options`: See [below](#ssl-options).
```erlang
{opentelemetry_exporter,
[{otlp_protocol, grpc},
{otlp_compression, gzip},
{otlp_endpoint, "https://api.honeycomb.io:443"},
{otlp_headers, [{"x-honeycomb-dataset", "experiments"}]}]}
```
An Elixir release uses `runtime.exs`:
```elixir
config :opentelemetry_exporter,
otlp_protocol: :grpc,
otlp_compression: :gzip,
otlp_endpoint: "https://api.honeycomb.io:443",
otlp_headers: [{"x-honeycomb-dataset", "experiments"}]
```
Furthermore, you need to configure Elixir apps to load `opentelemetry_exporter` before `opentelemetry`
itself, for more information see https://github.com/open-telemetry/opentelemetry-erlang#design.
### SSL options
The default SSL options for HTTPS requests are set using
[tls_certificate_check](https://hex.pm/packages/tls_certificate_check). This
package also provides the [CA certificates from Mozilla](https://curl.se/docs/caextract.html).
The user can override these options either as part of the endpoint or for all
endpoints used by the exporter with the Application environment variable
`ssl_options`:
```erlang
{opentelemetry_exporter,
[{otlp_endpoint, "https://example.com:4318"},
{ssl_options, [{cert, "..."}, {key, "..."}]}]}
```
```elixir
config :opentelemetry_exporter,
otlp_endpoint: "https://example.com:4318",
ssl_options: [cert: "...", key: "..."]
```
See [secure coding with
inets](https://erlef.github.io/security-wg/secure_coding_and_deployment_hardening/inets)
for more information on securing HTTP requests in Erlang.
### OS Environment
Lastly, configuring the exporter can be done with OS environment variables,
which take precedence:
- `OTEL_EXPORTER_OTLP_ENDPOINT`: The URL to send traces and metrics to, for traces the path `v1/traces` is appended to the path in the URL.
- `OTEL_EXPORTER_OTLP_TRACES_ENDPOINT`: URL to send only traces to. This takes precedence for exporting traces and the path of the URL is kept as is, no suffix is appended.
- `OTEL_EXPORTER_OTLP_HEADERS`: List of additional headers to add to export requests.
- `OTEL_EXPORTER_OTLP_TRACES_HEADERS`: Additional headers to add to only trace export requests.
- `OTEL_EXPORTER_OTLP_PROTOCOL`: The transport protocol to use, supported values: `grpc` and `http_protobuf`. Defaults to `http_protobuf`
- `OTEL_EXPORTER_OTLP_TRACES_PROTOCOL`: The transport protocol to use for exporting traces, supported values: `grpc` and `http_protobuf`. Defaults to `http_protobuf`.
- `OTEL_EXPORTER_OTLP_COMPRESSION`: Compression to use, supported value: gzip. Defaults to no compression.
- `OTEL_EXPORTER_OTLP_TRACES_COMPRESSION`: Compression to use when exporting traces, supported value: gzip. Defaults to no compression.
Example usage of setting the environment variables:
```
OTEL_EXPORTER_OTLP_TRACES_ENDPOINT=https://api.honeycomb.io:443
OTEL_EXPORTER_OTLP_TRACES_PROTOCOL=grpc
OTEL_EXPORTER_OTLP_TRACES_COMPRESSION=gzip
OTEL_EXPORTER_OTLP_TRACES_HEADERS=x-honeycomb-team=<HONEYCOMB API TOKEN>,x-honeycomb-dataset=experiments
```
### Options to span processor
In addition to using the environment variables the exporter accepts a map of
arguments. The argument to the exporter's `init` function can be configured as
part of the Span Processor (simple or batch) in the OpenTelemetry application
environment.
For an Erlang release in `sys.config`:
```erlang
{opentelemetry,
[{processors,
[{otel_batch_processor,
#{exporter => {opentelemetry_exporter, #{endpoints =>
["http://localhost:9090"],
headers => [{"x-honeycomb-dataset", "experiments"}]}}}}]}]}
```
The default protocol is `http_protobuf`, to override this and use grpc add
`protocol` to the config map:
```erlang
{opentelemetry,
[{processors,
[{otel_simple_processor,
#{exporter => {opentelemetry_exporter, #{protocol => grpc,
endpoints => ["http://localhost:9090"],
headers => [{"x-honeycomb-dataset", "experiments"}]}}}}]}]}
```
In Elixir, you can use `config.exs` or `runtime.exs`:
```elixir
config :opentelemetry, :processors,
otel_batch_processor: %{
exporter: {:opentelemetry_exporter, %{endpoints: ["http://localhost:9090"],
headers: [{"x-honeycomb-dataset", "experiments"}]}}
}
```
To explicitly disable exporting spans, the `traces_exporter` can be set to `none` in the
`opentelemetry` config:
```erlang
{opentelemetry, [{traces_exporter, none}]}
```
```elixir
config :opentelemetry, traces_exporter: :none
```
#### The configuration map
The second element of the configuration tuple is a configuration map. It can contain the following keys:
- `protocol` - one of: `http_protobuf`, `grpc` or `http_json`. Defaults to `http_protobuf`. `http_json` is not implemented yet.
- `endpoints` - A list of endpoints to send traces to. Can take one of the forms described below. By default, exporter sends data to `http://localhost:4318`.
- `headers` - a list of headers to send to the collector (i.e `[{<<"x-access-key">> <<"secret">>}]`). Defaults to an empty list.
- `compression` - an atom. Setting it to `gzip` enables gzip compression.
- `ssl_options` - a list of SSL options. See Erlang's [SSL docs](https://www.erlang.org/doc/man/ssl.html#TLS/DTLS%20OPTION%20DESCRIPTIONS%20-%20CLIENT) for what options are available.
### Upgrading OpenTelemetry Protos
The protos are in a separate repository,
[opentelemetry-proto](https://github.com/open-telemetry/opentelemetry-proto/),
and used as a submodule in this repo. To update the Erlang protobuf modules and
GRPC client first update the submodule and then use the [rebar3 grpcbox
plugin](https://github.com/tsloughter/grpcbox_plugin/) to generate the client:
```shell
$ pushd apps/opentelemetry_exporter/opentelemetry-proto
$ git fetch origin
$ git checkout <tag>
$ popd
# bug in grpcbox plugin means we need to delete _pb files first to regenerate them
$ rm ./apps/opentelemetry_exporter/src/opentelemetry_exporter_trace_service_pb.erl ./apps/opentelemetry_exporter/src/opentelemetry_exporter_metrics_service_pb.erl ./apps/opentelemetry_exporter/src/opentelemetry_exporter_logs_service_pb.erl
$ rebar3 grpc gen -t client
...
$ mv apps/opentelemetry_exporter/src/opentelemetry_proto_collector_trace_v_1_trace_service_client.erl apps/opentelemetry_exporter/src/opentelemetry_trace_service.erl
$ mv apps/opentelemetry_exporter/src/opentelemetry_proto_collector_logs_v_1_logs_service_client.erl apps/opentelemetry_exporter/src/opentelemetry_logs_service.erl
$ mv apps/opentelemetry_exporter/src/opentelemetry_proto_collector_metrics_v_1_metrics_service_client.erl apps/opentelemetry_exporter/src/opentelemetry_metrics_service.erl
```
Then open each moved module and fix the module name.
