This repository contains the OTLP protocol specification and the corresponding Language Independent Interface Types (.proto files).

The proto files can be consumed as GIT submodules or copied and built directly in the consumer project.

The compiled files are published to central repositories (Maven, ...) from OpenTelemetry client libraries.

See contribution guidelines if you would like to make any changes.

See additional requirements for OTLP/JSON wire representation here.

To generate the raw gRPC client libraries, use make gen-${LANGUAGE}. Currently supported languages are:

• cpp
• csharp
• go
• java
• objc
• openapi (swagger)
• php
• python
• ruby

1.0.0 and newer releases from this repository may contain unstable (alpha or beta) components as indicated by the Maturity table below.

(See Versioning and Stability for definition of maturity levels).

Components marked Stable provide the following guarantees:

• Field types, numbers and names will not change.
• Service names and service package names will not change.
• Service method names will not change. [from 1.0.0]
• Service method parameter names will not change. [from 1.0.0]
• Service method parameter types and return types will not change. [from 1.0.0]
• Service method kind (unary vs streaming) will not change.
• Names of messages and enums will not change. [from 1.0.0]
• Numbers assigned to enum choices will not change.
• Names of enum choices will not change. [from 1.0.0]
• The location of messages and enums, i.e. whether they are declared at the top lexical scope or nested inside another message will not change. [from 1.0.0]
• Package names and directory structure will not change. [from 1.0.0]
• optional and repeated declarators of existing fields will not change. [from 1.0.0]
• No existing symbol will be deleted. [from 1.0.0]

Note: guarantees marked [from 1.0.0] will go into effect when this repository is tagged with version number 1.0.0.

The following additive changes are allowed:

• Adding new fields to existing messages.
• Adding new messages or enums.
• Adding new choices to existing enums.
• Adding new choices to existing oneof fields.
• Adding new services.
• Adding new methods to existing services.

All the additive changes above must be accompanied by an explanation about how new and old senders and receivers that implement the version of the protocol before and after the change interoperate.

Sometimes we need to experiment with new components, for example to add a completely new signal to OpenTelemetry. In this case, to define new experimental components we recommend placing new proto files in a "development" sub-directory. Such isolated experimental components are excluded from above stability requirements.

We recommend using Development, Alpha, Beta, Release Candidate levels to communicate different grades of readiness of new components.

Experimental components may be removed completely at the end of the experiment, provided that they are not referenced from any Stable component.

Experiments which succeed, require a review to be marked Stable. Once marked Stable they become subject to the stability requirements.

New experimental fields or messages may be added in Development state to Stable components. The experimental fields and messages within Stable components are subject to the full stability requirements, and in addition, they must be clearly labeled as Development (or as any other non-Stable level) in the .proto file source code.

If an experiment concludes and the previously added field or message is not needed anymore, the field/message must stay, but it may be declared "deprecated". During all phases of experimentation it must be clearly specified that the field or message may be deprecated. Typically, deprecated fields are left empty by the senders and the recipients that participate in experiments must expect during all experimental phases (including after the experiment is concluded) that the experimental field or message has an empty value.

Experiments which succeed, require a review before the field or the message is marked Stable.

No guarantees are provided whatsoever about the stability of the code that is generated from the .proto files by any particular code generator.