chore: consolidate agent code for otlp

[duncanista]

Overview

Consolidates the OTLP agent code by merging grpc_agent.rs into agent.rs, eliminating ~280 lines of duplicated code. A single Agent struct now owns a shared TracePipeline and starts HTTP, gRPC, or both servers based on config.

Changes

• Introduced TracePipeline struct holding shared state (config, processor, trace channels, stats generator) with a process_and_send_traces method used by both HTTP and gRPC handlers
• TraceService (gRPC) is implemented directly on TracePipeline, removing the redundant OtlpGrpcService struct
• Agent now holds Option for http_port/grpc_port, spawning whichever protocols are configured
• Collapsed should_enable_otlp_http + should_enable_otlp_grpc into a single should_enable_otlp_agent
• Deleted grpc_agent.rs
• Simplified start_otlp_agent in main.rs: one Agent, one spawn

Bug fixes

• parse_port scheme handling — HTTP agent's split(':').nth(1) broke on endpoints with schemes like http://localhost:4318. Replaced with the gRPC version that strips http:///https:// prefixes and uses rsplit(':') for IPv6 support
• Empty trace check — HTTP handler checked size_of_val(&traces) == 0, which always evaluates to false (returns the 24-byte stack size of the Vec struct). Replaced with traces.iter().all(Vec::is_empty) in the shared pipeline

Tests

Merged and deduplicated parse_port tests (gained scheme-handling coverage), consolidated enablement tests into should_enable_otlp_agent. All 28 OTLP tests pass, zero clippy warnings.

[Copilot]

Pull request overview

Consolidates OTLP HTTP and gRPC agent implementations into a single Agent with a shared TracePipeline, removing the standalone grpc_agent.rs and reducing duplicated trace-processing logic.

Changes:

• Introduces TracePipeline shared between HTTP and gRPC, including a unified process_and_send_traces path.
• Implements OTLP gRPC TraceService directly on the shared pipeline and updates Agent to spawn HTTP, gRPC, or both based on config.
• Replaces separate enablement helpers with should_enable_otlp_agent, and simplifies OTLP agent startup in main.rs.

Reviewed changes

Copilot reviewed 3 out of 4 changed files in this pull request and generated 2 comments.

File	Description
bottlecap/src/otlp/mod.rs	Removes separate HTTP/gRPC enablement helpers in favor of should_enable_otlp_agent and updates tests.
bottlecap/src/otlp/grpc_agent.rs	Deletes the redundant gRPC agent implementation after consolidation.
bottlecap/src/otlp/agent.rs	Merges HTTP+gRPC handling into one agent with a shared pipeline; adds gRPC server startup and shared processing.
bottlecap/src/bin/bottlecap/main.rs	Switches OTLP startup to a single consolidated agent and enablement check.

Comments suppressed due to low confidence (1)

bottlecap/src/otlp/agent.rs:388

• For Protobuf error responses you are encoding tonic_types::Status (google.rpc.Status), but code is being set to the HTTP status code (e.g. 500). In OTLP, this code should be a gRPC/Google RPC code (e.g. INVALID_ARGUMENT, INTERNAL), not an HTTP status value. Map StatusCode to an appropriate tonic::Code/google::rpc::Code numeric value (or omit the Protobuf body on non-OTLP-protobuf errors).

                let status = ProtoStatus {
                    code: i32::from(status_code.as_u16()),
                    message: message.clone(),
                    details: vec![],
                };

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