OpenTelemetry Collector日志HTTP配置失效，请求协助排查

问题现象 #

指标与追踪可正常收集，但日志导出失败，报错如下：

grpc@v1.68.1/clientconn.go:1384 [core] [Channel #4 SubChannel #5]grpc: addrConn.createTransport failed to connect to {Addr: "loki:3100", ServerName: "loki:3100", }. Err: connection error: desc = "error reading server preface: http2: frame too large"   {"grpc_log": true}

配置信息 #

1. 服务端环境变量 #

- OTEL_LOGS_EXPORTER=otlp
- OTEL_EXPORTER_OTLP_LOGS_PROTOCOL=http/protobuf
- OTEL_EXPORTER_OTLP_LOGS_ENDPOINT=http://collector:4318/v1/logs

2. Collector配置 #

receivers:
  otlp:
    protocols:
      http:
        endpoint: collector:4318  
      grpc:
        endpoint: collector:4319  
  prometheus:
    config:
      scrape_configs:
        - job_name: "b2c-service-metric-otel"
          scrape_interval: 5s
          metrics_path: "/actuator/prometheus"
          static_configs:
            - targets:
                - "b2c-service:8081"

processors:
  batch:
    timeout: 30s

exporters:
  debug:
    verbosity: detailed
  otlp/tempo:
    endpoint: tempo:4317 
    compression: "gzip"
    tls:
      insecure: true 
  otlp/loki:
    #endpoint: loki:3100 
    endpoint: loki:3100 
    #endpoint: "grpc://loki:3100"  
    compression: "gzip"
    tls:
      insecure: true

service:
  pipelines:
    metrics: 
      receivers: [ otlp ]  
      processors: [ batch ]
      exporters: [ debug ]  
    traces:
      receivers: [otlp]
      processors: [batch]
      exporters: [otlp/tempo, debug]
    logs:
      receivers: [otlp]
      processors: [batch]
      exporters: [otlp/loki, debug]

问题原因 #

报错显示Collector尝试通过gRPC协议连接Loki的3100端口，但Loki的3100端口默认是HTTP协议监听端口，不支持gRPC通信，导致连接失败。

OTEL的otlp exporter默认使用gRPC协议，你仅在服务端指定了日志用HTTP/protobuf协议，但Collector的otlp/loki exporter未明确指定协议，因此默认走gRPC，与Loki的端口不匹配。

解决方案 #

修改Collector的otlp/loki exporter配置，明确指定使用HTTP/protobuf协议，并配置正确的Loki OTLP HTTP端点：

exporters:
  otlp/loki:
    endpoint: http://loki:3100/otlp/v1/logs
    protocol: http/protobuf
    compression: "gzip"
    tls:
      insecure: true

说明：

• protocol: http/protobuf 强制指定使用HTTP协议传输日志
• endpoint 改为Loki官方标准的OTLP HTTP端点（旧版本Loki可能为/v1/logs，可根据实际版本调整）

内容的提问来源于stack exchange，提问作者jinwoo