Buildkit无法正常运行：Jenkins代理Pod执行buildctl报错求助

问题背景 #

基于以下Dockerfile构建了Jenkins inbound agent + BuildKit镜像：

FROM jenkins/inbound-agent:alpine as jnlp

FROM moby/buildkit as buildkit

USER root

RUN apk update \
  && apk upgrade \
  && apk add --update openjdk11 tzdata curl unzip bash \
  && rm -rf /var/cache/apk/*

COPY --from=jnlp /usr/local/bin/jenkins-agent /usr/local/bin/jenkins-agent
COPY --from=jnlp /usr/share/jenkins/agent.jar /usr/share/jenkins/agent.jar

ENTRYPOINT ["/usr/local/bin/jenkins-agent"]

该镜像在Kubernetes中以Pod形式运行正常，但执行buildctl构建命令时报错：

+ buildctl build --frontend dockerfile.v0 --local 'context=.' --local 'dockerfile=.' --output 'type=image,name=docker.io/username/image'

错误信息：

error: listing workers for Build: failed to list workers: Unavailable: connection error: desc = "transport: error while dialing: dial unix /run/buildkit/buildkitd.sock: connect: no such file or directory"

Jenkins Helm Chart中BuildKit相关配置：

builkit:
    podName: buildkit
    customJenkinsLabels: buildkit
    image: "agent-buildkit"
    tag: "1.0"
    alwaysPullImage: true

问题原因 #

1. BuildKit守护进程未启动：镜像的ENTRYPOINT被替换为Jenkins agent的启动命令，导致buildkitd（BuildKit核心守护进程）没有运行，/run/buildkit/buildkitd.sock套接字文件自然不存在。
2. 进程管理缺失：未配置让buildkitd和Jenkins agent两个进程同时在Pod内运行，仅启动了Jenkins agent，BuildKit服务未就绪。

解决方案 #

需要修改Dockerfile，确保buildkitd和Jenkins agent能同时启动，且buildctl可正常连接到buildkitd。

方案1：用Supervisor管理多进程 #

修改Dockerfile如下：

FROM jenkins/inbound-agent:alpine as jnlp

FROM moby/buildkit:latest as buildkit

USER root

# 安装Supervisor用于进程管理
RUN apk update \
  && apk upgrade \
  && apk add --update openjdk11 tzdata curl unzip bash supervisor \
  && rm -rf /var/cache/apk/*

# 拷贝Jenkins agent文件
COPY --from=jnlp /usr/local/bin/jenkins-agent /usr/local/bin/jenkins-agent
COPY --from=jnlp /usr/share/jenkins/agent.jar /usr/share/jenkins/agent.jar

# 创建Supervisor配置目录
RUN mkdir -p /etc/supervisor.d/
# 拷贝Supervisor配置文件（需提前创建该文件）
COPY supervisord.conf /etc/supervisor.d/

# 设置Supervisor为ENTRYPOINT
ENTRYPOINT ["/usr/bin/supervisord", "-c", "/etc/supervisord.conf"]

配套的supervisord.conf文件内容：

[supervisord]
nodaemon=true

[program:buildkitd]
command=/usr/bin/buildkitd
autostart=true
autorestart=true
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0

[program:jenkins-agent]
command=/usr/local/bin/jenkins-agent
autostart=true
autorestart=true
stdout_logfile=/dev/stdout
stdout_logfile_maxbytes=0
stderr_logfile=/dev/stderr
stderr_logfile_maxbytes=0
environment=JENKINS_AGENT_WORKDIR=/home/jenkins/agent

方案2：自定义启动脚本后台启动buildkitd #

如果不想依赖Supervisor，可编写启动脚本：

FROM jenkins/inbound-agent:alpine as jnlp

FROM moby/buildkit:latest as buildkit

USER root

RUN apk update \
  && apk upgrade \
  && apk add --update openjdk11 tzdata curl unzip bash \
  && rm -rf /var/cache/apk/*

COPY --from=jnlp /usr/local/bin/jenkins-agent /usr/local/bin/jenkins-agent
COPY --from=jnlp /usr/share/jenkins/agent.jar /usr/share/jenkins/agent.jar

# 拷贝自定义启动脚本（需提前创建该文件）
COPY start-agent.sh /usr/local/bin/
RUN chmod +x /usr/local/bin/start-agent.sh

ENTRYPOINT ["/usr/local/bin/start-agent.sh"]

配套的start-agent.sh脚本内容：

#!/bin/bash

# 后台启动buildkitd
/usr/bin/buildkitd &

# 以exec方式启动Jenkins agent，保证信号能正确传递
exec /usr/local/bin/jenkins-agent "$@"

额外注意事项 #

• 若修改了buildkitd的套接字路径，需在buildctl命令中通过--addr参数指定，例如buildctl --addr unix:///custom/path/buildkitd.sock build ...
• 建议在Helm Chart中为该agent Pod配置足够的CPU和内存资源请求/限制，避免BuildKit因资源不足异常退出

内容的提问来源于stack exchange，提问作者raboy