Isolated Node compatibility jobs on self-hosted Linux
自托管 Linux 上隔离的 Node 兼容性作业
The Node 22.19, 24.9, and 26 compatibility jobs consume hosted Linux minutes even when the repository has selected its existing self-hosted Linux pool. Moving version installers onto a persistent shared machine can create tool-directory collisions and accumulate generated cache files outside runner cleanup.
English
Problem
The Node 22.19, 24.9, and 26 compatibility jobs consume hosted Linux minutes even when the repository has selected its existing self-hosted Linux pool. Moving version installers onto a persistent shared machine can create tool-directory collisions and accumulate generated cache files outside runner cleanup.
Decision
CI applies the Linux failover variable to these three jobs, requiring a non-Dependabot author and a non-fork head repository matching the current repository. The standard hosted fallback remains available. These predicates constrain this job, not every workflow admitted to the pool. Both repository identity and fork status remain explicit to preserve its trust restriction if repository settings change; existing sibling selectors are outside this migration. The blacksmith failover value's branch drops those predicates: it targets ephemeral Blacksmith runners, so repository identity and fork status do not gate it (see the blacksmith failover leg note).
The temporary tool cache trades repeated Node downloads for isolation across concurrent runners and Node versions. A setup-node-only ESM preload assigns the cache inside the action process: the Actions runner overwrites reserved environment variables after reading step configuration. An executed path check rejects installations outside runner temp; compatibility processes do not inherit the preload. pnpm keeps its existing private setup destination and persistent content-addressed store. Compile caches and node-gyp headers use runner temp before the first pnpm invocation. No global Node symlink or system package changes are introduced. Hosted jobs retain their tool and package caching; self-hosted jobs do not restore or upload hosted package caches. The runner owns temporary-directory cleanup between jobs, and the shared image supplies native npm packages’ compiler and Python prerequisites.
The failover runbook remains the owner of repository trust and pool switching. The serial reference decision remains the owner of master scheduling. Neither decision is superseded beyond the compatibility jobs' runner selection; both remain active.
Alternatives considered
Keep all compatibility jobs hosted. This avoids extra shared-host load but continues paying for Linux runtime checks that do not require a different operating system or architecture.
Use the shared Node installation or global version-manager links. The jobs must run different Node releases concurrently. Mutable shared links would make the selected version depend on another job's timing.
Move the Python SDK job in the same change. Its setup-python installation and global pip installation of uv need separate isolation evidence. Its short hosted job is not required for the Node optimization.
Consequences
The pool receives three additional jobs per trusted PR; each retains gate concurrency one, including the build-backed Node 22 leg. The September 6 inventory reports 31 Linux registrations, not 31 independent machines. The shared VM's contention and download latency remain rollout risks; the variable preserves hosted recovery. Test inventory, check names, and master scheduling are unchanged.
Verification
The focused workflow regression executes the actual routing expressions and environment setup. A negative control removing the fork condition fails the hosted-fallback assertion. It checks Dependabot reruns by a maintainer, repository mismatch, fork flags, disabled variables, and runner-scoped cache paths.
Successful standby run 33984559660 at the implementation base supplies Linux Node 24.19.0 and Windows Node 24.20.0 baseline evidence. Linux job 101359402557 uses runner-specific temporary and tool directories on the data volume. Read-only capability probe 34012679056 (job 101431064925) reports Linux x64, 192 online logical CPUs, GCC/G++ 13.3, Make 4.3, and Python 3.12.3. Python 3.10 is absent, reinforcing the separate SDK provisioning requirement. PR run 34013779750 verifies Node 22.19.0, 24.9.0, and 26.8.1 on self-hosted Linux, including setup, executable-path checks, compatibility tests, and post actions. The executables reside under each runner’s _temp/node-compat-toolcache/node/<version>/x64/bin; the completed jobs take 228s, 94s, and 101s respectively. These observations establish version and path compatibility, not an exclusive-host capacity guarantee.
中文
问题
即使仓库已经选择现有的自托管 Linux 池，Node 22.19、24.9 和 26 兼容性作业仍消耗托管 Linux 分钟数。将版本安装器移到持久化共享机器上可能造成工具目录冲突，并让生成的缓存文件积累在运行器清理范围之外。
决策
CI 将 Linux 故障切换变量应用于这三个作业，要求作者不是 Dependabot，且非 fork 的头部仓库与当前仓库相同。标准托管回退仍然可用。这些条件约束本作业，而非所有可进入该池的工作流。仓库身份和 fork 状态均显式保留，以便在仓库设置改变时保持本作业的信任限制；现有兄弟选择器不属于本次迁移范围。blacksmith 故障切换取值下的分支放弃这些条件：它面向临时的 Blacksmith 运行器，因此仓库身份与 fork 状态不参与门控（见 blacksmith 故障切换支路笔记）。
临时工具缓存以重复下载 Node 为代价，换取并发运行器与 Node 版本之间的隔离。仅用于 setup-node 的 ESM 预加载模块 在 action 进程内指定缓存：Actions 运行器在读取步骤配置后会覆盖保留的环境变量。实际执行的路径检查拒绝运行器临时目录之外的安装；兼容性进程不继承预加载设置。pnpm 保留现有的私有安装目录和持久化内容寻址 store。编译缓存与 node-gyp 头文件在首次调用 pnpm 前就使用运行器临时目录。不引入全局 Node 符号链接或系统软件包变更。托管作业保留其工具与软件包缓存；自托管作业不恢复或上传托管软件包缓存。运行器负责作业之间的临时目录清理，共享镜像提供原生 npm 软件包所需的编译器和 Python 前置依赖。
故障切换手册 仍拥有仓库信任与池切换规则。串行参考决策 仍拥有 master 调度规则。除兼容性作业的运行器选择外，这两个决策都未被取代；两者均保持活跃。
曾考虑的替代方案
让所有兼容性作业保持托管。 这避免额外的共享主机负载，但继续为不需要不同操作系统或架构的 Linux 运行时检查付费。
使用共享 Node 安装或全局版本管理器链接。 这些作业必须并发运行不同的 Node 版本。可变的共享链接会使选中的版本取决于另一作业的时序。
在同一改动中迁移 Python SDK 作业。 其 setup-python 安装和通过全局 pip 安装 uv 需要单独的隔离证据。这个短暂的托管作业不是 Node 优化的必需部分。
后果
每个可信 PR（Pull Request）会为池增加三个作业；每个作业保留门禁并发度一，包括需要构建的 Node 22 条目。9 月 6 日的清单报告了 31 个 Linux 注册实例，而不是 31 台独立机器。共享虚拟机的资源争用和下载延迟仍是上线风险；变量保留托管恢复路径。测试清单、检查名称和 master 调度保持不变。
验证
聚焦的工作流回归测试 执行真实的路由表达式和环境设置。移除 fork 条件的负对照使托管回退断言失败。它检查维护者重跑 Dependabot PR、仓库不匹配、fork 标志、禁用变量以及运行器范围内的缓存路径。
实施基线上的成功热备运行 33984559660 提供 Linux Node 24.19.0 和 Windows Node 24.20.0 基线证据。Linux 作业 101359402557 使用数据卷上运行器专属的临时目录和工具目录。只读能力探测 34012679056 (job 101431064925) 报告 Linux x64、192 个在线逻辑 CPU、GCC/G++ 13.3、Make 4.3 和 Python 3.12.3。Python 3.10 缺失，进一步说明 SDK 需要单独配置。PR 运行 34013779750 验证了自托管 Linux 上的 Node 22.19.0、24.9.0 和 26.8.1，包括设置、可执行文件路径检查、兼容性测试和 post actions。可执行文件位于各运行器的 _temp/node-compat-toolcache/node/<version>/x64/bin 下；完成的作业分别耗时 228s、94s 和 101s。这些观测证明版本与路径兼容性，而非独占主机的容量保证。