Documentation
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Overview ¶
Package sysproxy chooses the proxy an outbound HTTP request goes through the way .NET, and so PowerShell, chooses it on the same host (ADR-0464).
Why ¶
Go's default transport reads only the HTTPS_PROXY family of variables. A Windows server is usually configured the other way: a PAC script or a proxy in Internet Options, set by group policy, and no variable at all. There every PowerShell a Worker starts finds the proxy and every Go Worker goes direct — into a firewall that drops the packets, so the request fails on a timeout rather than with a message. One host then has two network paths, and which one a task takes depends on the language its Worker is written in.
The choice, made once at startup ¶
- ATLAS_SYSTEM_PROXY=off keeps Go's own behaviour: the variables, nothing else.
- A proxy variable (HTTPS_PROXY, HTTP_PROXY, either case) wins, as it does in .NET, and Go's transport reads it as it always has.
- Otherwise, on Windows, the account's proxy settings as WinHTTP reports them: a PAC URL, automatic detection (WPAD), a manual proxy and its bypass list. That is what .NET's HttpWindowsProxy reads, and the rules below are its rules.
- Anywhere else, or with no settings, nothing changes.
The rules for one request ¶
Loopback and the host's own addresses never go through a proxy, whatever a PAC script says: a supervised Worker reaches its own server over 127.0.0.1, or over the address the server listens on. Auto-configuration, when set, is asked first and its answer is final, DIRECT included; when it cannot answer, the manual proxy applies with its bypass list; with neither, the request goes direct. Auto-detection that found nothing is not tried again for two minutes, because WPAD discovery can take seconds. An answer is believed for five minutes per scheme, host and port; a fallback after a failure for thirty seconds, so a passing PAC outage does not pin a host to the wrong route. Only the first proxy of a list is used: Go's transport takes one per request, where .NET fails over along the list.
Index ¶
Constants ¶
const EnvSwitch = "ATLAS_SYSTEM_PROXY"
EnvSwitch turns the Windows settings off: off, false, 0 or no keeps Go's default.
Variables ¶
This section is empty.
Functions ¶
func Install ¶
Install points http.DefaultTransport's proxy at the choice described in the package documentation, and reports which it made and the settings it follows. Call it once at startup, before anything clones the default transport.
func InstallAndLog ¶ added in v0.25.0
InstallAndLog makes this process's outbound HTTP take the route .NET takes on the same host — a proxy variable when one is set, otherwise on Windows the system's proxy settings (ADR-0464) — and logs which it took. Called once, after logging is set up and before the first request; every client that leaves its transport to the default inherits the choice, every Worker Type's among them.
Types ¶
type Mode ¶
type Mode string
Mode says where this process takes its outbound proxy from.
const ( // ModeEnvironment: a proxy variable is set, and Go's transport reads it. ModeEnvironment Mode = "environment" // ModeWindows: the Windows proxy settings, read the way .NET reads them. ModeWindows Mode = "windows" // ModeOff: ATLAS_SYSTEM_PROXY switched the Windows settings off. ModeOff Mode = "off" // ModeNone: no system settings to follow — not Windows, or none configured. ModeNone Mode = "none" )
Source Files