Go Reverse Proxy

A simple configuration-driven reverse proxy written in Go.

It has zero dependencies outside of the Go standard library.

Configuration

Define a slice of type Config, with the minimum set of fields being: Path and Upstream.

Configuration is defined in the routing/configuration file.

Upstreams are defined in the upstreams file.

Example Config

Below we explain the actual routing configuration committed into this repo...

• Proxy Request
• Proxy Request using Regular Expression
• Proxy Request with Modified Path
• Override with Modified Path
• Modified Path + Override with Modified Path
• Override to Different Upstream
• Query String Override
• Query String Override with Regular Expression

Proxy Request

Config{
  Path:     "/anything/standard",
  Upstream: upstreams.HTTPBin,
}

Requests

• /anything/standard

Result

The request will be proxied straight through to the specified upstream without any modifications.

Proxy Request using Regular Expression

Config{
  Path:     "/anything/(?:foo|bar)$",
  Upstream: upstreams.HTTPBin,
}

Requests

• /anything/foo
• /anything/bar

Result

Both requests will be proxied straight through to the specified upstream without any modifications.

Proxy Request with Modified Path

Config{
  Path:       `/(?P<cap>foo\w{3})`,
  Upstream:   upstreams.HTTPBin,
  ModifyPath: "/anything/${cap}",
}

Requests

• /fooabc
• /fooxyz

Result

Both requests will be proxied through to the specified upstream but the path will be modified to include the captured information: /anything/abc and /anything/xyz.

Override with Modified Path

Config{
  Path:     "/(?P<start>anything)/(?P<cap>foobar)$",
  Upstream: upstreams.HTTPBin,
  Override: Override{
    Header:     "X-BF-Testing",
    Match:      "integralist",
    ModifyPath: "/anything/newthing${cap}",
  },
}

Requests

• /anything/foobar
• /anything/foobar (+ HTTP Request Header X-BF-Testing: integralist)

Result

The request will be proxied straight through to the specified upstream without any modifications.

If the relevant request header is specified, then the request will be proxied through to the specified upstream but the path will be modified to include the captured information: /anything/newthingfoobar.

Modified Path + Override with Modified Path

Config{
  Path:       "/(?P<cap>double-checks)$",
  Upstream:   upstreams.HTTPBin,
  ModifyPath: "/anything/toplevel-modified-${cap}",
  Override: Override{
    Header:     "X-BF-Testing",
    Match:      "integralist",
    ModifyPath: "/anything/override-modified-${cap}",
  },
}

Requests

• /double-checks
• /double-checks (+ HTTP Request Header X-BF-Testing: integralist)

Result

The request will be proxied through to the specified upstream but the path will be modified to include the captured information: /anything/toplevel-modified-double-checks.

If the relevant request header is specified, then the request will be proxied through to the specified upstream but the path will be modified to include the captured information: /anything/override-modified-double-checks.

Override to Different Upstream

Config{
  Path:     "/anything/(?P<cap>integralist)",
  Upstream: upstreams.HTTPBin,
  Override: Override{
    Header:     "X-BF-Testing",
    Match:      "integralist",
    ModifyPath: "/about",
    Upstream:   upstreams.Integralist,
  },
}

Requests

• /anything/integralist
• /anything/integralist (+ HTTP Request Header X-BF-Testing: integralist)

Result

The request will be proxied straight through to the specified upstream without any modifications.

If the relevant request header is specified, then the request will be proxied through to a different specified upstream and the path will also be modified.

Note: although we use a named capture group, we don't actually utilise it anywhere in the rest of the configuration, so it's effectively a no-op.

Query String Override

Config{
  Path:     "/about",
  Upstream: upstreams.HTTPBin,
  Override: Override{
    Query:    "s",
    Match:    "integralist",
    Upstream: upstreams.Integralist,
  },
}

Requests

• /about
• /about?s=integralist

Result

The request will be proxied straight through to the specified upstream without any modifications.

If the relevant query parameter is specified, then the request will be proxied through to a different specified upstream.

Query String Override with Regular Expression

Config{
  Path:     "/anything/querytest",
  Upstream: upstreams.HTTPBin,
  Override: Override{
    Query:      "s",
    Match:      `integralist(?P<cap>\d{1,3})$`,
    MatchType:  "regex",
    ModifyPath: "/anything/newthing${cap}",
  },
}

Requests

• /anything/querytest
• /anything/querytest?s=integralist123
• /anything/querytest?s=integralist456

Result

The first request will be proxied straight through to the specified upstream without any modifications.

If the relevant query parameter is specified, then the second and third requests will have their path modified to include the captured information: /anything/newthing123 and /anything/newthing456.

Response Headers

We set the following response headers (not all will be set depending on the configuration):

X-Forwarded-Host
X-Origin-Host
X-Router-Upstream
X-Router-Upstream-OriginalHost
X-Router-Upstream-OriginalPath
X-Router-Upstream-OriginalPathModified
X-Router-Upstream-Override
X-Router-Upstream-OverrideHost
X-Router-Upstream-OverridePath

Usage

make run

Note: the application listens on port 9001.

curl -v http://localhost:9001/some/path/you/configured

Tests

make test

Load Test

We use vegeta for load testing, so make sure you have that installed.

make stress

Example output:

Requests      [total, rate]            1500, 50.03
Duration      [total, attack, wait]    30.11237994s, 29.982166788s, 130.213152ms
Latencies     [mean, 50, 95, 99, max]  154.522948ms, 96.76258ms, 358.770472ms, 1.076826656s, 2.954136535s
Bytes In      [total, mean]            2039772, 1359.85
Bytes Out     [total, mean]            0, 0.00
Success       [ratio]                  100.00%
Status Codes  [code:count]             200:1500
Error Set:

TODO

• Look at implementing thread pool processing on a host or server basis.
• Verify if DNS caching (or request memoization) would affect latency results?
• Review 301 redirect behaviour to be sure we don't need to handle that differently.
• Flesh out some unit tests (not just integration testing)