varnish_httpcache

httpcache.py

#!/usr/bin/env python3
# Easier Frontend for varnishd
# Example: ./httpcache.py -u google.com
# Then, requests to localhost:8080 forwarded to google.com and cached
# Licence: MIT

import os
import tempfile
import subprocess
import shutil
import argparse

def parse_upstream(upstream: str) -> tuple[str, str]:
    # handle protocol
    defPort = "80"
    if upstream.startswith("http://"):
        upstream = upstream[7:]
        defPort = "80"
    elif upstream.startswith("https://"):
        upstream = upstream[8:]
        defPort = "443"

    # handle port
    port_index = upstream.find(":")
    if port_index == -1:
        return upstream, defPort
    else:
         return upstream[:port_index], upstream[port_index+1:]


# Parse command line arguments
parser = argparse.ArgumentParser(description='HTTP Cache with Varnish')
parser.add_argument('--upstream', '-u', type=str, required=True, help='Backend host')
parser.add_argument('--port', '-p', type=str, default='8080', help='Varnish port')
parser.add_argument('--verbose', '-v', action="count")
args = parser.parse_args()

# Configuration

upstream_host, upstream_port = parse_upstream(args.upstream)

# VCL template with placeholders
vcl_content = """
vcl 4.0;

backend default {
    .host = "{upstream_host}";
    .port = "{upstream_port}";
    .host_header = "{upstream_host}:{upstream_port}";
}

sub vcl_backend_fetch {
    unset bereq.http.host;
}

sub vcl_recv {
    # Add custom logic here if needed
}

sub vcl_backend_response {
    set beresp.ttl = 24h;  # Set TTL for cached objects
}

sub vcl_deliver {
    if (obj.hits > 0) {
        set resp.http.X-Cache = "HIT";
    } else {
        set resp.http.X-Cache = "MISS";
    }
}
"""

vcl_content = vcl_content.replace("{upstream_host}", upstream_host)
vcl_content = vcl_content.replace("{upstream_port}", upstream_port)

tmpdir = tempfile.TemporaryDirectory(delete=False).name
if args.verbose:
    print("Varnish tmp folder:", tmpdir)

# Create a temporary VCL file
tmp_vcl_file = os.path.join(tmpdir, "file.vcl")
with open(tmp_vcl_file, "wb") as file:
    file.write(vcl_content.encode('utf-8'))

try:
    print(f"Varnish started on port {args.port} with backend {upstream_host}:{upstream_port}")
    proc = subprocess.run([
        "varnishd",
        "-F",
        "-a", f":{args.port}",
        "-f", tmp_vcl_file,
        "-s", "malloc,256m",
        "-n", os.path.join(tmpdir, "cache")
    ], check=False, capture_output=not args.verbose)
    # Process has finished

    if not args.verbose and proc.returncode != 0:
        print("varnishd crashed. Logs:")
        print("\nStdout:")
        print(proc.stdout.decode('utf-8'))
        print("\nStderr:")
        print(proc.stderr.decode('utf-8'))
        exit(1)
    
finally:
    shutil.rmtree(tmpdir)