问题
I'm using varnish in front of a tile server to cache mapbox tiles. To remove old tiles, I intended to use bans to effectively remove a large number of cached tiles. My problem is that varnish still uses the cached objects (at least the age in the response indicates this) and doesn't contact the backend.
I'm first requesting http://varnish/5/3/4.pbf, then adding a ban with curl -X BAN -H 'X-Purge-Regex: 5/3/4.pbf' varnish or alternatively varnishadm and then ban obj.http.url ~ 5/3/4.pbf and afterwards requesting http://varnish/5/3/4.pbf again.
In the beginning my ban list is empty:
Present bans:
1610117471.434488 1 C
The ban is added succesfully with curl -X BAN -H 'X-Purge-Regex: 5/3/4.pbf' varnish
<!DOCTYPE html>
<html>
<head>
<title>200 Ban added</title>
</head>
<body>
<h1>Error 200 Ban added</h1>
<p>Ban added</p>
<h3>Guru Meditation:</h3>
<p>XID: 8</p>
<hr>
<p>Varnish cache server</p>
</body>
</html>
and shows up in the ban list
Present bans:
1610117369.028870 0 - obj.http.url ~ 5/3/4.pbf
1610117307.220739 1 C
After requesting http://varnish/5/3/4.pbf again, the ban list indicates that the ban was used
Present bans:
1610117471.434488 1 - obj.http.url ~ 5/3/4.pbf
but the age of the response is not 0, because it's still the object from the first request.
After a short time the ban is removed:
Present bans:
1610117471.434488 1 C
My vcl_recv looks like this but the error is probably somewhere else as it also doesn't work with varnishadm:
sub vcl_recv {
unset req.http.cookie;
# Allowing PURGE from localhost
if (req.method == "BAN"||req.method == "PURGE") {
if (!client.ip ~ purge) {
return(synth(405,"Not allowed."));
}
if (req.method == "BAN") {
ban("obj.http.url ~ " + req.http.X-Purge-Regex);
# Throw a synthetic page so the
# request won't go to the backend.
return(synth(200, "Ban added"));
}
if (req.method == "PURGE") {
return (purge);
}
}
}
I also tried to use the vcl_purge from https://stackoverflow.com/a/61507014 but this doesn't seem to help for bans (?).
I'm using the X-Purge-Regex header to not worry about having to escape special characters like in https://stackoverflow.com/a/38526921 but just a ban like obj.http.url ~ 0 doesn't work.
I'm using varnish 6.5 with vcl 4.0.
Ban request
* << Request >> 54
- Begin req 53 rxreq
- Timestamp Start: 1610121483.345437 0.000000 0.000000
- Timestamp Req: 1610121483.345437 0.000000 0.000000
- VCL_use boot
- ReqStart 192.168.48.2 50882 http
- ReqMethod BAN
- ReqURL /
- ReqProtocol HTTP/1.1
- ReqHeader Host: varnish-volatile
- ReqHeader User-Agent: curl/7.64.0
- ReqHeader Accept: */*
- ReqHeader X-Purge-Regex: 0
- ReqHeader X-Forwarded-For: 192.168.48.2
- VCL_call RECV
- VCL_acl MATCH purge "importer"
- VCL_return synth
- VCL_call HASH
- VCL_return lookup
- RespProtocol HTTP/1.1
- RespStatus 200
- RespReason Ban added
- RespHeader Date: Fri, 08 Jan 2021 15:58:03 GMT
- RespHeader Server: Varnish
- RespHeader X-Varnish: 54
- VCL_call SYNTH
- RespHeader Content-Type: text/html; charset=utf-8
- RespHeader Retry-After: 5
- VCL_return deliver
- Timestamp Process: 1610121483.347281 0.001844 0.001844
- RespHeader Content-Length: 246
- Storage malloc Transient
- Filters
- RespHeader Accept-Ranges: bytes
- RespHeader Connection: keep-alive
- Timestamp Resp: 1610121483.347557 0.002120 0.000276
- ReqAcct 98 0 98 218 246 464
- End
GET after adding ban
* << Request >> 32806
- Begin req 32805 rxreq
- Timestamp Start: 1610121552.733872 0.000000 0.000000
- Timestamp Req: 1610121552.733872 0.000000 0.000000
- VCL_use boot
- ReqStart 192.168.48.1 55176 http
- ReqMethod GET
- ReqURL /public.snow_db/0/0/0.pbf
- ReqProtocol HTTP/1.1
- ReqHeader Host: localhost:8090
- ReqHeader User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:84.0) Gecko/20100101 Firefox/84.0
- ReqHeader Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/webp,*/*;q=0.8
- ReqHeader Accept-Language: en-US,en;q=0.5
- ReqHeader Accept-Encoding: gzip, deflate
- ReqHeader DNT: 1
- ReqHeader Connection: keep-alive
- ReqHeader Upgrade-Insecure-Requests: 1
- ReqHeader Pragma: no-cache
- ReqHeader Cache-Control: no-cache
- ReqHeader X-Forwarded-For: 192.168.48.1
- VCL_call RECV
- ReqUnset Host: localhost:8090
- ReqHeader host: localhost:8090
- VCL_return hash
- ReqUnset Accept-Encoding: gzip, deflate
- ReqHeader Accept-Encoding: gzip
- VCL_call HASH
- VCL_return lookup
- Hit 28 601789.331504 10.000000 0.000000
- VCL_call HIT
- VCL_return deliver
- RespProtocol HTTP/1.1
- RespStatus 200
- RespReason OK
- RespHeader content-encoding: gzip
- RespHeader content-type: application/x-protobuf
- RespHeader date: Fri, 08 Jan 2021 15:09:02 GMT
- RespHeader Vary: Accept-Encoding
- RespHeader X-Varnish: 32806 28
- RespHeader Age: 3010
- RespHeader Via: 1.1 varnish (Varnish/6.5)
- VCL_call DELIVER
- VCL_return deliver
- Timestamp Process: 1610121552.734070 0.000197 0.000197
- Filters
- RespHeader Accept-Ranges: bytes
- RespHeader Content-Length: 295
- RespHeader Connection: keep-alive
- Timestamp Resp: 1610121552.734217 0.000345 0.000147
- ReqAcct 414 0 414 272 295 567
- End
Reproducing the issue
To reproduce the bug:
git clone https://github.com/Baschdl/varnish-ban-setup.git && cd varnish-ban-setupdocker-compose up- Open http://localhost:8092/5/3/1.pbf
docker-compose exec varnish varnishadm ban obj.http.url ~ pbf- Open http://localhost:8092/5/3/1.pbf again and you will get the old object
回答1:
The obj.http.url ~ 5/3/4.pbf ban that you are issuing, is matching a url response header.
Remember: the URL is a request header, not a response header. No reason to panic, what you're doing makes perfect sense, and is related to the scope of the so-called ban lurker.
Ban lurker
The ban lurker is a thread that asynchronously processes bans on the ban list and matches objects to the bans in order to remove patterns of objects from the cache.
The ban lurker doesn't operate within a request scope, but only is aware of the object scope.
In order to successfully match request information, request context can be added as a response header. And that's what you're doing via obj.http.url
So why doesn't the ban work?
The reason why your ban isn't working, is because you didn't set obj.http.url in your VCL file. As a result, the ban lurker cannot match any objects to it.
How to fix the issue
The solution is simple: set the missing headers in the backend response context, as illustrated below:
sub vcl_backend_response {
set beresp.http.url = bereq.url;
set beresp.http.host = bereq.http.host;
}
When the backend responds, and right before the object gets stored in cache, we can set the missing headers.
After that, the ban lurker will be able to match the ban expression to the right objects, and remove them from cache.
Don't forget the objects aren't immediately matched: they are only removed when they reach the ban_lurker_age, which is set to 1 minute by default.
来源：https://stackoverflow.com/questions/65632023/varnish-ban-is-added-but-old-object-is-returned