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From Chris Gamache <cgama...@gmail.com>
Subject Switching contexts using a valve
Date Fri, 05 Dec 2014 16:01:59 GMT
Currently we use haproxy to direct users to certain versions of our
software based on a cookie. This is so that the user can select which
version of the software they want to use (e.g. Legacy, Stable, Beta) ...
Having that kind of application functionality in the load balancer is
something I'd rather not do. I'd rather have Tomcat read the cookie and
switch contexts based on the cookie. I'd like to be able to simply pass the
connection on to a different context and not have to 3XX redirect the
client, but I don't see where that functionality exists.

I might be looking at the problem the wrong way though.

I would love some suggestions on safe and simple ways to get this done.
Here's what I have so far as a skeleton. For fun, it will flop based on the
time you access the service from one service to the next:

public class ProxyValve extends ValveBase {
 private enum BaseType {LEGACY, STABLE, BETA};
 private String legacyBase;
private String stableBase;
private String betaBase;
private String base;
 /**
     * The descriptive information related to this implementation.
     */
    private static final String info =
"org.apache.catalina.valves.ProxyValve/0.0";


    /**
     * Return descriptive information about this Valve implementation.
     */
    @Override
    public String getInfo() {
        return (info);
    }

 public void invoke(Request request, Response response) throws IOException,
ServletException {
if (request.getContextPath().equals(base)) {
BaseType bt = convertBase();
switchContexts(bt, request, response);
}
getNext().invoke(request, response);
}

private void switchContexts(BaseType bt, Request request, Response
response) throws IOException {
Context c = request.getContext();
String path = request.getContextPath();
switch(bt) {
case BETA:
path = betaBase;
break;
case LEGACY:
path = legacyBase;
break;
case STABLE:
path = stableBase;
break;
}
 if (!path.equals(base)) {
//do the switch here. But how? :)
}
 }
 private BaseType convertBase() { Date d = new Date(); switch
(d.getSeconds() % 3) { case 0: return BaseType.LEGACY; case 1: return
BaseType.STABLE; case 2: return BaseType.BETA; } return BaseType.STABLE; }


public String getLegacyBase() {
return legacyBase;
}

public void setLegacyBase(String legacyBase) {
this.legacyBase = legacyBase;
}

public String getStableBase() {
return stableBase;
}

public void setStableBase(String stableBase) {
this.stableBase = stableBase;
}

public String getBetaBase() {
return betaBase;
}

public void setBetaBase(String betaBase) {
this.betaBase = betaBase;
}

public String getBase() {
return base;
}

public void setBase(String base) {
this.base = base;
}
}

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