Mastering Service Routing: Strategies, Rules, and Real-World Examples

Service routing selects appropriate service nodes for a consumer based on specific requirements, especially when services are deployed across multiple IDC groups.

Typical Scenarios

Grouped calls – route requests to a specific IDC group.

Gray release – pre‑release to a subset of nodes before full rollout.

Traffic switching – redirect traffic from a failed data center to a healthy one.

Read/write separation – route read‑heavy methods to read‑only nodes and write‑heavy methods to write nodes.

Condition‑Based Routing Rules

Routing rules are expressed as condition expressions. The left side matches consumer criteria; the right side filters providers.

condition://0.0.0.0/dubbo.test.interfaces.TestService?category=routers&dynamic=true&priority=2&enabled=true&rule="host=10.20.153.10=>host=10.20.153.11"

Examples: => host != 172.22.3.91 Exclude a specific provider. host != 10.20.153.10,10.20.153.11 => Whitelist the listed consumers. host = 10.20.153.10,10.20.153.11 => Blacklist the listed consumers. host = 172.22.3.* => host = 172.22.3.* IDC isolation – only same‑subnet consumers can call same‑subnet providers.

method = find*,list*,get*,is* => host =172.22.3.94,172.22.3.95
method != find*,list*,get*,is* => host =172.22.3.97,172.22.3.98

Read/write separation based on method name patterns.

Script‑Based Routing

Rules can be defined with scripts (JavaScript, Groovy, etc.). The rule URL contains the script source encoded.

script://0.0.0.0/com.foo.BarService?category=routers&dynamic=false&rule="(function route(invokers){...})(invokers)"

Concrete JavaScript example that only allows consumer IP 10.20.153.10:

function route(invokers){
  var result = new java.util.ArrayList(invokers.size());
  for (var i = 0; i < invokers.size(); i++) {
    if ("10.20.153.10".equals(invokers.get(i).getUrl().getHost())) {
      result.add(invokers.get(i));
    }
  }
  return result;
}(invokers);

Rule Storage and Distribution

Routing rules can be stored in three ways. The evaluation order is:

Local configuration – consumer reads a static file on its own machine.

Dynamic push – an operator updates rules via a governance console; the updated rule is pushed to consumers in real time.

Configuration‑center management – all consumers fetch the same rule set from a central store.

Priority: local configuration > dynamic push > configuration‑center.

Conclusion

Service routing provides fine‑grained control for grouped invocation, gray release, traffic switching, read/write separation, black/white lists, and IDC isolation. Small deployments may use simple local rules, but as the system scales across multiple data centers, centralizing rules in a configuration center and using dynamic pushes improves availability and manageability.