A21-Service-Config-Error-Handling

A21-Service-Config-Error-Handling.md

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+Service Config Error Handling
+----
+* Author: yashkt
+* Approver: markdroth
+* Status: Draft
+* Implemented in:
+* Last updated: 09-17-2018
+* Discussion at: https://groups.google.com/forum/#!topic/grpc-io/bAxyse6c2eI
+
+## Abstract
+
+This document proposes a methodology to handle errors in a resolved service
+config.
+
+## Background
+
+The
+[service config](https://github.com/grpc/grpc/blob/master/doc/service_config.md)
+is a mechanism that allows service owners to publish
+parameters that clients could use. If the received service config is malformed
+or has unknown fields or has invalid values, the client could either ignore the
+invalid service config or partially accept the service config while ignoring
+certain parts.
+
+
+### Related Proposals:
+* [A2-Service Config via DNS](A2-service-configs-in-dins.md)
+
+## Proposal
+
+If a resolved service config is badly formatted or contains invalid values for
+known fields, the client should ignore that service config in its entirety.
+Unknown fields in the service config should be ignored. If there was a service
+config that the client was previously using, it should continue using those
+parameters when communicating with the service. If there was no service config
+being used, then the client should continue behaving as if it never received a
+service config update from the resolver. On the other hand, if it is a new
+client, then the client should fail to start, i.e., not act on the resolution
+result till a valid service config is received.
+
+## Rationale
+
+By discarding invalid service configs instead of ignoring fields that have
+invalid values, we prevent clients from resorting to using default values which
+might be unwanted for certain systems. The clause that existing clients continue
+using older service configs prevents an invalid service config from bringing
+down the entire system, while newer clients which do not have a previously
+received valid service config fail to start, avoiding new traffic for the
+duration that the service is set with an invalid config.
+
+Examples of invalid service configs :
+
+* Badly Formatted service config
+“serviceConfig” : {
+  “MethodConfig” :
+   {
+   “Service // bad format
+  }
+
+* Fields with invalid values are not allowed
+“serviceConfig” : {
+      “loadBalancingPolicy” : “UnknownPolicy”
+}
+
+## Implementation
+
+C -
+JAVA -
+Go -
+
+## Open issues (if applicable)
+
+N/A