Add conditional validation, allow sending empty capacity scaler for r…

…egional backend service (#3033) (#351)

* fix region backend service capacity scaler

* add capacity scaler to fr example

* remove recopied handwritten test

* move constant list into expanders for tpg conversion

* change licenses

Signed-off-by: Modular Magician <[email protected]>

.changelog/3033.txt

@@ -0,0 +1,9 @@
+```release-note:breakingchange
+compute: Added conditional requirement of `google_compute_**region**_backend_service` `backend.capacity_scaler` to no longer accept the API default if not INTERNAL. Non-INTERNAL backend services must now specify `capacity_scaler` explicitly and have a total capacity greater than 0. In addition, API default of 1.0 must now be explicitly set and will be treated as nil or zero if not set in config.
+```
+```release-note:bug
+compute: Fixed `google_compute_**region**_backend_service` so it no longer has a permadiff if `backend.capacity_scaler` is unset in config by requiring capacity scaler. 
+```
+```release-note:bug
+compute: Fixed `backend.capacity_scaler` to actually set zero (0.0) value.
+```

docs/resources/google_compute_region_backend_service.md

@@ -34,27 +34,27 @@ Properties that can be accessed from the `google_compute_region_backend_service`
 
     * `balancing_mode`: Specifies the balancing mode for this backend. Defaults to CONNECTION.
 
-    * `capacity_scaler`: A multiplier applied to the group's maximum servicing capacity (based on UTILIZATION, RATE or CONNECTION).  Default value is 1, which means the group will serve up to 100% of its configured capacity (depending on balancingMode). A setting of 0 means the group is completely drained, offering 0% of its available Capacity. Valid range is [0.0,1.0].
+    * `capacity_scaler`: A multiplier applied to the group's maximum servicing capacity (based on UTILIZATION, RATE or CONNECTION).  ~>**NOTE**: This field cannot be set for INTERNAL region backend services (default loadBalancingScheme), but is required for non-INTERNAL backend service. The total capacity_scaler for all backends must be non-zero.  A setting of 0 means the group is completely drained, offering 0% of its available Capacity. Valid range is [0.0,1.0].
 
     * `description`: An optional description of this resource. Provide this property when you create the resource.
 
     * `failover`: (Beta only) This field designates whether this is a failover backend. More than one failover backend can be configured for a given RegionBackendService.
 
     * `group`: The fully-qualified URL of an Instance Group or Network Endpoint Group resource. In case of instance group this defines the list of instances that serve traffic. Member virtual machine instances from each instance group must live in the same zone as the instance group itself. No two backends in a backend service are allowed to use same Instance Group resource.  For Network Endpoint Groups this defines list of endpoints. All endpoints of Network Endpoint Group must be hosted on instances located in the same zone as the Network Endpoint Group.  Backend services cannot mix Instance Group and Network Endpoint Group backends.  When the `load_balancing_scheme` is INTERNAL, only instance groups are supported.  Note that you must specify an Instance Group or Network Endpoint Group resource using the fully-qualified URL, rather than a partial URL.
 
-    * `max_connections`: The max number of simultaneous connections for the group. Can be used with either CONNECTION or UTILIZATION balancing modes.  For CONNECTION mode, either maxConnections or one of maxConnectionsPerInstance or maxConnectionsPerEndpoint, as appropriate for group type, must be set.
+    * `max_connections`: The max number of simultaneous connections for the group. Can be used with either CONNECTION or UTILIZATION balancing modes. Cannot be set for INTERNAL backend services.  For CONNECTION mode, either maxConnections or one of maxConnectionsPerInstance or maxConnectionsPerEndpoint, as appropriate for group type, must be set.
 
-    * `max_connections_per_instance`: The max number of simultaneous connections that a single backend instance can handle. This is used to calculate the capacity of the group. Can be used in either CONNECTION or UTILIZATION balancing modes.  For CONNECTION mode, either maxConnections or maxConnectionsPerInstance must be set.
+    * `max_connections_per_instance`: The max number of simultaneous connections that a single backend instance can handle. Cannot be set for INTERNAL backend services.  This is used to calculate the capacity of the group. Can be used in either CONNECTION or UTILIZATION balancing modes. For CONNECTION mode, either maxConnections or maxConnectionsPerInstance must be set.
 
-    * `max_connections_per_endpoint`: The max number of simultaneous connections that a single backend network endpoint can handle. This is used to calculate the capacity of the group. Can be used in either CONNECTION or UTILIZATION balancing modes.  For CONNECTION mode, either maxConnections or maxConnectionsPerEndpoint must be set.
+    * `max_connections_per_endpoint`: The max number of simultaneous connections that a single backend network endpoint can handle. Cannot be set for INTERNAL backend services.  This is used to calculate the capacity of the group. Can be used in either CONNECTION or UTILIZATION balancing modes. For CONNECTION mode, either maxConnections or maxConnectionsPerEndpoint must be set.
 
-    * `max_rate`: The max requests per second (RPS) of the group.  Can be used with either RATE or UTILIZATION balancing modes, but required if RATE mode. Either maxRate or one of maxRatePerInstance or maxRatePerEndpoint, as appropriate for group type, must be set.
+    * `max_rate`: The max requests per second (RPS) of the group. Cannot be set for INTERNAL backend services.  Can be used with either RATE or UTILIZATION balancing modes, but required if RATE mode. Either maxRate or one of maxRatePerInstance or maxRatePerEndpoint, as appropriate for group type, must be set.
 
-    * `max_rate_per_instance`: The max requests per second (RPS) that a single backend instance can handle. This is used to calculate the capacity of the group. Can be used in either balancing mode. For RATE mode, either maxRate or maxRatePerInstance must be set.
+    * `max_rate_per_instance`: The max requests per second (RPS) that a single backend instance can handle. This is used to calculate the capacity of the group. Can be used in either balancing mode. For RATE mode, either maxRate or maxRatePerInstance must be set. Cannot be set for INTERNAL backend services.
 
-    * `max_rate_per_endpoint`: The max requests per second (RPS) that a single backend network endpoint can handle. This is used to calculate the capacity of the group. Can be used in either balancing mode. For RATE mode, either maxRate or maxRatePerEndpoint must be set.
+    * `max_rate_per_endpoint`: The max requests per second (RPS) that a single backend network endpoint can handle. This is used to calculate the capacity of the group. Can be used in either balancing mode. For RATE mode, either maxRate or maxRatePerEndpoint must be set. Cannot be set for INTERNAL backend services.
 
-    * `max_utilization`: Used when balancingMode is UTILIZATION. This ratio defines the CPU utilization target for the group. Valid range is [0.0, 1.0].
+    * `max_utilization`: Used when balancingMode is UTILIZATION. This ratio defines the CPU utilization target for the group. Valid range is [0.0, 1.0]. Cannot be set for INTERNAL backend services.
 
   * `circuit_breakers`: (Beta only) Settings controlling the volume of connections to a backend service. This field is applicable only when the `load_balancing_scheme` is set to INTERNAL_MANAGED and the `protocol` is set to HTTP, HTTPS, or HTTP2.