fix(aws-ecs): set permissions for 'awslogs' log driver

Make sure that tasks using the 'awslogs' Log Driver have the correct IAM
permissions to actually write logs. Add grant() methods to IAM LogGroups
to make this nicer to write.

Fixes #1279.

packages/@aws-cdk/aws-ecs/lib/container-definition.ts

@@ -229,6 +229,7 @@ export class ContainerDefinition extends cdk.Construct {
     this.memoryLimitSpecified = props.memoryLimitMiB !== undefined || props.memoryReservationMiB !== undefined;
 
     props.image.bind(this);
+    if (props.logging) { props.logging.bind(this); }
   }
 
   /**

packages/@aws-cdk/aws-ecs/lib/log-drivers/aws-log-driver.ts

@@ -1,5 +1,6 @@
 import logs = require('@aws-cdk/aws-logs');
 import cdk = require('@aws-cdk/cdk');
+import { ContainerDefinition } from '../container-definition';
 import { cloudformation } from '../ecs.generated';
 import { LogDriver } from "./log-driver";
 
@@ -61,6 +62,13 @@ export class AwsLogDriver extends LogDriver {
     });
   }
 
+  /**
+   * Called when the log driver is configured on a container
+   */
+  public bind(containerDefinition: ContainerDefinition): void {
+    this.logGroup.grantWrite(containerDefinition.taskDefinition.obtainExecutionRole());
+  }
+
   /**
    * Return the log driver CloudFormation JSON
    */

packages/@aws-cdk/aws-ecs/lib/log-drivers/log-driver.ts

@@ -1,4 +1,5 @@
 import cdk = require('@aws-cdk/cdk');
+import { ContainerDefinition } from '../container-definition';
 import { cloudformation } from '../ecs.generated';
 
 /**
@@ -9,4 +10,9 @@ export abstract class LogDriver extends cdk.Construct {
    * Return the log driver CloudFormation JSON
    */
   public abstract renderLogDriver(): cloudformation.TaskDefinitionResource.LogConfigurationProperty;
+
+  /**
+   * Called when the log driver is configured on a container
+   */
+  public abstract bind(containerDefinition: ContainerDefinition): void;
 }

packages/@aws-cdk/aws-ecs/test/fargate/integ.asset-image.expected.json

@@ -759,6 +759,19 @@
               ],
               "Effect": "Allow",
               "Resource": "*"
+            },
+            {
+              "Action": [
+                "logs:CreateLogStream",
+                "logs:PutLogEvents"
+              ],
+              "Effect": "Allow",
+              "Resource": {
+                "Fn::GetAtt": [
+                  "FargateServiceLoggingLogGroup9B16742A",
+                  "Arn"
+                ]
+              }
             }
           ],
           "Version": "2012-10-17"