rabbah commented on a change in pull request #4314: CosmosDB Cache Invalidation Service URL: https://github.com/apache/incubator-openwhisk/pull/4314#discussion_r267398493
########## File path: core/cosmosdb/cache-invalidator/README.md ########## @@ -0,0 +1,67 @@ +<!-- +# +# Licensed to the Apache Software Foundation (ASF) under one or more +# contributor license agreements. See the NOTICE file distributed with +# this work for additional information regarding copyright ownership. +# The ASF licenses this file to You under the Apache License, Version 2.0 +# (the "License"); you may not use this file except in compliance with +# the License. You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. +# +--> +# OpenWhisk Cache Invalidator Service + +This service performs cache invalidation in OpenWhisk cluster to enable cache event propagation in multi region setups. + +## Design + +OpenWhisk cluster uses a Kafka topic `cacheInvalidation` to communicate changes to any cached entity. Messages on this +topic are of the form + +```json +{"instanceId":"controller0","key":{"mainId":"guest/hello"}} +``` + +When deploying multiple seprate cluster of OpenWhisk which do not share same Kafka instance we would need a way to +propagate the cache change event across cluster. For CosmosDB based setups this can be done by using [CosmosDB ChangeFeed][1] +support. It enables reading changes that are made to any specific collection. + +This service makes use of [change feed processor java][2] library and listen to changes happening in `whisks` and `subject` +collection and then convert them into Kafka message events which can be sent to `cacheInvalidation` topic of local cluster + +## Usage + +The service needs following env variables to be set + +- `KAFKA_HOSTS` - For local env it can be set to `172.17.0.1:9093`. When using [OpenWhisk Devtools][3] based setup use `kafka` +- `COSMOSDB_ENDPOINT` - Endpoint URL like https://<account>.documents.azure.com:443/ +- `COSMOSDB_KEY` - DB Key +- `COSMOSDB_NAME` - DB name + +Upon startup it would create a collection to manage the lease data with name `cache-invalidator-lease`. For events sent by +this service `instanceId` would be set to `cache-invalidator` + +## Local Run + +Setup the OpenWhisk cluster using [devtools][3] but have it connect to CosmosDB. This would also start +the [Kafka Topic UI][4] at port `8001`. Then if any change is made to db then you would see events set to Kafka topic like Review comment: Then when changes are made to the database, you should see events sent to the Kafka topic. For example, if a a package is created with `wsk package create test-package` using the `guest` account, the following event is generated: ---------------------------------------------------------------- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. For queries about this service, please contact Infrastructure at: [email protected] With regards, Apache Git Services
