Baseline code to query Spanner using DynamoDB queries

Dockerfile

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+# Copyright 2020 Google LLC
+#
+# Licensed 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.
+
+FROM golang:1.12
+
+
+# Set the Current Working Directory inside the container
+WORKDIR /go/src/db-driver
+
+# Force the go compiler to use modules
+ENV GO111MODULE=on
+
+# We want to populate the module cache based on the go.{mod,sum} files.
+COPY go.mod .
+COPY go.sum .
+
+#This is the 'magic' step that will download all the dependencies that are specified in
+# the go.mod and go.sum file.
+# Because of how the layer caching system works in Docker, the  go mod download 
+# command will _ only_ be re-run when the go.mod or go.sum file change 
+# (or when we add another docker instruction this line)
+RUN go mod download
+
+# Copy everything from the current directory to the PWD(Present Working Directory) inside the container
+COPY . .
+
+# Set active environment
+ARG ACTIVE_ENV
+ENV ACTIVE_ENV ${ACTIVE_ENV}
+
+# Download all the dependencies
+# https://stackoverflow.com/questions/28031603/what-do-three-dots-mean-in-go-command-line-invocations
+#RUN go get -d -v ./...
+
+# Install the package
+RUN go install -v ./...
+
+# Run the executable
+CMD ["db-driver"]

README.md

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 [![Join the chat at
 https://gitter.im/cloudspannerecosystem/dynamodb-adapter](https://badges.gitter.im/cloudspannerecosystem/dynamodb-adapter.svg)](https://gitter.im/cloudspannerecosystem/dynamodb-adapter?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
 
-Work in progress -- please check back later!
+
+## Introduction
+Dynamodb-adapter is an API tool that translates AWS DynamoDB queries to Cloud Spanner equivalent queries and runs those queries on Cloud Spanner. By running this project locally or in the cloud, this would work seamlessly.
+
+Additionally, it also supports primary and secondary indexes in a similar way as DynamoDB.
+
+It will be helpful for moving to Cloud Spanner from DynamoDB environment without changing the code for DynamoDB queries. The APIs created by this project can be directly consumed where DynamoDB queries are used in your application.
+
+This project requires two tables to store metadata and configuration for the project:
+* dynamodb_adapter_table_ddl (for meta data of all tables)
+* dynamodb_adapter_config_manager (for pubsub configuration)
+
+It supports two mode  - 
+* Production
+* Staging
+
+## Usage
+Follow the given steps to setup the project and generate the apis.
+
+### 1. Creation of the required configuration tables in Spanner
+#### Table: dynamodb_adapter_table_ddl
+This table will be used to store the metadata for other tables. It will be used at the time of initiation of project to create a map for all the columns names present in Spanner tables with the columns of tables present in DynamoDB. This mapping is required by because dynamoDB supports the special characters in column names while spanner does not support special characters other than underscores(_). 
+For more: [Spanner Naming Conventions](https://cloud.google.com/spanner/docs/data-definition-language#naming_conventions)
+
+```
+CREATE TABLE 
+dynamodb_adapter_table_ddl 
+(
+ column		    STRING(MAX),
+ tableName	    STRING(MAX),
+ dataType 	    STRING(MAX),
+ originalColumn     STRING(MAX),
+) PRIMARY KEY (tableName, column)
+```
+
+Add the meta data of all the tables in the similar way as shown below.
+
+![dynamodb_adapter_table_ddl sample data](images/config_spanner.png)
+
+#### Table: dynamodb_adapter_config_manager
+This table will be used to store the configuration info for publishing the data in Pub/Sub topic for other processes on change of data. It will be used to do some additional operation required on the change of data in tables. It can trigger New and Old data on given Pub/Sub topic. 
+
+```
+CREATE TABLE 
+dynamodb_adapter_config_manager 
+(
+ tableName 	STRING(MAX),
+ config 	STRING(MAX),
+ cronTime 	STRING(MAX),
+ enabledStream 	STRING(MAX),
+ pubsubTopic    STRING(MAX),
+ uniqueValue    STRING(MAX),
+) PRIMARY KEY (tableName)
+```
+
+
+### 2. Creation for configuration files
+There are two folders in [config-files](./config-files). 
+* **production** : It will be used to store the config files related to Production Environment.
+* **staging** : It will be used to store the config files related to Production Environment. 
+
+Add the configuration in the given files:
+#### config.{env}.json 
+| Key | Used For |
+| ------ | ------ |
+| GOOGLE_PROJECT_ID | Your Google Project ID |
+| SPANNER_DB | Your Spanner Database Name |
+
+For example:
+```
+{
+    "GOOGLE_PROJECT_ID" : "first-project",
+    "SPANNER_DB"        : "test-db"
+}
+```
+
+#### spanner.{env}.json
+It is a mapping file for table name with instance id. It will be helpful to query data on particular instance.
+The instance-id of all tables should be stored in this file in the following format:
+"TableName" : "instance-id"
+
+For example:
+
+```
+{
+    "dynamodb_adapter_table_ddl": "spanner-2 ",
+    "dynamodb_adapter_config_manager": "spanner-2",
+    "tableName1": "spanner-1",
+    "tableName2": "spanner-1"
+    ...
+    ...
+}
+```
+
+#### tables.{env}.json
+All table's primary key, columns, index information will be stored here.
+
+| Key | Used For |
+| ------ | ------ |
+| tableName | table name present in dynamoDb |
+| partitionKey | Primary key |
+| sortKey| Sorting key |
+| attributeTypes | Column names and type present |
+| indices | indexes present in the table |
+
+
+For example:
+
+```
+{
+    "tableName":{
+        "partitionKey":"primary key or Partition key",
+        "sortKey": "sorting key of dynamoDB adapter",
+        "attributeTypes": {
+			"ColumnName1": "N",
+			"ColumnName2": "S"
+        },
+        "indices": { 
+			"indexName1": {
+				"sortKey": "sort key for indexName1",
+				"partitionKey": "partition key for indexName1"
+			}
+		}
+    },
+    .....
+    .....
+}
+```
+
+
+### 3. Creation of rice-box.go file
+
+##### install rice package
+This package is required to load the config files. This is required in the first step of the running dynamoDB-adapter.
+
+```
+go get github.com/GeertJohan/go.rice
+go get github.com/GeertJohan/go.rice/rice
+```
+##### run command for creating the file.
+This is required to increase the performance when any config file is changed so that configuration files can be loaded directly from go file.
+```
+rice embed-go
+```
+
+### 4. Run 
+* Setup GCP project on **gcloud cli** 
+
+    If **gcloud cli** is not installed then firstly install **gcloud cli** [reference](https://cloud.google.com/sdk/docs/install)
+    Then run the following commands for setting up the project which has Cloud Spanner Database.
+    ```
+    gcloud auth login 
+    gcloud projects list
+    gcloud config set project `PROJECT NAME`
+    ```
+    [Reference](https://cloud.google.com/sdk/gcloud/reference/auth/login) for `gcloud auth login` 
+
+    [Reference](https://cloud.google.com/sdk/gcloud/reference/projects/list) for `gcloud auth login` 
+
+    [Reference](https://cloud.google.com/sdk/gcloud/reference/config/set) for `gcloud auth login`
+
+* Run for **staging**
+    ```
+    go run main.go
+    ```
+* Run for **Production**
+    ```
+    export ACTIVE_ENV=PRODUCTION
+    go run main.go
+    ```
+
+## Starting Process
+* Step 1: DynamoDB-adapter will load the configuration according the Environment Variable *ACTIVE_ENV*
+* Step 2: DynamoDB-adapter will initialize all the connections for all the instances so that it doesn't need to start the connection again and again for every request.
+* Step 3: DynamoDB-adapter will parse the data inside dynamodb_adapter_table_ddl table and will store in ram for faster access of data.
+* Step 4: DynamoDB-adapter will parse the dynamodb_adapter_config_manager table then will load it in ram. It will check for every 1 min if data has been changed in this table or not. If data is changed then It will update the data for this in ram. 
+* Step 5: After all these steps, DynamoDB-adapter will start the APIs which are similar to dynamodb APIs.
+
+
+## API Documentation
+This is can be imported in Postman or can be used for Swagger UI.
+You can get open-api-spec file here [here](https://github.com/cldcvr/dynamodb-adapter/wiki/Open-API-Spec)

api/api.go

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+// Copyright 2020 Google LLC
+//
+// Licensed 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.
+
+// Package api implements the apis versions
+// Different api version can be grouped here
+package api
+
+import (
+	v1 "github.com/cloudspannerecosystem/dynamodb-adapter/api/v1"
+
+	"github.com/gin-gonic/gin"
+)
+
+// InitAPI - initialize api
+func InitAPI(g *gin.Engine) {
+	r := g.Group("/v1")
+	v1.InitDBAPI(r)
+
+}