Migrator tool: fix dependencies and update docs

tools/pom.xml

@@ -56,6 +56,10 @@
             <artifactId>cassandra-all</artifactId>
             <version>3.11.4</version>
         </dependency>
+        <dependency>
+            <groupId>com.datastax.cassandra</groupId>
+            <artifactId>cassandra-driver-core</artifactId>
+        </dependency>
         <dependency>
             <groupId>commons-io</groupId>
             <artifactId>commons-io</artifactId>

tools/src/main/java/org/thingsboard/client/tools/migrator/PgCaLatestMigrator.java

@@ -5,7 +5,7 @@
  * 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
+ * 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,

tools/src/main/java/org/thingsboard/client/tools/migrator/README.md

@@ -1,5 +1,6 @@
 # Description:
-Tool used for migrating ThingsBoard into hybrid mode from Postgres.   
+This tool used for migrating ThingsBoard into hybrid mode from Postgres.
+   
 Performance of this tool depends on disk type and instance type (mostly on CPU resources).
 But in general here are few benchmarks:
 1. Creating Dump of the postgres ts_kv table -> 100GB = 90 minutes
@@ -7,56 +8,80 @@ But in general here are few benchmarks:
 3. Generation SSTables from dump -> 100GB = 3 hours
 4. 100GB Dump file will be converted into SSTable with size about 18GB
 
-# How to build Tool:
-Switch to `tools` project in Command Line and execute 
-`mvn clean compile assembly:single`
-It will generate single jar with dependencies.
+# Tool build Instruction:
+Switch to `tools` module in Command Line and execute 
 
-# Instruction:
+    mvn clean compile assembly:single
+    
+It will generate single jar file with all required dependencies inside `target dir` -> `tools-2.4.1-SNAPSHOT-jar-with-dependencies.jar`.
+
+
+# Prepare requred files and run Tool:
+
+#### Dump data from the source Postgres Database
+*Do not use compression if possible because Tool can only work with uncompressed file
+
+1. Dump table `ts_kv` table:
+
+    `pg_dump -h localhost -U postgres -d thingsboard -t ts_kv > ts_kv.dmp`
+
+2. Dump table `ts_kv_latest` table:
 
-1. Dump Telemetry table from the source Postgres table. Do not use compression if possible because Tool can only work with uncompressed file
-dump ts_kv table -> `pg_dump -h localhost -U postgres -d thingsboard -t ts_kv > ts_kv.dmp`
+    `pg_dump -h localhost -U postgres -d thingsboard -t ts_kv_latest > ts_kv_latest.dmp`
 
-2. Dump Latest Telemetry table from the source Postgres table. Do not use compression if possible because Tool can only work with uncompressed file
-dump ts_kv_latest -> `pg_dump -h localhost -U postgres -d thingsboard -t ts_kv_latest > ts_kv_latest.dmp`
+3. [Optional] move table dumps to the instance where cassandra will be hosted
 
-3. [Optional] - move dumped files to the machine where cassandra will be hosted
+#### Prepare directory structure for SSTables
+Tool use 3 different directories for saving SSTables - `ts_kv_cf`, `ts_kv_latest_cf`, `ts_kv_partitions_cf`
 
-4. Prepare directory structure:
-Tool will use 3 different directories for saving SSTables - ts_kv_cf, ts_kv_latest_cf, ts_kv_partitions_cf
 Create 3 empty directories. For example:
+
     /home/ubunut/migration/ts
     /home/ubunut/migration/ts_latest
     /home/ubunut/migration/ts_partition
     
-5. Run tool:
-*Note: if you run this tool on remote instance - don't forget to execute this command in screen to avoid unexpected termination
+#### Run tool
+*Note: if you run this tool on remote instance - don't forget to execute this command in `screen` to avoid unexpected termination
+
+```
 java -jar ./tools-2.4.1-SNAPSHOT-jar-with-dependencies.jar 
-        -latestFrom ./source/ts_kv_latest.dmp 
+        -latestFrom ./source/ts_kv_latest.dmp
         -latestOut /home/ubunut/migration/ts_latest 
         -tsFrom ./source/ts_kv.dmp
         -tsOut /home/ubunut/migration/ts  
         -partitionsOut /home/ubunut/migration/ts_partition
-        -castEnable false  
+        -castEnable false
+```  
 
+Tool execution time depends on DB size, CPU resources and Disk throughput
 
-## After tool finished
-1. install Cassandra on the instance
-2. Using `cqlsh` create `thingsboard` keyspace and requred tables from this file `schema-ts.cql`
+## Adding SSTables into Cassandra
+* Note that this this part works only for single node Cassandra Cluster. If you have more nodes - it is better to use `sstableloader` tool.
+
+1. [Optional] install Cassandra on the instance
+2. [Optional] Using `cqlsh` create `thingsboard` keyspace and requred tables from this file `schema-ts.cql`
 3. Stop Cassandra
 4. Copy generated SSTable files into cassandra data dir:
+
+```
     sudo find /home/ubunut/migration/ts -name '*.*' -exec mv {} /var/lib/cassandra/data/thingsboard/ts_kv_cf-0e9aaf00ee5511e9a5fa7d6f489ffd13/ \;
     sudo find /home/ubunut/migration/ts_latest -name '*.*' -exec mv {} /var/lib/cassandra/data/thingsboard/ts_kv_latest_cf-161449d0ee5511e9a5fa7d6f489ffd13/ \;
     sudo find /home/ubunut/migration/ts_partition -name '*.*' -exec mv {} /var/lib/cassandra/data/thingsboard/ts_kv_partitions_cf-12e8fa80ee5511e9a5fa7d6f489ffd13/ \;
+```   
     
 5. Start Cassandra service and trigger compaction
+
+```
     trigger compactions: nodetool compact thingsboard
     check compaction status: nodetool compactionstats
+```
     
-6. Switch Thignsboard to hybrid mode:
+## Switch Thignsboard into Hybrid Mode
+
 Modify Thingsboard properites file `thingsboard.yml`
+
     - DATABASE_TS_TYPE = cassandra
-    - TS_KV_PARTITIONING = MONTHS
-    - [optional] - connection properties for cassandra
+    - TS_KV_PARTITIONING = MONTHS    
     
-7. Start Thingsboard
+# Final steps
+Start Thingsboard and verify migration