How to print change data logs at stdout in yugabyte? - yugabytedb

Question

I am using yugabyte db 1.3.0.0 and following https://docs.yugabyte.com/latest/deploy/cdc/use-cdc/ to learn yugabyte db cdc.
Procedure Followed:
a) generate users dynamically and insert into table, yugastore.users continuously through script
b) downloaded yb-cdc-connector.jar using command, wget -O yb-cdc-connector.jar https://github.com/yugabyte/yb-kafka-connector/blob/master/yb-cdc/yb-cdc-connector.jar?raw=true
c)copied yb-cdc-connector.jar to jre/lib/ext using command cp -a /root/yb-cdc-connector.jar /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-0.el7_7.x86_64/jre/lib/ext/
d) java -jar /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-0.el7_7.x86_64/jre/lib/ext/yb_cdc_connector.jar --table_name yugastore.users --master_addrs 127.0.0.1 --stream_id 1 --log_only
Error Logs:
[root#srvr0 ~]# java -jar /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-0.el7_7.x86_64/jre/lib/ext/yb_cdc_connector.jar --table_name yugastore.users --master_addrs 127.0.0.1 --stream_id 1 --log_only
Error: Unable to access jarfile /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-0.el7_7.x86_64/jre/lib/ext/yb_cdc_connector.jar
Records Insertion:
yugastore=> select count(*) from yugastore.users;
count
-------
59414
(1 row)
yugastore=> select count(*) from yugastore.users;
count
-------
60066
(1 row)
yugastore=> select count(*) from yugastore.users;
count
-------
79341
(1 row)
yugastore=>
java:
[root#srvr0 ~]# java -version
openjdk version "1.8.0_232"
OpenJDK Runtime Environment (build 1.8.0_232-b09)
OpenJDK 64-Bit Server VM (build 25.232-b09, mixed mode)
Availability of yb-cdc-connector.jar:
[root#srvr0 ~]# ll /usr/lib/jvm/java-1.8.0-openjdk-1.8.0.232.b09-0.el7_7.x86_64/jre/lib/ext/
total 54756
-rw-r--r--. 1 root root 4003855 Oct 22 12:18 cldrdata.jar
-rw-r--r--. 1 root root 9445 Oct 22 12:18 dnsns.jar
-rw-r--r--. 1 root root 48733 Oct 22 12:18 jaccess.jar
-rw-r--r--. 1 root root 1204895 Oct 22 12:18 localedata.jar
-rw-r--r--. 1 root root 617 Oct 22 12:18 meta-index
-rw-r--r--. 1 root root 2033680 Oct 22 12:18 nashorn.jar
-rw-r--r--. 1 root root 52079 Oct 22 12:18 sunec.jar
-rw-r--r--. 1 root root 304504 Oct 22 12:18 sunjce_provider.jar
-rw-r--r--. 1 root root 279788 Oct 22 12:18 sunpkcs11.jar
-rw-r--r--. 1 root root 48026360 Jan 16 08:31 yb-cdc-connector.jar
-rw-r--r--. 1 root root 78006 Oct 22 12:18 zipfs.jar
Please help me in printing change logs at stdout!
Update1:
small correction required in the doc: edit yb_cdc_connector.jar to yb-cdc-connector.jar in the document command, as wget downloads as yb_cdc_connector.jar.
Though there are changes happening (inserts and deletes) to the table, it showing polling but no cdc is printed.
Logs:
[root#srvr0 ~]# java -jar ./yb_cdc_connector.jar --table_name yugastore.users --master_addrs 127.0.0.1 --stream_id 1 --log_only
[2020-01-22 01:37:24,221] INFO Starting CDC Kafka Connector... (org.yb.cdc.Main:28)
2020-01-22 01:37:24,393 [INFO|org.yb.cdc.KafkaConnector|KafkaConnector] Creating new YB client...
[2020-01-22 01:37:28,344] INFO Discovered tablet YB Master for table YB Master with partition ["", "") (org.yb.client.AsyncYBClient:1593)
2020-01-22 01:37:28,839 [INFO|org.yb.cdc.KafkaConnector|KafkaConnector] Polling for new tablet c6f3d759202341ecad87e2617579371c
2020-01-22 01:37:28,842 [INFO|org.yb.cdc.KafkaConnector|KafkaConnector] Polling for new tablet e94b1748d1a742289500a30a38ff9eda
Insertion:
time: 01:37:49.980 cumulative records: 10
time: 01:37:52.169 cumulative records: 20
time: 01:37:52.410 cumulative records: 30
time: 01:37:52.425 cumulative records: 40
...
time: 01:39:28.139 cumulative records: 970
time: 01:39:28.171 cumulative records: 980
time: 01:39:28.208 cumulative records: 990
time: 01:39:28.246 cumulative records: 1000
Deletion :
yugastore=# delete from yugastore.users;
DELETE 21314
yugastore=# select count(*) from yugastore.users;
count
-------
0
(1 row)

Answer 1

The error shows that the jar file cannot be accessed in the system directory you moved. Most likely a permission issue. Note that you don't even need to move this jar into a system directory. So keeping the jar is some normal directory is the simplest option.
Also, you don't need the stream_id as well since you want the default behavior most times. So try the following command in a user directory where you have the jar file.
java -jar ./yb_cdc_connector.jar \
--table_name yugastore.users \
--master_addrs 127.0.0.1:7100 \
--log_only