[admin] Enable peeking encrypted batch messages

[massakam]

Motivation

We can peek non-batched messages successfully, even if they are encrypted:

$ ./bin/pulsar-admin topics peek-messages -s sub1 persistent://public/default/non-batch

Message ID: 2:0
Tenants:
"publish-time    2021-07-07T13:43:07.621+09:00"
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| f5 ac 6c 84 87 21 ec 67 8c 84 62 1c d5 ff 1f e0 |..l..!.g..b.....|
|00000010| 6a 87 be 62 10                                  |j..b.           |
+--------+-------------------------------------------------+----------------+

On the other hand, if batched messages are encrypted, an exception will be thrown when peeking:

$ ./bin/pulsar-admin topics peek-messages -s sub1 persistent://public/default/batch

13:48:29.578 [AsyncHttpClient-7-1] ERROR org.apache.pulsar.client.admin.internal.TopicsImpl - Exception occurred while trying to get BatchMsgId: 0:0:0
java.lang.IllegalArgumentException: Invalid unknonwn tag type: 6
        at org.apache.pulsar.common.api.proto.LightProtoCodec.skipUnknownField(LightProtoCodec.java:270) ~[pulsar-common.jar:2.9.0-SNAPSHOT]
        at org.apache.pulsar.common.api.proto.SingleMessageMetadata.parseFrom(SingleMessageMetadata.java:470) ~[pulsar-common.jar:2.9.0-SNAPSHOT]
        at org.apache.pulsar.common.protocol.Commands.deSerializeSingleMessageInBatch(Commands.java:1624) ~[pulsar-common.jar:2.9.0-SNAPSHOT]
        at org.apache.pulsar.client.admin.internal.TopicsImpl.getIndividualMsgsFromBatch(TopicsImpl.java:1558) ~[pulsar-client-admin-original.jar:2.9.0-SNAPSHOT]
        at org.apache.pulsar.client.admin.internal.TopicsImpl.getMessagesFromHttpResponse(TopicsImpl.java:1540) ~[pulsar-client-admin-original.jar:2.9.0-SNAPSHOT]
        at org.apache.pulsar.client.admin.internal.TopicsImpl.access$100(TopicsImpl.java:90) ~[pulsar-client-admin-original.jar:2.9.0-SNAPSHOT]
        at org.apache.pulsar.client.admin.internal.TopicsImpl$15.completed(TopicsImpl.java:1027) ~[pulsar-client-admin-original.jar:2.9.0-SNAPSHOT]
        at org.apache.pulsar.client.admin.internal.TopicsImpl$15.completed(TopicsImpl.java:1022) ~[pulsar-client-admin-original.jar:2.9.0-SNAPSHOT]
        ...

This is probably because the payload of the batch message is encrypted and it fails to retrieve the individual payloads from it.

Modifications

When an encrypted message is peeked, the broker returns a response with the value of the X-Pulsar-Is-Encrypted header set to true. Then, admin client treats it as a non-batch message and creates a MessageImpl instance. This fix enables us to peek the message without throwing an exception.

$ ./bin/pulsar-admin topics peek-messages -s sub1 persistent://public/default/batch

Message ID: 17:0
Tenants:
"X-Pulsar-batch-size    -292"
"X-Pulsar-num-batch-message    1"
"publish-time    2021-07-07T16:10:45.014+09:00"
         +-------------------------------------------------+
         |  0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f |
+--------+-------------------------------------------------+----------------+
|00000000| 73 3c bf c9 d9 c7 bd 56 6f ac 71 e8 8d 7b fa 33 |s<.....Vo.q..{.3|
|00000010| 2a 46 1e 9e 30 bb e2 7e ff 8c 41 9e a2          |*F..0..~..A..   |
+--------+-------------------------------------------------+----------------+