[rocketmq-clients] branch master updated: Docs: complete the part about message identifier (#16)

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The following commit(s) were added to refs/heads/master by this push:
     new 3475874  Docs: complete the part about message identifier (#16)
3475874 is described below

commit 34758741fd6d6d905aae173744fcb29ea034a8a2
Author: Aaron Ai <ya...@gmail.com>
AuthorDate: Fri Jun 24 15:06:03 2022 +0800

    Docs: complete the part about message identifier (#16)
---
 docs/artwork/message_id.png | Bin 107463 -> 106718 bytes
 docs/message_id.md          |  18 +++++++++++++++---
 2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/docs/artwork/message_id.png b/docs/artwork/message_id.png
index 058aed0..72b26fc 100644
Binary files a/docs/artwork/message_id.png and b/docs/artwork/message_id.png differ
diff --git a/docs/message_id.md b/docs/message_id.md
index 89e7c1e..aa58cb7 100644
--- a/docs/message_id.md
+++ b/docs/message_id.md
@@ -6,8 +6,8 @@ Here is the new design for message identifier.
 
 In the past, there are two types of implementation of message identifier.
 
-1. Message identifier based on the broker address and the offset in message queue, find in [MessageDecoder#createMessageId](https://github.com/apache/rocketmq/blob/release-4.9.3/common/src/main/java/org/apache/rocketmq/common/message/MessageDecoder.java#L62-L71).
-2. Message identifier based on the client IP and unix timestamp, find in [MessageClientIDSetter#createUniqID](https://github.com/apache/rocketmq/blob/release-4.9.3/common/src/main/java/org/apache/rocketmq/common/message/MessageClientIDSetter.java#L114-L131).
+1. Message identifier based on the broker address and the offset in message queue, see [MessageDecoder#createMessageId](https://github.com/apache/rocketmq/blob/release-4.9.3/common/src/main/java/org/apache/rocketmq/common/message/MessageDecoder.java#L62-L71).
+2. Message identifier based on the client IP and unix timestamp, see [MessageClientIDSetter#createUniqID](https://github.com/apache/rocketmq/blob/release-4.9.3/common/src/main/java/org/apache/rocketmq/common/message/MessageClientIDSetter.java#L114-L131).
 
 The first type of message identifier is purely based on server-side information, which makes each message stored on the broker absolutely unique. The second message identifier is purely based on client information.
 
@@ -19,4 +19,16 @@ As for the second type, there are some major flaws in the algorithm design. Firs
 
 ## Detailed Design
 
-![The Message Identifier Illustration](../docs/artwork/message_id.png)
\ No newline at end of file
+![The Message Identifier Illustration](../docs/artwork/message_id.png)
+
+This illustration shows an example of message identifier. The version number of the newly designed version is 0x01, and number of all previous versions is 0x00. The message identifier's length is 17 bytes if its version is higher than 0x00, then we convert it to uppercase hexadecimal to get the message identifier in string format.
+
+>**Note**: Big endian byte order is used to place data in message identifier.
+
+Take the message identifier in the figure as an example, it could be divided into 5 parts:
+
+* **0x01**: fixed 1 byte for current version.
+* **0x56F7E71C361B**: lower 6 bytes of local mac address.
+* **0x21BC**: lower 2 bytes of process id.
+* **0x024CCDBE**: seconds since 2021-01-01 00:00:00(UTC+0, lower 4 bytes).
+* **0x00000000**: sequence number(4 bytes).