MINOR: Fix indentation for several doc pages (#10766)
Fixes the indentation of the code listings for:
api.html
configuration.html
design.html
implementation.html
toc.html
These changes consist of whitespaces added or removed for consistency. It also contains a couple of fixes on unbalanced html tags.
Reviewers: Luke Chen <showuon@gmail.com>, Bill Bejeck <bbejeck@apache.org>
Broker properties (quota.producer.default, quota.consumer.default) can also be used to set defaults of network bandwidth quotas for client-id groups. These properties are being deprecated and will be removed in a later release.
Default quotas for client-id can be set in Zookeeper similar to the other quota overrides and defaults.
<p> Note that when compression is enabled, the compressed record data is serialized directly following the count of the number of records. </p>
<p>The CRC covers the data from the attributes to the end of the batch (i.e. all the bytes that follow the CRC). It is located after the magic byte, which
@ -71,13 +71,13 @@
@@ -71,13 +71,13 @@
<h5class="anchor-heading"><aid="controlbatch"class="anchor-link"></a><ahref="#controlbatch">5.3.1.1 Control Batches</a></h5>
<p>A control batch contains a single record called the control record. Control records should not be passed on to applications. Instead, they are used by consumers to filter out aborted transactional messages.</p>
<p> The key of a control record conforms to the following schema: </p>
<p><preclass="line-numbers"><codeclass="language-java">version: int16 (current version is 0)
type: int16 (0 indicates an abort marker, 1 indicates a commit)</code></pre></p>
<preclass="line-numbers"><codeclass="language-text">version: int16 (current version is 0)
type: int16 (0 indicates an abort marker, 1 indicates a commit)</code></pre>
<p>The schema for the value of a control record is dependent on the type. The value is opaque to clients.</p>
<p>We use the same varint encoding as Protobuf. More information on the latter can be found <ahref="https://developers.google.com/protocol-buffers/docs/encoding#varints">here</a>. The count of headers in a record
message => crc magic_byte attributes timestamp key value
@ -134,9 +134,10 @@
@@ -134,9 +134,10 @@
bit 4~7: unused
timestamp => INT64
key => BYTES
value => BYTES</code></pre></p>
value => BYTES</code></pre>
<p>
In versions prior to Kafka 0.10, the only supported message format version (which is indicated in the magic value) was 0. Message format version 1 was introduced with timestamp support in version 0.10.
</p>
<ul>
<li>Similarly to version 2 above, the lowest bits of attributes represent the compression type.</li>
<li>In version 1, the producer should always set the timestamp type bit to 0. If the topic is configured to use log append time,
@ -144,7 +145,6 @@
@@ -144,7 +145,6 @@
the broker will overwrite the timestamp type and the timestamp in the message set.</li>
<li>The highest bits of attributes must be set to 0.</li>
</ul>
</p>
<p>In message format versions 0 and 1 Kafka supports recursive messages to enable compression. In this case the message's attributes must be set
to indicate one of the compression types and the value field will contain a message set compressed with that type. We often refer
to the nested messages as "inner messages" and the wrapping message as the "outer message." Note that the key should be null
@ -163,7 +163,7 @@
@@ -163,7 +163,7 @@
A log for a topic named "my_topic" with two partitions consists of two directories (namely <code>my_topic_0</code> and <code>my_topic_1</code>) populated with data files containing the messages for that topic. The format of the log files is a sequence of "log entries""; each log entry is a 4 byte integer <i>N</i> storing the message length which is followed by the <i>N</i> message bytes. Each message is uniquely identified by a 64-bit integer <i>offset</i> giving the byte position of the start of this message in the stream of all messages ever sent to that topic on that partition. The on-disk format of each message is given below. Each log file is named with the offset of the first message it contains. So the first file created will be 00000000000.kafka, and each additional file will have an integer name roughly <i>S</i> bytes from the previous file where <i>S</i> is the max log file size given in the configuration.
</p>
<p>
The exact binary format for records is versioned and maintained as a standard interface so record batches can be transferred between producer, broker, and client without recopying or conversion when desirable. The previous section included details about the on-disk format of records.</p>
The exact binary format for records is versioned and maintained as a standard interface so record batches can be transferred between producer, broker, and client without recopying or conversion when desirable. The previous section included details about the on-disk format of records.
</p>
<p>
The use of the message offset as the message id is unusual. Our original idea was to use a GUID generated by the producer, and maintain a mapping from GUID to offset on each broker. But since a consumer must maintain an ID for each server, the global uniqueness of the GUID provides no value. Furthermore, the complexity of maintaining the mapping from a random id to an offset requires a heavy weight index structure which must be synchronized with disk, essentially requiring a full persistent random-access data structure. Thus to simplify the lookup structure we decided to use a simple per-partition atomic counter which could be coupled with the partition id and node id to uniquely identify a message; this makes the lookup structure simpler, though multiple seeks per consumer request are still likely. However once we settled on a counter, the jump to directly using the offset seemed natural—both after all are monotonically increasing integers unique to a partition. Since the offset is hidden from the consumer API this decision is ultimately an implementation detail and we went with the more efficient approach.
Josep Prat
3 years ago
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