kafka connector 使用總結以及自定義connector開發

時間  2019-11-26
標籤 kafka connector 使用 總結 以及 自定義 開發 欄目 Kafka 简体版
原文   原文鏈接

Kafaka connect 是一種用於在Kafka和其餘系統之間可擴展的、可靠的流式傳輸數據的工具。它使得可以快速定義將大量數據集合移入和移出Kafka的鏈接器變得簡單。Kafka Connect能夠從數據庫或應用程序服務器收集數據到Kafka topic，使數據可用於低延遲的流處理。導出做業能夠將數據從Kafka topic傳輸到二次存儲和查詢系統，或者傳遞到批處理系統以進行離線分析。html

Kafaka connect的核心組件：
Source：負責將外部數據寫入到kafka的topic中。
Sink：負責從kafka中讀取數據到本身須要的地方去，好比讀取到HDFS，hbase等。java


Connectors ：經過管理任務來協調數據流的高級抽象
Tasks：數據寫入kafk和從kafka中讀出數據的具體實現，source和sink使用時都須要Taskgit

Workers：運行connectors和tasks的進程github

Converters：kafka connect和其餘存儲系統直接發送或者接受數據之間轉換數據，mongodb

converter會把bytes數據轉換成kafka connect內部的格式，也能夠把kafka connect內部存儲格式的數據轉變成bytes，converter對connector來講是解耦的，因此其餘的connector均可以重用，例如，使用了avro converter，那麼jdbc connector能夠寫avro格式的數據到kafka，固然，hdfs connector也能夠從kafka中讀出avro格式的數據。數據庫

 

Transforms：一種輕量級數據調整的工具
Kafka connect 工做模式：
Kafka connect 有兩種工做模式：
standalone：在standalone模式中，全部的worker都在一個獨立的進程中完成。
distributed：distributed模式具備高擴展性，以及提供自動容錯機制。你可使用一個group.ip來啓動不少worker進程，在有效的worker進程中它們會自動的去協調執行connector和task，若是你新加了一個worker或者掛了一個worker，其餘的worker會檢測到而後在從新分配connector和task。express

本文做者：張永清，轉載請註明出處：http://www.javashuo.com/article/p-hmfroyuv-dd.html apache

在分佈式模式下經過rest api來管理connector。
connector的常見管理操做API：json

GET /connectors – 返回全部正在運行的connector名。
POST /connectors – 新建一個connector; 請求體必須是json格式而且須要包含name字段和config字段，name是connector的名字，config是json格式，必須包含你的connector的配置信息。
GET /connectors/{name} – 獲取指定connetor的信息。
GET /connectors/{name}/config – 獲取指定connector的配置信息。
PUT /connectors/{name}/config – 更新指定connector的配置信息。
GET /connectors/{name}/status – 獲取指定connector的狀態，包括它是否在運行、中止、或者失敗，若是發生錯誤，還會列出錯誤的具體信息。
GET /connectors/{name}/tasks – 獲取指定connector正在運行的task。
GET /connectors/{name}/tasks/{taskid}/status – 獲取指定connector的task的狀態信息。
PUT /connectors/{name}/pause – 暫停connector和它的task，中止數據處理知道它被恢復。
PUT /connectors/{name}/resume – 恢復一個被暫停的connector。
POST /connectors/{name}/restart – 重啓一個connector，尤爲是在一個connector運行失敗的狀況下比較經常使用
POST /connectors/{name}/tasks/{taskId}/restart – 重啓一個task，通常是由於它運行失敗才這樣作。
DELETE /connectors/{name} – 刪除一個connector，中止它的全部task並刪除配置。

如何開發本身的Connector：bootstrap

一、引入maven依賴。

        <dependency>
            <groupId>org.apache.kafka</groupId>
            <artifactId>connect-api</artifactId>
            <version>${kafka.version}</version>
        </dependency>

二、開發自定義的Source

開發自定義的Source 須要繼承實現SourceConnector和SourceTask這兩個抽象類，實現抽象類中的未實現的方法或者重寫抽象類中的方法。

本文做者：張永清，轉載請註明出處：http://www.javashuo.com/article/p-hmfroyuv-dd.html 

A、開發自定義的SourceConnector

/**
 *
 */
public class ExampleSourceConnector extends SourceConnector{
    @Override
    public void start(Map<String, String> map) {

    }
    //返回須要指定的TASK
    @Override
    public Class<? extends Task> taskClass() {
        return ExampleSourceTask.class;
    }
    //TASK的配置
    @Override
    public List<Map<String, String>> taskConfigs(int i) {
        return null;
    }

    @Override
    public void stop() {

    }

    @Override
    public ConfigDef config() {
        return null;
    }

    @Override
    public String version() {
        return AppInfoParser.getVersion();
    }
}

B、開發Source對應的Task

public class ExampleSourceTask extends SourceTask {
    @Override
    public String version() {
        return new ExampleSourceConnector().version();
    }
    //任務啓動
    @Override
    public void start(Map<String, String> map) {

    }
    //須要發送到kafka的數據。
    @Override
    public List<SourceRecord> poll() throws InterruptedException {
        return null;
    }
    //任務中止
    @Override
    public void stop() {

    }
}

三、開發自定義的Sink

　　開發自定義的Sink 須要繼承實現SinkConnector和SinkTask這兩個抽象類，實現抽象類中的未實現的方法或者重寫抽象類中的方法。

A、開發自定義的SinkConnector

/**
 *
 */
public class ExampleSinkConnector extends SinkConnector{
    @Override
    public void start(Map<String, String> map) {

    }
    //指定Task執行的類
    @Override
    public Class<? extends Task> taskClass() {
        return ExampleSinkTask.class;
    }
    //task對應的config
    @Override
    public List<Map<String, String>> taskConfigs(int i) {
        return null;
    }

    @Override
    public void stop() {

    }
    //配置定義
    @Override
    public ConfigDef config() {
        return null;
    }

    @Override
    public String version() {
        return AppInfoParser.getVersion();
    }
}

B、開發Sink對應的Task　　

/**
 *
 */
public class ExampleSinkTask extends SinkTask {
    @Override
    public String version() {
        return new ExampleSinkConnector().version();
    }
    //task啓動
    @Override
    public void start(Map<String, String> map) {

    }
    //數據put
    @Override
    public void put(Collection<SinkRecord> collection) {

    }
    @Override
    public void flush(Map<TopicPartition, OffsetAndMetadata> offsets){
    //Task中止。
    }
    @Override
    public void stop() {

    }
}

Kafka Connect Configs

 開源的實現的比較好的connector項目：

https://github.com/debezium/debezium 

https://github.com/confluentinc

 

 

 https://docs.confluent.io/current/connect/managing/connectors.html

 

 這裏咱們以https://github.com/debezium/debezium 中的debezium-connector-mongodb 爲例配置connector的standalone模式運行

從github中獲取debezium-connector-mongodb-0.9.5.Final.jar 包，放到kafka的libs目錄下，而且把mongodb相關的jar包一塊兒放入到libs下。

在config目錄下新建對應的mongodb.properties 屬性配置文件

name=mongodb
connector.class=io.debezium.connector.mongodb.MongoDbConnector
mongodb.hosts=configs/10.100.xx.xx:27017
tasks.max=1
mongodb.name=mongo-test
#mongodb.user=root
#mongodb.password=123456
database.whitelist=kafkaTest
collection.whitelist=kafkaTest.kafkaTest
connect.max.attempts=12
max.queue.size=8192
max.batch.size=2048
poll.interval.ms=1000
connect.backoff.initial.delay.ms=1000
connect.backoff.max.delay.ms=2000
mongodb.ssl.enabled=false
mongodb.ssl.invalid.hostname.allowed=false
snapshot.mode=initial
initial.sync.max.threads=2
tombstones.on.delete=true
mongodb.members.auto.discover=true
source.struct.version=v2

 配置解釋以下：

詳情參考：https://debezium.io/documentation/reference/0.10/connectors/mongodb.html

https://docs.confluent.io/current/connect/debezium-connect-mongodb/mongodb_source_connector_config.html

Property Default Description

name

  

Unique name for the connector. Attempting to register again with the same name will fail. (This property is required by all Kafka Connect connectors.)

connector.class

  

The name of the Java class for the connector. Always use a value of io.debezium.connector.mongodb.MongoDbConnector for the MongoDB connector.

mongodb.hosts

  

The comma-separated list of hostname and port pairs (in the form 'host' or 'host:port') of the MongoDB servers in the replica set. The list can contain a single hostname and port pair. If mongodb.members.auto.discover is set to false, then the host and port pair should be prefixed with the replica set name (e.g., rs0/localhost:27017).

mongodb.name

  

A unique name that identifies the connector and/or MongoDB replica set or sharded cluster that this connector monitors. Each server should be monitored by at most one Debezium connector, since this server name prefixes all persisted Kafka topics emanating from the MongoDB replica set or cluster.

mongodb.user

  

Name of the database user to be used when connecting to MongoDB. This is required only when MongoDB is configured to use authentication.

mongodb.password

  

Password to be used when connecting to MongoDB. This is required only when MongoDB is configured to use authentication.

mongodb.ssl.enabled

false

Connector will use SSL to connect to MongoDB instances.

mongodb.ssl.invalid.hostname.allowed

false

When SSL is enabled this setting controls whether strict hostname checking is disabled during connection phase. If true the connection will not prevent man-in-the-middle attacks.

database.whitelist

empty string

An optional comma-separated list of regular expressions that match database names to be monitored; any database name not included in the whitelist will be excluded from monitoring. By default all databases will be monitored. May not be used with database.blacklist.

database.blacklist

empty string

An optional comma-separated list of regular expressions that match database names to be excluded from monitoring; any database name not included in the blacklist will be monitored. May not be used with database.whitelist.

collection.whitelist

empty string

An optional comma-separated list of regular expressions that match fully-qualified namespaces for MongoDB collections to be monitored; any collection not included in the whitelist will be excluded from monitoring. Each identifier is of the form databaseName.collectionName. By default the connector will monitor all collections except those in the local and admin databases. May not be used with collection.blacklist.

collection.blacklist

empty string

An optional comma-separated list of regular expressions that match fully-qualified namespaces for MongoDB collections to be excluded from monitoring; any collection not included in the blacklist will be monitored. Each identifier is of the form databaseName.collectionName. May not be used with collection.whitelist.

snapshot.mode

initial

Specifies the criteria for running a snapshot (eg. initial sync) upon startup of the connector. The default is initial, and specifies the connector reads a snapshot when either no offset is found or if the oplog no longer contains the previous offset. The never option specifies that the connector should never use snapshots, instead the connector should proceed to tail the log.

field.blacklist

empty string

An optional comma-separated list of the fully-qualified names of fields that should be excluded from change event message values. Fully-qualified names for fields are of the form databaseName.collectionName.fieldName.nestedFieldName, where databaseName and collectionName may contain the wildcard (*) which matches any characters.

field.renames

empty string

An optional comma-separated list of the fully-qualified replacements of fields that should be used to rename fields in change event message values. Fully-qualified replacements for fields are of the form databaseName.collectionName.fieldName.nestedFieldName:newNestedFieldName, where databaseName and collectionName may contain the wildcard (*) which matches any characters, the colon character (:) is used to determine rename mapping of field. The next field replacement is applied to the result of the previous field replacement in the list, so keep this in mind when renaming multiple fields that are in the same path.

tasks.max

1

The maximum number of tasks that should be created for this connector. The MongoDB connector will attempt to use a separate task for each replica set, so the default is acceptable when using the connector with a single MongoDB replica set. When using the connector with a MongoDB sharded cluster, we recommend specifying a value that is equal to or more than the number of shards in the cluster, so that the work for each replica set can be distributed by Kafka Connect.

initial.sync.max.threads

1

Positive integer value that specifies the maximum number of threads used to perform an intial sync of the collections in a replica set. Defaults to 1.

tombstones.on.delete

true

Controls whether a tombstone event should be generated after a delete event.
When true the delete operations are represented by a delete event and a subsequent tombstone event. When false only a delete event is sent.
Emitting the tombstone event (the default behavior) allows Kafka to completely delete all events pertaining to the given key once the source record got deleted.

snapshot.delay.ms

  

An interval in milli-seconds that the connector should wait before taking a snapshot after starting up;
Can be used to avoid snapshot interruptions when starting multiple connectors in a cluster, which may cause re-balancing of connectors.

snapshot.fetch.size

0

Specifies the maximum number of documents that should be read in one go from each collection while taking a snapshot. The connector will read the collection contents in multiple batches of this size.
Defaults to 0, which indicates that the server chooses an appropriate fetch size.

The following advanced configuration properties have good defaults that will work in most situations and therefore rarely need to be specified in the connector’s configuration.

Property Default Description

max.queue.size

8192

Positive integer value that specifies the maximum size of the blocking queue into which change events read from the database log are placed before they are written to Kafka. This queue can provide backpressure to the oplog reader when, for example, writes to Kafka are slower or if Kafka is not available. Events that appear in the queue are not included in the offsets periodically recorded by this connector. Defaults to 8192, and should always be larger than the maximum batch size specified in the max.batch.size property.

max.batch.size

2048

Positive integer value that specifies the maximum size of each batch of events that should be processed during each iteration of this connector. Defaults to 2048.

poll.interval.ms

1000

Positive integer value that specifies the number of milliseconds the connector should wait during each iteration for new change events to appear. Defaults to 1000 milliseconds, or 1 second.

connect.backoff.initial.delay.ms

1000

Positive integer value that specifies the initial delay when trying to reconnect to a primary after the first failed connection attempt or when no primary is available. Defaults to 1 second (1000 ms).

connect.backoff.max.delay.ms

1000

Positive integer value that specifies the maximum delay when trying to reconnect to a primary after repeated failed connection attempts or when no primary is available. Defaults to 120 seconds (120,000 ms).

connect.max.attempts

16

Positive integer value that specifies the maximum number of failed connection attempts to a replica set primary before an exception occurs and task is aborted. Defaults to 16, which with the defaults for connect.backoff.initial.delay.ms and connect.backoff.max.delay.msresults in just over 20 minutes of attempts before failing.

mongodb.members.auto.discover

true

Boolean value that specifies whether the addresses in 'mongodb.hosts' are seeds that should be used to discover all members of the cluster or replica set (true), or whether the address(es) in mongodb.hosts should be used as is (false). The default is true and should be used in all cases except where MongoDB is fronted by a proxy.

source.struct.version

v2

Schema version for the source block in CDC events; Debezium 0.10 introduced a few breaking
changes to the structure of the source block in order to unify the exposed structure across all the connectors.
By setting this option to v1 the structure used in earlier versions can be produced. Note that this setting is not recommended and is planned for removal in a future Debezium version.

heartbeat.interval.ms

0

Controls how frequently heartbeat messages are sent.
This property contains an interval in milli-seconds that defines how frequently the connector sends messages into a heartbeat topic. This can be used to monitor whether the connector is still receiving change events from the database. You also should leverage heartbeat messages in cases where only records in non-captured collections are changed for a longer period of time. In such situation the connector would proceed to read the oplog from the database but never emit any change messages into Kafka, which in turn means that no offset updates will be committed to Kafka. This will cause the oplog files to be rotated out but connector will not notice it so on restart some events are no longer available which leads to the need of re-execution of the initial snapshot.

Set this parameter to 0 to not send heartbeat messages at all.
Disabled by default.

heartbeat.topics.prefix

__debezium-heartbeat

Controls the naming of the topic to which heartbeat messages are sent.
The topic is named according to the pattern <heartbeat.topics.prefix>.<server.name>.

sanitize.field.names

true when connector configuration explicitly specifies the key.converter or value.converterparameters to use Avro, otherwise defaults to false.

Whether field names will be sanitized to adhere to Avro naming requirements. See Avro namingfor more details.

這裏以standalone的模式運行，在connect-standalone.properties中作以下配置：

# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements.  See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); 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
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# These are defaults. This file just demonstrates how to override some settings.
bootstrap.servers=localhost:9092
rest.port=9093
# The converters specify the format of data in Kafka and how to translate it into Connect data. Every Connect user will
# need to configure these based on the format they want their data in when loaded from or stored into Kafka
key.converter=org.apache.kafka.connect.json.JsonConverter
value.converter=org.apache.kafka.connect.json.JsonConverter
# Converter-specific settings can be passed in by prefixing the Converter's setting with the converter we want to apply
# it to
key.converter.schemas.enable=false
value.converter.schemas.enable=false
rest.host.name=0.0.0.0
offset.storage.file.filename=/data4/kafka/connect/connect.offsets
# Flush much faster than normal, which is useful for testing/debugging
offset.flush.interval.ms=10000

# Set to a list of filesystem paths separated by commas (,) to enable class loading isolation for plugins
# (connectors, converters, transformations). The list should consist of top level directories that include
# any combination of:
# a) directories immediately containing jars with plugins and their dependencies
# b) uber-jars with plugins and their dependencies
# c) directories immediately containing the package directory structure of classes of plugins and their dependencies
# Note: symlinks will be followed to discover dependencies or plugins.
# Examples:
# plugin.path=/usr/local/share/java,/usr/local/share/kafka/plugins,/opt/connectors,
plugin.path=/opt/kafka/kafka_2.11-2.0.0/plugin

standalone模式下啓動方式以下：

bin/connect-standalone.sh config/connect-standalone.properties connector1.properties[connector2.properties ...]   一次能夠啓動多個connector，只須要在參數中加上connector的配置文件路徑便可。

例如：connect-standalone.sh config/connect-standalone.properties mongodb.properties

distribute模式部署：

一、修改配置connect-distributed.properties

# broker列表
bootstrap.servers=10.120.241.1:9200
 
# 同一集羣中group.id須要配置一致，且不能和別的消費者同名
group.id=connect-cluster
 
# The converters specify the format of data in Kafka and how to translate it into Connect data. Every Connect user will
# need to configure these based on the format they want their data in when loaded from or stored into Kafka
key.converter=org.apache.kafka.connect.json.JsonConverter
value.converter=org.apache.kafka.connect.json.JsonConverter
# 使用json數據一樣配置成false
key.converter.schemas.enable=false
value.converter.schemas.enable=false
····

二、手動建立集羣模式所必須的kafka的幾個topic

# config.storage.topic=connect-configs
$ bin/kafka-topics --create --zookeeper localhost:2181 --topic connect-configs --replication-factor 3 --partitions 1 --config cleanup.policy=compact
 
# offset.storage.topic=connect-offsets
$ bin/kafka-topics --create --zookeeper localhost:2181 --topic connect-offsets --replication-factor 3 --partitions 50 --config cleanup.policy=compact
 
# status.storage.topic=connect-status
$ $ bin/kafka-topics --create --zookeeper localhost:2181 --topic connect-status --replication-factor 3 --partitions 10 --config cleanup.policy=compact
  • config.storage.topic：topic用於存儲connector和任務配置；注意，這應該是一個單個的partition，多副本的topic
  • offset.storage.topic：用於存儲offsets；這個topic應該配置多個partition和副本。
  • status.storage.topic：用於存儲狀態；這個topic 能夠有多個partitions和副本

三、 啓動worker

啓動distributed模式命令以下：

./bin/connect-distributed ./etc/kafka/connect-distributed.properties   

四、使用restful啓動connect
curl 'http://localhost:8083/connectors' -X POST -i -H "Content-Type:application/json" -d   
    '{ "name":"elasticsearch-sink",  
       "config":{"connector.class":"io.confluent.connect.elasticsearch.ElasticsearchSinkConnector",  
                "tasks.max":10,  
                "topics":"estest1012",  
                "key.ignore":true,  
                "schema.ignore":true,  
                "connection.url":"http://10.120.241.194:9200",  
                "type.name":"kafka-connect"}  
    }'　

常見問題：

一、在啓動的過程當中出現各類各樣的java.lang.ClassNotFoundException。

在啓動connector的時候，一開始老是會報各個各樣的ClassNotFoundException，不是這個包就是那個包，查找問題一直說要麼缺乏包要麼是包衝突，那麼要排除依賴衝突或者看下是否是少了jar包。

二、在connector.properties中的key.converter.schemas.enable=false和value.converter.schemas.enable=false的問題。

這個選項默認在connect-standalone.properties中是true的，這個時候發送給topic的Json格式是須要使用avro格式。例如：
{
    "schema": {
        "type": "struct",
        "fields": [{
            "type": "int32",
            "optional": true,
            "field": "c1"
        }, {
            "type": "string",
            "optional": true,
            "field": "c2"
        }, {
            "type": "int64",
            "optional": false,
            "name": "org.apache.kafka.connect.data.Timestamp",
            "version": 1,
            "field": "create_ts"
        }, {
            "type": "int64",
            "optional": false,
            "name": "org.apache.kafka.connect.data.Timestamp",
            "version": 1,
            "field": "update_ts"
        }],
        "optional": false,
        "name": "foobar"
    },
    "payload": {
        "c1": 10000,
        "c2": "bar",
        "create_ts": 1501834166000,
        "update_ts": 1501834166000
    }
}

若是想發送普通的json格式而不是avro格式的話，很簡單key.converter.schemas.enable和value.converter.schemas.enable設置爲false就行。這樣就能發送普通的json格式數據。

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