offset | 易学教程

rocketmq3.26研究之五DefaultMQPushConsumer

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DefaultMQPushConsumer rocketmq客户端消费者实现，从名字上已经可以看出其消息获取方式为broker往消费端推送数据，其内部实现了流控，消费位置上报等等。重要字段 1 String consumerGroup 消费者组名，必须设置需要注意的是，多个消费者如果具有同样的组名，那么这些消费者必须只消费同一个topic，具体原因参见 rocketmq问题汇总-一个consumerGroup只对应一个topic 2 MessageModel messageModel 消费的方式，分为两种： 2.1 BROADCASTING 广播模式，即所有的消费者可以消费同样的消息 2.2 CLUSTERING 集群模式，即所有的消费者平均来消费一组消息 3 ConsumeFromWhere consumeFromWhere 消费者从那个位置消费，分别为： 3.1 CONSUME_FROM_LAST_OFFSET：第一次启动从队列最后位置消费，后续再启动接着上次消费的进度开始消费 3.2 CONSUME_FROM_FIRST_OFFSET：第一次启动从队列初始位置消费，后续再启动接着上次消费的进度开始消费 3.3 CONSUME_FROM_TIMESTAMP：第一次启动从指定时间点位置消费，后续再启动接着上次消费的进度开始消费以上所说的第一次启动是指从来没有消费过的消费者

10、kafka消费者配置参数说明

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Consumer Configuration在kafka 0.9+使用Java Consumer替代了老版本的scala Consumer。新版的配置如下： bootstrap.servers 在启动consumer时配置的broker地址的。不需要将cluster中所有的broker都配置上，因为启动后会自动的发现cluster所有的broker。它配置的格式是：host1:port1;host2:port2… key.descrializer、value.descrializer Message record 的key, value的反序列化类。 group.id 用于表示该consumer想要加入到哪个group中。默认值是 “”。 heartbeat.interval.ms 心跳间隔。心跳是在consumer与coordinator之间进行的。心跳是确定consumer存活，加入或者退出group的有效手段。这个值必须设置的小于session.timeout.ms ，因为：当Consumer由于某种原因不能发Heartbeat到coordinator时，并且时间超过session.timeout.ms时，就会认为该consumer已退出，它所订阅的partition会分配到同一group 内的其它的consumer上。通常设置的值要低于session.timeout

Offset selectionChange Angular

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I have a form which contains 1 drop-down list and 2 inputs. I have a drop down list which contains several objects. When I select one of them, I can retrieve the whole object and I am supposed to filled the two other inputs with the value from the selected object. However, it seems there is an offset when I do that. For instance I have an object banana in my list. If i select it nothing will happen. The 2 other inputs will not be filled at first. Then if I select another object such as apple, the banana values will be retrieved and so on if I select Orange, Apple's values will be retrieved. In

Undefined offset error, but offset is not undefined

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问题 I'm getting: Notice: Undefined offset: 0 in my code, however I can print_r the element I am trying to get and its clearly defined. function get_members($entries_found) { $members = $entries_found[0]['member']; ... } If I print_r($members) I get the expected output, however I'm still getting the Notice. Any clues? 回答1: Do var_dump($entries_found); To check that the array does indeed have an offset of zero. Other things you can try would be reseting the array pointer reset($entries_found); of

Making sense of 'OFFSET/FETCH' in SSMS 2012

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Just installed Microsoft SQL Server Management Studio 2012 today. In familiarizing myself with the pagination feature addition of ORDER BY, I keep running into this error: Msg 102, Level 15, State 1, Line 5 Incorrect syntax near 'OFFSET'. Msg 153, Level 15, State 2, Line 6 Invalid usage of the option NEXT in the FETCH statement. Here is my query: SELECT SingleWomansName, NumberOfCats FROM CatLadies WHERE NumberOfCats > 1 ORDER BY NumberOfCats OFFSET 10 ROWS FETCH NEXT 5 ROWS ONLY I've seen plenty of how-to articles with similar syntax. What gives? http://msdn.microsoft.com/en-us/library

Mapview on tablet: How can I center the map with an offset?

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问题 Hint: Here is a similar post with HTML. In the current tablet implementation of my app, I have a fullscreen MapView with some informations displayed in a RelativeLayout on a left panel, like this: (My layout is quite trivial, and I guess there is no need to post it for readability) The problem comes when I want to center the map on a specific point... If I use this code: mapController.setCenter(point); I will of course get the point in the center of the screen and not in the center of the

jQuery Offset returns negative value

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问题 am having a scenario like this below : In my ui, I will have a textbox. If I have enter a number in the textbox,I need to scroll down to the respective page number. In Dom , I will have some divs with the respective id's. If user entered a page number as 5. I will check for 5th div offset in dom and get top value. By using scrollTop It will scrolled to the 5th div. Here, Issue is after scrolled down to the 5th div. If again, entered a page number as 2. offset top value in negative. Hence

Read from a specific spot in a file C++

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问题 I have a program in C++ that needs to return a line that a specific word appears in. For instance, if my file looks like this: the cow jumped over the moon with the green cheese in his mouth and I need to print the line that has "with". All the program gets is the offset from the beginning of the file (in this case 24, since "with" is 24 characters from the beginning of the file). How do I print the whole line "the moon with the", with just the offset? Thanks a lot! 回答1: A good solution is

Google maps API: Marker image positioning

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问题 I have changed the image that I use for a marker on Google maps. The new image is much wider than the old one and I have noticed that the marker is aligned with the lat and lng so that the marker rests with it's horizontal midpoint over the lat and lng . This is not what I want, I want to have the lat and lng aligned with the markers left hand side - I want to offset the marker from the default position by about 80px to the right. 回答1: Try this on for size. var markerImage = new google.maps

RocketMq在SparkStreaming中的应用

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　　其实Rocketmq的给第三方的插件已经全了，如果大家有兴趣的话请移步 https://github.com/apache/rocketmq-externals 。本文主要是结合笔者已有的rmq在spark中的应用经验对rocketmq做简单介绍以及经验总结，当然免不了会将rocketmq和如今特别火爆的kafka做一些对比（Ps：为了方便打字rmq后面会是rocketmq的缩写）。　　首先对rocktmq做一些流行的消息队列对比。　　提到mq不得不提消息队列，对应于数据结构里面的“先进先出”的队列。而rocketmq就是应用于大数据时代拥有高吞吐低延迟特性的分布式消息拥有发布订阅功能的队列系统。这样的分布式消息系统主要提供应用解耦、流量消峰、消息分发等功能。本片不会对安装集群做过多的介绍，安装单机版本rmq的教程移步官方文档 http://rocketmq.apache.org/docs/quick-start/ 。 rocktmq是阿里研发主要作用于双十一这样的高峰期实时流数据处理，起初是基于activemq，但是随着对吞吐量的要求逐步提高，阿里的开发者们逐渐把眼光向kafka转移，但是kafka并不具备低延迟和高可靠性。因此阿里决定研究这样一个兼并传统的订阅消息系统的发布订阅场景与高并发零误差低延时的传输系统。　　

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