mnesia | 易学教程

RabbitMQ

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windows系统上安装rabbitmq时，参照http://blog.csdn.net/lu1005287365/article/details/52315786 这个教程安装完成之后，发现在执行 http://localhost:15672/ 提示该页无法访问 cmd进入rabbitmq安装目录sbin目录（D:\RabbitMQ Server\rabbitmq_server-3.7.0\sbin）下分别执行这两句（1） rabbitmq-plugins enable rabbitmq_management （2）rabbitmqctl start_app 之后再访问就ok了以下转载自:http://blog.csdn.net/sxf359/article/details/78239382 在执行 http://localhost:15672/ 提示该页无法访问，因为这是rabbitmq安装后的一个web管理平台入口。当安装后就能访问了。需要在cmd窗口执行一个命令： rabbitmq-plugins enable rabbitmq_management 此命令执行要先定位到rabbitmq的安装目录下的sbin文件夹下。执行后仍然不能访问，通过cmd中的提示，说是需要执行rabbitmqctl start_app 但是执行后提示： starting node

RabbitMQ学习之二：管理单节点RabbitMQ

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环境准备： [root@master ~]# cat /etc/redhat-release CentOS Linux release 7.7.1908 (Core) [root@master ~]# uname -a Linux master 3.10.0-514.el7.x86_64 #1 SMP Tue Nov 22 16:42:41 UTC 2016 x86_64 x86_64 x86_64 GNU/Linux [root@master ~]# ip addr ens33: inet 192.168.0.201/24 brd 192.168.0.255 scope global ens33 当前Erlang和RabbitMQ版本： [root@master ~]# erl Erlang/OTP 22 [erts-10.7.1] [source] [64-bit] [smp:1:1] [ds:1:1:10] [async-threads:1] [hipe] [root@master ~]# rabbitmqctl version 3.8.3 一、部署单节点RabbitMQ 通常所说的RabbitMQ节点，其实是RabbitMQ应用程序和其所在的Erlang虚拟机。类似于JAVA应用程序和JVM虚拟机。 Erlang能让应用程序无须知道对方是否在同一台机器上即可相互通信。 1

【运维随笔】记录一次rabbitmq启动故障排查

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由于故障排查已经过了一段时间再写的这个随便，故这次无相关截图某天，运行正常的rabbitmq挂掉了，然后去重启的时候报错，启动不了，通过查看systemctl status rabbitmq -l 和journalctl -u rabbitmq 查看错误信息，发现也没有什么有价值的信息。然后尝试着把/var/lib/rabbitmq/mnesia/ 目录下的文件移走，再重新启动，发现依然是报一样的启动错误，也没有可参考的信息。接下来再次检查了配置文件，确认配置文件没有写错，关键是检查看有没有格式标点错误，或者被人修改过检查完和集群其他机器也对比了，无任何有问题的地方。最后尝试直接使用rabbitmq-server 这种方式直接启动，想着看看前台会输出什么错误信息可供参考。运行启动程序后，直接输出了一个no space相关的信息。然后df -h 一看，发现确实是没空间了，但是空间刚好还剩一点点，所以在运行命令的时候也还是可以正常的tab补全，导致一开始没有想到空间的问题来源： oschina 链接： https://my.oschina.net/u/4399154/blog/3291132

RabbitMQ精讲9：镜像模式集群搭建，整合KeepAlived+HaProxy组件

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目录 1. 镜像模式集群搭建 1.1 集群节点安装 1、安装依赖包 2、下载安装包 3、安装服务命令 4、修改集群用户与连接心跳检测 5、安装管理插件 6、服务指令 1.2 文件同步步骤 1.3 组成集群步骤 1、停止MQ服务 2、组成集群操作 3、slave加入集群操作（重新加入集群也是如此，以最开始的主节点为加入节点） 4、修改集群名称 5、查看集群状态 6、管控台界面 1.4 配置镜像队列 1.5 安装Ha-Proxy 1、Haproxy简介 HAProxy如何实现性能最大化 2、Haproxy安装 3、Haproxy配置 4、启动haproxy 5、访问haproxy 6、关闭haproxy 1.6 安装KeepAlived 1、Keepalived简介 Keepalived特性 Keepalived高可用原理 2、Keepalived安装 3、Keepalived配置 79节点（Master）配置如下 80节点（backup）配置如下 4、执行脚本编写 5、执行脚本赋权 6、启动keepalived 7、高可用测试 1.7 集群配置文件环境变量配置文件：rabbitmq-env.conf 配置信息配置文件：rabbitmq.config 2. RabbitMQ集群恢复与故障转移场景一：A先停, B后停场景二：A, B同时停机场景三：A先停, B后停, 且A无法恢复

What's the simplest way to update mnesia schema?

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问题 For example, I saved {id, name} in mnesia and want to update to {id, name, age} , do I have to call transform_table every time I change schema? 回答1: The simplest way is to delete the table and recreate it. If you need to keep the data in the table, mnesia:transform_table is the way to go. 来源： https://stackoverflow.com/questions/15998244/whats-the-simplest-way-to-update-mnesia-schema

rabbitmq queues filling up with celery tasks

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问题 I am using Celery to call multiple hardware units by their ip address. Each unit will return a list of values. Application code below # create a list of tasks modbus_calls = [] for site in sites: call = call_plc.apply_async((site.name, site.address), expires=120) # expires after 2 minutes? modbus_calls.append(call) # below checks all tasks are complete (values returned), then move forward out of the while loop ready_list = [False] while not all(ready_list): ready_list = [] for task in modbus

Managing incremental counters in mnesia DBMS?

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问题 I have realised that mnesia doesnot support auto-increment feature as does MySQL or other RDBMS do.The counters talked about in mnesia documentation are not really well explained. forexample i have found sofar one function in the entire documentation which manipulates counters mnesia:dirty_update_counter({Tab::atom(),Key::any()}, Val::positive_integer()) So, this has disturbed me for a time coz it works with records of type {TabName, Key, Integer} This is also unclear and possibly because no

docker

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【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> #--restart=always #-e RABBITMQ_VM_MEMORY_HIGH_WATERMARK=1024MiB docker run -d \ --name rabbitmq \ --hostname myrabbit \ -e RABBITMQ_DEFAULT_USER=admin \ -e RABBITMQ_DEFAULT_PASS=admin \ -e RABBITMQ_DEFAULT_VHOST=vhost \ -p 15672:15672 \ -p 5672:5672 \ -v /usr/local/rabbitmq:/etc/rabbitmq \ -v /usr/local/rabbitmq/data:/var/lib/rabbitmq \ -v /usr/local/rabbitmq/log/:/var/log/rabbitmq \ rabbitmq:management docker run -d \ --name rabbitmq \ --hostname myrabbit \ -e RABBITMQ_DEFAULT_USER=xxx\ -e RABBITMQ_DEFAULT_PASS=xxx\ -e RABBITMQ_DEFAULT_VHOST=vhost \ -p

i am getting a error when trying to register a user using smack api(4.2) on android device on ejabberd (17.07)

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问题 I tried to find the reason of the error but cannot found it. If anyone can suggest a way it will be highly appreciated. Earlier I was using ejabberd version 2.1 with default mnesia, which was working fine. I was able to register users from the android app. But now when I installed new ejabberd 17.07 with mysql, it gave me error as follow: Connection XMPPTCPConnection[not-authenticated] (5) closed with error org.jivesoftware.smack.XMPPException$StreamErrorException: not-authorized You can read

erlang - how can I match tuple contents with qlc and mnesia?

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问题 I have a mnesia table for this record. -record(peer, { peer_key, %% key is the tuple {FileId, PeerId} last_seen, last_event, uploaded = 0, downloaded = 0, left = 0, ip_port, key }). Peer_key is a tuple {FileId, ClientId}, now I need to extract the ip_port field from all peers that have a specific FileId. I came up with a workable solution, but I'm not sure if this is a good approach: qlc:q([IpPort || #peer{peer_key={FileId,_}, ip_port=IpPort} <- mnesia:table(peer), FileId=:=RequiredFileId])

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