[推荐] 用CW代理监控ec2的内存和磁盘指标

上一篇介绍了如何在ec2上下载脚本，通过运行两个perl文件来监控特定ec2的内存占用情况，今天和大家一起学习下如何用官方推荐的方式-安装cloudwatch代理（以下简称CW）来实现对 ec2 内存和磁盘占用的监(窥)控(探)。

-- D.C

老规矩:给EC2创建IAM Role

进入IAM界面，点击左侧的 Roles, 再点击右侧窗口的 Create role, use case 选择 EC2, 点击 Next:Permissions, 搜索并选中 CloudWatchAgentServerPolicy, 一路点下一步，命名为 CloudWatchAgentServerRole。

iam_role

选中对应的EC2，点击 Actions - Instance Settings - Attach/Replace IAM Role, 选择 CloudWatchAgentServerRole，点击 Apply。

iam_role_ec2

这里提一句：如果我们原本用iam role来控制ec2对s3的访问，且没有在ec2上设置AKSK信息，那么替换掉role之后，ec2访问s3就会有问题。

解决方法：
方案1. 在角色 CloudWatchAgentServerRole 上再加attach一条Policy如 AmazonS3ReadOnlyAccess 或 AmazonS3FullAccess就可以了。
方案2. 在ec2上设置aws configure的全部信息（包括AKSK信息，不推荐）。

iam_role_adds3

登录ec2安装CW代理

登录ec2，下载CW代理包(57M)。

Linux:

wget https://s3.amazonaws.com/amazoncloudwatch-agent/amazon_linux/amd64/latest/amazon-cloudwatch-agent.rpm

如果下载速度太慢可以wget这个链接：
https://publicuse.s3.cn-northwest-1.amazonaws.com.cn/amazon-cloudwatch-agent.rpm
或者
Baidu云盘下载再上传到ec2。

其他操作系统代理链接：

Centos:
https://s3.amazonaws.com/amazoncloudwatch-agent/centos/amd64/latest/amazon-cloudwatch-agent.rpm

Ubuntu:
https://s3.amazonaws.com/amazoncloudwatch-agent/ubuntu/amd64/latest/amazon-cloudwatch-agent.deb

安装代理包并运行监控命令，只要没有error就成。

$ sudo rpm -U ./amazon-cloudwatch-agent.rpm

$ sudo /opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent-ctl -a fetch-config -m ec2 -s

/opt/aws/amazon-cloudwatch-agent/bin/config-downloader --output-dir /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.d --download-source default --mode ec2 --config /opt/aws/amazon-cloudwatch-agent/etc/common-config.toml --multi-config default
Successfully fetched the config and saved in /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.d/default.tmp
Start configuration validation...
/opt/aws/amazon-cloudwatch-agent/bin/config-translator --input /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.json --input-dir /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.d --output /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.toml --mode ec2 --config /opt/aws/amazon-cloudwatch-agent/etc/common-config.toml --multi-config default
2020/02/06 08:16:03 Reading json config file path: /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.d/default.tmp ...
Valid Json input schema.
I! Detecting runasuser...
No csm configuration found.
No log configuration found.
Configuration validation first phase succeeded
/opt/aws/amazon-cloudwatch-agent/bin/amazon-cloudwatch-agent -schematest -config /opt/aws/amazon-cloudwatch-agent/etc/amazon-cloudwatch-agent.toml
Configuration validation second phase succeeded
Configuration validation succeeded
Created symlink from /etc/systemd/system/multi-user.target.wants/amazon-cloudwatch-agent.service to /etc/systemd/system/amazon-cloudwatch-agent.service.
Redirecting to /bin/systemctl restart amazon-cloudwatch-agent.service

关于amazon-cloudwatch-agent-ctl脚本使用说明：

usage: amazon-cloudwatch-agent-ctl -a stop|start|status|fetch-config|append-config|remove-config [-m ec2|onPremise|auto] [-c default|ssm:<parameter-store-name>|file:<file-path>] [-s]

e.g.
1. apply a SSM parameter store config on EC2 instance and restart the agent afterwards:
    amazon-cloudwatch-agent-ctl -a fetch-config -m ec2 -c ssm:AmazonCloudWatch-Config.json -s
2. append a local json config file on onPremise host and restart the agent afterwards:
    amazon-cloudwatch-agent-ctl -a append-config -m onPremise -c file:/tmp/config.json -s
3. query agent status:
    amazon-cloudwatch-agent-ctl -a status

-a: action
    stop:                                   stop the agent process.
    start:                                  start the agent process.
    status:                                 get the status of the agent process.
    fetch-config:                           use this json config as the agent's only configuration.
    append-config:                          append json config with the existing json configs if any.
    remove-config:                          remove json config based on the location (ssm parameter store name, file name)

-m: mode
    ec2:                                    indicate this is on ec2 host.
    onPremise:                              indicate this is on onPremise host.
    auto:                                   use ec2 metadata to determine the environment, may not be accurate if ec2 metadata is not available for some reason on EC2.

-c: configuration
    default:                                default configuration for quick trial.
    ssm:<parameter-store-name>:             ssm parameter store name
    file:<file-path>:                       file path on the host

-s: optionally restart after configuring the agent configuration
    this parameter is used for 'fetch-config', 'append-config', 'remove-config' action only.

vim新建一个测试的bash脚本testmem.sh，消耗1g内存1个小时，后面会用到。

测试内存小脚本：

#!/bin/bash
mkdir /tmp/memory
mount -t tmpfs -o size=1024M tmpfs /tmp/memory
dd if=/dev/zero of=/tmp/memory/block
sleep 3600
rm /tmp/memory/block
umount /tmp/memory
rmdir /tmp/memory

进入CW查看监控

在aws主页面上方的 Service 的搜索框内搜 CloudWatch，进到CW界面以后点击左侧的 Metrics。

cw_metrics

[选项1] 可以看到右侧界面出现了 CWAgent，点击进去后，选择择ImageId,InstanceId, InstanceTypeGraph search，可以看到监控内存的ec2列表。选择 ImageId, InstanceId, InstanceType, device, fstype, path，可以看到监控磁盘的ec2列表。
[选项2] 将我们要监控的 ec2 的 id 输入到搜索框，回车，也能快速找到和这台机器有关的监控指标，点击CWAgent > ImageId, InstanceId, InstanceType,可以看到监控内存的ec2列表。选择 CWAgent >ImageId, InstanceId, InstanceType, device, fstype, path，可以看到监控磁盘的ec2列表。
选中对应的ec2，我们就能从上面的图中看到内存/磁盘监控的动态曲线了。
这个时候回到ec2，运行测试脚本testmem.sh,再回到 CW 查看内存监控的变化。

$ sudo bash testmem.sh &
[1] 3337
2097153+0 records in
2097152+0 records out
1073741824 bytes (1.1 GB) copied, 2.78481 s, 386 MB/s

cw_metrics_memchange

坚持很重要，若非不得已，不要放弃！

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