阿里云ECS 无法使用composer update

使用阿里云ecs，运行composer update，更新到一半，总是会提示 ：

   Downloading: 100%
    Failed to download 2amigos/yii2-ckeditor-widget from dist: The "https://api.github.com/repos/2amigos/yii2-ckeditor-widget/zipball/023eb29fedfc3c3121c17688ed237e8688f5eb50" file could not be downloaded: php_network_getaddresses: getaddrinfo failed: Name or service not known
failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known
    Now trying to download from source
  - Installing 2amigos/yii2-ckeditor-widget (1.0.4)
    Cloning 023eb29fedfc3c3121c17688ed237e8688f5eb50

	 Failed to download 2amigos/yii2-date-time-picker-widget from dist: The "https://api.github.com/repos/2amigos/yii2-date-time-picker-widget/zipball/1248491c959d7080ab45c5284429e3d9222ed282" file could not be downloaded: php_network_getaddresses: getaddrinfo failed: Name or service not known
failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known
    Now trying to download from source

	php -r  "getaddrinfo('api.github.com');" | php
	

但ping api.github.com 却是可以ping得通，而一开始可以访问，到后来却无法下载。奇怪的事情。

在linode vps上使用composer update从来都没遇到任何问题。国内的VPS各种

- Installing yiisoft/yii2 (2.0.4)

Downloading: 100%

Downloading: 100%

Downloading: 100%

Failed to download yiisoft/yii2 from dist: The "https://api.github.com/repos/yiisoft/yii2-f                      ramework/zipball/726867caee3f23aa7a6975c801e64b6021e14f86" file could not be downloaded: php_ne                      twork_getaddresses: getaddrinfo
failed: Name or service not known

failed to open stream: php_network_getaddresses: getaddrinfo failed: Name or service not known

Now trying to download from source

- Installing yiisoft/yii2 (2.0.4)

Cloning 726867caee3f23aa7a6975c801e64b6021e14f86