mirror of https://github.com/ceph/ceph
157 lines
5.8 KiB
ReStructuredText
157 lines
5.8 KiB
ReStructuredText
==========================
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RGW Data caching and CDN
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==========================
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.. versionadded:: Octopus
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.. contents::
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This feature adds to RGW the ability to securely cache objects and offload the workload from the cluster, using Nginx.
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After an object is accessed the first time it will be stored in the Nginx cache directory.
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When data is already cached, it need not be fetched from RGW. A permission check will be made against RGW to ensure the requesting user has access.
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This feature is based on some Nginx modules, ngx_http_auth_request_module, https://github.com/kaltura/nginx-aws-auth-module, Openresty for Lua capabilities.
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Currently, this feature will cache only AWSv4 requests (only s3 requests), caching-in the output of the 1st GET request
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and caching-out on subsequent GET requests, passing thru transparently PUT,POST,HEAD,DELETE and COPY requests.
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The feature introduces 2 new APIs: Auth and Cache.
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NOTE: The `D3N RGW Data Cache`_ is an alternative data caching mechanism implemented natively in the Rados Gateway.
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New APIs
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-------------------------
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There are 2 new APIs for this feature:
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Auth API - The cache uses this to validate that a user can access the cached data
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Cache API - Adds the ability to override securely Range header, that way Nginx can use it is own smart cache on top of S3:
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https://www.nginx.com/blog/smart-efficient-byte-range-caching-nginx/
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Using this API gives the ability to read ahead objects when clients asking a specific range from the object.
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On subsequent accesses to the cached object, Nginx will satisfy requests for already-cached ranges from the cache. Uncached ranges will be read from RGW (and cached).
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Auth API
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This API Validates a specific authenticated access being made to the cache, using RGW's knowledge of the client credentials and stored access policy.
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Returns success if the encapsulated request would be granted.
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Cache API
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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This API is meant to allow changing signed Range headers using a privileged user, cache user.
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Creating cache user
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::
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$ radosgw-admin user create --uid=<uid for cache user> --display-name="cache user" --caps="amz-cache=read"
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This user can send to the RGW the Cache API header ``X-Amz-Cache``, this header contains the headers from the original request(before changing the Range header).
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It means that ``X-Amz-Cache`` built from several headers.
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The headers that are building the ``X-Amz-Cache`` header are separated by char with ASCII code 177 and the header name and value are separated by char ASCII code 178.
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The RGW will check that the cache user is an authorized user and if it is a cache user,
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if yes it will use the ``X-Amz-Cache`` to revalidate that the user has permissions, using the headers from the X-Amz-Cache.
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During this flow, the RGW will override the Range header.
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Using Nginx with RGW
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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Download the source of Openresty:
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::
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$ wget https://openresty.org/download/openresty-1.15.8.3.tar.gz
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git clone the AWS auth Nginx module:
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::
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$ git clone https://github.com/kaltura/nginx-aws-auth-module
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untar the openresty package:
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::
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$ tar xvzf openresty-1.15.8.3.tar.gz
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$ cd openresty-1.15.8.3
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Compile openresty, Make sure that you have pcre lib and openssl lib:
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::
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$ sudo yum install pcre-devel openssl-devel gcc curl zlib-devel nginx
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$ ./configure --add-module=<the nginx-aws-auth-module dir> --with-http_auth_request_module --with-http_slice_module --conf-path=/etc/nginx/nginx.conf
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$ gmake -j $(nproc)
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$ sudo gmake install
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$ sudo ln -sf /usr/local/openresty/bin/openresty /usr/bin/nginx
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Put in-place your Nginx configuration files and edit them according to your environment:
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All Nginx conf files are under:
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https://github.com/ceph/ceph/tree/main/examples/rgw/rgw-cache
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`nginx.conf` should go to `/etc/nginx/nginx.conf`
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`nginx-lua-file.lua` should go to `/etc/nginx/nginx-lua-file.lua`
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`nginx-default.conf` should go to `/etc/nginx/conf.d/nginx-default.conf`
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The parameters that are most likely to require adjustment according to the environment are located in the file `nginx-default.conf`
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Modify the example values of *proxy_cache_path* and *max_size* at:
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::
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proxy_cache_path /data/cache levels=2:2:2 keys_zone=mycache:999m max_size=20G inactive=1d use_temp_path=off;
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And modify the example *server* values to point to the RGWs URIs:
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::
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server rgw1:8000 max_fails=2 fail_timeout=5s;
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server rgw2:8000 max_fails=2 fail_timeout=5s;
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server rgw3:8000 max_fails=2 fail_timeout=5s;
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| It is important to substitute the *access key* and *secret key* located in the `nginx.conf` with those belong to the user with the `amz-cache` caps
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| for example, create the `cache` user as following:
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::
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radosgw-admin user create --uid=cacheuser --display-name="cache user" --caps="amz-cache=read" --access-key <access> --secret <secret>
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It is possible to use Nginx slicing which is a better method for streaming purposes.
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For using slice you should use `nginx-slicing.conf` and not `nginx-default.conf`
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Further information about Nginx slicing:
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https://docs.nginx.com/nginx/admin-guide/content-cache/content-caching/#byte-range-caching
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If you do not want to use the prefetch caching, It is possible to replace `nginx-default.conf` with `nginx-noprefetch.conf`
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Using `noprefetch` means that if the client is sending range request of 0-4095 and then 0-4096 Nginx will cache those requests separately, So it will need to fetch those requests twice.
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Run Nginx(openresty):
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::
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$ sudo systemctl restart nginx
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Appendix
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~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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**A note about performance:** In certain instances like development environment, disabling the authentication by commenting the following line in `nginx-default.conf`:
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::
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#auth_request /authentication;
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may (depending on the hardware) increases the performance significantly as it forgoes the auth API calls to radosgw.
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.. _D3N RGW Data Cache: ../d3n_datacache/
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