How to enable Agent dependency caching in Bamboo Data Center
Platform Notice: Data Center Only - This article only applies to Atlassian products on the Data Center platform.
Note that this KB was created for the Data Center version of the product. Data Center KBs for non-Data-Center-specific features may also work for Server versions of the product, however they have not been tested. Support for Server* products ended on February 15th 2024. If you are running a Server product, you can visit the Atlassian Server end of support announcement to review your migration options.
*Except Fisheye and Crucible
Summary
This article explains how to configure your reverse proxy to cache content for your Bamboo Agents, enhancing performance and reducing the load on your Bamboo server.
Environment
Bamboo Data Center
Bamboo Agents (Remote, Ephemeral)
Reverse Proxy or Load Balancer with content caching
Diagnosis
Bamboo Data Center supports proxy functionality for caching Agent dependencies. This feature can reduce Agents' startup time by enabling content caching on your reverse proxy. Once you activate this on the proxy side, Bamboo will confirm the change by displaying information in the agent log file.
You'll see the following INFO message in the <BAMBOO_AGENT_HOME>/atlassian-bamboo-agent.log file when content caching is enabled:
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INFO [WrapperSimpleAppMain] [ClasspathBuilder] Content caching is enabled for high performance bootstrap.In case content caching is disabled, you'll see the following WARN message:
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WARN [WrapperSimpleAppMain] [ClasspathBuilder] Content caching is not enabled. This can cause performance impact on servers with high-tier licenses.The dependencies being discussed are the JAR files that the Agent must download from the server during startup. To speed up the Agent's startup time, it’s possible to cache plugin information at the proxy level. This means you won’t need to make any changes on the Bamboo side; all adjustments will be made at the reverse proxy level. Importantly, you don’t need to specify which items should be cached; Bamboo will handle that for you once content caching is enabled.
This should work with most reverse proxies that support content caching. In this article, you'll find instructions to enable agent dependency caching specifically for Apache HTTP Server and NGINX.
Solution
Configuring Apache HTTP Server
Since Apache HTTP Server is not an Atlassian product, Atlassian does not guarantee to provide support for its configuration. You should consider the material on this page to be for your information only; use it at your own risk. If you encounter problems with configuring Apache HTTP Server, we recommend that you refer to the Apache HTTP Server Support page.
Note that any changes you make to the httpd.conf file will be effective upon starting or re-starting Apache HTTP Server.
Step 1: Enable mod_cache and mod_cache_disk in Apache HTTP Server
Load mod_cache and mod_cache_disk dynamically, using the LoadModule directive; that means un-commenting the following lines in the httpd.conf file:
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LoadModule cache_module libexec/apache2/mod_cache.so
LoadModule cache_disk_module libexec/apache2/mod_cache_disk.soStep 2: Configure Apache HTTP Server's caching features
Include the following Cache directives in the context (protocol type, virtual server, or location) for which you want to cache server responses:
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<VirtualHost *:80>
...
CacheRoot /etc/apache2/cache/
CacheEnable disk /
CacheDirLevels 2
CacheDirLength 1
CacheHeader on
</VirtualHost>The
CacheRootdirective defines the name of the directory on the disk to contain cache files. You must ensure that the user running the Apache service has read/write access to this directory.The
CacheEnabledirective instructsmod_cacheto cache urls at or below url-string and cache_type disk to instructmod_cacheto use the disk based storage manager implemented bymod_cache_disk.The
CacheDirLevelsdirective sets the number of subdirectory levels in the cache. Cached data will be saved this many directory levels below theCacheRootdirectory.The
CacheDirLengthdirective sets the number of characters for each subdirectory name in the cache hierarchy. It can be used in conjunction withCacheDirLevelsto determine the approximate structure of your cache hierarchy.When the
CacheHeaderdirective is switched on, an X-Cache header will be added to the response with the cache status of this response.
Configuring NGINX
Since NGINX is not an Atlassian product, Atlassian does not guarantee to provide support for its configuration. You should consider the material on this page to be for your information only; use it at your own risk. If you encounter problems with configuring NGINX, we recommend that you refer to the NGINX Support page.
Step 1: Include proxy_cache_path to the top‑level http context
Include the proxy_cache_path directive in the top‑level http context; that means add the following line to the nginx.conf file:
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http {
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proxy_cache_path /data/nginx/cache levels=1 keys_zone=bamboo_server:10m max_size=1024m inactive=20m use_temp_path=off;
}The mandatory first parameter is the local filesystem path for cached content, and the mandatory keys_zone parameter defines the name and size of the shared memory zone that is used to store metadata about cached items.
You must ensure that the user running the NGINX service has read/write access to this directory.
In this example we'll name the cache bamboo_server and limit the amount of cached response data to 1024m.
Set inactive to 20 minutes. Cached data that are not accessed for over 20 minutes get removed from the cache regardless of their freshness.
Step 2: Include add_header and proxy_cache to start caching responses
Include the add_header directive using the 'X-Cache-Status' name and value '$upstream_cache_status'. This way the X-Cache-Status header will be added to the response with the cache status of the response. Include the proxy_cache directive in the context (protocol type, virtual server, or location) for which you want to cache server responses, specifying the zone name defined by the keys_zone parameter to the proxy_cache_path directive (in this case, bamboo_server):
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server {
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add_header 'X-Cache-Status' '$upstream_cache_status';
location / {
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proxy_cache bamboo_server;
}
}There are several other attributes you can add to tweak cache settings, as pointed out in the NGINX Content Caching documentation. This is highly customizable. However, as mentioned previously in this article, for Agent content caching you just need to enable the content caching on the proxy and Bamboo will tell the cache what to store.
Testing Agent dependency caching
The following cURL command will help you test whether caching is successful even before starting up an agent. You don't need to have an agent installed for the purpose of this test.
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$ curl -I --http1.1 http://<BAMBOO_BASE_URL>/agentServer/bootstrap/content-cache-testYou should see X-Cache-Status HIT. Similar to the following:
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HTTP/1.1 200
Server: nginx
Date: Wed, 18 Dec 2024 06:35:18 GMT
Content-Type: text/plain;charset=UTF-8
Content-Length: 5002
Connection: keep-alive
Strict-Transport-Security: max-age=31536000
Referrer-Policy: no-referrer-when-downgrade
X-XSS-Protection: 1; mode=block
X-Frame-Options: SAMEORIGIN
X-Content-Type-Options: nosniff
X-Seraph-LoginReason: AUTHENTICATED_FAILED
Last-Modified: Wed, 18 Dec 2024 06:25:22 GMT
Cache-Control: public, max-age=30
X-Cache-Status: HITThis means the entity was fresh, and was served from cache. If you see MISS then the entity was fetched from the upstream server and was not served from cache.
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