Previous versions of OpenACS required to know the IP addresses of the cluster nodes in advance, which is a show-stopper for many cloud applications.
The new functionality allows arbitrary nodes to register as client nodes at the canonical server, provided that these know a shared secret. All messages of the intra-cluster talk are now cryptographically signed using this shared secret.
In the current version, the shared secret key has to be specified in the NaviServer configuration file (ClusterSecret). Later versions will support the use of other measures such as generated keys, kept as files.
Also in the new version it is still possible to use static peer addresses (which do not have to register during startup).
- Support for multiple protocols for intra-cluster talk
Previous version of OpenACS required the communication of the intra-cluster talk over HTTP. With these changes, multiple protocols are supported. Most prominently HTTPS can be used, which is required by some organization for all web communication, especially for cloud applications. Other protocols might be added later (e.g. UDP).
- Nodes (such as the canonical server) can be specified via URL locations. These location specifier have the following advantages over classical IP address and port.
* support different protocols (http, https, udp) * support of IP addresses or DNS names * when DNS names map to multiple IP addresses (e.g. multiple IPv4 and/or multiple IPv6 addresses) the new parameter PreferredLocationRegexp can be use to select the wanted. When this regexp does not match any of the addresses, the first address is used. * ports are now optional (except UDP) * for location specifier: https://openacs.org
- Support for cluster communication statistics (requires xotcl-request-monitor)
These statistics show the amount of intra-server communication. The following statistics are collected per node: - number of broadcast operations - number of send operations (active flushes) - number of receive operation (passive flushes) For N cluster nodes, the send operations are basically the number of broadcast operations times the number of nodes minus one.
These statistics can also be used prior to cluster enabling, to obtain the number of potential broadcast operations.
Kernel Parameters
CanonicalServer : location of the canonical server ClusterAuthorizedIP : obsolete ClusterEnabledP : unchanged ClusterPeerIP : obsolete EnableLoggingP : unchanged PreferredLocationRegexp : new DynamicClusterPeers : new, no not edit
Differences between old and new value for "CanonicalServer": old: - specify IP address with port - example: 137.208.116.31:443 new: - specify URL location - support different protocols (http, https, udp) - support of IP address or domain name - when domain name maps to different IP addresses (e.g. multiple IPv4 and/or multiple IPv6 addresses) PreferredLocationRegexp can be use to select the wanted. When the provided regexp does not match any of the addresses, take the first address. - port is optional - example: https://openacs.org
# # Cluster secret for intra-cluster communications in NaviServer # configuration file. Clustering will not be enabled if no value is # provided. # ns_section ns/server/$server/acs { # ... ns_param ClusterSecret "please change me" }
#----------------------------------------------------------------------- # Support for munin statistics # # 1) install munin plugins for naviserver (munin-plugins-ns.git) # 2) add link to the munin plugins (replace "openacs" by the name # of your server in the munin configuration) # /etc/munin/plugins/naviserver_openacs_count_cluster -> /usr/share/munin/plugins/naviserver_count # 3) in the plugin plugin configuration (e.g., etc/munin/plugin-conf.d/naviserver) # add a section like the following (again, replace "openacs" by the server name you used) # # [naviserver_openacs_count_cluster] # env.title Cluster # env.vars cluster:broadcast cluster:sent cluster:received # # 4) restart munin
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