Some cluster-level APIs may operate on a subset of the nodes which can be specified with node filters. For example, the Task Management, Nodes Stats, and Nodes Info APIs can all report results from a filtered set of nodes rather than from all nodes.
Node filters are written as a comma-separated list of individual filters, each of which adds or removes nodes from the chosen subset. Each filter can be one of the following:
_all, to add all nodes to the subset.
_local, to add the local node to the subset.
_master, to add the currently-elected master node to the subset.
- a node id or name, to add this node to the subset.
- an IP address or hostname, to add all matching nodes to the subset.
- a pattern, using
*wildcards, which adds all nodes to the subset whose name, address or hostname matches the pattern.
coordinating_only:true, which respectively add to the subset all master-eligible nodes, all data nodes, all ingest nodes, and all coordinating-only nodes.
coordinating_only:false, which respectively remove from the subset all master-eligible nodes, all data nodes, all ingest nodes, and all coordinating-only nodes.
- a pair of patterns, using
*wildcards, of the form
attrname:attrvalue, which adds to the subset all nodes with a custom node attribute whose name and value match the respective patterns. Custom node attributes are configured by setting properties in the configuration file of the form
node filters run in the order in which they are given, which is important
if using filters that remove nodes from the set. For example
_all,master:false means all the nodes except the master-eligible ones, but
master:false,_all means the same as
_all because the
_all filter runs
if no filters are given, the default is to select all nodes. However, if
any filters are given then they run starting with an empty chosen subset. This
means that filters such as
master:false which remove nodes from the chosen
subset are only useful if they come after some other filters. When used on its
master:false selects no nodes.
Here are some examples of the use of node filters with the Nodes Info APIs.
# If no filters are given, the default is to select all nodes GET /_nodes # Explicitly select all nodes GET /_nodes/_all # Select just the local node GET /_nodes/_local # Select the elected master node GET /_nodes/_master # Select nodes by name, which can include wildcards GET /_nodes/node_name_goes_here GET /_nodes/node_name_goes_* # Select nodes by address, which can include wildcards GET /_nodes/10.0.0.3,10.0.0.4 GET /_nodes/10.0.0.* # Select nodes by role GET /_nodes/_all,master:false GET /_nodes/data:true,ingest:true GET /_nodes/coordinating_only:true # Select nodes by custom attribute (e.g. with something like `node.attr.rack: 2` in the configuration file) GET /_nodes/rack:2 GET /_nodes/ra*:2 GET /_nodes/ra*:2*