you may have encountered this problem like this
"SharePoint 2013 Search Topology Activation Error: "Unable to retrieve topology component health states. This may be because of the admin component is not up and running".
or like this, having index partition or any other of the 5 components with a warn or error (image is edited to fit).
a more common case we had was having noderunner limited to 300MB.
so the solution was to bring it up to 500.
C:\Program Files\Microsoft Office Servers\15.0\Search\Runtime\1.0\noderunner.exe.config
the conclusion is that noderunner without enough memory eventually throw an error.