nginx+lua magic to allow "docker seach" to work with a V2.1 docker registry

gistfile1.txt

  location /v1/search {
    content_by_lua '
      local cjson = require "cjson"
      local args = ngx.req.get_uri_args()
      local query = args["q"]
      -- Create structure for V1 search endpoint output
      local output = { ["num_results"] = 0, ["query"] = query, ["results"] = {} }
      -- Fetch data from V2 catalog endpoint
      local res = ngx.location.capture("/v2/_catalog")
      -- Parse JSON and iterate over it
      local data = cjson.new().decode(res.body)
      for k, repo in pairs(data["repositories"]) do
        if not (string.match(repo, query) == nil) then
          output["num_results"] = output["num_results"] + 1
          table.insert(output["results"], { ["name"] = repo })
        end
      end
      -- If there are no results, add a dummy entry. This is necessary because
      -- cjson treats an empty table as a JSON object rather than an array,
      -- which causes the Docker client to barf on the output
      if output["num_results"] == 0 then
        table.insert(output["results"], { ["name"] = "dummy", ["description"] = "dummy entry because Lua" })
        output["num_results"] = 1
      end
      -- Encode the output structure as JSON and send to client
      ngx.print(cjson.new().encode(output))
    ';
  }