Created
March 8, 2010 15:29
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(defmulti watch-changes | |
"Provided a database (database meta, java.net.URL, or database name) and a callback, watches | |
for changes to the database and executes the given callback (takes one argument) on every change | |
to a document in the given database, using the meta of the changed document as the only | |
argument of the callback." | |
database-arg-type) | |
(defn- watch-changes-handler | |
[url-str agnt] | |
(if (h/success? agnt) | |
(loop [lines (io/read-lines (h/stream agnt))] | |
(if-let [watched-db (@watched-databases url-str)] | |
(when (not (empty? lines)) | |
(future | |
(let [line (first lines)] | |
(try | |
((:callback watched-db) (binding [json-read/*json-keyword-keys* true] | |
(json-read/read-json line))) | |
(catch Exception e | |
(dosync | |
(if (@watched-databases url-str) | |
(alter watched-databases update-in [url-str :last-error] | |
(constantly {:execption e :time (java.util.Date.) :data line})))))))) | |
(recur (rest lines))))))) | |
(defmethod watch-changes :name | |
[db-name callback & options] | |
(apply watch-changes (assoc @*defaults* :name db-name) callback options)) | |
(defmethod watch-changes :url | |
[url callback & options] | |
(apply watch-changes (utils/url->db-meta url) callback options)) | |
(defmethod watch-changes :meta | |
[db-meta callback & options] | |
(let [url-str (utils/db-meta->url db-meta) | |
options-map (merge (first options) {:heartbeat 30 :feed "continuous"})] | |
(dosync | |
(if (contains? @watched-databases url-str) | |
(alter watched-databases update-in [url-str :callback] (constantly callback)) | |
(alter watched-databases assoc url-str | |
{:http-agent (h/http-agent | |
(str url-str "/_changes" (utils/map-to-query-str options-map false)) | |
:method "GET" | |
:handler (partial watch-changes-handler url-str)) | |
:callback callback}))) | |
db-meta)) |
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