{"action":"created","comment":{"url":"https://api.github.com/repos/caskdata/cdap/pulls/comments/23624910","id":23624910,"diff_hunk":"@@ -0,0 +1,72 @@\n+# User Profiles Example\n+\n+Example application that manages user profiles in a Table. The fields of a user\n+profile are updated in different ways:\n+\n+- Attributes like name and email address are changed through a REST\n+  call when the user updates his profile;\n+- The time of the last login is updated by a sign-on service every\n+  time the user logs in, also through a REST call;\n+- The time of the last activity is updated by a flow that processes\n+  events whenever it encounters an event from that user.\n+\n+Features introduced: Column-Level Conflict Detection.\n+\n+This application uses a table with conflict detection at the column level.\n+A conflict occurs if two transactions (for example, a flowlet's process method\n+and a service handler) that overlap in time modify the same data in a table.\n+Such a conflict is detected at the time that the transactions are committed,\n+and the transaction that attempts to commit last is rolled back.\n+\n+- By default, the granularity of the conflict detection is at the row level.\n+  That means, it is sufficient for two overlapping transactions to write to\n+  the same row of a table to cause a conflict, even if they write different\n+  columns.\n+- Specifying a conflict detection level of COLUMN means that a conflict is\n+  only detected if both transactions modify the same column of the same row.\n+  This is more precise but also requires more book-keeping in the transaction\n+  system and therefore can impact performance.\n+\n+Column-level conflict detection should be enabled if it is known that different\n+transactions can modify different columns of the same rows.\n+\n+This application uses:\n+\n+- A stream ``events`` to receive events of user activity;\n+- A dataset ``profiles`` to store user profiles with conflict detection at the column level;\n+- A dataset ``counters`` to count events by URL (this is not essential for the purpose of the example);\n+- A service ``UserProfileService`` to create, delete, and update profiles;\n+- A flow ``ActivityFlow`` to count events and also maintain the time of last activity for the users.\n+\n+To run the example, build and deploy the application, then start both the flow and the service. Now\n+populate the ``profiles`` tables with users using the script ``bin/add-users.sh``. Now, from two","path":"cdap-examples/UserProfiles/README.md","position":42,"original_position":42,"commit_id":"19162643b0623c009d71ff69edd8a998bb9ae002","original_commit_id":"19162643b0623c009d71ff69edd8a998bb9ae002","user":{"login":"awholegunch","id":6394794,"avatar_url":"https://avatars.githubusercontent.com/u/6394794?v=3","gravatar_id":"","url":"https://api.github.com/users/awholegunch","html_url":"https://github.com/awholegunch","followers_url":"https://api.github.com/users/awholegunch/followers","following_url":"https://api.github.com/users/awholegunch/following{/other_user}","gists_url":"https://api.github.com/users/awholegunch/gists{/gist_id}","starred_url":"https://api.github.com/users/awholegunch/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/awholegunch/subscriptions","organizations_url":"https://api.github.com/users/awholegunch/orgs","repos_url":"https://api.github.com/users/awholegunch/repos","events_url":"https://api.github.com/users/awholegunch/events{/privacy}","received_events_url":"https://api.github.com/users/awholegunch/received_events","type":"User","site_admin":false},"body":"Populate the ``profiles`` tables with users using the script ``bin/add-users.sh``. \\[drop \"Now\"]","created_at":"2015-01-27T17:21:16Z","updated_at":"2015-01-27T17:21:16Z","html_url":"https://github.com/caskdata/cdap/pull/1135#discussion_r23624910","pull_request_url":"https://api.github.com/repos/caskdata/cdap/pulls/1135","_links":{"self":{"href":"https://api.github.com/repos/caskdata/cdap/pulls/comments/23624910"},"html":{"href":"https://github.com/caskdata/cdap/pull/1135#discussion_r23624910"},"pull_request":{"href":"https://api.github.com/repos/caskdata/cdap/pulls/1135"}}},"pull_request":{"url":"https://api.github.com/repos/caskdata/cdap/pulls/1135","id":28084370,"html_url":"https://github.com/caskdata/cdap/pull/1135","diff_url":"https://github.com/caskdata/cdap/pull/1135.diff","patch_url":"https://github.com/caskdata/cdap/pull/1135.patch","issue_url":"https://api.github.com/repos/caskdata/cdap/issues/1135","number":1135,"state":"open","locked":false,"title":"[CDAP-1016] add an example that avoid conflicts by using column level detection","user":{"login":"anew","id":483004,"avatar_url":"https://avatars.githubusercontent.com/u/483004?v=3","gravatar_id":"","url":"https://api.github.com/users/anew","html_url":"https://github.com/anew","followers_url":"https://api.github.com/users/anew/followers","following_url":"https://api.github.com/users/anew/following{/other_user}","gists_url":"https://api.github.com/users/anew/gists{/gist_id}","starred_url":"https://api.github.com/users/anew/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/anew/subscriptions","organizations_url":"https://api.github.com/users/anew/orgs","repos_url":"https://api.github.com/users/anew/repos","events_url":"https://api.github.com/users/anew/events{/privacy}","received_events_url":"https://api.github.com/users/anew/received_events","type":"User","site_admin":false},"body":"This application maintains user profiles.\r\n\r\n- It allows to update the last login time (through a service) and the last active time (through a flow that reads events by userid) for a user separately. \r\n- Two scripts are included, one that makes calls to the service to update the login time, one that sends events to the flow via a stream.\r\n- When both scripts run concurrently, we would get conflicts at the row level. But this app uses column-level conflict detection\r\n\r\nThis PR includes the app itself plus the scripts. I will add the documentation (Readme, plus a couple of paragraphs of text in the dev guide) in a follow-up 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