partial fix for docs cron (#3941)

This commit aims at mitigating two issues we have noticed with the
0.13.41 release:

1. The initial cron run for that release got interrupted at the 50
minutes mark, which happened to be right in the middle of the s3 upload.
This means it had already changed the versions.json file, but had not
finished updating the actual html files. Right now, the docs.daml.com
website shows version 0.13.41 in the drop-down, but actually displays
the content for 0.13.40. Additionally, trying to explicitly visit the
website for 0.13.41 (https://docs.daml.com/0.13.41) yields a 404. Note
that this also means the cron job did not reach the "tell HubSpot"
point, so 0.13.41 did not get announced.
2. As the script also did not reach the "clear cache" step, subsequent
runs have been rebuilding the documentation for no reason as the
sequence of steps was: check versions.json through HTTP, get cached one,
see it's not up-to-date, build docs, check versions.json through s3 API,
bypassing the cache, see it's up-to-date, stop.

To address those issues, this PR changes the cron to:
1. Increase the timeout to 2h instead of 50 minutes.
2. Always check the versions.json file through s3, rather than go
through the HTTP cache first.

These are not complete solutions but I'm not sure how to do better given
that s3 does not have atomic operations.

azure-cron.yml

@@ -26,7 +26,7 @@ trigger: none
 
 jobs:
   - job: docs
-    timeoutInMinutes: 50
+    timeoutInMinutes: 120
     pool:
       name: 'linux-pool'
     steps:

ci/cron/src/Main.hs

@@ -102,19 +102,12 @@ http_post url headers body = do
       2 -> return $ HTTP.responseBody response
       _ -> Exit.die $ "POST " <> url <> " failed with " <> show status <> "."
 
-github_versions :: [GitHubVersion] -> Set.Set String
-github_versions vs = Set.fromList $ map name vs
-
-remove_prereleases :: [GitHubVersion] -> [GitHubVersion]
-remove_prereleases = filter (\v -> not (prerelease v))
-
-docs_versions :: H.HashMap String String -> Set.Set String
-docs_versions json =
-    Set.fromList $ H.keys json
-
 newtype Version = Version (Int, Int, Int)
   deriving (Eq, Ord)
 
+instance Show Version where
+    show (Version (a, b, c)) = show a <> "." <> show b <> "." <> show c
+
 to_v :: String -> Version
 to_v s = case map read $ Split.splitOn "." s of
     [major, minor, patch] -> Version (major, minor, patch)
@@ -149,13 +142,15 @@ build_docs_folder path versions = do
         shell_ $ "tar xzf bazel-bin/docs/html.tar.gz --strip-components=1 -C" <> path <> "/" <> version
     shell_ $ "git checkout " <> cur_sha
 
-check_s3_versions :: Set.Set String -> IO Bool
-check_s3_versions gh_versions = do
+fetch_s3_versions :: IO (Set.Set Version)
+fetch_s3_versions = do
     temp <- shell "mktemp"
     shell_ $ "aws s3 cp s3://docs-daml-com/versions.json " <> temp
     s3_raw <- shell $ "cat " <> temp
-    case JSON.decode $ LBS.fromString s3_raw of
-      Just s3_json -> return $ docs_versions s3_json == gh_versions
+    let type_annotated_value :: Maybe JSON.Object
+        type_annotated_value = JSON.decode $ LBS.fromString s3_raw
+    case type_annotated_value of
+      Just s3_json -> return $ Set.fromList $ map (to_v . Text.unpack) $ H.keys s3_json
       Nothing -> Exit.die "Failed to get versions from s3"
 
 push_to_s3 :: String -> IO ()
@@ -240,31 +235,38 @@ instance JSON.FromJSON GitHubVersion where
 name :: GitHubVersion -> String
 name gh = tail $ tag_name gh
 
+fetch_gh_versions :: IO (Set.Set Version, GitHubVersion)
+fetch_gh_versions = do
+    resp <- http_get "https://api.github.com/repos/digital-asset/daml/releases"
+    let releases = filter (not . prerelease) resp
+    let versions = Set.fromList $ map (to_v . name) releases
+    let latest = List.maximumOn (to_v . name) resp
+    return (versions, latest)
+
 main :: IO ()
 main = do
     robustly_download_nix_packages
     putStrLn "Checking for new version..."
-    gh_resp <- remove_prereleases <$> http_get "https://api.github.com/repos/digital-asset/daml/releases"
-    docs_resp <- docs_versions <$> http_get "https://docs.daml.com/versions.json"
-    if github_versions gh_resp == docs_resp
+    (gh_versions, gh_latest) <- fetch_gh_versions
+    s3_versions_before <- fetch_s3_versions
+    if s3_versions_before == gh_versions
     then do
         putStrLn "No new version found, skipping."
         Exit.exitSuccess
     else do
         Temp.withTempDir $ \docs_folder -> do
             putStrLn "Building docs listing"
-            build_docs_folder docs_folder $ List.sortOn (Ord.Down . to_v) $ map name gh_resp
+            build_docs_folder docs_folder $ map show $ List.sortOn Ord.Down $ Set.toList gh_versions
             putStrLn "Done building docs bundle. Checking versions again to avoid race condition..."
-            s3_matches <- check_s3_versions (github_versions gh_resp)
-            if s3_matches
+            s3_versions_after <- fetch_s3_versions
+            if s3_versions_after == gh_versions
             then do
                 putStrLn "No more new version, another process must have pushed already."
                 Exit.exitSuccess
             else do
                 push_to_s3 docs_folder
-                let gh_latest = List.maximumOn (to_v . name) gh_resp
-                let docs_latest = List.maximumOn to_v $ Set.toList docs_resp
-                if to_v (name gh_latest) > to_v docs_latest
+                let prev_latest = List.maximum $ Set.toList s3_versions_before
+                if to_v (name gh_latest) > prev_latest
                 then do
                     putStrLn "New version detected, telling HubSpot"
                     tell_hubspot gh_latest