milestone 30: overview as a dashboard, explicit health contract, period aggregations

src/web/handlers/queries.zig

@@ -126,8 +126,6 @@ pub fn list(
     io: std.Io,
     request: *http_util.Request,
 ) http_util.HandlerError!void {
-    _ = io;
-
     var buffers: Buffers = .{};
     const filter = parseFilter(request.query, &buffers) catch |err| {
         return http_util.respondError(request, .bad_request, message(err));
@@ -136,7 +134,7 @@ pub fn list(
     const database = state.querylog_db orelse
         return http_util.respondError(request, .service_unavailable, "query log unavailable");
 
-    const result = page(database, request.arena, filter) catch |err| {
+    const result = readPage(state, io, database, request.arena, filter) catch |err| {
         // The one thing this handler logs: a database fault is a property of
         // the box, not of the request, and the client is told nothing about it.
         log.warn("query log read failed: {s}", .{@errorName(err)});
@@ -156,12 +154,10 @@ pub fn detail(
     io: std.Io,
     request: *http_util.Request,
 ) http_util.HandlerError!void {
-    _ = io;
-
     const database = state.querylog_db orelse
         return http_util.respondError(request, .service_unavailable, "query log unavailable");
 
-    const row = queries_repo.detailById(database, request.arena, request.id.?) catch |err| {
+    const row = detailRow(state, io, database, request.arena, request.id.?) catch |err| {
         log.warn("query log read failed: {s}", .{@errorName(err)});
         return http_util.respondError(request, .internal_server_error, "internal error");
     };
@@ -172,6 +168,40 @@ pub fn detail(
     return http_util.respondJson(request, .ok, provenance_view.fromDetail(found), &.{});
 }
 
+/// The rows and the coverage watermark come from one database state, so a
+/// prune between them cannot tag pre-prune rows with a post-prune
+/// `available_since`.
+fn readPage(
+    state: *server.WebState,
+    io: std.Io,
+    database: *db.Db,
+    arena: Allocator,
+    filter: queries_repo.QueryFilter,
+) db.Error!Page {
+    var scope = try server.QuerylogRead.open(state, io, database);
+    errdefer scope.abort();
+    const result = try page(database, arena, filter);
+    try scope.commit();
+    return result;
+}
+
+/// One row, read under the shared lock. There is nothing to keep consistent
+/// with a second statement here; the lock is what keeps this read out of
+/// another response's open transaction.
+fn detailRow(
+    state: *server.WebState,
+    io: std.Io,
+    database: *db.Db,
+    arena: Allocator,
+    id: i64,
+) db.Error!?queries_repo.QueryDetail {
+    var scope = try server.QuerylogRead.open(state, io, database);
+    errdefer scope.abort();
+    const row = try queries_repo.detailById(database, arena, id);
+    try scope.commit();
+    return row;
+}
+
 // ---------------------------------------------------------------------------
 // tests
 // ---------------------------------------------------------------------------