Clarify how often usage reports are sent (#928)

Closes #921.

lib/model/query/analytics.js

@@ -603,13 +603,18 @@ const previewMetrics = () => (({ Analytics }) => Promise.all([
   return metrics;
 }));
 
-// Get most recent 'analytics' audit from the past N days
-const AUDIT_SCHEDULE = config.has('default.taskSchedule.analytics')
+// Usage reports are sent on a fixed interval: a usage report is sent a fixed
+// number of days after the previous report. The default is to send a report
+// every 31 days. However, that number is configurable so that usage reporting
+// can be verified during regression testing.
+const ANALYTICS_SCHEDULE = config.has('default.taskSchedule.analytics')
   ? config.get('default.taskSchedule.analytics')
-  : 30; // Default is 30 days
+  : 31; // Default is 31 days
 
+// Returns the latest recent attempt to send a usage report. If there is no
+// recent attempt, then it is time for a new report to be sent.
 const getLatestAudit = () => ({ maybeOne }) => maybeOne(sql`select * from audits
-  where action='analytics' and "loggedAt" >= current_date - cast(${AUDIT_SCHEDULE} as int)
+  where action='analytics' and current_date - "loggedAt"::date < ${ANALYTICS_SCHEDULE}
   order by "loggedAt" desc limit 1`);
 
 module.exports = {

test/integration/other/analytics-queries.js

@@ -1205,24 +1205,26 @@ describe('analytics task queries', () => {
 
   describe('latest analytics audit log utility', () => {
     it('should find recently created analytics audit log', testService(async (service, container) => {
-      // eslint-disable-next-line object-curly-spacing
       await container.Audits.log(null, 'analytics', null, { test: 'foo', success: true });
       const res = await container.Analytics.getLatestAudit().then((o) => o.get());
       res.details.test.should.equal('foo');
     }));
 
-    it('should find nothing if no recent analytics audit log', testService(async (service, container) => {
-      // make all submissions so far in the distant past
-      //await container.all(sql`update submissions set "createdAt" = '1999-1-1' where true`);
+    it('should find nothing if no analytics audit log', testService(async (service, container) => {
       const res = await container.Analytics.getLatestAudit();
       res.isEmpty().should.equal(true);
     }));
 
+    it('should find analytics audit log created 30 days ago', testService(async (service, container) => {
+      await container.Audits.log(null, 'analytics', null, { test: 'foo', success: true });
+      await container.all(sql`update audits set "loggedAt" = current_timestamp - interval '30 days' where action = 'analytics'`);
+      const res = await container.Analytics.getLatestAudit();
+      res.isDefined().should.equal(true);
+    }));
+
     it('should not return analytics audit log more than 30 days prior', testService(async (service, container) => {
-      // eslint-disable-next-line object-curly-spacing
       await container.Audits.log(null, 'analytics', null, { test: 'foo', success: true });
-      // make all analytics audits so far in the distant past
-      await container.all(sql`update audits set "loggedAt" = '1999-1-1' where action = 'analytics'`);
+      await container.all(sql`update audits set "loggedAt" = current_timestamp - interval '31 days' where action = 'analytics'`);
       const res = await container.Analytics.getLatestAudit();
       res.isEmpty().should.equal(true);
     }));