[metrics-bugs] #26711 [Metrics/Onionoo]: Missing recent bridge descriptors cause trouble with history file on fresh Onionoo instance

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#26711: Missing recent bridge descriptors cause trouble with history file on fresh
Onionoo instance
---------------------------------+--------------------------
     Reporter:  karsten          |      Owner:  metrics-team
         Type:  defect           |     Status:  new
     Priority:  High             |  Milestone:
    Component:  Metrics/Onionoo  |    Version:
     Severity:  Normal           |   Keywords:
Actual Points:                   |  Parent ID:
       Points:                   |   Reviewer:
      Sponsor:                   |
---------------------------------+--------------------------
 It's been 3 days now that CollecTor provided the last sanitized bridge
 descriptors, and this means that its `recent/` directory is now empty.
 Apparently, we don't handle this unusual situation very well:

 {{{
 Exception in thread "main" java.lang.IllegalStateException: Operation is
 not permitted before finishing to read.
         at
 org.torproject.descriptor.impl.DescriptorReaderImpl.getExcludedFiles(DescriptorReaderImpl.java:68)
         at
 org.torproject.onionoo.updater.DescriptorQueue.writeHistoryFile(DescriptorQueue.java:113)
         at
 org.torproject.onionoo.updater.DescriptorSource.writeHistoryFiles(DescriptorSource.java:222)
         at org.torproject.onionoo.cron.Main.shutDown(Main.java:195)
         at org.torproject.onionoo.cron.Main.run(Main.java:130)
         at
 org.torproject.onionoo.cron.Main.runOrScheduleExecutions(Main.java:102)
         at org.torproject.onionoo.cron.Main.main(Main.java:34)
 }}}

 Working hotfix:

 {{{
 diff --git
 a/src/main/java/org/torproject/onionoo/updater/DescriptorQueue.java
 b/src/main/java/org/torproject/onionoo/updater/DescriptorQueue.java
 index c19fabd..0f3e9e7 100644
 --- a/src/main/java/org/torproject/onionoo/updater/DescriptorQueue.java
 +++ b/src/main/java/org/torproject/onionoo/updater/DescriptorQueue.java
 @@ -108,6 +108,11 @@ class DescriptorQueue {
      if (this.historyFile == null) {
        return;
      }
 +    if (null == this.descriptors) {
 +      log.warn("Not writing history file {}, because we did not read a
 single "
 +          + "descriptor from {}.", this.historyFile, this.directory);
 +      return;
 +    }
      SortedMap<String, Long> excludedAndParsedFiles = new TreeMap<>();
      excludedAndParsedFiles.putAll(
          this.descriptorReader.getExcludedFiles());
 }}}

 Log output:

 {{{
 2018-07-09 19:41:28,344 DEBUG o.t.o.u.DescriptorSource:220 Writing parse
 histories for recent descriptors...
 2018-07-09 19:41:28,347 WARN o.t.o.u.DescriptorQueue:112 Not writing
 history file status/collector.torproject.org/bridge-server-hi
 story, because we did not read a single descriptor from
 status/collector.torproject.org/recent/bridge-descriptors/server-descripto
 rs.
 2018-07-09 19:41:28,347 WARN o.t.o.u.DescriptorQueue:112 Not writing
 history file status/collector.torproject.org/bridge-extrainfo
 -history, because we did not read a single descriptor from
 status/collector.torproject.org/recent/bridge-descriptors/extra-infos.
 2018-07-09 19:41:28,347 WARN o.t.o.u.DescriptorQueue:112 Not writing
 history file status/collector.torproject.org/bridge-status-hi
 story, because we did not read a single descriptor from
 status/collector.torproject.org/recent/bridge-descriptors/statuses.
 2018-07-09 19:41:28,347 INFO o.t.o.cron.Main:196 Wrote parse histories
 }}}

 Let's look more into this and possibly finding a better fix as long as the
 situation exists that we don't have recent bridge descriptors from
 CollecTor.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/26711>
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