in src/java/org/apache/nutch/crawl/CrawlDbReducer.java [65:324]
public void reduce(Text key, Iterable<CrawlDatum> values,
Context context) throws IOException, InterruptedException {
CrawlDatum fetch = new CrawlDatum();
CrawlDatum old = new CrawlDatum();
boolean fetchSet = false;
boolean oldSet = false;
byte[] signature = null;
boolean multiple = false; // avoid deep copy when only single value exists
linked.clear();
org.apache.hadoop.io.MapWritable metaFromParse = null;
for (CrawlDatum datum : values) {
if (!multiple)
multiple = true;
if (CrawlDatum.hasDbStatus(datum)) {
if (!oldSet) {
if (multiple) {
old.set(datum);
} else {
// no need for a deep copy - this is the only value
old = datum;
}
oldSet = true;
} else {
// always take the latest version
if (old.getFetchTime() < datum.getFetchTime())
old.set(datum);
}
continue;
}
if (CrawlDatum.hasFetchStatus(datum)) {
if (!fetchSet) {
if (multiple) {
fetch.set(datum);
} else {
fetch = datum;
}
fetchSet = true;
} else {
// always take the latest version
if (fetch.getFetchTime() < datum.getFetchTime())
fetch.set(datum);
}
continue;
}
switch (datum.getStatus()) { // collect other info
case CrawlDatum.STATUS_LINKED:
CrawlDatum link;
if (multiple) {
link = new CrawlDatum();
link.set(datum);
} else {
link = datum;
}
linked.insert(link);
break;
case CrawlDatum.STATUS_SIGNATURE:
signature = datum.getSignature();
break;
case CrawlDatum.STATUS_PARSE_META:
metaFromParse = datum.getMetaData();
break;
default:
LOG.warn("Unknown status, key: " + key + ", datum: " + datum);
}
}
// copy the content of the queue into a List
// in reversed order
int numLinks = linked.size();
List<CrawlDatum> linkList = new ArrayList<>(numLinks);
for (int i = numLinks - 1; i >= 0; i--) {
linkList.add(linked.pop());
}
// if it doesn't already exist, skip it
if (!oldSet && !additionsAllowed)
return;
// if there is no fetched datum, perhaps there is a link
if (!fetchSet && linkList.size() > 0) {
fetch = linkList.get(0);
fetchSet = true;
}
// still no new data - record only unchanged old data, if exists, and return
if (!fetchSet) {
if (oldSet) {// at this point at least "old" should be present
// set score for orphaned pages (not fetched in the current cycle and
// with no inlinks)
try {
scfilters.orphanedScore(key, old);
} catch (ScoringFilterException e) {
LOG.warn("Couldn't update orphaned score, key={}: {}", key, e);
}
context.write(key, old);
context.getCounter("CrawlDB status",
CrawlDatum.getStatusName(old.getStatus())).increment(1);
} else {
LOG.warn("Missing fetch and old value, signature={}",
StringUtil.toHexString(signature));
}
return;
}
if (signature == null)
signature = fetch.getSignature();
long prevModifiedTime = oldSet ? old.getModifiedTime() : 0L;
long prevFetchTime = oldSet ? old.getFetchTime() : 0L;
// initialize with the latest version, be it fetch or link
result.set(fetch);
if (oldSet) {
// copy metadata from old, if exists
if (old.getMetaData().size() > 0) {
result.putAllMetaData(old);
// overlay with new, if any
if (fetch.getMetaData().size() > 0)
result.putAllMetaData(fetch);
}
// set the most recent valid value of modifiedTime
if (old.getModifiedTime() > 0 && fetch.getModifiedTime() == 0) {
result.setModifiedTime(old.getModifiedTime());
}
}
switch (fetch.getStatus()) { // determine new status
case CrawlDatum.STATUS_LINKED: // it was link
if (oldSet) { // if old exists
result.set(old); // use it
} else {
result = schedule.initializeSchedule(key, result);
result.setStatus(CrawlDatum.STATUS_DB_UNFETCHED);
try {
scfilters.initialScore(key, result);
} catch (ScoringFilterException e) {
LOG.warn("Cannot filter init score for url {}, using default: {}",
key, e.getMessage());
result.setScore(0.0f);
}
}
break;
case CrawlDatum.STATUS_FETCH_SUCCESS: // succesful fetch
case CrawlDatum.STATUS_FETCH_REDIR_TEMP: // successful fetch, redirected
case CrawlDatum.STATUS_FETCH_REDIR_PERM:
case CrawlDatum.STATUS_FETCH_NOTMODIFIED: // successful fetch, notmodified
// https://issues.apache.org/jira/browse/NUTCH-1656
if (metaFromParse != null) {
for (Entry<Writable, Writable> e : metaFromParse.entrySet()) {
result.getMetaData().put(e.getKey(), e.getValue());
}
}
// determine the modification status
int modified = FetchSchedule.STATUS_UNKNOWN;
if (fetch.getStatus() == CrawlDatum.STATUS_FETCH_NOTMODIFIED) {
modified = FetchSchedule.STATUS_NOTMODIFIED;
} else if (fetch.getStatus() == CrawlDatum.STATUS_FETCH_SUCCESS) {
// only successful fetches (but not redirects, NUTCH-1422)
// are detected as "not modified" by signature comparison
if (oldSet && old.getSignature() != null && signature != null) {
if (SignatureComparator._compare(old.getSignature(), signature) != 0) {
modified = FetchSchedule.STATUS_MODIFIED;
} else {
modified = FetchSchedule.STATUS_NOTMODIFIED;
}
}
}
// set the schedule
result = schedule.setFetchSchedule(key, result, prevFetchTime,
prevModifiedTime, fetch.getFetchTime(), fetch.getModifiedTime(),
modified);
// set the result status and signature
if (modified == FetchSchedule.STATUS_NOTMODIFIED) {
result.setStatus(CrawlDatum.STATUS_DB_NOTMODIFIED);
// NUTCH-1341 The page is not modified according to its signature, let's
// reset lastModified as well
result.setModifiedTime(prevModifiedTime);
if (oldSet)
result.setSignature(old.getSignature());
} else {
switch (fetch.getStatus()) {
case CrawlDatum.STATUS_FETCH_SUCCESS:
result.setStatus(CrawlDatum.STATUS_DB_FETCHED);
break;
case CrawlDatum.STATUS_FETCH_REDIR_PERM:
result.setStatus(CrawlDatum.STATUS_DB_REDIR_PERM);
break;
case CrawlDatum.STATUS_FETCH_REDIR_TEMP:
result.setStatus(CrawlDatum.STATUS_DB_REDIR_TEMP);
break;
default:
LOG.warn("Unexpected status: " + fetch.getStatus()
+ " resetting to old status.");
if (oldSet)
result.setStatus(old.getStatus());
else
result.setStatus(CrawlDatum.STATUS_DB_UNFETCHED);
}
result.setSignature(signature);
}
// if fetchInterval is larger than the system-wide maximum, trigger
// an unconditional recrawl. This prevents the page to be stuck at
// NOTMODIFIED state, when the old fetched copy was already removed with
// old segments.
if (maxInterval < result.getFetchInterval())
result = schedule.forceRefetch(key, result, false);
break;
case CrawlDatum.STATUS_SIGNATURE:
LOG.warn("Lone CrawlDatum.STATUS_SIGNATURE: {}", key);
return;
case CrawlDatum.STATUS_FETCH_RETRY: // temporary failure
if (oldSet) {
result.setSignature(old.getSignature()); // use old signature
}
result = schedule.setPageRetrySchedule(key, result, prevFetchTime,
prevModifiedTime, fetch.getFetchTime());
if (result.getRetriesSinceFetch() < retryMax) {
result.setStatus(CrawlDatum.STATUS_DB_UNFETCHED);
} else {
result.setStatus(CrawlDatum.STATUS_DB_GONE);
result = schedule.setPageGoneSchedule(key, result, prevFetchTime,
prevModifiedTime, fetch.getFetchTime());
}
break;
case CrawlDatum.STATUS_FETCH_GONE: // permanent failure
if (oldSet)
result.setSignature(old.getSignature()); // use old signature
result.setStatus(CrawlDatum.STATUS_DB_GONE);
result = schedule.setPageGoneSchedule(key, result, prevFetchTime,
prevModifiedTime, fetch.getFetchTime());
break;
default:
throw new RuntimeException("Unknown status: " + fetch.getStatus() + " "
+ key);
}
try {
scfilters.updateDbScore(key, oldSet ? old : null, result, linkList);
} catch (Exception e) {
LOG.warn("Couldn't update score, key={}: {}", key, e);
}
// remove generation time, if any
result.getMetaData().remove(Nutch.WRITABLE_GENERATE_TIME_KEY);
context.write(key, result);
context.getCounter("CrawlDB status",
CrawlDatum.getStatusName(result.getStatus())).increment(1);
}