Golang Messages.Slice方法代碼示例

//.........這裏部分代碼省略.........
			clog.node_log("Previous term of %v doesn't match previousMessageTerm of %v\n", previousTerm, previousMessageTerm)
			return nextIndex, false, nil
		}

		//clog.node_log("Our last index is %v.  Leader thinks our last index is %v and we are trying to append %v messages\n", lastIndex, previousIndex, msgs.GetCount())
		// How many messages overlap?  If len(msgs) is shorter than the gap between lastIndex and previousIndex, use that.
		// How many messages overlap?  If we have 10 messages and previousIndex was 8 then we have two left to check (9 & 10)
		// How many messages overlap?  If we have a lastIndex of 10 and previousIndex of 8 then we have two left to check (9 & 10)
		msgsToCheck := msgs.GetCount()
		// We have already checked the first message, does the rest push us beyond the lastIndex?
		// E.g. len (msgs) = 2, previousIndex = 5, lastIndex = 7.
		if (int64(msgsToCheck) + previousIndex) >= lastIndex {
			msgsToCheck = int(lastIndex - previousIndex)
		}

		// Next question - do all messages beyond the previousMessage match the contents of the new messages?
		checkMessagesIndex := previousIndex

		if msgsToCheck > 0 {
			overlappingMessages, err := clog.getAtLeastMessages(checkMessagesIndex+1, int64(msgsToCheck))
			clog.node_log("Retrieved %v messages from index %v to check for overlaps (needed at least %v)\n", overlappingMessages.GetCount(), checkMessagesIndex+1, msgsToCheck)
			if err != nil {
				return nextIndex, false, err
			}

			for i := 0; i < overlappingMessages.GetCount(); i++ {
				// Check terms match for the given index
				// TODO: Check payload and CRC as well?
				checkMessagesIndex++
				//clog.node_log("Loop index %v, overlapMessageCount: %v\n", i, overlapMessageCount)
				overlappingMessagesTerm, err := overlappingMessages.GetMessageTerm(i)
				if err != nil {
					return nextIndex, false, err
				}
				msgsTerm, err := msgs.GetMessageTerm(overlapMessageCount)
				if err != nil {
					return nextIndex, false, err
				}
				if overlappingMessagesTerm != msgsTerm {
					// We need to truncate from here to the end of the log.
					clog.node_log("Truncating log due to mismatching terms to index %v.\n", checkMessagesIndex)
					clog.log.TruncateMessages(int64(checkMessagesIndex))
					break
				}
				// If we get this far then we have an overlapping message
				overlapMessageCount++
			}
		}
	} else {
		if previousIndex != 0 {
			clog.node_log("Empty log, but previousIndex of %v given by leader\n", previousIndex)
			return nextIndex, false, nil
		}
		// We have our first messages - use AppendFirstMessages to set the index correctly (first message isn't always 1)
		if msgs.GetCount() > 0 {
			//clog.node_log("Attempting to append %v messages\n", len(msgsToAppend))
			lastID, err := clog.log.AppendFirstMessages(msgs, leaderFirstIndex)
			if err != nil {
				clog.node_log("Error attempting to Append messages to the log: %v\n", err)
				return nextIndex, false, nil
			} else if clog.syncPolicy == WRITE_SYNC {
				err = clog.log.Sync()
				if err != nil {
					clog.node_log("Error attempting to sync Append messages to the log: %v\n", err)
					return nextIndex, false, nil
				}
			}

			nextIndex = lastID + 1
			return nextIndex, true, nil
		}
	}

	// All messages beyond overlapMessageCount should now be appended.
	msgsToAppend, err := msgs.Slice(overlapMessageCount, msgs.GetCount())
	if err != nil {
		clog.node_log("Error slicing overlapping messages: %v\n", err)
		return nextIndex, false, nil
	}
	if msgsToAppend.GetCount() > 0 {
		//clog.node_log("Attempting to append %v messages\n", len(msgsToAppend))
		lastID, err := clog.log.AppendMessages(msgsToAppend)
		if err != nil {
			clog.node_log("Error attempting to Append messages to the log: %v\n", err)
			return nextIndex, false, nil
		} else if clog.syncPolicy == WRITE_SYNC {
			err = clog.log.Sync()
			if err != nil {
				clog.node_log("Error attempting to sync Append messages to the log: %v\n", err)
				return nextIndex, false, nil
			}
		}

		nextIndex = lastID + 1
	} else {
		//clog.node_log("Call to append, but not message to add.\n")
	}

	return nextIndex, true, nil
}