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Update waitForTableReplicaToProcessLogEntry comments

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This commit is contained in:
Nicolae Vartolomei 2021-06-07 11:01:57 +01:00
parent a9d108fc5f
commit 19f64b3f25
1 changed files with 4 additions and 14 deletions
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18
src/Storages/StorageReplicatedMergeTree.cpp
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@ -5318,14 +5318,10 @@ bool StorageReplicatedMergeTree::waitForTableReplicaToProcessLogEntry(
String entry_str = entry.toString();
String log_node_name;
/** Two types of entries can be passed to this function
* 1. (more often) From `log` directory - a common log, from where replicas copy entries to their queue.
* 2. From the `queue` directory of one of the replicas.
/** Wait for entries from `log` directory (a common log, from where replicas copy entries to their queue) to be processed.
*
* The problem is that the numbers (`sequential` node) of the queue elements in `log` and in `queue` do not match.
* (And the numbers of the same log element for different replicas do not match in the `queue`.)
*
* Therefore, you should consider these cases separately.
*/
/** First, you need to wait until replica takes `queue` element from the `log` to its queue,
@ -5348,9 +5344,7 @@ bool StorageReplicatedMergeTree::waitForTableReplicaToProcessLogEntry(
if (startsWith(entry.znode_name, "log-"))
{
/** In this case, just take the number from the node name `log-xxxxxxxxxx`.
*/
/// Take the number from the node name `log-xxxxxxxxxx`.
UInt64 log_index = parse<UInt64>(entry.znode_name.substr(entry.znode_name.size() - 10));
log_node_name = entry.znode_name;
@ -5375,14 +5369,10 @@ bool StorageReplicatedMergeTree::waitForTableReplicaToProcessLogEntry(
else
throw Exception("Logical error: unexpected name of log node: " + entry.znode_name, ErrorCodes::LOGICAL_ERROR);
if (!log_node_name.empty())
LOG_DEBUG(log, "Looking for node corresponding to {} in {} queue", log_node_name, replica);
else
LOG_DEBUG(log, "Looking for corresponding node in {} queue", replica);
LOG_DEBUG(log, "Looking for node corresponding to {} in {} queue", log_node_name, replica);
/** Second - find the corresponding entry in the queue of the specified replica.
* Its number may match neither the `log` node nor the `queue` node of the current replica (for us).
* Therefore, we search by comparing the content.
* Its number may not match the `log` node. Therefore, we search by comparing the content.
*/
Strings queue_entries = getZooKeeper()->getChildren(fs::path(table_zookeeper_path) / "replicas" / replica / "queue");