A report containing information about the number of rows ingested, and any parse exceptions that occurred is available for both completed tasks and running tasks.
Compaction tasks can generate multiple sets of segment output reports based on how the input interval is split. So the overall report contains mappings from each split to each report.
For some task types, the indexing task can wait for the newly ingested segments to become available for queries after ingestion completes. The below fields inform the end user regarding the duration and result of the availability wait. For batch ingestion task types, refer to `tuningConfig` docs to see if the task supports an availability waiting period.
|Field|Description|
|---|---|
|`segmentAvailabilityConfirmed`|Whether all segments generated by this ingestion task had been confirmed as available for queries in the cluster before the task completed.|
|`segmentAvailabilityWaitTimeMs`|Milliseconds waited by the ingestion task for the newly ingested segments to be available for query after completing ingestion was completed.|
When a task is running, a live report containing ingestion state, unparseable events and moving average for number of events processed for 1 min, 5 min, 15 min time window can be retrieved at:
Only batch tasks have the DETERMINE_PARTITIONS phase. Realtime tasks such as those created by the Kafka Indexing Service do not have a DETERMINE_PARTITIONS phase.
`unparseableEvents` contains lists of exception messages that were caused by unparseable inputs. This can help with identifying problematic input rows. There will be one list each for the DETERMINE_PARTITIONS and BUILD_SEGMENTS phases. Note that the Hadoop batch task does not support saving of unparseable events.
the `rowStats` map contains information about row counts. There is one entry for each ingestion phase. The definitions of the different row counts are shown below:
-`processedBytes`: Total number of uncompressed bytes processed by the task. This reports the total byte size of all rows i.e. even those that are included in `processedWithError`, `unparseable` or `thrownAway`.
-`processedWithError`: Number of rows that were ingested, but contained a parsing error within one or more columns. This typically occurs where input rows have a parseable structure but invalid types for columns, such as passing in a non-numeric String value for a numeric column.
-`thrownAway`: Number of rows skipped. This includes rows with timestamps that were outside of the ingestion task's defined time interval and rows that were filtered out with a [`transformSpec`](ingestion-spec.md#transformspec), but doesn't include the rows skipped by explicit user configurations. For example, the rows skipped by `skipHeaderRows` or `hasHeaderRow` in the CSV format are not counted.
-`unparseable`: Number of rows that could not be parsed at all and were discarded. This tracks input rows without a parseable structure, such as passing in non-JSON data when using a JSON parser.
The [native batch task](native-batch.md), the Hadoop batch task, and Kafka and Kinesis ingestion tasks support retrieval of row stats while the task is running.
An example report is shown below. The `movingAverages` section contains 1 minute, 5 minute, and 15 minute moving averages of increases to the four row counters, which have the same definitions as those in the completion report. The `totals` section shows the current totals.
For the Kafka Indexing Service, a GET to the following Overlord API will retrieve live row stat reports from each task being managed by the supervisor and provide a combined report.
the generated segments could potentially overshadow each other, which could lead to incorrect query results.
To avoid this problem, tasks will attempt to get locks prior to creating any segment in Druid.
There are two types of locks, i.e., _time chunk lock_ and _segment lock_.
When the time chunk lock is used, a task locks the entire time chunk of a data source where generated segments will be written.
For example, suppose we have a task ingesting data into the time chunk of `2019-01-01T00:00:00.000Z/2019-01-02T00:00:00.000Z` of the `wikipedia` data source.
With the time chunk locking, this task will lock the entire time chunk of `2019-01-01T00:00:00.000Z/2019-01-02T00:00:00.000Z` of the `wikipedia` data source
before it creates any segments. As long as it holds the lock, any other tasks will be unable to create segments for the same time chunk of the same data source.
The segments created with the time chunk locking have a _higher_ major version than existing segments. Their minor version is always `0`.
When the segment lock is used, a task locks individual segments instead of the entire time chunk.
As a result, two or more tasks can create segments for the same time chunk of the same data source simultaneously
if they are reading different segments.
For example, a Kafka indexing task and a compaction task can always write segments into the same time chunk of the same data source simultaneously.
The reason for this is because a Kafka indexing task always appends new segments, while a compaction task always overwrites existing segments.
The segments created with the segment locking have the _same_ major version and a _higher_ minor version.
If you want to unset it for all tasks, you would want to set `druid.indexer.tasklock.forceTimeChunkLock` to false in the [overlord configuration](../configuration/index.md#overlord-operations).
Each task type has a different default lock priority. The below table shows the default priorities of different task types. Higher the number, higher the priority.
Task actions are overlord actions performed by tasks during their lifecycle. Some typical task actions are:
-`lockAcquire`: acquires a time-chunk lock on an interval for the task
-`lockRelease`: releases a lock acquired by the task on an interval
-`segmentTransactionalInsert`: publishes new segments created by a task and optionally overwrites and/or drops existing segments in a single transaction
-`segmentAllocate`: allocates pending segments to a task to write rows
### Batching `segmentAllocate` actions
In a cluster with several concurrent tasks, `segmentAllocate` actions on the overlord can take a long time to finish, causing spikes in the `task/action/run/time`. This can result in ingestion lag building up while a task waits for a segment to be allocated.
The root cause of such spikes is likely to be one or more of the following:
- several concurrent tasks trying to allocate segments for the same datasource and interval
- large number of metadata calls made to the segments and pending segments tables
- concurrency limitations while acquiring a task lock required for allocating a segment
Since the contention typically arises from tasks allocating segments for the same datasource and interval, you can improve the run times by batching the actions together.
To enable batched segment allocation on the overlord, set `druid.indexer.tasklock.batchSegmentAllocation` to `true`. See [overlord configuration](../configuration/index.md#overlord-operations) for more details.
When configuring [automatic compaction](../data-management/automatic-compaction.md), set the task context configurations in `taskContext` rather than in `context`.
|`forceTimeChunkLock`|_Setting this to false is still experimental._<br/> Force to use time chunk lock. When `true`, this parameter overrides the overlord runtime property `druid.indexer.tasklock.forceTimeChunkLock` [configuration for the overlord](../configuration/index.md#overlord-operations). If neither this parameter nor the runtime property is `true`, each task automatically chooses a lock type to use. See [Locking](#locking) for more details.|`true`|
|`priority`|Task priority|Depends on the task type. See [Priority](#priority) for more details.|
|`storeCompactionState`|Enables the task to store the compaction state of created segments in the metadata store. When `true`, the segments created by the task fill `lastCompactionState` in the segment metadata. This parameter is set automatically on compaction tasks. |`true` for compaction tasks, `false` for other task types|
|`storeEmptyColumns`|Enables the task to store empty columns during ingestion. When `true`, Druid stores every column specified in the [`dimensionsSpec`](ingestion-spec.md#dimensionsspec). When `false`, Druid SQL queries referencing empty columns will fail. If you intend to leave `storeEmptyColumns` disabled, you should either ingest dummy data for empty columns or else not query on empty columns.<br/><br/>When set in the task context, `storeEmptyColumns` overrides the system property [`druid.indexer.task.storeEmptyColumns`](../configuration/index.md#additional-peon-configuration).|`true`|
|`taskLockTimeout`|Task lock timeout in milliseconds. For more details, see [Locking](#locking).<br/><br/>When a task acquires a lock, it sends a request via HTTP and awaits until it receives a response containing the lock acquisition result. As a result, an HTTP timeout error can occur if `taskLockTimeout` is greater than `druid.server.http.maxIdleTime` of Overlords.|300000|
|`useLineageBasedSegmentAllocation`|Enables the new lineage-based segment allocation protocol for the native Parallel task with dynamic partitioning. This option should be off during the replacing rolling upgrade from one of the Druid versions between 0.19 and 0.21 to Druid 0.22 or higher. Once the upgrade is done, it must be set to `true` to ensure data correctness.|`false` in 0.21 or earlier, `true` in 0.22 or later|
Once the task has been submitted to the Overlord it remains `WAITING` for locks to be acquired. Worker slot allocation is then `PENDING` until the task can actually start executing.
The task then starts creating logs in a local directory of the middle manager (or indexer) in a `log` directory for the specific `taskId` at [`druid.worker.baseTaskDirs`](../configuration/index.md#middlemanager-configuration).
When the task completes - whether it succeeds or fails - the middle manager (or indexer) will push the task log file into the location specified in [`druid.indexer.logs`](../configuration/index.md#task-logging).
Task logs on the Druid web console are retrieved via an [API](../api-reference/service-status-api.md#overlord) on the Overlord. It automatically detects where the log file is, either in the middleManager / indexer or in long-term storage, and passes it back.
You can check the middleManager / indexer logs locally to see if there was a push failure. If there was not, check the Overlord's own process logs to see why the task failed before it started.
You can configure retention periods for logs in milliseconds by setting `druid.indexer.logs.kill` properties in [configuration](../configuration/index.md#task-logging). The Overlord will then automatically manage task logs in log directories along with entries in task-related metadata storage tables.
Automatic log file deletion typically works based on the log file's 'modified' timestamp in the back-end store. Large clock skews between Druid processes and the long-term store might result in unintended behavior.
Tasks sometimes need to use local disk for storage of things while the task is active. For example, for realtime ingestion tasks to accept broadcast segments for broadcast joins. Or intermediate data sets for Multi-stage Query jobs
Task storage sizes are configured through a combination of three properties:
1.`druid.worker.capacity` - i.e. the "number of task slots"
2.`druid.worker.baseTaskDirs` - i.e. the list of directories to use for task storage.
3.`druid.worker.baseTaskDirSize` - i.e. the amount of storage to use on each storage location
While it seems like one task might use multiple directories, only one directory from the list of base directories will be used for any given task, as such, each task is only given a singular directory for scratch space.
The actual amount of memory assigned to any given task is computed by determining the largest size that enables all task slots to be given an equivalent amount of disk storage. For example, with 5 slots, 2 directories (A and B) and a size of 300 GB, 3 slots would be given to directory A, 2 slots to directory B and each slot would be allowed 100 GB
