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How to Reclaim Database Space

Sometimes it's necessary to reduce the number of documents in MongoDB collections to speed up searches, reduce index sizes, and possibly improve the speed of classifying alarms, excluding those that are too old to reopen. It can also be used to free up space occupied by collections.

Cleaning Archived Alarms

Mechanism: Copying all archived alarms that were closed before a specific date into archive collections, followed by removal from the main collection.


To configure this process, you need to specify the settings in etc/settings.yml or in KV Consul (/Root/noc/bi/alarms_archive_policy) (make sure it is present in NOC_CONFIG in the tower). The settings include:

  • 4m – Keep data for 4 months.
  • 5y – Keep data for 5 years.
  • quarterly – How often to create new collections. You can experiment with this setting.

By setting it to quarterly, you ensure that within a year, you will have 4 archive collections for each quarter. When the closure date of an alarm crosses the quarter boundary, it goes into the next collection.

Available options are:

  • weekly
  • monthly
  • quarterly
  • yearly
  alarms_archive_policy: quarterly
  clean_delay_alarms: 4m
  clean_delay_reboots: 5y
  enable_alarms_archive: true
  enable_managedobjects: true
  enable_reboots: true
  enable_alarms: true

After configuring the settings, you should verify that the correct values for the variables have been loaded. You can do this as follows:

./noc config dump bi
This command will display the configuration settings. Here's an example:
./noc config dump bi

  alarms_archive_batch_limit: 10000
  alarms_archive_policy: quarterly
  chunk_size: 3000
  clean_delay_alarms: 4m
  clean_delay_reboots: 5y
  enable_alarms: true
  enable_alarms_archive: true
  enable_managedobjects: true
  enable_reboots: true
  extract_delay_alarms: 1h
  extract_delay_reboots: 1h
  extract_window: 1d
  language: en
  query_threads: 10
  reboot_interval: 1M
./noc bi clean

test run without real data deletion. When running without --force key:

./noc bi clean

[reboots] Cleaned before 2013-11-13 11:32:58.424000 ...
[alarms] Cleaned before 2018-07-15 11:51:58.543000 ...
[managedobjects] Cleaned before 2018-09-13 12:00:07.948000 ...
Attention: The data WILL BE copied to archive collections alarms.y* but WILL NOT BE deleted from the main collection noc.alarms.archived.

If you have performed a test run, make sure to clean all archive collections alarms.y20XX* to avoid any issues when running the operation again.

./noc bi clean --force
Real Data Transfer In a real run, after displaying the dates, there will be a countdown before making any changes. You have time to reconsider.
./noc bi clean --force

[reboots] Cleaned before 2013-11-13 11:32:58.424000 ...
All data before reboots from collection 2013-11-13 11:32:58.424000 will be Remove..



To Verify that Everything Worked:

  1. Run ./noc mongo to access MongoDB.
  2. Use show collections; to list collections and make sure there are no collections starting with alarms.y. If they exist, you may have used the command before.
  3. Run db.noc.alarms.archived.find().sort({"timestamp": 1}).limit(1) to retrieve the "clear_timestamp" of the first closed alarm. After cleaning, the time should be later than the cleaning time.
  4. Execute db.noc.alarms.archived.count() to check the number of documents in the archive alarms collection. Remember this count. After cleaning, verify that the count has decreased.
  5. Use db.alarms.y2018_quarter3.count() to check the number of documents in the archive collection.
  6. Finally, run ./noc bi clean --force and then analyze the collections in MongoDB.

Note: If you decide to drop archive collections, you can drop all alarm.y* collections EXCEPT the last one, as it may still contain alarms.

Event Cleanup

Operation Mechanism: All events older than 4 weeks will be dropped. This is the default behavior, but you can specify your own parameter using --before, as shown in the code.

./noc events clean --before 2019-11-27
./noc events clean --before-days 365


./noc events clean
It will show how many events can be (but will not be) dropped during the periods:

Before is not set, use default

[events] Cleaned before 2018-10-15 15:12:35.931421 ...
Interval: 2018-04-30 13:10:59, 2018-05-07 13:10:59; Count: 1
Interval: 2018-05-07 13:10:59, 2018-05-14 13:10:59; Count: 4
Interval: 2018-10-08 13:10:59, 2018-10-15 13:10:59; Count: 21131
Interval: 2018-10-15 13:10:59, 2018-10-22 13:10:59; Count: 20412

./noc events clean --force
./noc events clean --force --before 2019-11-07
For example, Before and After cleaning:
./noc mongo – идём в монгу
Everything is ready.

Clearing Datastreams Collections

Operation Mechanism: All documents older than the N_ttl parameter specified in the datastream settings will be deleted. If 0 is specified, no deletions will occur. To view the current settings: ./noc config dump datastream


./noc datastream clean --datastream alarm
where alarm is the datastream name.

Check the operation:

./noc mongo
    "ns" : "noc.ds_alarm",
    "size" : 9083632515,
    "count" : 4675331,
    "avgObjSize" : 1942,
    "storageSize" : 1519890432,
    "freeStorageSize" : 9973760,

./noc datastream clean --datastream alarm

    "ns" : "noc.ds_alarm",
    "size" : 766903963,
    "count" : 389807,
    "avgObjSize" : 1967,
    "storageSize" : 1546620928,
    "freeStorageSize" : 1415208960,
The collection size has been reduced, but disk space has not been freed due to MongoDB's working peculiarities.

MongoDB Compact

Starting from version 4.4, it is possible to compact collections and reclaim space marked as free.

Caution: Developers recommend creating backups of the database BEFORE performing such an operation.


use noc
db.runCommand({ compact: "ds_alarm", force:true })

    "bytesFreed" : 1619468288,
    "ok" : 1,
    "$clusterTime" : {
        "clusterTime" : Timestamp(1648810501, 640),
        "signature" : {
            "hash" : BinData(0,"bVXq9xHXqN3VNYj/qnh/z1ZBzkQ="),
            "keyId" : NumberLong("7029149395098533889")
    "operationTime" : Timestamp(1648810501, 639)
1.5 GB was freed in this example. This operation can be helpful in critical situations. The most effective compaction can be performed on the following collections:
  • noc.alarms.archived
  • ds_* - if data is updated frequently.


There is no need to delete archived items externally. It may be advisable to monitor the database logs.


The mechanism for cleaning archived data is implemented based on the TTL (Time To Live) configuration in the 'Main/Setup/CH Policies' interface.

Configuration Example tables for configuration:

  • raw_cpu
  • raw_interface
  • raw_mac
  • raw_ping
  • raw_alarms
  • raw_memory
  • raw_reboots
  • raw_environment

Set TTL as desired, for example, use 30 for raw_mac.

Usage Example

To view the amount of data that will be removed, use the following command:

./noc ch-policy apply --host

To delete the data, use the --approve flag:

noc ch-policy apply --host --approve