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(DOCSP-45308) Convert page to table, removing embedded verifier. (#531)
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‎source/reference/verification.txt‎

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@@ -16,101 +16,128 @@ Verify Data Transfer
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:depth: 2
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:class: singlecol
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When :ref:`mongosync <c2c-mongosync>` has fully committed, verify the
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successful transfer of your data before you switch your application to using
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the destination cluster. You can verify your data transfer using document
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counts, hash comparison, document comparison, or the Migration Verifier.
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Use Cases
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---------
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You should verify your data after every sync. This is important in
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cases where you plan to move your application load from the source to the
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destination cluster.
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Verification methods:
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- :ref:`c2c-verify-with-doc-counts`
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- :ref:`c2c-verify-with-hash-comp`
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- :ref:`c2c-verify-with-doc-comp`
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- :ref:`c2c-verify-with-verifier`
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The specific method you use to verify your data depends on your application
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workload and the complexity of the data.
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Before you switch your application load from the source cluster
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to the destination cluster, you should verify that the migration
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was successful.
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.. _c2c-verify-method:
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Tasks
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-------
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.. _c2c-verify-with-doc-counts:
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Document Counts
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~~~~~~~~~~~~~~~
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The most basic method of verification is to compare the number of documents
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in each synced collection on the source cluster to the number on the
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destination cluster.
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This method only verifies a successful sync when run against clusters with
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insert-only workloads.
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For more information, see :ref:`c2c-verify-doc-counts`.
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.. _c2c-verify-with-hash-comp:
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Hash Comparison
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~~~~~~~~~~~~~~~
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You can verify sync by comparing MD5 hashes of collections synced from the
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source cluster to the destination cluster.
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While hash comparison ensures that the destination cluster has received all
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changes from the source, the :dbcommand:`dbHash` command locks the cluster,
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preventing additional writes until it completes.
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-----
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You should verify your data after every sync. This is important
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in cases where you plan to move your application load from the
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source to the destination cluster.
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.. list-table::
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:widths: 20 80
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:header-rows: 1
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:stub-columns: 1
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* - Verification Method
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- Description
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* - :ref:`Document Counts <c2c-verify-doc-counts>`
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- The most basic method of verification is to compare the
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number of documents in each synced collection on the
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source cluster to the number on the destination cluster.
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Before you can verify data transfer with this method,
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``mongosync`` must be in the ``COMMITTED`` state.
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This method only verifies a successful sync when run
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against clusters with insert-only workloads.
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* - :ref:`Hash Comparison <c2c-verify-hash-comp>`
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- You can verify sync by comparing MD5 hashes of
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collections synced from the source cluster to the
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destination cluster.
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Before you can verify data transfer with this method,
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``mongosync`` must be in the ``COMMITTED`` state.
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While hash comparison ensures that the destination
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cluster has received all changes from the source, the
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:dbcommand:`dbHash` command locks the cluster, preventing
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additional writes until it completes.
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Hash comparison is **not** possible with sharded
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clusters. It also does not work with standalone servers
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and replica sets that use MongoDB 4.4 or earlier
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releases, since the document field order can vary.
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* - Document Comparison
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- You can verify sync by comparing documents on the source
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and destination clusters.
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Write a script that queries collections on the source
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cluster and then checks that the correct documents,
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indexes, collections, metadata, and views exist with the
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same values on the destination cluster.
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Before you can verify data transfer with this method,
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``mongosync`` must be in the ``COMMITTED`` state.
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* - .. _c2c-index-comparison:
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Index Comparison
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- To verify the transfer of indexes, run the
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:method:`db.collection.getIndexes` method on the source
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and destination clusters and compare the results.
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* - .. _c2c-metadata-comparison:
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Metadata Comparison
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- To verify the transfer of metadata, run the
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:method:`db.getCollectionInfos` method on the source and
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destination clusters and compare the results.
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* - .. _c2c-shardkey-comparison:
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Shard Key Comparison
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- To verify the transfer of shard keys to a synced collection, run a query on the ``config.collections``
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collection to find a document whose ``_id`` value is the namespace of the target collection.
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Compare the ``key`` value of this document in the source and destination clusters.
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For example, for a collection named ``pets`` in the ``records`` database, you can verify the shard key
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using the following query in :binary:`mongosh`:
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.. io-code-block::
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:copyable: true
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.. input::
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:language: javascript
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db.getSiblingDB("config").collections.find({ _id : "records.pets" })
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.. output::
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:language: javascript
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:emphasize-lines: 5-7
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:visible: false
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{
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"_id" : "records.pets",
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"lastmod" : ISODate("2021-07-21T15:48:15.193Z"),
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"timestamp": Timestamp(1626882495, 1),
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"key" : {
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"_id" : 1
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},
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"unique" : false,
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"lastmodEpoch" : ObjectId("5078407bd58b175c5c225fdc"),
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"uuid" : UUID("f8669e52-5c1b-4ea2-bbdc-a00189b341da")
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}
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* - :ref:`Migration Verifier <c2c-migration-verifier>`
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- Migration Verifier connects to the source and destination
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clusters and performs a series of verification checks,
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comparing documents, views, and indexes to confirm the
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sync was successful.
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.. note::
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Hash comparison is not possible with sharded clusters. It also does not
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work for standalone servers and replica sets that use MongoDB 4.4 or earlier
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releases, since the document field order can vary.
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For more information, see :ref:`c2c-verify-hash-comp`.
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.. _c2c-verify-with-doc-comp:
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Document Comparison
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~~~~~~~~~~~~~~~~~~~
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You can verify sync by comparing documents on the source and destination
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clusters. Write a script that queries collections on the source cluster and
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then checks that the document exists with the same values on the destination
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cluster.
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.. _c2c-verify-with-verifier:
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Migration Verifier
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~~~~~~~~~~~~~~~~~~
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Migration Verifier connects to the source and destination clusters and performs
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a series of verification checks, comparing documents, views, and indexes to
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confirm the sync was successful.
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.. important::
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Migration Verifier is an experimental and unsupported tool.
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For installation instructions, see
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`GitHub <https://github.com/mongodb-labs/migration-verifier>`__.
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Unlike other verification methods, Migration Verifier can run concurrent
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with ``mongosync``, checking documents on the destination cluster as they
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sync.
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For more information, see :ref:`c2c-migration-verifier`.
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Migration Verifier is an experimental and unsupported
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tool.
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The specific method you use to verify your data depends on your
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application workload and the complexity of the data.
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.. toctree::
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:hidden:
@@ -122,11 +149,6 @@ For more information, see :ref:`c2c-migration-verifier`.
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Learn More
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----------
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For more information, see:
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- :method:`db.collection.countDocuments`
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- :dbcommand:`dbHash`
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- :dbcommand:`dbHash`

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