Questions tagged [wiredtiger]

WiredTiger is a pluggable storage engine for MongoDB 3.0. This tag should only be used for questions surrounding the MongoDB system when used in combination with the WiredTiger storage engine.

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indexSize mismatch between primary and secondary members on wired tiger engine

we are using mongoDB 4.0 on wired tiger engine. For the last couple of days, we are observing that indexSize of primary server(marked in blue in attached file) went up drastically compared to its ...
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2answers
42 views

usage percentage of Mongodb internal cache

I've ran two performance test on a MongoDB server with identical environment/settings AFAIK. I found that the throughput was 10% apart. When I inspected the mongostat logs, I found that Mongodb in ...
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52 views

Is MongoDB secondary index size affected by primary key size?

If I understand correctly, secondary index leaf nodes in MySQL InnoDB engine hold the table primary key value (at least for a unique index). Thus, looking up a value in the secondary index results ...
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47 views

MongoDB - Does WiredTiger benefit from virtual cpus cores the same way it does with physical cores?

According to https://docs.mongodb.com/manual/administration/production-notes/#id5 The WiredTiger storage engine is multithreaded and can take advantage of additional CPU cores. We will be running ...
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2answers
100 views

How to influence files (pre)allocation steps (max growing value) in MongoDB 3.4 with WiredTiger

We have in environment deployed some really small DBs (5GB) as directory per DB.Under dirs is LVM with XFS, where we have implemented logic for "brake" when DB space should be full-filled (all is due ...
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1answer
231 views

First query is really slow with WiredTiger, not with mmapv1

We recently upgraded to MongoDB 4.0. Loving the performance improvements with WiredTiger, but all of a sudden our test suite is timing out on certain machines. Before running our tests, we run the ...
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1answer
1k views

Restore mongoDB by --repair and WiredTiger

We accidentally deleted the directory rm -rf /data/db which was our MongoDB path, and thanks to extundelete, we recovered it and got the directory /data/db. Here are our files in the directory, and ...
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1answer
233 views

MongoDB UserNotFound when starting mongod

I have a MongoDB version 2.4 that i wish to upgrade to 4.0. The official solution is to upgrade from 2.4 to 2.6, then to 3.0, and so on. I am attempting to upgrade from 2.6 to 3.0, and also to change ...
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444 views

How to Recover Mongodb database

I have transferred my mongodb database to a new computer and am having trouble opening the database. I don't get any errors, it just won't show the 'finance' database. Here is the response when I say ...
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1answer
240 views

MongoDB Migrating away from RocksDB to WiredTiger

We have been working for some time with RocksDB as our engine and we are now trying to migrate to WiredTiger. We have some pretty big databases around 4~12 TB of data and according to the process ...
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245 views

Should Azure host write-caching be enabled when using MongoDB's WiredTiger storage engine

I have several virtual machines on Azure running a mongoDB replicaSet with the WiredTiger storage engine. I'm not sure about the proper host caching option to set on the disks that contain the MongoDB ...
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106 views

MongoDB secondaries become unresponsive during replication

We got 3 Servers running. One Primary, two as secondaries. Primary has 4 vcpus, 16 GB memory, both secondaries have 8 vcpus, 64 GB memory. Every night, we run a full sync with several large ...
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1answer
452 views

How many files are created by default using WiredTiger storage engine?

So, I got a question on a test (without answer unfortunately) that left me with a big doubt whether it's true or false. The question is this: "By default, WiredTiger storage engine creates one file ...
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1answer
783 views

Meaning of “update conflicts” in CollStats result

db.collection.stats() returns wiredTiger: { ..... "transaction" : { "update conflicts" : NumberInt(1410) }, .... } It's MongoDB 3.6, but I don't use its new features ...
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1answer
3k views

How to copy wt files from another mongo instance? [closed]

I received a copy of mongo dbpath directory copy from a peer. I copied entire content to my local dbpath with an intention to work on the collections. However, my local is not recognizing the ...
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1answer
3k views

How to restore .wt backup file to local MongoDB?

This is a question that was asked before, but I have tried all solutions, and simply cannot get it right. I have spent quite some time researching before posting this question. I have looked at the ...
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2answers
1k views

Mongodb how to cancel a --fork without mongod service 'option'

I am currently having issues with sudo service mongod start/stop/etc so instead I have been running mongo with sudo mongod --storageEngine wiredTiger --dbpath /data --bind_ip_all --logpath /var/log/...
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1answer
308 views

Mongodb 3.6.3 disappears after 2 weeks on centos 7 ec2 instance

My Mongodb has disappeared 2 times, after 2 weeks, over the weekend within a 4 week time period. I had a snapshot to recover from but I can't keep on recovering my db every 2 weeks. In an ec2 ...
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1answer
200 views

Slow MongoDB start time when data is replicated to a new machine

We have a 3.2.13 Mongodb replica set with WiredTiger on AWS. We are observing a strange behaviour: when stopping and starting the mongod service, the start time is about 10 minutes, but when stopping ...
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192 views

Quickest way to partially restore a mongodb instance from AWS snapshots?

I have multiple large mongodb clusters running mongodb 3.4 configured with wiredtiger. I would like to set up standalone instances with just a few DBs from these clusters, all on the same EC2 instance....
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399 views

MongoDB background index builds block secondary

We recently experienced a disruptive incident in a MongoDB 3.2 cluster related to index creation. Scenario: Several indexes were created on the primary using background: true. Indexes were ...
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1answer
32 views

MongoS clients not seeing databases after config server change to CSRS

The three config servers were migrated to CSRS and WiredTiger last week. Followed the documentation here : https://docs.mongodb.com/manual/tutorial/upgrade-config-servers-to-replica-set/ Since the ...
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1answer
1k views

MongoDB wiredTiger Error: collection-*.wt does not appear to be a WiredTiger file (Window10)

mongoDB version: 3.4.2 os: win10 Question: Cannot start mongoDB due to .wt file corruption When reset mongoDB database path, cmd give the error as in picture Any hint would be appreciated, thanks
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1answer
792 views

mongodb v3.4 - wiredtiger - compact does not work

I am using mongo v3.4.10 with WiredTiger. I run the following command: db.runCommand({ compact: "my_collection" }); the response is: /* 1 */ { "ok" : 1.0 } and the mongo log shows: 2017-10-...
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1answer
422 views

WiredTiger panic when attempting to rename .turtle leads to loss of all data

We've seen this twice this week on separate servers (one staging, one production). 2017-10-19T12:50:37.525-0400 I ACCESS [conn266] Successfully authenticated as principal ********* on admin 2017-10-...
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165 views

MongoDB WiredTiger cache contents

I'm running MongoDB 3.4.7 cluster (primary + 2 secondaries). Primary's cache usage is 95%, and I try to figure out what the cache contains. I ran collStats for all collections (±18,000) and ...
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1answer
5k views

MongoDB Maxing CPU Usage

I have a weird one here. We have set up our production MongoDB which was populated by our test one so we had something to work off of. As soon as we started the service we hit instant 100% CPU load ...
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1answer
116 views

In MongoDB serverStatus(), what is the meaning of “connection data handles currently active”?

When running db.serverStatus() in the MongoDB shell (3.4, WiredTiger), the results contain the following data: { "connection data handles currently active" : 94862, "connection sweep ...
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580 views

MongoDB + WiredTiger cache usage stuck on 95%

I'm running a mongo 3.4.7 cluster (8 CPU, 120GB ram, primary + 2 secondaries) with ±130 open connections, each one of them to a separate DB with ±50 collections. After a few minutes of running, cache ...
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2answers
505 views

MongoDB Write Concern when Journaling is off

I'm running mongo 3.4.7 (WiredTiger) replica set with two secondaries. According to the docs, when journaling is enabled and write concern is {w: "majority", j: 0}, the ack is sent after the data is ...
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2answers
4k views

Mongodb Not Restarting with Collections, WiredTiger.wt may be corrupt

I believe my MongoDB did not have a clean shutdown. I am able to restart it in a new location which doesn't have all of my collections. If I try to repair or start it in the old location, it gives the ...
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1answer
4k views

Recover MongoDB data without WiredTiger.wt file

We have recovered a MongoDB database from filesystem, but the WiredTiger.wt file has changed since then (i.e. the collection has been dropped). So is it possible to read data (documents) from some ....
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1answer
672 views

MongoDB responds slowly during the WiredTiger Checkpoint writing process

We have 3 instances of MongoDB 3.2.12 configured as a replica set. Journaling is enabled, the storage engine is WiredTiger. Most of the time our application produces a very low load on the database ...
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2answers
2k views

Disable Journaling in MongoDB + WiredTiger

We have a cluster of 3 Mongo 3.2.13 instances running with journaling enabled, with hundreds of DBs and collections which are accessed simultaneously. We are checking the option to disable journaling,...
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4answers
3k views

MongoDB / WiredTiger: reduce storage size after deleting properties from documents

I use MongoDB 3.4 with WiredTiger storage engine on a replica set of 4 nodes. I shrinked a lot a documents by removing properties that takes most of the space, but the documentation says that this ...
2
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1answer
423 views

WiredTiger prefix compression for index on MongoDB

According to the MongoDB documentation (at least this blog entry https://www.mongodb.com/blog/post/new-compression-options-mongodb-30), prefix compression is enabled by default on MongoDB. However, ...
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2answers
3k views

WiredTiger internal cache

It is stated in the MongoDB documentation FAQ (https://docs.mongodb.com/manual/faq/storage/#wiredtiger-storage-engine) : Avoid increasing the WiredTiger internal cache size above its default value. ...
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1answer
258 views

change journalCompressor to none - not default snappy

Quote from ObjectRocket Support Hi, Fyodor! The journalCompressor setting is specifically related to the journal files. Journals are typically not compressed because compressing them causes ...
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1answer
2k views

Read concern level of majority error while upgrading Sharded Cluster from 3.2 to 3.4

I have upgraded MongodDB sharded cluster having two replica sets from 3.2 to 3.4. Current storage engine is MMAPv1. After successfully upgrading all the secondary, primary, config server and mongos to ...
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1answer
1k views

Mongodb crash after WiredTiger Cannot allocate memory error

I am using MongoDB (3.2.6) as storage for my application and since a couple of weeks MongoDB started to crash usually every 1 or 2 weeks. The crash seems to come from an issue during WiredTiger memory ...
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605 views

WiredTiger memory usage vs cache usage

We have a sharded MongoDB cluster running on 3 m4.large AWS EC2 instances (8GB RAM each) Our Data size is 1.2GB We set the WiredTiger CacheSizeGB to 2GB I can see on the mongodb monitoring Memory ...
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3answers
39k views

MongoDB using too much memory

We've been using MongoDB for several weeks now, the overall trend that we've seen has been that mongodb is using way too much memory (much more than the whole size of its dataset + indexes). I've ...
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124 views

MongoDB backup sizes same with MMAPv1 and wiredTiger

while migrating from 3.0.10 to 3.2.8, I came to know that data backup sizes for MMAPv1 and wiredTiger are same. Is this how it should work, or am I doing something wrong? Version 3.0.10 with MMAPv1 ...
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167 views

Performance impact of having Polymorphic collections in MongoDB?

Say one document(Level 1) is supposed to have N(k) different kinds of items as sub-document arrays(Level 2), and these are stored in a separate collection(s?) due to lack of query optimisation for ...
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3answers
8k views

'mongod wiredTiger' on Ubuntu?

I cannot use wiredTiger as a service for MongoDB. I followed this step by step guide; http://docs.mongodb.org/manual/release-notes/3.0-upgrade/ Step-1: Start 3.0 mongod.OK, I did. Step-2: Export ...