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Neo4j Cache & db hits

Hello

Can't I see the cache hit information in the community version? (Neo4j 4.0.5 version in use.)

dbms.memory.pagecache.size=1g 

PROFILE just show about 'db hits',
Memory usage in machine is going up, but I can't find any pagecache information.

can you explain why?

17 REPLIES 17

Hello @phantasmicmeans

Normally, it should work too on community.
Did you try to restart the database?

Regards,
Cobra

Hello @Cobra
I just restart the database but it doesn't change.

I added below options in neo4j.conf.

* dbms.memory.pagecache.size=1g
* dbms.query_cache_size=1000

I run the same query twice after the restart, the speed difference is huge. Therefore, it seems right that caching is being applied.

But I can't find any information about pagecache.

Did you try to run a small request like RETURN 1 and then do :sysinfo ?

What is the power of your machine?
Can you share the neo4j.conf file?

RETURN 1 and then do :sysinfo <- It doesn't work.

  • 4vcpu / 8gb / centos7

neo4j.conf

#*****************************************************************
# Neo4j configuration
#
# For more details and a complete list of settings, please see
# https://neo4j.com/docs/operations-manual/4.0/reference/configuration-settings/
#*****************************************************************

# The name of the default database
#dbms.default_database=neo4j

# Paths of directories in the installation.
#dbms.directories.data=data
dbms.directories.plugins=plugins
#dbms.directories.logs=logs
#dbms.directories.lib=lib
#dbms.directories.run=run
#dbms.directories.transaction.logs.root=data/transactions

# This setting constrains all `LOAD CSV` import files to be under the `import` directory. Remove or comment it out to
# allow files to be loaded from anywhere in the filesystem; this introduces possible security problems. See the
# `LOAD CSV` section of the manual for details.
dbms.directories.import=import

# Whether requests to Neo4j are authenticated.
# To disable authentication, uncomment this line
#dbms.security.auth_enabled=false

# Enable this to be able to upgrade a store from an older version.
#dbms.allow_upgrade=true

# Java Heap Size: by default the Java heap size is dynamically
# calculated based on available system resources.
# Uncomment these lines to set specific initial and maximum
# heap size.
#dbms.memory.heap.initial_size=512m
#dbms.memory.heap.max_size=512m

# The amount of memory to use for mapping the store files, in bytes (or
# kilobytes with the 'k' suffix, megabytes with 'm' and gigabytes with 'g').
# If Neo4j is running on a dedicated server, then it is generally recommended
# to leave about 2-4 gigabytes for the operating system, give the JVM enough
# heap to hold all your transaction state and query context, and then leave the
# rest for the page cache.
# The default page cache memory assumes the machine is dedicated to running
# Neo4j, and is heuristically set to 50% of RAM minus the max Java heap size.
dbms.memory.pagecache.size=1g

#*****************************************************************
# Network connector configuration
#*****************************************************************

# With default configuration Neo4j only accepts local connections.
# To accept non-local connections, uncomment this line:
dbms.default_listen_address=0.0.0.0

# You can also choose a specific network interface, and configure a non-default
# port for each connector, by setting their individual listen_address.

# The address at which this server can be reached by its clients. This may be the server's IP address or DNS name, or
# it may be the address of a reverse proxy which sits in front of the server. This setting may be overridden for
# individual connectors below.
#dbms.default_advertised_address=localhost

# You can also choose a specific advertised hostname or IP address, and
# configure an advertised port for each connector, by setting their
# individual advertised_address.

# By default, encryption is turned off.
# To turn on encryption, an ssl policy for the connector needs to be configured
# Read more in SSL policy section in this file for how to define a SSL policy.

# Bolt connector
dbms.connector.bolt.enabled=true
#dbms.connector.bolt.tls_level=DISABLED
#dbms.connector.bolt.listen_address=:7687

# HTTP Connector. There can be zero or one HTTP connectors.
dbms.connector.http.enabled=true
#dbms.connector.http.listen_address=:7474

# HTTPS Connector. There can be zero or one HTTPS connectors.
dbms.connector.https.enabled=false
#dbms.connector.https.listen_address=:7473

# Number of Neo4j worker threads.
#dbms.threads.worker_count=

#*****************************************************************
# SSL policy configuration
#*****************************************************************

# Each policy is configured under a separate namespace, e.g.
#    dbms.ssl.policy.<scope>.*
#    <scope> can be any of 'bolt', 'https', 'cluster' or 'backup'
#
# The scope is the name of the component where the policy will be used
# Each component where the use of an ssl policy is desired needs to declare at least one setting of the policy.
# Allowable values are 'bolt', 'https', 'cluster' or 'backup'.

# E.g if bolt and https connectors should use the same policy, the following could be declared
#   dbms.ssl.policy.bolt.base_directory=certificates/default
#   dbms.ssl.policy.https.base_directory=certificates/default
# However, it's strongly encouraged to not use the same key pair for multiple scopes.
#
# N.B: Note that a connector must be configured to support/require
#      SSL/TLS for the policy to actually be utilized.
#
# see: dbms.connector.*.tls_level

# SSL settings (dbms.ssl.policy.<scope>.*)
#  .base_directory       Base directory for SSL policies paths. All relative paths within the
#                        SSL configuration will be resolved from the base dir.
#
#  .private_key          A path to the key file relative to the '.base_directory'.
#
#  .private_key_password The password for the private key.
#
#  .public_certificate   A path to the public certificate file relative to the '.base_directory'.
#
#  .trusted_dir          A path to a directory containing trusted certificates.
#
#  .revoked_dir          Path to the directory with Certificate Revocation Lists (CRLs).
#
#  .verify_hostname      If true, the server will verify the hostname that the client uses to connect with. In order
#                        for this to work, the server public certificate must have a valid CN and/or matching
#                        Subject Alternative Names.
#
#  .client_auth          How the client should be authorized. Possible values are: 'none', 'optional', 'require'.
#
#  .tls_versions         A comma-separated list of allowed TLS versions. By default only TLSv1.2 is allowed.
#
#  .trust_all            Setting this to 'true' will ignore the trust truststore, trusting all clients and servers.
#                        Use of this mode is discouraged. It would offer encryption but no security.
#
#  .ciphers              A comma-separated list of allowed ciphers. The default ciphers are the defaults of
#                        the JVM platform.

# Bolt SSL configuration
#dbms.ssl.policy.bolt.enabled=true
#dbms.ssl.policy.bolt.base_directory=certificates/bolt
#dbms.ssl.policy.bolt.private_key=private.key
#dbms.ssl.policy.bolt.public_certificate=public.crt

# Https SSL configuration
#dbms.ssl.policy.https.enabled=true
#dbms.ssl.policy.https.base_directory=certificates/https
#dbms.ssl.policy.https.private_key=private.key
#dbms.ssl.policy.https.public_certificate=public.crt

# Cluster SSL configuration
#dbms.ssl.policy.cluster.enabled=true
#dbms.ssl.policy.cluster.base_directory=certificates/cluster
#dbms.ssl.policy.cluster.private_key=private.key
#dbms.ssl.policy.cluster.public_certificate=public.crt

# Backup SSL configuration
#dbms.ssl.policy.backup.enabled=true
#dbms.ssl.policy.backup.base_directory=certificates/backup
#dbms.ssl.policy.backup.private_key=private.key
#dbms.ssl.policy.backup.public_certificate=public.crt

#*****************************************************************
# Logging configuration
#*****************************************************************

# To enable HTTP logging, uncomment this line
#dbms.logs.http.enabled=true

# Number of HTTP logs to keep.
#dbms.logs.http.rotation.keep_number=5

# Size of each HTTP log that is kept.
#dbms.logs.http.rotation.size=20m

# To enable GC Logging, uncomment this line
#dbms.logs.gc.enabled=true

# GC Logging Options
# see https://docs.oracle.com/en/java/javase/11/tools/java.html#GUID-BE93ABDC-999C-4CB5-A88B-1994AAAC74D5
#dbms.logs.gc.options=-Xlog:gc*,safepoint,age*=trace

# Number of GC logs to keep.
#dbms.logs.gc.rotation.keep_number=5

# Size of each GC log that is kept.
#dbms.logs.gc.rotation.size=20m

# Log level for the debug log. One of DEBUG, INFO, WARN and ERROR. Be aware that logging at DEBUG level can be very verbose.
#dbms.logs.debug.level=INFO

# Size threshold for rotation of the debug log. If set to zero then no rotation will occur. Accepts a binary suffix "k",
# "m" or "g".
#dbms.logs.debug.rotation.size=20m

# Maximum number of history files for the internal log.
#dbms.logs.debug.rotation.keep_number=7

#*****************************************************************
# Miscellaneous configuration
#*****************************************************************

# Enable this to specify a parser other than the default one.
#cypher.default_language_version=3.5

# Determines if Cypher will allow using file URLs when loading data using
# `LOAD CSV`. Setting this value to `false` will cause Neo4j to fail `LOAD CSV`
# clauses that load data from the file system.
#dbms.security.allow_csv_import_from_file_urls=true


# Value of the Access-Control-Allow-Origin header sent over any HTTP or HTTPS
# connector. This defaults to '*', which allows broadest compatibility. Note
# that any URI provided here limits HTTP/HTTPS access to that URI only.
#dbms.security.http_access_control_allow_origin=*

# Value of the HTTP Strict-Transport-Security (HSTS) response header. This header
# tells browsers that a webpage should only be accessed using HTTPS instead of HTTP.
# It is attached to every HTTPS response. Setting is not set by default so
# 'Strict-Transport-Security' header is not sent. Value is expected to contain
# directives like 'max-age', 'includeSubDomains' and 'preload'.
#dbms.security.http_strict_transport_security=

# Retention policy for transaction logs needed to perform recovery and backups.
dbms.tx_log.rotation.retention_policy=1 days

# Only allow read operations from this Neo4j instance. This mode still requires
# write access to the directory for lock purposes.
#dbms.read_only=false

# Comma separated list of JAX-RS packages containing JAX-RS resources, one
# package name for each mountpoint. The listed package names will be loaded
# under the mountpoints specified. Uncomment this line to mount the
# org.neo4j.examples.server.unmanaged.HelloWorldResource.java from
# neo4j-server-examples under /examples/unmanaged, resulting in a final URL of
# http://localhost:7474/examples/unmanaged/helloworld/{nodeId}
#dbms.unmanaged_extension_classes=org.neo4j.examples.server.unmanaged=/examples/unmanaged

# A comma separated list of procedures and user defined functions that are allowed
# full access to the database through unsupported/insecure internal APIs.
dbms.security.procedures.unrestricted=apoc.**

# A comma separated list of procedures to be loaded by default.
# Leaving this unconfigured will load all procedures found.
dbms.security.procedures.whitelist=apoc.*,apoc.coll.*,apoc.load.*

#********************************************************************
# JVM Parameters
#********************************************************************

# G1GC generally strikes a good balance between throughput and tail
# latency, without too much tuning.
dbms.jvm.additional=-XX:+UseG1GC

# Have common exceptions keep producing stack traces, so they can be
# debugged regardless of how often logs are rotated.
dbms.jvm.additional=-XX:-OmitStackTraceInFastThrow

# Make sure that `initmemory` is not only allocated, but committed to
# the process, before starting the database. This reduces memory
# fragmentation, increasing the effectiveness of transparent huge
# pages. It also reduces the possibility of seeing performance drop
# due to heap-growing GC events, where a decrease in available page
# cache leads to an increase in mean IO response time.
# Try reducing the heap memory, if this flag degrades performance.
dbms.jvm.additional=-XX:+AlwaysPreTouch

# Trust that non-static final fields are really final.
# This allows more optimizations and improves overall performance.
# NOTE: Disable this if you use embedded mode, or have extensions or dependencies that may use reflection or
# serialization to change the value of final fields!
dbms.jvm.additional=-XX:+UnlockExperimentalVMOptions
dbms.jvm.additional=-XX:+TrustFinalNonStaticFields

# Disable explicit garbage collection, which is occasionally invoked by the JDK itself.
dbms.jvm.additional=-XX:+DisableExplicitGC

# Restrict size of cached JDK buffers to 256 KB
dbms.jvm.additional=-Djdk.nio.maxCachedBufferSize=262144

# More efficient buffer allocation in Netty by allowing direct no cleaner buffers.
dbms.jvm.additional=-Dio.netty.tryReflectionSetAccessible=true

# Exits JVM on the first occurrence of an out-of-memory error. Its preferrable to restart VM in case of out of memory errors.
# dbms.jvm.additional=-XX:+ExitOnOutOfMemoryError

# Remote JMX monitoring, uncomment and adjust the following lines as needed. Absolute paths to jmx.access and
# jmx.password files are required.
# Also make sure to update the jmx.access and jmx.password files with appropriate permission roles and passwords,
# the shipped configuration contains only a read only role called 'monitor' with password 'Neo4j'.
# For more details, see: http://download.oracle.com/javase/8/docs/technotes/guides/management/agent.html
# On Unix based systems the jmx.password file needs to be owned by the user that will run the server,
# and have permissions set to 0600.
# For details on setting these file permissions on Windows see:
#     http://docs.oracle.com/javase/8/docs/technotes/guides/management/security-windows.html
#dbms.jvm.additional=-Dcom.sun.management.jmxremote.port=3637
#dbms.jvm.additional=-Dcom.sun.management.jmxremote.authenticate=true
#dbms.jvm.additional=-Dcom.sun.management.jmxremote.ssl=false
#dbms.jvm.additional=-Dcom.sun.management.jmxremote.password.file=/absolute/path/to/conf/jmx.password
#dbms.jvm.additional=-Dcom.sun.management.jmxremote.access.file=/absolute/path/to/conf/jmx.access

# Some systems cannot discover host name automatically, and need this line configured:
#dbms.jvm.additional=-Djava.rmi.server.hostname=$THE_NEO4J_SERVER_HOSTNAME

# Expand Diffie Hellman (DH) key size from default 1024 to 2048 for DH-RSA cipher suites used in server TLS handshakes.
# This is to protect the server from any potential passive eavesdropping.
dbms.jvm.additional=-Djdk.tls.ephemeralDHKeySize=2048

# This mitigates a DDoS vector.
dbms.jvm.additional=-Djdk.tls.rejectClientInitiatedRenegotiation=true

# Enable remote debugging
#dbms.jvm.additional=-agentlib:jdwp=transport=dt_socket,server=y,suspend=n,address=*:5005

# This filter prevents deserialization of arbitrary objects via java object serialization, addressing potential vulnerabilities.
# By default this filter whitelists all neo4j classes, as well as classes from the hazelcast library and the java standard library.
# These defaults should only be modified by expert users!
# For more details (including filter syntax) see: https://openjdk.java.net/jeps/290
#dbms.jvm.additional=-Djdk.serialFilter=java.**;org.neo4j.**;com.neo4j.**;com.hazelcast.**;net.sf.ehcache.Element;com.sun.proxy.*;org.openjdk.jmh.**;!*

#********************************************************************
# Wrapper Windows NT/2000/XP Service Properties
#********************************************************************
# WARNING - Do not modify any of these properties when an application
#  using this configuration file has been installed as a service.
#  Please uninstall the service before modifying this section.  The
#  service can then be reinstalled.

# Name of the service
dbms.windows_service_name=neo4j

#********************************************************************
# Other Neo4j system properties
#********************************************************************
#
dbms.query_cache_size=10000
apoc.import.file.enabled=true
apoc.export.file.enabled=true

Can you uncomment these rows, restart the database and retry?

dbms.memory.heap.initial_size=512m
dbms.memory.heap.max_size=512m

It doesn't work.

alwas 'db hits' ...

How many RAM is available (this is the most important)?

after restart I ran some query and now is below.
2X_6_65fd08f2842695f046dc09a81c77e3f9b3a2007a.png

dbms.memory.heap.initial_size=512m
dbms.memory.heap.max_size=3g
dbms.memory.pagecache.size=3g
dbms.query_cache_size=10000

:sysinfo still doesn't work?

Is it also supported by community version?

It should normally

Do you get this when you start your database in Neo4j Desktop?

If you click on Monitor of System information, you should see the same thing as :sysinfo.

How did you restart the database?

When i connect to my local environment, it works.
And It contains Movie Database.

But I'm using Neo4j Browser connection with my test server.
My test server has the following data.

2X_6_6e43303c0ad1d1bacc9dc46497fed7d54b6138f7.png

Is there a possibility that there is an issue with my data?

I don't think it's coming from your data but more from the configuration of the server

That's why I would like to know how you restart the remote server , is it a service?

No it's not a service.
I just restart the neo4j with 'neo4j restart' command!

Oh indeed, I just try on my remote server (Neo4j pro) and I get the same thing :sysinfo: is not working

Can you check Page Cache Information When you run the query with PROFILE?

I can see the plan but after I'm not an admin system, I only know the basics

When I have an issue, I just find the answer here