Configuration

This page describes methods for configuring QuestDB server settings. Configuration can be set either:

  • In the server.conf configuration file available in the root directory
  • Using environment variables

When a key is absent from both the configuration file and the environment variables, the default value is used. Configuration of logging is handled separately and details of configuring this behavior can be found at the logging section below.

Environment variables#

All settings in the configuration file can be set or overridden using environment variables. If a key is set in both the server.conf file and via an environment variable, the environment variable will take precedence and the value in the server configuration file will be ignored.

To make these configuration settings available to QuestDB via environment variables, they must be in the following format:

QDB_<KEY_OF_THE_PROPERTY>

Where <KEY_OF_THE_PROPERTY> is equal to the configuration key name. To properly format a server.conf key as an environment variable it must have:

  1. QDB_ prefix
  2. uppercase characters
  3. all . period characters replaced with _ underscore

For example, the server configuration key for shared workers must be passed as described below:

server.conf keyenv var
shared.worker.countQDB_SHARED_WORKER_COUNT
note

QuestDB applies these configuration changes on startup and a running instance must be restarted in order for configuration changes to take effect

Examples#

The following configuration property customizes the number of worker threads shared across the application:

conf/server.conf
shared.worker.count=5
Customizing the worker count via environment variable
export QDB_SHARED_WORKER_COUNT=5

Docker#

This section describes how to configure QuestDB server settings when running QuestDB in a Docker container. A command to run QuestDB via Docker with default interfaces is as follows:

Example of running docker container with built-in storage
docker run -p 9000:9000 \
-p 9009:9009 \
-p 8812:8812 \
-p 9003:9003 \
questdb/questdb

This publishes the following ports:

The examples in this section change the default HTTP and REST API port from 9000 to 4000 for illustrative purposes, and demonstrate how to publish this port with a non-default property.

Environment variables#

Server configuration can be passed to QuestDB running in Docker by using the -e flag to pass an environment variable to a container:

docker run -p 4000:4000 -e QDB_HTTP_BIND_TO=0.0.0.0:4000 questdb/questdb

Mounting a volume#

A server configuration file can be provided by mounting a local directory in a QuestDB container. Given the following configuration file which overrides the default HTTP bind property:

./server.conf
http.bind.to=0.0.0.0:4000

Running the container with the -v flag allows for mounting the current directory to QuestDB's conf directory in the container. With the server configuration above, HTTP ports for the web console and REST API will be available on localhost:4000:

docker run -v "$(pwd):/var/lib/questdb/conf" -p 4000:4000 questdb/questdb

To mount the full root directory of QuestDB when running in a Docker container, provide a the configuration in a conf directory:

./conf/server.conf
http.bind.to=0.0.0.0:4000

Mount the current directory using the -v flag:

docker run -v "$(pwd):/var/lib/questdb/" -p 4000:4000 questdb/questdb

The current directory will then have data persisted to disk:

Current directory contents
โ”œโ”€โ”€ conf
โ”‚ โ””โ”€โ”€ server.conf
โ”œโ”€โ”€ db
โ””โ”€โ”€ public

Keys and default values#

This section lists the configuration keys available to QuestDB by topic or subsystem. Parameters for specifying buffer and memory page sizes are provided in the format n<unit>, where <unit> can be one of the following:

  • m for MB
  • k for kB

For example:

Setting maximum send buffer size to 2MB per TCP socket
http.net.connection.sndbuf=2m

Shared worker#

Shared worker threads service SQL execution subsystems and (in the default configuration) every other subsystem.

PropertyDefaultDescription
shared.worker.countNumber of worker threads shared across the application. Increasing this number will increase parallelism in the application at the expense of CPU resources.
shared.worker.affinityComma-delimited list of CPU ids, one per thread specified in shared.worker.count. By default, threads have no CPU affinity.
shared.worker.haltOnErrorfalseToggle whether worker should stop on error.

Minimal HTTP server#

This server runs embedded in a QuestDB instance by default and enables health checks of an instance via HTTP. It responds to all requests with a HTTP status code of 200 unless the QuestDB process dies.

info

Port 9003 also provides a /metrics endpoint with Prometheus metrics exposed. Examples of how to use the min server and Prometheus endpoint can be found on the health monitoring page.

PropertyDefaultDescription
http.min.enabledtrueEnable or disable Minimal HTTP server.
http.min.bind.to0.0.0.0:9003IPv4 address and port of the server. 0 means it will bind to all network interfaces, otherwise the IP address must be one of the existing network adapters.
http.min.net.connection.limit4Active connection limit.
http.min.net.connection.timeout300000Idle connection timeout is milliseconds.
http.min.net.connection.hintfalseWindows specific flag to overcome OS limitations on TCP backlog size.
http.min.worker.countBy default, minimal HTTP server uses shared thread pool for CPU core count 16 and below. It will use dedicated thread for core count above 16. When 0, the server will use the shared pool. Do not set pool size to more than 1.
http.min.worker.affinityCore number to pin thread to.

HTTP server#

This section describes configuration settings for the Web Console available by default on port 9000. For details on the use of this component, refer to the web console documentation page.

PropertyDefaultDescription
http.enabledtrueEnable or disable HTTP server.
http.bind.to0.0.0.0:9000IP address and port of HTTP server. A value of 0 means that the HTTP server will bind to all network interfaces. You can specify IP address of any individual network interface on your system.
http.net.connection.limit64The maximum number permitted for simultaneous TCP connection to the HTTP server. The rationale of the value is to control server memory consumption.
http.net.connection.timeout300000TCP connection idle timeout in milliseconds. Connection is closed by HTTP server when this timeout lapses.
http.net.connection.sndbuf2mMaximum send buffer size on each TCP socket. If this value is -1, the socket send buffer size remains unchanged from the OS defaults.
http.net.connection.rcvbuf2mMaximum receive buffer size on each TCP socket. If this value is -1, the socket receive buffer size remains unchanged from the OS defaults.
http.net.connection.hintfalseWindows specific flag to overcome OS limitations on TCP backlog size
http.connection.pool.initial.capacity4Initial size of pool of reusable objects that hold connection state. The pool should be configured to maximum realistic load so that it does not resize at runtime.
http.connection.string.pool.capacity128Initial size of the string pool shared by the HTTP header and multipart content parsers.
http.multipart.header.buffer.size512Buffer size in bytes used by the HTTP multipart content parser.
http.multipart.idle.spin.count10000How long the code accumulates incoming data chunks for column and delimiter analysis.
http.receive.buffer.size1mSize of receive buffer.
http.request.header.buffer.size64kSize of internal buffer allocated for HTTP request headers. The value is rounded up to the nearest power of 2. When HTTP requests contain headers that exceed the buffer size server will disconnect the client with HTTP error in server log.
http.response.header.buffer.size32kSize of the internal response buffer. The value will be rounded up to the nearest power of 2. The buffer size should be large enough to accommodate max size of server response headers.
http.worker.count0Number of threads in private worker pool. When 0, HTTP server will be using shared worker pool of the server. Values above 0 switch on private pool.
http.worker.affinityComma separated list of CPU core indexes. The number of items in this list must be equal to the worker count.
http.worker.haltOnErrorfalseChanging the default value is strongly discouraged. Flag that indicates if worker thread must shutdown on unhandled error.
http.send.buffer.size2mSize of the internal send buffer. Larger buffer sizes result in fewer I/O interruptions the server is making at the expense of memory usage per connection. There is a limit of send buffer size after which increasing it stops being useful in terms of performance. 2MB seems to be optimal value.
http.static.index.file.nameindex.htmlName of index file for the Web Console.
http.frozen.clockfalseSets the clock to always return zero. This configuration parameter is used for internal testing.
http.allow.deflate.before.sendfalseFlag that indicates if Gzip compression of outgoing data is allowed.
http.keep-alive.timeout5Used together with http.keep-alive.max to set the value of HTTP Keep-Alive response header. This instructs browser to keep TCP connection open. Has to be 0 when http.version is set to HTTP/1.0.
http.keep-alive.max10000See http.keep-alive.timeout. Has to be 0 when http.version is set to HTTP/1.0.
http.static.public.directorypublicThe name of directory for public web site.
http.text.date.adapter.pool.capacity16Size of date adapter pool. This should be set to the anticipated maximum number of DATE fields a text input can have. The pool is assigned to connection state and is reused alongside of connection state object.
http.text.json.cache.limit16384JSON parser cache limit. Cache is used to compose JSON elements that have been broken up by TCP protocol. This value limits the maximum length of individual tag or tag value.
http.text.json.cache.size8192Initial size of JSON parser cache. The value must not exceed http.text.json.cache.limit and should be set to avoid cache resizes at runtime.
http.text.max.required.delimiter.stddev0.1222dThe maximum standard deviation value for the algorithm that calculates text file delimiter. Usually when text parser cannot recognise the delimiter it will log the calculated and maximum standard deviation for the delimiter candidate.
http.text.max.required.line.length.stddev0.8Maximum standard deviation value for the algorithm that classifies input as text or binary. For the values above configured stddev input will be considered binary.
http.text.metadata.string.pool.capacity128The initial size of pool for objects that wrap individual elements of metadata JSON, such as column names, date pattern strings and locale values.
http.text.roll.buffer.limit4mThe limit of text roll buffer. See http.text.roll.buffer.size for description.
http.text.roll.buffer.size1024Roll buffer is a structure in the text parser that holds a copy of a line that has been broken up by TCP. The size should be set to the maximum length of text line in text input.
http.text.analysis.max.lines1000Number of lines to read on CSV import for heuristics which determine column names & types. Lower line numbers may detect CSV schemas quicker, but possibly with less accuracy. 1000 lines is the maximum for this value.
http.text.lexer.string.pool.capacity64The initial capacity of string fool, which wraps STRING column types in text input. The value should correspond to the maximum anticipated number of STRING columns in text input.
http.text.timestamp.adapter.pool.capacity64Size of timestamp adapter pool. This should be set to the anticipated maximum number of TIMESTAMP fields a text input can have. The pool is assigned to connection state and is reused alongside of connection state object.
http.text.utf8.sink.size4096Initial size of UTF-8 adapter sink. The value should correspond the maximum individual field value length in text input.
http.json.query.connection.check.frequency1000000Changing the default value is strongly discouraged. The value to throttle check if client socket has been disconnected.
http.json.query.float.scale4The scale value of string representation of FLOAT values.
http.json.query.double.scale12The scale value of string representation of DOUBLE values.
http.query.cache.enabledtrueEnable or disable the query cache. Cache capacity is number_of_blocks * number_of_rows.
http.query.cache.block.count4Number of blocks for the query cache.
http.query.cache.row.count16Number of rows for the query cache.
http.security.readonlyfalseForces HTTP read only mode when true, disabling commands which modify the data or data structure, e.g. INSERT, UPDATE, or CREATE TABLE.
http.security.max.response.rows2^63-1Limit the number of response rows over HTTP.
http.security.interrupt.on.closed.connectiontrueSwitch to enable termination of SQL processing if the HTTP connection is closed. The mechanism affects performance so the connection is only checked after circuit.breaker.throttle calls are made to the check method. The mechanism also reads from the input stream and discards it since some HTTP clients send this as a keep alive in between requests, circuit.breaker.buffer.size denotes the size of the buffer for this.
circuit.breaker.throttle2000000Number of internal iterations such as loops over data before checking if the HTTP connection is still open
circuit.breaker.buffer.size32Size of buffer to read from HTTP connection. If this buffer returns zero and the HTTP client is no longer sending data, SQL processing will be terminated.
http.server.keep.alivetrueIf set to false, the server will disconnect the client after completion of each request.
http.versionHTTP/1.1Protocol version, other supported value is HTTP/1.0.

Cairo engine#

This section describes configuration settings for the Cairo SQL engine in QuestDB.

PropertyDefaultDescription
query.timeout.sec60A global timeout (in seconds) for long-running queries.
cairo.max.uncommitted.rows500000Maximum number of uncommitted rows per table, when the number of pending rows reaches this parameter on a table, a commit will be issued.
cairo.commit.lag300000Expected maximum time lag for out-of-order rows in milliseconds.
cairo.sql.backup.rootnullOutput root directory for backups.
cairo.sql.backup.dir.datetime.formatnullDate format for backup directory.
cairo.sql.backup.dir.tmp.nametmpName of tmp directory used during backup.
cairo.sql.backup.mkdir.mode509Permission used when creating backup directories.
cairo.snapshot.instance.idempty stringInstance id to be included into disk snapshots.
cairo.snapshot.recovery.enabledtrueWhen false, disables snapshot recovery on database start.
cairo.rootdbDirectory for storing db tables and metadata. This directory is inside the server root directory provided at startup.
cairo.commit.modenosyncHow changes to table are flushed to disk upon commit. Choices: nosync, async (flush call schedules update, returns immediately), sync (waits for flush on the appended column files to complete).
cairo.create.as.select.retry.count5Number of types table creation or insertion will be attempted.
cairo.default.map.typefastType of map used. Options: fast (speed at the expense of storage), compact.
cairo.default.symbol.cache.flagtrueWhen true, symbol values will be cached on Java heap instead of being looked up in the database files.
cairo.default.symbol.capacity256Specifies approximate capacity for SYMBOL columns. It should be equal to number of unique symbol values stored in the table and getting this value badly wrong will cause performance degradation. Must be power of 2.
cairo.file.operation.retry.count30Number of attempts to open files.
cairo.idle.check.interval300000Frequency of writer maintenance job in milliseconds.
cairo.inactive.reader.ttl-120000Frequency of reader pool checks for inactive readers in milliseconds.
cairo.inactive.writer.ttl-600000Frequency of writer pool checks for inactive writers in milliseconds.
cairo.index.value.block.size256Approximation of number of rows for a single index key, must be power of 2.
cairo.max.swap.file.count30Number of attempts to open swap files.
cairo.mkdir.mode509File permission mode for new directories.
cairo.parallel.index.threshold100000Minimum number of rows before allowing use of parallel indexation.
cairo.reader.pool.max.segments5Number of attempts to get TableReader.
cairo.spin.lock.timeout1000Timeout when attempting to get BitmapIndexReaders in millisecond.
cairo.character.store.capacity1024Size of the CharacterStore.
cairo.character.store.sequence.pool.capacity64Size of the CharacterSequence pool.
cairo.column.pool.capacity4096Size of the Column pool in the SqlCompiler.
cairo.compact.map.load.factor0.7Load factor for CompactMaps.
cairo.expression.pool.capacity8192Size of the ExpressionNode pool in SqlCompiler.
cairo.fast.map.load.factor0.5Load factor for all FastMaps.
cairo.sql.join.context.pool.capacity64Size of the JoinContext pool in SqlCompiler.
cairo.lexer.pool.capacity2048Size of FloatingSequence pool in GenericLexer.
cairo.sql.map.key.capacity2mKey capacity in FastMap and CompactMap.
cairo.sql.map.max.resizes2^31Number of map resizes in FastMap and CompactMap before a resource limit exception is thrown, each resize doubles the previous size.
cairo.sql.map.page.size4mMemory page size for FastMap and CompactMap.
cairo.sql.map.max.pages2^31Memory max pages for CompactMap.
cairo.model.pool.capacity1024Size of the QueryModel pool in the SqlCompiler.
cairo.sql.sort.key.page.size4mMemory page size for storing keys in LongTreeChain.
cairo.sql.sort.key.max.pages2^31Max number of pages for storing keys in LongTreeChain before a resource limit exception is thrown.
cairo.sql.sort.light.value.page.size1048576Memory page size for storing values in LongTreeChain.
cairo.sql.sort.light.value.max.pages2^31Max pages for storing values in LongTreeChain.
cairo.sql.hash.join.value.page.size16777216Memory page size of the slave chain in full hash joins.
cairo.sql.hash.join.value.max.pages2^31Max pages of the slave chain in full hash joins.
cairo.sql.latest.by.row.count1000Number of rows for LATEST BY.
cairo.sql.hash.join.light.value.page.size1048576Memory page size of the slave chain in light hash joins.
cairo.sql.hash.join.light.value.max.pages2^31Max pages of the slave chain in light hash joins.
cairo.sql.sort.value.page.size16777216Memory page size of file storing values in SortedRecordCursorFactory.
cairo.sql.sort.value.max.pages2^31Max pages of file storing values in SortedRecordCursorFactory.
cairo.work.steal.timeout.nanos10000Latch await timeout in nanos for stealing indexing work from other threads.
cairo.parallel.indexing.enabledtrueAllows parallel indexation. Works in conjunction with cairo.parallel.index.threshold.
cairo.sql.join.metadata.page.size16384Memory page size for JoinMetadata file.
cairo.sql.join.metadata.max.resizes2^31Number of map resizes in JoinMetadata before a resource limit exception is thrown, each resize doubles the previous size.
cairo.sql.analytic.column.pool.capacity64Size of AnalyticColumn pool in SqlParser.
cairo.sql.create.table.model.pool.capacity16Size of CreateTableModel pool in SqlParser.
cairo.sql.column.cast.model.pool.capacity16Size of CreateTableModel pool in SqlParser.
cairo.sql.rename.table.model.pool.capacity16Size of RenameTableModel pool in SqlParser.
cairo.sql.with.clause.model.pool.capacity128Size of WithClauseModel pool in SqlParser.
cairo.sql.insert.model.pool.capacity64Size of InsertModel pool in SqlParser.
cairo.sql.copy.model.pool.capacity32Size of CopyModel pool in SqlParser.
cairo.sql.copy.buffer.size2mSize of buffer used when copying tables.
cairo.sql.double.cast.scale12Maximum number of decimal places that types cast as doubles have.
cairo.sql.float.cast.scale4Maximum number of decimal places that types cast as floats have.
cairo.sql.copy.formats.file/text_loader.jsonName of file with user's set of date and timestamp formats.
cairo.sql.jit.modeonJIT compilation for SQL queries. May be disabled by setting this value to off.
cairo.date.localeenThe locale to handle date types.
cairo.timestamp.localeenThe locale to handle timestamp types.
cairo.o3.column.memory.size16MMemory page size per column for O3 operations. Please be aware O3 will use 2x of this RAM per column.
cairo.writer.data.append.page.size16Mmmap sliding page size that table writer uses to append data for each column.
cairo.writer.data.index.key.append.page.size512kmmap page size for appending index key data.
cairo.writer.data.index.value.append.page.size16Mmmap page size for appending value data.
cairo.writer.misc.append.page.size4kmmap page size for mapping small files, default value is OS page size (4k Linux, 64K windows, 16k OSX M1). Overriding this rounds to the nearest (greater) multiple of the OS page size.
cairo.writer.data.index.key.append.page.size512kmmap page size for appending index key data; key data is number of distinct symbol values times 4 bytes.
cairo.sql.column.purge.queue.capacity128Purge column version job queue. Increase the size if column version not automatically cleanup after execution of UPDATE SQL statement. Reduce to decrease initial memory footprint.
cairo.sql.column.purge.task.pool.capacity256Column version task object pool capacity. Increase to reduce GC, reduce to decrease memory footprint.
cairo.sql.column.purge.retry.delay10000Initial delay (ฮผs) before re-trying purge of stale column files.
cairo.sql.column.purge.retry.delay.multiplier10.0Multiplier used to increases retry delay with each iteration.
cairo.sql.column.purge.retry.delay.limit60000000Delay limit (ฮผs), upon reaching which, the re-try delay remains constant.
cairo.sql.column.purge.retry.limit.days31Number of days purge system will continue to re-try deleting stale column files before giving up.
cairo.system.table.prefixsys.Prefix of the tables used for QuestDB internal data storage. These tables are hidden from QuestDB web console.

CSV import#

This section describes configuration settings for using COPY to import large CSV files.

Mandatory settings to enable COPY:

PropertyDefaultDescription
cairo.sql.copy.rootnullInput root directory for CSV imports via COPY SQL. This path should not overlap with other directory (e.g. db, conf) of running instance, otherwise import may delete or overwrite existing files.
cairo.sql.copy.work.rootnullTemporary import file directory. Same as cairo.sql.copy.root if not set explicitly.

Optional settings for COPY:

PropertyDefaultDescription
cairo.iouring.enabledtrueEnable or disable io_uring implementation. Applicable to newer Linux kernels only. Can be used to switch io_uring interface usage off if there's a kernel bug affecting it.
cairo.sql.copy.buffer.size2 MiBSize of read buffers used in import.
cairo.sql.copy.log.retention.days3Number of days to keep import messages in sys.text_import_log.
cairo.sql.copy.max.index.chunk.size100mMaximum size of index chunk file used to limit total memory requirements of import. Indexing phase should use roughly thread_count * cairo.sql.copy.max.index.chunk.size of memory.
cairo.sql.copy.queue.capacity32Size of copy task queue. Should be increased if there's more than 32 import workers.

CSV import configuration for Docker#

For QuestDB instances using Docker:

  • cairo.sql.copy.root must be defined using one of the following settings:
    • The environment variable QDB_CAIRO_SQL_COPY_ROOT.
    • The cairo.sql.copy.root in server.conf.
  • The path for the source CSV file is mounted.
  • The source CSV file path and the path defined by QDB_CAIRO_SQL_COPY_ROOT are identical.
  • It is optional to define QDB_CAIRO_SQL_COPY_WORK_ROOT.

The following is an example command to start a QuestDB instance on Docker, in order to import a CSV file:

docker run -p 9000:9000 \
-v "/tmp/questdb:/var/lib/questdb" \
-v "/tmp/questdb/my_input_root:/var/lib/questdb/questdb_import" \
-e QDB_CAIRO_SQL_COPY_ROOT=/var/lib/questdb/questdb_import \
questdb/questdb

Where:

  • -v "/tmp/questdb/my_input_root:/var/lib/questdb/questdb_import": Defining a source CSV file location to be /tmp/questdb/my_input_root on local machine and mounting it to /var/lib/questdb/questdb_import in the container.
  • -e QDB_CAIRO_SQL_COPY_ROOT=/var/lib/questdb/questdb_import: Defining the copy root directory to be /var/lib/questdb/questdb_import.

It is important that the two path are identical (/var/lib/questdb/questdb_import in the example).

Parallel SQL execution#

This section describes settings that can affect parallelism level of SQL execution and therefore performance.

PropertyDefaultDescription
cairo.sql.parallel.filter.enabledtrueEnable or disable parallel SQL filter execution. JIT compilation takes place only when this setting is enabled.
cairo.sql.parallel.filter.pretouch.enabledtrueEnable column pre-touch as part of the parallel SQL filter execution, to improve query performance for large tables.
cairo.page.frame.shard.count4Number of shards for both dispatch and reduce queues. Shards reduce queue contention between SQL statements that are executed concurrently.
cairo.page.frame.reduce.queue.capacity64Reduce queue is used for data processing and should be large enough to supply tasks for worker threads (shared worked pool).
cairo.page.frame.rowid.list.capacity256Row ID list initial capacity for each slot of the reduce queue. Larger values reduce memory allocation rate, but increase minimal RSS size.
cairo.page.frame.column.list.capacity16Column list capacity for each slot of the reduce queue. Used by JIT-compiled filter functions. Larger values reduce memory allocation rate, but increase minimal RSS size.
cairo.page.frame.task.pool.capacity4Initial object pool capacity for local reduce tasks. These tasks are used to avoid blocking query execution when the reduce queue is full.

Postgres wire protocol#

This section describes configuration settings for client connections using PostgresSQL wire protocol.

PropertyDefaultDescription
pg.enabledtrueConfiguration for enabling or disabling the Postres interface.
pg.net.bind.to0.0.0.0:8812IP address and port of Postgres wire protocol server. 0 means that the server will bind to all network interfaces. You can specify IP address of any individual network interface on your system.
pg.net.connection.limit64The maximum number permitted for simultaneous Postgres connections to the server. This value is intended to control server memory consumption.
pg.net.connection.timeout300000Connection idle timeout in milliseconds. Connections are closed by the server when this timeout lapses.
pg.net.connection.rcvbuf-1Maximum send buffer size on each TCP socket. If value is -1 socket send buffer remains unchanged from OS default.
pg.net.connection.sndbuf-1Maximum receive buffer size on each TCP socket. If value is -1, the socket receive buffer remains unchanged from OS default.
pg.net.connection.hintfalseWindows specific flag to overcome OS limitations on TCP backlog size
pg.security.readonlyfalseForces PGWire read only mode when true, disabling commands which modify the data or data structure, e.g. INSERT, UPDATE, or CREATE TABLE.
pg.character.store.capacity4096Size of the CharacterStore.
pg.character.store.pool.capacity64Size of the CharacterStore pool capacity .
pg.connection.pool.capacity64The maximum amount of pooled connections this interface may have.
pg.passwordquestPostgres database password.
pg.useradminPostgres database username.
pg.select.cache.enabledtrueEnable or disable the SELECT query cache. Cache capacity is number_of_blocks * number_of_rows.
pg.select.cache.block.count16Number of blocks to cache SELECT query execution plan against text to speed up execution.
pg.select.cache.row.count16Number of rows to cache for SELECT query execution plan against text to speed up execution.
pg.insert.cache.enabledtrueEnable or disable the INSERT query cache. Cache capacity is number_of_blocks * number_of_rows.
pg.insert.cache.block.count8Number of blocks to cache INSERT query execution plan against text to speed up execution.
pg.insert.cache.row.count8Number of rows to cache for INSERT query execution plan against text to speed up execution.
pg.update.cache.enabledtrueEnable or disable the UPDATE query cache. Cache capacity is number_of_blocks * number_of_rows.
pg.update.cache.block.count8Number of blocks to cache UPDATE query execution plan against text to speed up execution.
pg.update.cache.row.count8Number of rows to cache for UPDATE query execution plan against text to speed up execution.
pg.max.blob.size.on.query512kFor binary values, clients will receive an error when requesting blob sizes above this value.
pg.recv.buffer.size1mSize of the buffer for receiving data.
pg.send.buffer.size1mSize of the buffer for sending data.
pg.date.localeenThe locale to handle date types.
pg.timestamp.localeenThe locale to handle timestamp types.
pg.worker.count0Number of dedicated worker threads assigned to handle PGWire queries. When 0, the jobs will use the shared pool.
pg.worker.affinityComma-separated list of thread numbers which should be pinned for Postgres ingestion. Example pg.worker.affinity=1,2,3.
pg.halt.on.errorfalseWhether ingestion should stop upon internal error.

InfluxDB line protocol#

This section describes ingestion settings for incoming messages using InfluxDB line protocol.

PropertyDefaultDescription
line.default.partition.byDAYThe default partitioning strategy applied to new tables dynamically created by sending records via ILP.

TCP specific settings#

PropertyDefaultDescription
line.tcp.enabledtrueEnable or disable line protocol over TCP.
line.tcp.net.bind.to0.0.0.0:9009IP address of the network interface to bind listener to and port. By default, TCP receiver listens on all network interfaces.
line.tcp.net.connection.limit256The maximum number permitted for simultaneous connections to the server. This value is intended to control server memory consumption.
line.tcp.net.connection.timeout300000Connection idle timeout in milliseconds. Connections are closed by the server when this timeout lapses.
line.tcp.net.connection.hintfalseWindows specific flag to overcome OS limitations on TCP backlog size
line.tcp.net.connection.rcvbuf-1Maximum buffer receive size on each TCP socket. If value is -1, the socket receive buffer remains unchanged from OS default.
line.tcp.auth.db.pathPath which points to the authentication db file.
line.tcp.connection.pool.capacity64The maximum amount of pooled connections this interface may have.
line.tcp.timestampnInput timestamp resolution. Possible values are n, u, ms, s and h.
line.tcp.msg.buffer.size32768Size of the buffer read from queue. Maximum size of write request, regardless of the number of measurements.
line.tcp.maintenance.job.interval1000Maximum amount of time (in milliseconds) between maintenance jobs committing any uncommitted data on inactive tables.
line.tcp.min.idle.ms.before.writer.release500Minimum amount of idle time (in milliseconds) before a table writer is released.
line.tcp.commit.interval.fraction0.5Commit lag fraction. Used to calculate commit interval for the table according to the following formula: commit_interval = commit_lag โˆ— fraction. The calculated commit interval defines how long uncommitted data will need to remain uncommitted.
line.tcp.commit.interval.default2000Default commit interval in milliseconds. Used when no commit lag set for a table or the fraction is set to 0.
line.tcp.max.measurement.size32768Maximum size of any measurement.
line.tcp.writer.queue.size128Size of the queue between network I/O and writer jobs. Each queue entry represents a measurement.
line.tcp.writer.worker.countNumber of dedicated I/O worker threads assigned to write data to tables. When 0, the writer jobs will use the shared pool.
line.tcp.writer.worker.affinityComma-separated list of thread numbers which should be pinned for line protocol ingestion over TCP. CPU core indexes are 0-based.
line.tcp.io.worker.countNumber of dedicated I/O worker threads assigned to parse TCP input. When 0, the writer jobs will use the shared pool.
line.tcp.io.worker.affinityComma-separated list of thread numbers which should be pinned for line protocol ingestion over TCP. CPU core indexes are 0-based.
line.tcp.default.partition.byDAYTable partition strategy to be used with tables that are created automatically by ILP. Possible values are: HOUR, DAY, MONTH and YEAR
line.tcp.disconnect.on.errortrueDisconnect TCP socket that sends malformed messages.

UDP specific settings#

note

The UDP receiver is deprecated since QuestDB version 6.5.2. We recommend the TCP receiver instead.

PropertyDefaultDescription
line.udp.join232.1.2.3Multicast address receiver joins. This values is ignored when receiver is in "unicast" mode.
line.udp.bind.to0.0.0.0:9009IP address of the network interface to bind listener to and port. By default UDP receiver listens on all network interfaces.
line.udp.commit.rate1000000For packet bursts the number of continuously received messages after which receiver will force commit. Receiver will commit irrespective of this parameter when there are no messages.
line.udp.msg.buffer.size2048Buffer used to receive single message. This value should be roughly equal to your MTU size.
line.udp.msg.count10000Only for Linux. On Linux, QuestDB will use the recvmmsg() system call. This is the max number of messages to receive at once.
line.udp.receive.buffer.size8388608UDP socket buffer size. Larger size of the buffer will help reduce message loss during bursts.
line.udp.enabledtrueEnable or disable UDP receiver.
line.udp.own.threadfalseWhen true, UDP receiver will use its own thread and busy spin that for performance reasons. "false" makes receiver use worker threads that do everything else in QuestDB.
line.udp.own.thread.affinity-1-1 does not set thread affinity. OS will schedule thread and it will be liable to run on random cores and jump between the. 0 or higher pins thread to give core. This property is only valid when UDP receiver uses own thread.
line.udp.unicastfalseWhen true, UDP will use unicast. Otherwise multicast.
line.udp.timestampnInput timestamp resolution. Possible values are n, u, ms, s and h.
line.udp.commit.modenosyncCommit durability. Available values are nosync, sync and async.

Config Validation#

The database startup phase checks for configuration issues, such as invalid or deprecated settings. Issues may be classified as advisories or errors. Advisory issues are logged without causing the database to stop its startup sequence: These are usually setting deprecation warnings. Configuration errors can optionally cause the database to fail its startup.

PropertyDefaultDescription
config.validation.strictfalseWhen enabled, startup fails if there are configuration errors.

We recommended enabling strict validation.

Telemetry#

QuestDB sends anonymous telemetry data with information about usage which helps us improve the product over time. We do not collect any personally-identifying information, and we do not share any of this data with third parties.

PropertyDefaultDescription
telemetry.enabledtrueEnable or disable anonymous usage metrics collection.

Logging#

The logging behavior of QuestDB may be set in dedicated configuration files or by environment variables. This section describes how to configure logging using these methods.

Configuration file#

Logs may be configured via a dedicated configuration file log.conf.

log.conf
# list of configured writers
writers=file,stdout
# file writer
#w.file.class=io.questdb.log.LogFileWriter
#w.file.location=questdb-debug.log
#w.file.level=INFO,ERROR
# rolling file writer
#w.file.class=io.questdb.log.LogRollingFileWriter
#w.file.location=${log.dir}/questdb-rolling.log.${date:yyyyMMdd}
#w.file.level=INFO,ERROR
#rollEvery accepts: day, hour, minute, month
#w.file.rollEvery=day
#w.file.rollSize=1g
# stdout
w.stdout.class=io.questdb.log.LogConsoleWriter
w.stdout.level=INFO,ERROR

QuestDB will look for /log.conf first in conf/ directory and then on the classpath unless this name is overridden via a command line property: -Dout=/something_else.conf. QuestDB will create conf/log.conf using default values If -Dout is not set and file doesn't exist .

On Windows log messages go to depending on run mode :

  • interactive session - console and $dataDir\log\stdout-%Y-%m-%dT%H-%M-%S.txt (default is .\log\stdout-%Y-%m-%dT%H-%M-%S.txt )
  • service - $dataDir\log\service-%Y-%m-%dT%H-%M-%S.txt (default is C:\Windows\System32\qdbroot\log\service-%Y-%m-%dT%H-%M-%S.txt )

Environment variables#

Values in the log configuration file can be overridden with environment variables. All configuration keys must be formatted as described in the environment variables section above.

For example, to set logging on ERROR level only:

Setting log level to ERROR in log-stdout.conf
w.stdout.level=ERROR

This can be passed as an environment variable as follows:

Setting log level to ERROR via environment variable
export QDB_LOG_W_STDOUT_LEVEL=ERROR

Configuring Docker logging#

When mounting a volume to a Docker container, a logging configuration file may be provided in the container located at ./conf/log.conf. For example, a file with the following contents can be created:

./conf/log.conf
# list of configured writers
writers=file,stdout,http.min
# file writer
w.file.class=io.questdb.log.LogFileWriter
w.file.location=questdb-docker.log
w.file.level=INFO,ERROR,DEBUG
# stdout
w.stdout.class=io.questdb.log.LogConsoleWriter
w.stdout.level=INFO
# min http server, used monitoring
w.http.min.class=io.questdb.log.LogConsoleWriter
w.http.min.level=ERROR
w.http.min.scope=http-min-server

The current directory can be mounted:

Mount the current directory to a QuestDB container
docker run -p 9000:9000 -v "$(pwd):/var/lib/questdb/" questdb/questdb

The container logs will be written to disk using the logging level and file name provided in the ./conf/log.conf file, in this case in ./questdb-docker.log.

Prometheus Alertmanager#

QuestDB includes a log writer that sends any message logged at critical level (logger.critical("may-day")) to Prometheus Alertmanager over a TCP/IP socket. Details for configuring this can be found in the Prometheus documentation. To configure this writer, add it to the writers config alongside other log writers.

log.conf
# Which writers to enable
writers=stdout,alert
# stdout
w.stdout.class=io.questdb.log.LogConsoleWriter
w.stdout.level=INFO
# Prometheus Alerting
w.alert.class=io.questdb.log.LogAlertSocketWriter
w.alert.level=CRITICAL
w.alert.location=/alert-manager-tpt.json
w.alert.alertTargets=localhost:9093,localhost:9096,otherhost:9093
w.alert.defaultAlertHost=localhost
w.alert.defaultAlertPort=9093
# The `inBufferSize` and `outBufferSize` properties are the size in bytes for the
# socket write buffers.
w.alert.inBufferSize=2m
w.alert.outBufferSize=4m
# Delay in milliseconds between two consecutive attempts to alert when
# there is only one target configured
w.alert.reconnectDelay=250

Of all properties, only w.alert.class and w.alert.level are required, the rest assume default values as stated above (except for w.alert.alertTargets which is empty by default).

Alert targets are specified using w.alert.alertTargets as a comma-separated list of up to 12 host:port TCP/IP addresses. Specifying a port is optional and defaults to the value of defaultAlertHost. One of these alert managers is picked at random when QuestDB starts, and a connection is created.

All alerts will be sent to the chosen server unless it becomes unavailable. If it is unavailable, the next server is chosen. If there is only one server configured and a fail-over cannot occur, a delay of 250 milliseconds is added between send attempts.

The w.alert.location property refers to the path (absolute, otherwise relative to -d database-root) of a template file. By default, it is a resource file which contains:

/alert-manager-tpt.json
[
{
"Status": "firing",
"Labels": {
"alertname": "QuestDbInstanceLogs",
"service": "QuestDB",
"category": "application-logs",
"severity": "critical",
"version": "${QDB_VERSION}",
"cluster": "${CLUSTER_NAME}",
"orgid": "${ORGID}",
"namespace": "${NAMESPACE}",
"instance": "${INSTANCE_NAME}",
"alertTimestamp": "${date: yyyy/MM/ddTHH:mm:ss.SSS}"
},
"Annotations": {
"description": "ERROR/cl:${CLUSTER_NAME}/org:${ORGID}/ns:${NAMESPACE}/db:${INSTANCE_NAME}",
"message": "${ALERT_MESSAGE}"
}
}
]

Four environment variables can be defined, and referred to with the ${VAR_NAME} syntax:

  • ORGID
  • NAMESPACE
  • CLUSTER_NAME
  • INSTANCE_NAME

Their default value is GLOBAL, they mean nothing outside a cloud environment.

In addition, ALERT_MESSAGE is a placeholder for the actual critical message being sent, and QDB_VERSION is the runtime version of the QuestDB instance sending the alert. The ${date: <format>} syntax can be used to produce a timestamp at the time of sending the alert.

Debug#

QuestDB logging can be quickly forced globally to DEBUG via either providing the java option -Debug or setting the environment variable QDB_DEBUG=true.