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Problem: A long running table metadata operation (e.g. refresh) could prevent any other metadata operation from making progress if it coincided with the catalog topic creation operations. The problem was due to the conservative locking scheme used when catalog topics were created. In particular, in order to collect a consistent snapshot of metadata changes, the global catalog lock was held for the entire duration of that operation. Solution: To improve the concurrency of catalog operations the following changes are performed: * A range of catalog versions determines the catalog changes to be included in a catalog update. Any catalog changes that do not fall in the specified range are ignored (to be processed in subsequent catalog topic updates). * The catalog allows metadata operations to make progress while collecting catalog updates. * To prevent starvation of catalog updates (i.e. frequently updated catalog objects skipping catalog updates indefinitely), we keep track of the number of times a catalog object has skipped an update and if that number exceeds a threshold it is included in the next catalog topic update even if its version is not in the specified topic update version range. Hence, the same catalog object may be sent in two consecutive catalog topic updates. This commit also changes the way deletions are handled in the catalog and disseminated to the impalad nodes through the statestore. In particular: * Deletions in the catalog are explicitly recorded in a log with the catalog version in which they occurred. As before, added and deleted catalog objects are sent to the statestore. * Topic entries associated with deleted catalog objects have non-empty values (besided keys) that contain minimal object metadata including the catalog version. * Statestore is no longer using the existence or not of topic entry values in order to identify deleted topic entries. Deleted topic entries should be explicitly marked as such by the statestore subscribers that produce them. * Statestore subscribers now use the 'deleted' flag to determine if a topic entry corresponds to a deleted item. * Impalads use the deleted objects' catalog versions when updating the local catalog cache from a catalog update and not the update's maximum catalog version. Testing: - No new tests were added as these paths are already exercised by existing tests. - Run all core and exhaustive tests. Change-Id: If12467a83acaeca6a127491d89291dedba91a35a Reviewed-on: http://gerrit.cloudera.org:8080/7731 Reviewed-by: Dimitris Tsirogiannis <dtsirogiannis@cloudera.com> Tested-by: Impala Public Jenkins Reviewed-on: http://gerrit.cloudera.org:8080/8752
Welcome to Impala
Lightning-fast, distributed SQL queries for petabytes of data stored in Apache Hadoop clusters.
Impala is a modern, massively-distributed, massively-parallel, C++ query engine that lets you analyze, transform and combine data from a variety of data sources:
- Best of breed performance and scalability.
- Support for data stored in HDFS, Apache HBase and Amazon S3.
- Wide analytic SQL support, including window functions and subqueries.
- On-the-fly code generation using LLVM to generate CPU-efficient code tailored specifically to each individual query.
- Support for the most commonly-used Hadoop file formats, including the Apache Parquet project.
- Apache-licensed, 100% open source.
More about Impala
To learn more about Impala as a business user, or to try Impala live or in a VM, please visit the Impala homepage.
If you are interested in contributing to Impala as a developer, or learning more about Impala's internals and architecture, visit the Impala wiki.
Supported Platforms
Impala only supports Linux at the moment.
Export Control Notice
This distribution uses cryptographic software and may be subject to export controls. Please refer to EXPORT_CONTROL.md for more information.
Build Instructions
See bin/bootstrap_build.sh.
Detailed Build Notes
Impala can be built with pre-built components, downloaded from S3, or can be built with an in-place toolchain located in the thirdparty directory (not recommended). The components needed to build Impala are Apache Hadoop, Hive, HBase, and Sentry. If you need to manually override the locations or versions of these components, you can do so through the environment variables and scripts listed below.
Scripts and directories
| Location | Purpose |
|---|---|
| bin/impala-config.sh | This script must be sourced to setup all environment variables properly to allow other scripts to work |
| bin/impala-config-local.sh | A script can be created in this location to set local overrides for any environment variables |
| bin/impala-config-branch.sh | A version of the above that can be checked into a branch for convenience. |
| bin/bootstrap_build.sh | A helper script to bootstrap some of the build requirements. |
| bin/bootstrap_development.sh | A helper script to bootstrap a developer environment. Please read it before using. |
| be/build/ | Impala build output goes here. |
| be/generated-sources/ | Thrift and other generated source will be found here. |
Build Related Variables
| Environment variable | Default value | Description |
|---|---|---|
| IMPALA_HOME | Top level Impala directory | |
| IMPALA_TOOLCHAIN | "${IMPALA_HOME}/toolchain" | Native toolchain directory (for compilers, libraries, etc.) |
| SKIP_TOOLCHAIN_BOOTSTRAP | "false" | Skips downloading the toolchain any python dependencies if "true" |
| CDH_COMPONENTS_HOME | "${IMPALA_HOME}/toolchain/cdh_components" OR "${IMPALA_HOME}/thirdparty" (if detected) | If a thirdparty directory is present, components found here will override anything in IMPALA_TOOLCHAIN. |
| CDH_MAJOR_VERSION | "5" | Identifier used to uniqueify paths for potentially incompatible component builds. |
| IMPALA_CONFIG_SOURCED | "1" | Set by ${IMPALA_HOME}/bin/impala-config.sh (internal use) |
| JAVA_HOME | "/usr/lib/jvm/${JAVA_VERSION}" | Used to locate Java |
| JAVA_VERSION | "java-7-oracle-amd64" | Can override to set a local Java version. |
| JAVA | "${JAVA_HOME}/bin/java" | Java binary location. |
| CLASSPATH | See bin/set-classpath.sh for details. | |
| PYTHONPATH | Will be changed to include: "${IMPALA_HOME}/shell/gen-py" "${IMPALA_HOME}/testdata" "${THRIFT_HOME}/python/lib/python2.7/site-packages" "${HIVE_HOME}/lib/py" "${IMPALA_HOME}/shell/ext-py/prettytable-0.7.1/dist/prettytable-0.7.1" "${IMPALA_HOME}/shell/ext-py/sasl-0.1.1/dist/sasl-0.1.1-py2.7-linux-x "${IMPALA_HOME}/shell/ext-py/sqlparse-0.1.14/dist/sqlparse-0.1.14-py2 |
Source Directories for Impala
| Environment variable | Default value | Description |
|---|---|---|
| IMPALA_BE_DIR | "${IMPALA_HOME}/be" | Backend directory. Build output is also stored here. |
| IMPALA_FE_DIR | "${IMPALA_HOME}/fe" | Frontend directory |
| IMPALA_COMMON_DIR | "${IMPALA_HOME}/common" | Common code (thrift, function registry) |
Various Compilation Settings
| Environment variable | Default value | Description |
|---|---|---|
| IMPALA_BUILD_THREADS | "8" or set to number of processors by default. | Used for make -j and distcc -j settings. |
| IMPALA_MAKE_FLAGS | "" | Any extra settings to pass to make. Also used when copying udfs / udas into HDFS. |
| USE_SYSTEM_GCC | "0" | If set to any other value, directs cmake to not set GCC_ROOT, CMAKE_C_COMPILER, CMAKE_CXX_COMPILER, as well as setting TOOLCHAIN_LINK_FLAGS |
| IMPALA_CXX_COMPILER | "default" | Used by cmake (cmake_modules/toolchain and clang_toolchain.cmake) to select gcc / clang |
| USE_GOLD_LINKER | "true" | Directs backend cmake to use gold. |
| IS_OSX | "false" | (Experimental) currently only used to disable Kudu. |
Dependencies
| Environment variable | Default value | Description |
|---|---|---|
| HADOOP_HOME | "${CDH_COMPONENTS_HOME}/hadoop-${IMPALA_HADOOP_VERSION}/" | Used to locate Hadoop |
| HADOOP_INCLUDE_DIR | "${HADOOP_HOME}/include" | For 'hdfs.h' |
| HADOOP_LIB_DIR | "${HADOOP_HOME}/lib" | For 'libhdfs.a' or 'libhdfs.so' |
| HIVE_HOME | "${CDH_COMPONENTS_HOME}/{hive-${IMPALA_HIVE_VERSION}/" | |
| HIVE_SRC_DIR | "${HIVE_HOME}/src" | Used to find Hive thrift files. |
| HBASE_HOME | "${CDH_COMPONENTS_HOME}/hbase-${IMPALA_HBASE_VERSION}/" | |
| SENTRY_HOME | "${CDH_COMPONENTS_HOME}/sentry-${IMPALA_SENTRY_VERSION}/" | Used to setup test data |
| THRIFT_HOME | "${IMPALA_TOOLCHAIN}/thrift-${IMPALA_THRIFT_VERSION}" |