Support non-blocking, retryable record reading by riversand963 · Pull Request #4602 · facebook/rocksdb

riversand963 · 2018-10-29T21:04:15Z

Add TryReadRecord method to log::Reader so that caller can call TryReadRecord
multiple times until a complete record is read. When a complete record is read,
TryReadRecord returns true; when a record has remaining part yet to be
read, or an error has occurred, TryReadRecord returns false. The caller can
implement different retry policies.

Also add unit test for non-blocking record read.

Example usage:

log::Reader reader(...);
Slice record;
std::string scratch;
while (reader.TryReadRecord(&record, &scratch)) {
  // process record
}
if (reader.reader_error_) {
 // handle error
} else {
 // consider retry
}

Note that reader_error_ is not exposed at the moment. Furthermore, we need
finer-grained error handling according to error type that is not exposed
either.

Test plan:

$make clean && make -j32 all check
$./log_test
$./log_test --gtest_filter=bool/RetriableLogTest.NonBlockingReadFullRecord/*

riversand963 · 2018-10-29T21:08:10Z

@siying and @miasantreble , could you take a look and see if this looks good? If so, I'll continue to add more tests.

p.s. I'm considering removing retry_after_eof because it sounds a little confusing combined with non-blocking.

Update:
I think retry_after_eof is still needed because we do not want to clear the buffer once we call ReadMore again after EOF.

Update on 10/31/2018:
I removed retry_after_eof from log::Reader because I think it is better to provide a non-blocking log read interface in log reader, and move anything related to retry to higher levels.

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facebook-github-bot · 2018-11-01T16:34:49Z

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facebook-github-bot · 2018-11-02T00:38:56Z

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facebook-github-bot · 2018-11-13T18:54:08Z

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facebook-github-bot · 2018-11-19T18:09:32Z

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facebook-github-bot · 2018-11-28T00:12:36Z

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facebook-github-bot · 2018-12-06T23:59:47Z

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facebook-github-bot · 2018-12-18T00:55:34Z

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Add TryReadRecord method to log::Reader so that caller can call `TryReadRecord` multiple times until a complete record is read. When a complete record is read, `TryReadRecord` returns `true`; when a record has remaining part yet to be read, or an error has occurred, `TryReadRecord` returns false. The caller can implement different retry *policies*. Also add unit test for non-blocking record read. Example usage: ``` log::Reader reader(...); Slice record; std::string scratch; while (reader.TryReadRecord(&record, &scratch)) { // process record } if (reader.reader_error_) { // handle error } else { // consider retry } ``` Note that `reader_error_` is not exposed at the moment. Furthermore, we need finer-grained error handling according to error type that is not exposed either. Update log test and rebase. Test plan: ``` $make clean && make -j32 all check $./log_test $./log_test --gtest_filter=bool/RetriableLogTest.NonBlockingReadFullRecord/* ```

facebook-github-bot · 2019-01-08T19:47:08Z

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riversand963 · 2019-01-18T18:53:33Z

Moved to #4899

Summary: This PR allows RocksDB to run in single-primary, multi-secondary process mode. The writer is a regular RocksDB (e.g. an `DBImpl`) instance playing the role of a primary. Multiple `DBImplSecondary` processes (secondaries) share the same set of SST files, MANIFEST, WAL files with the primary. Secondaries tail the MANIFEST of the primary and apply updates to their own in-memory state of the file system, e.g. `VersionStorageInfo`. This PR has several components: 1. (Originally in #4745). Add a `PathNotFound` subcode to `IOError` to denote the failure when a secondary tries to open a file which has been deleted by the primary. 2. (Similar to #4602). Add `FragmentBufferedReader` to handle partially-read, trailing record at the end of a log from where future read can continue. 3. (Originally in #4710 and #4820). Add implementation of the secondary, i.e. `DBImplSecondary`. 3.1 Tail the primary's MANIFEST during recovery. 3.2 Tail the primary's MANIFEST during normal processing by calling `ReadAndApply`. 3.3 Tailing WAL will be in a future PR. 4. Add an example in 'examples/multi_processes_example.cc' to demonstrate the usage of secondary RocksDB instance in a multi-process setting. Instructions to run the example can be found at the beginning of the source code. Pull Request resolved: #4899 Differential Revision: D14510945 Pulled By: riversand963 fbshipit-source-id: 4ac1c5693e6012ad23f7b4b42d3c374fecbe8886

Summary: This PR allows RocksDB to run in single-primary, multi-secondary process mode. The writer is a regular RocksDB (e.g. an `DBImpl`) instance playing the role of a primary. Multiple `DBImplSecondary` processes (secondaries) share the same set of SST files, MANIFEST, WAL files with the primary. Secondaries tail the MANIFEST of the primary and apply updates to their own in-memory state of the file system, e.g. `VersionStorageInfo`. This PR has several components: 1. (Originally in facebook#4745). Add a `PathNotFound` subcode to `IOError` to denote the failure when a secondary tries to open a file which has been deleted by the primary. 2. (Similar to facebook#4602). Add `FragmentBufferedReader` to handle partially-read, trailing record at the end of a log from where future read can continue. 3. (Originally in facebook#4710 and facebook#4820). Add implementation of the secondary, i.e. `DBImplSecondary`. 3.1 Tail the primary's MANIFEST during recovery. 3.2 Tail the primary's MANIFEST during normal processing by calling `ReadAndApply`. 3.3 Tailing WAL will be in a future PR. 4. Add an example in 'examples/multi_processes_example.cc' to demonstrate the usage of secondary RocksDB instance in a multi-process setting. Instructions to run the example can be found at the beginning of the source code. Pull Request resolved: facebook#4899 Differential Revision: D14510945 Pulled By: riversand963 fbshipit-source-id: 4ac1c5693e6012ad23f7b4b42d3c374fecbe8886

riversand963 added the WIP Work in progress label Oct 29, 2018

riversand963 self-assigned this Oct 29, 2018

riversand963 requested review from miasantreble and siying October 29, 2018 21:04

facebook-github-bot added the CLA Signed label Oct 29, 2018

riversand963 changed the title ~~Support non-blocking, retryable record reading~~ [WIP] Support non-blocking, retryable record reading Oct 29, 2018

riversand963 force-pushed the non_blocking_log_read branch 2 times, most recently from bea41cf to 0005dc3 Compare October 31, 2018 00:36

riversand963 changed the title ~~[WIP] Support non-blocking, retryable record reading~~ Support non-blocking, retryable record reading Oct 31, 2018

riversand963 removed the WIP Work in progress label Oct 31, 2018

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riversand963 mentioned this pull request Nov 22, 2018

Add support for MANIFEST tailing #4710

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riversand963 mentioned this pull request Jan 18, 2019

Support for single-primary, multi-secondary instances #4899

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riversand963 mentioned this pull request Jan 29, 2019

[ABANDON] Support for single-primary, multi-secondary processes #4931

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