Alternator request sizes can be up to 16 MB, but the current implementation
had the Seastar HTTP server read the entire request as a contiguous string,
and then processed it. We can't avoid reading the entire request up-front -
we want to verify its integrity before doing any additional processing on it.
But there is no reason why the entire request needs to be stored in one big
*contiguous* allocation. This always a bad idea. We should use a non-
contiguous buffer, and that's the goal of this patch.
We use a new Seastar HTTPD feature where we can ask for an input stream,
instead of a string, for the request's body. We then begin the request
handling by reading lthe content of this stream into a
vector<temporary_buffer<char>> (which we alias "chunked_content"). We then
use this non-contiguous buffer to verify the request's signature and
if successful - parse the request JSON and finally execute it.
Beyond avoiding contiguous allocations, another benefit of this patch is
that while parsing a long request composed of chunks, we free each chunk
as soon as its parsing completed. This reduces the peak amount of memory
used by the query - we no longer need to store both unparsed and parsed
versions of the request at the same time.
Although we already had tests with requests of different lengths, most
of them were short enough to only have one chunk, and only a few had
2 or 3 chunks. So we also add a test which makes a much longer request
(a BatchWriteItem with large items), which in my experiment had 17 chunks.
The goal of this test is to verify that the new signature and JSON parsing
code which needs to cross chunk boundaries work as expected.
Fixes#7213.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Message-Id: <20210309222525.1628234-1-nyh@scylladb.com>
Client libraries (e.g. PynamoDB) expect the UnprocessedKeys
and UnprocessedItems attributes to appear in the response
unconditionally - it's hereby added, along with a simple test case.
Fixes#6569
Tests: unit(dev)
To make the tests in alternator-test runnable by test.py, we need to
move the directory alternator-test/ to test/alternator, because test.py
only looks for tests in subdirectories of test/. Then, we need to create
a test/alternator/suite.yaml saying that this test directory is of type
"Run", i.e., it has a single run script "run" which runs all its tests.
The "run" script had to be slightly modified to be aware of its new
location relative to the source directory.
To run the Alternator tests from test.py, do:
./test.py --mode dev alternator
Note that in this version, the "--mode" has no effect - test/alternator/run
always runs the latest compiled Scylla, regardless of the chosen mode.
The Alternator tests can still be run manually and individually against
a running Scylla or DynamoDB as before - just go to the test/alternator
directory (instead of alternator-test previously) and run "pytest" with
the desired parameters.
Fixes#6046
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
