This PR adds support for non-interactive transaction query endpoint.
It accepts an array of queries and parameters and returns an array of
query results. The queries will be run in a single transaction one
after another on the proxy side.
In #4743, we'd like to convert the read path to use `async` rust. In
preparation of that, this PR switches some functions that are calling
lower level functions like `BlockReader::read_blk`,
`BlockCursor::read_blob`, etc into `async`. The PR does not switch all
functions however, and only focuses on the ones which are easy to
switch.
This leaves around some async functions that are (currently)
unnecessarily `async`, but on the other hand it makes future changes
smaller in diff.
Part of #4743 (but does not completely address it).
## Problem
We use a patched version of `sharded-slab` with increased MAX_THREADS
[1]. It is not required anymore because safekeepers are async now.
A valid comment from the original PR tho [1]:
> Note that patch can affect other rust services, not only the
safekeeper binary.
- [1] https://github.com/neondatabase/neon/pull/4122
## Summary of changes
- Remove patch for `sharded-slab`
## Problem
`cargo +nightly doc` is giving a lot of warnings: broken links, naked
URLs, etc.
## Summary of changes
* update the `proc-macro2` dependency so that it can compile on latest
Rust nightly, see https://github.com/dtolnay/proc-macro2/pull/391 and
https://github.com/dtolnay/proc-macro2/issues/398
* allow the `private_intra_doc_links` lint, as linking to something
that's private is always more useful than just mentioning it without a
link: if the link breaks in the future, at least there is a warning due
to that. Also, one might enable
[`--document-private-items`](https://doc.rust-lang.org/cargo/commands/cargo-doc.html#documentation-options)
in the future and make these links work in general.
* fix all the remaining warnings given by `cargo +nightly doc`
* make it possible to run `cargo doc` on stable Rust by updating
`opentelemetry` and associated crates to version 0.19, pulling in a fix
that previously broke `cargo doc` on stable:
https://github.com/open-telemetry/opentelemetry-rust/pull/904
* Add `cargo doc` to CI to ensure that it won't get broken in the
future.
Fixes#2557
## Future work
* Potentially, it might make sense, for development purposes, to publish
the generated rustdocs somewhere, like for example [how the rust
compiler does
it](https://doc.rust-lang.org/nightly/nightly-rustc/rustc_driver/index.html).
I will file an issue for discussion.
## Problem
Binaries created from PRs (both in docker images and for tests) have
wrong git-env versions, they point to phantom merge commits.
## Summary of changes
- Prefer GIT_VERSION env variable even if git information was accessible
- Use `${{ github.event.pull_request.head.sha || github.sha }}` instead
of `${{ github.sha }}` for `GIT_VERSION` in workflows
So the builds will still happen from this phantom commit, but we will
report the PR commit.
---------
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
## Problem
While pbkdf2 is a simple algorithm, we should probably use a well tested
implementation
## Summary of changes
* Use pbkdf2 crate
* Use arrays like the hmac comment says
## Checklist before requesting a review
- [X] I have performed a self-review of my code.
- [X] If it is a core feature, I have added thorough tests.
- [ ] Do we need to implement analytics? if so did you add the relevant
metrics to the dashboard?
- [ ] If this PR requires public announcement, mark it with
/release-notes label and add several sentences in this section.
Allure does not support ansi colored logs, yet `compute_ctl` has them.
Upgrade criterion to get rid of atty dependency, disable ansi colors,
remove atty dependency and disable ansi feature of tracing-subscriber.
This is a heavy-handed approach. I am not aware of a workflow where
you'd want to connect a terminal directly to for example `compute_ctl`,
usually you find the logs in a file. If someone had been using colors,
they will now need to:
- turn the `tracing-subscriber.default-features` to `true`
- edit their wanted project to have colors
I decided to explicitly disable ansi colors in case we would have in
future a dependency accidentally enabling the feature on
`tracing-subscriber`, which would be quite surprising but not
unimagineable.
By getting rid of `atty` from dependencies we get rid of
<https://github.com/advisories/GHSA-g98v-hv3f-hcfr>.
## Problem
#4528
## Summary of changes
Add a 60 seconds default timeout to the reqwest client
Add retries for up to 3 times to call into the metric consumption
endpoint
---------
Co-authored-by: Christian Schwarz <christian@neon.tech>
There were few problems with null handling:
* query_raw_txt() accepted vector of string so it always (erroneously)
treated "null" as a string instead of null. Change rust pg client
to accept the vector of Option<String> instead of just Strings. Adopt
coding here to pass nulls as None.
* pg_text_to_json() had a check that always interpreted "NULL" string
as null. That is wrong and nulls were already handled by match None.
This bug appeared as a bad attempt to parse arrays containing NULL
elements. Fix coding by checking presence of quotes while parsing an
array (no quotes -> null, quoted -> "null" string).
Array parser fix also slightly changes behavior by always cleaning
current entry when pushing to the resulting vector. This seems to be
an omission by previous coding, however looks like it was harmless
as entry was not cleared only at the end of the nested or to-level
array.
## Problem
close https://github.com/neondatabase/neon/issues/4266
## Summary of changes
With this PR, rust-analyzer should be able to give lints and auto
complete in `mod tests`, and this makes writing tests easier.
Previously, rust-analyzer cannot do auto completion.
---------
Signed-off-by: Alex Chi <iskyzh@gmail.com>
We currently have a semaphore based rate limiter which we hope will keep
us under S3 limits. However, the semaphore does not consider time, so
I've been hesitant to raise the concurrency limit of 100.
See #3698.
The PR Introduces a leaky-bucket based rate limiter instead of the
`tokio::sync::Semaphore` which will allow us to raise the limit later
on. The configuration changes are not contained here.
This PR refactors the original page_binutils with a single tool pagectl,
use clap derive for better command line parsing, and adds the dump kv
tool to extract information from delta file. This helps me better
understand what's inside the page server. We can add support for other
types of file and more functionalities in the future.
---------
Signed-off-by: Alex Chi <iskyzh@gmail.com>
This commit introduces an SQL-over-HTTP endpoint in the proxy, with a JSON
response structure resembling that of the node-postgres driver. This method,
using HTTP POST, achieves smaller amortized latencies in edge setups due to
fewer round trips and an enhanced open connection reuse by the v8 engine.
This update involves several intricacies:
1. SQL injection protection: We employed the extended query protocol, modifying
the rust-postgres driver to send queries in one roundtrip using a text
protocol rather than binary, bypassing potential issues like those identified
in https://github.com/sfackler/rust-postgres/issues/1030.
2. Postgres type compatibility: As not all postgres types have binary
representations (e.g., acl's in pg_class), we adjusted rust-postgres to
respond with text protocol, simplifying serialization and fixing queries with
text-only types in response.
3. Data type conversion: Considering JSON supports fewer data types than
Postgres, we perform conversions where possible, passing all other types as
strings. Key conversions include:
- postgres int2, int4, float4, float8 -> json number (NaN and Inf remain
text)
- postgres bool, null, text -> json bool, null, string
- postgres array -> json array
- postgres json and jsonb -> json object
4. Alignment with node-postgres: To facilitate integration with js libraries,
we've matched the response structure of node-postgres, returning command tags
and column oids. Command tag capturing was added to the rust-postgres
functionality as part of this change.
This PR is simply the patch from
https://github.com/neondatabase/neon/issues/4008 except we enabled
`force_path_style` for custom endpoints. This is because at some
version, the s3 sdk by default uses the virtual-host style access, which
is not supported by MinIO in the default configuration. By enforcing
path style access for custom endpoints, we can pass all e2e test cases.
SDK 0.55 is not the latest version and we can bump it further later when
all flaky tests in this PR are resolved.
This PR also (hopefully) fixes flaky test
`test_ondemand_download_timetravel`.
close https://github.com/neondatabase/neon/issues/4008
Signed-off-by: Alex Chi <iskyzh@gmail.com>
Add essential safekeeper and pageserver::walreceiver metrics. Mostly
counters, such as the number of received queries, broker messages,
removed WAL segments, or connection switches events in walreceiver.
Also logs broker push loop duration.
Add patch directive to Cargo.toml to use patched version of
sharded-slab:
98d16753ab
Patch changes the MAX_THREADS limit from 4096 to 32768. This is a
temporary workaround for using tracing from many threads in safekeepers
code, until async safekeepers patch is merged to the main.
Note that patch can affect other rust services, not only the safekeeper
binary.
Add HTTP endpoint to initialize safekeeper timeline from peer
safekeepers. This is useful for initializing new safekeeper to replace
failed safekeeper. Not fully "correct" in all cases, but should work in
most.
This code is not suitable for production workloads but can be tested on
staging to get started. New endpoint is separated from usual cases and
should not affect anything if no one explicitly uses a new endpoint. We
can rollback this commit in case of issues.
Introduce read timeouts to our `page_service` connections. Without read
timeouts, we essentially leak connections.
This is a port of #3995. Split the refactorings to the other PR: #4097.
Fixes#4028.
- Remove repeated tenant & timeline from span
- Demote logging of the path to debug level
- Log completion at info level, in the same function where we log errors
- distinguish between layer file download success & on-demand download
succeeding as a whole in the log message wording
- Assert that the span contains a tenant id and a timeline id
fixes https://github.com/neondatabase/neon/issues/3945
Before:
```
INFO compaction_loop{tenant_id=$TENANT_ID}:compact_timeline{timeline=$TIMELINE_ID}:download_remote_layer{tenant_id=$TENANT_ID timeline_id=$TIMELINE_ID layer=000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000020C8A71-00000000020CAF91}: download complete: /storage/pageserver/data/tenants/$TENANT_ID/timelines/$TIMELINE_ID/000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000020C8A71-00000000020CAF91
INFO compaction_loop{tenant_id=$TENANT_ID}:compact_timeline{timeline=$TIMELINE_ID}:download_remote_layer{tenant_id=$TENANT_ID timeline_id=$TIMELINE_ID layer=000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000020C8A71-00000000020CAF91}: Rebuilt layer map. Did 9 insertions to process a batch of 1 updates.
```
After:
```
INFO compaction_loop{tenant_id=$TENANT_ID}:compact_timeline{timeline=$TIMELINE_ID}:download_remote_layer{layer=000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000020C8A71-00000000020CAF91}: layer file download finished
INFO compaction_loop{tenant_id=$TENANT_ID}:compact_timeline{timeline=$TIMELINE_ID}:download_remote_layer{layer=000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000020C8A71-00000000020CAF91}: Rebuilt layer map. Did 9 insertions to process a batch of 1 updates.
INFO compaction_loop{tenant_id=$TENANT_ID}:compact_timeline{timeline=$TIMELINE_ID}:download_remote_layer{layer=000000000000000000000000000000000000-FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF__00000000020C8A71-00000000020CAF91}: on-demand download successful
```
See https://github.com/neondatabase/neon/pull/3991
Brings the changes back with the right way to use new `toml_edit` to
deserialize values and a unit test for this.
All non-trivial updates extracted into separate commits, also `carho hakari` data and its manifest format were updated.
3 sets of crates remain unupdated:
* `base64` — touches proxy in a lot of places and changed its api (by 0.21 version) quite strongly since our version (0.13).
* `opentelemetry` and `opentelemetry-*` crates
```
error[E0308]: mismatched types
--> libs/tracing-utils/src/http.rs:65:21
|
65 | span.set_parent(parent_ctx);
| ---------- ^^^^^^^^^^ expected struct `opentelemetry_api::context::Context`, found struct `opentelemetry::Context`
| |
| arguments to this method are incorrect
|
= note: struct `opentelemetry::Context` and struct `opentelemetry_api::context::Context` have similar names, but are actually distinct types
note: struct `opentelemetry::Context` is defined in crate `opentelemetry_api`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/opentelemetry_api-0.19.0/src/context.rs:77:1
|
77 | pub struct Context {
| ^^^^^^^^^^^^^^^^^^
note: struct `opentelemetry_api::context::Context` is defined in crate `opentelemetry_api`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/opentelemetry_api-0.18.0/src/context.rs:77:1
|
77 | pub struct Context {
| ^^^^^^^^^^^^^^^^^^
= note: perhaps two different versions of crate `opentelemetry_api` are being used?
note: associated function defined here
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/tracing-opentelemetry-0.18.0/src/span_ext.rs:43:8
|
43 | fn set_parent(&self, cx: Context);
| ^^^^^^^^^^
For more information about this error, try `rustc --explain E0308`.
error: could not compile `tracing-utils` due to previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `tracing-utils` due to previous error
```
`tracing-opentelemetry` of version `0.19` is not yet released, that is supposed to have the update we need.
* similarly, `rustls`, `tokio-rustls`, `rustls-*` and `tls-listener` crates have similar issue:
```
error[E0308]: mismatched types
--> libs/postgres_backend/tests/simple_select.rs:112:78
|
112 | let mut make_tls_connect = tokio_postgres_rustls::MakeRustlsConnect::new(client_cfg);
| --------------------------------------------- ^^^^^^^^^^ expected struct `rustls::client::client_conn::ClientConfig`, found struct `ClientConfig`
| |
| arguments to this function are incorrect
|
= note: struct `ClientConfig` and struct `rustls::client::client_conn::ClientConfig` have similar names, but are actually distinct types
note: struct `ClientConfig` is defined in crate `rustls`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/rustls-0.21.0/src/client/client_conn.rs:125:1
|
125 | pub struct ClientConfig {
| ^^^^^^^^^^^^^^^^^^^^^^^
note: struct `rustls::client::client_conn::ClientConfig` is defined in crate `rustls`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/rustls-0.20.8/src/client/client_conn.rs:91:1
|
91 | pub struct ClientConfig {
| ^^^^^^^^^^^^^^^^^^^^^^^
= note: perhaps two different versions of crate `rustls` are being used?
note: associated function defined here
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-postgres-rustls-0.9.0/src/lib.rs:23:12
|
23 | pub fn new(config: ClientConfig) -> Self {
| ^^^
For more information about this error, try `rustc --explain E0308`.
error: could not compile `postgres_backend` due to previous error
warning: build failed, waiting for other jobs to finish...
```
* aws crates: I could not make new API to work with bucket endpoint overload, and console e2e tests failed.
Other our tests passed, further investigation is worth to be done in https://github.com/neondatabase/neon/issues/4008
Reason and backtrace are added to the Broken state. Backtrace is automatically collected when tenant entered the broken state. The format for API, CLI and metrics is changed and unified to return tenant state name in camel case. Previously snake case was used for metrics and camel case was used for everything else. Now tenant state field in TenantInfo swagger spec is changed to contain state name in "slug" field and other fields (currently only reason and backtrace for Broken variant in "data" field). To allow for this breaking change state was removed from TenantInfo swagger spec because it was not used anywhere.
Please note that the tenant's broken reason is not persisted on disk so the reason is lost when pageserver is restarted.
Requires changes to grafana dashboard that monitors tenant states.
Closes#3001
---------
Co-authored-by: theirix <theirix@gmail.com>
All non-trivial updates extracted into separate commits, also `carho
hakari` data and its manifest format were updated.
3 sets of crates remain unupdated:
* `base64` — touches proxy in a lot of places and changed its api (by
0.21 version) quite strongly since our version (0.13).
* `opentelemetry` and `opentelemetry-*` crates
```
error[E0308]: mismatched types
--> libs/tracing-utils/src/http.rs:65:21
|
65 | span.set_parent(parent_ctx);
| ---------- ^^^^^^^^^^ expected struct `opentelemetry_api::context::Context`, found struct `opentelemetry::Context`
| |
| arguments to this method are incorrect
|
= note: struct `opentelemetry::Context` and struct `opentelemetry_api::context::Context` have similar names, but are actually distinct types
note: struct `opentelemetry::Context` is defined in crate `opentelemetry_api`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/opentelemetry_api-0.19.0/src/context.rs:77:1
|
77 | pub struct Context {
| ^^^^^^^^^^^^^^^^^^
note: struct `opentelemetry_api::context::Context` is defined in crate `opentelemetry_api`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/opentelemetry_api-0.18.0/src/context.rs:77:1
|
77 | pub struct Context {
| ^^^^^^^^^^^^^^^^^^
= note: perhaps two different versions of crate `opentelemetry_api` are being used?
note: associated function defined here
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/tracing-opentelemetry-0.18.0/src/span_ext.rs:43:8
|
43 | fn set_parent(&self, cx: Context);
| ^^^^^^^^^^
For more information about this error, try `rustc --explain E0308`.
error: could not compile `tracing-utils` due to previous error
warning: build failed, waiting for other jobs to finish...
error: could not compile `tracing-utils` due to previous error
```
`tracing-opentelemetry` of version `0.19` is not yet released, that is
supposed to have the update we need.
* similarly, `rustls`, `tokio-rustls`, `rustls-*` and `tls-listener`
crates have similar issue:
```
error[E0308]: mismatched types
--> libs/postgres_backend/tests/simple_select.rs:112:78
|
112 | let mut make_tls_connect = tokio_postgres_rustls::MakeRustlsConnect::new(client_cfg);
| --------------------------------------------- ^^^^^^^^^^ expected struct `rustls::client::client_conn::ClientConfig`, found struct `ClientConfig`
| |
| arguments to this function are incorrect
|
= note: struct `ClientConfig` and struct `rustls::client::client_conn::ClientConfig` have similar names, but are actually distinct types
note: struct `ClientConfig` is defined in crate `rustls`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/rustls-0.21.0/src/client/client_conn.rs:125:1
|
125 | pub struct ClientConfig {
| ^^^^^^^^^^^^^^^^^^^^^^^
note: struct `rustls::client::client_conn::ClientConfig` is defined in crate `rustls`
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/rustls-0.20.8/src/client/client_conn.rs:91:1
|
91 | pub struct ClientConfig {
| ^^^^^^^^^^^^^^^^^^^^^^^
= note: perhaps two different versions of crate `rustls` are being used?
note: associated function defined here
--> /Users/someonetoignore/.cargo/registry/src/github.com-1ecc6299db9ec823/tokio-postgres-rustls-0.9.0/src/lib.rs:23:12
|
23 | pub fn new(config: ClientConfig) -> Self {
| ^^^
For more information about this error, try `rustc --explain E0308`.
error: could not compile `postgres_backend` due to previous error
warning: build failed, waiting for other jobs to finish...
```
* aws crates: I could not make new API to work with bucket endpoint
overload, and console e2e tests failed.
Other our tests passed, further investigation is worth to be done in
https://github.com/neondatabase/neon/issues/4008
TCP_KEEPALIVE is not enabled by default, so this prevents hanged up connections
in case of abrupt client termination. Add 'closed' flag to PostgresBackendReader
and pass it during handles join to prevent attempts to read from socket if we
errored out previously -- now with timeouts this is a common situation.
It looks like
2023-04-10T18:08:37.493448Z INFO {cid=68}:WAL
receiver{ttid=59f91ad4e821ab374f9ccdf918da3a85/16438f99d61572c72f0c7b0ed772785d}:
terminated: timed out
Presumably fixes https://github.com/neondatabase/neon/issues/3971
This is in preparation of using compute_ctl to launch postgres nodes
in the neon_local control plane. And seems like a good idea to
separate the public interfaces anyway.
One non-mechanical change here is that the 'metrics' field is moved
under the Mutex, instead of using atomics. We were not using atomics
for performance but for convenience here, and it seems more clear to
not use atomics in the model for the HTTP response type.
This patch adds a pageserver-global background loop that evicts layers
in response to a shortage of available bytes in the $repo/tenants
directory's filesystem.
The loop runs periodically at a configurable `period`.
Each loop iteration uses `statvfs` to determine filesystem-level space
usage. It compares the returned usage data against two different types
of thresholds. The iteration tries to evict layers until app-internal
accounting says we should be below the thresholds. We cross-check this
internal accounting with the real world by making another `statvfs` at
the end of the iteration. We're good if that second statvfs shows that
we're _actually_ below the configured thresholds. If we're still above
one or more thresholds, we emit a warning log message, leaving it to the
operator to investigate further.
There are two thresholds:
- `max_usage_pct` is the relative available space, expressed in percent
of the total filesystem space. If the actual usage is higher, the
threshold is exceeded.
- `min_avail_bytes` is the absolute available space in bytes. If the
actual usage is lower, the threshold is exceeded.
The iteration evicts layers in LRU fashion with a reservation of up to
`tenant_min_resident_size` bytes of the most recent layers per tenant.
The layers not part of the per-tenant reservation are evicted
least-recently-used first until we're below all thresholds. The
`tenant_min_resident_size` can be overridden per tenant as
`min_resident_size_override` (bytes).
In addition to the loop, there is also an HTTP endpoint to perform one
loop iteration synchronous to the request. The endpoint takes an
absolute number of bytes that the iteration needs to evict before
pressure is relieved. The tests use this endpoint, which is a great
simplification over setting up loopback-mounts in the tests, which would
be required to test the statvfs part of the implementation. We will rely
on manual testing in staging to test the statvfs parts.
The HTTP endpoint is also handy in emergencies where an operator wants
the pageserver to evict a given amount of space _now. Hence, it's
arguments documented in openapi_spec.yml. The response type isn't
documented though because we don't consider it stable. The endpoint
should _not_ be used by Console but it could be used by on-call.
Co-authored-by: Joonas Koivunen <joonas@neon.tech>
Co-authored-by: Dmitry Rodionov <dmitry@neon.tech>
Co-authored-by: Heikki Linnakangas <heikki@neon.tech>
After enabling autoscaling, we faced the issue that customers are not
able to get the number of CPUs they use at this moment. Therefore I've
added these two options:
1. Postgresql function to allow customers to call it whenever they want
2. `compute_ctl` endpoint to show these number in console
1) Remove allocation and data copy during each message read. Instead, parsing
functions now accept BytesMut from which data they form messages, with
pointers (e.g. in CopyData) pointing directly into BytesMut buffer. Accordingly,
move ConnectionError containing IO error subtype into framed.rs providing this
and leave in pq_proto only ProtocolError.
2) Remove anyhow from pq_proto.
3) Move FeStartupPacket out of FeMessage. Now FeStartupPacket::parse returns it
directly, eliminating dead code where user wants startup packet but has to match
for others.
proxy stream.rs is adapted to framed.rs with minimal changes. It also benefits
from framed.rs improvements described above.
- Add support for splitting async postgres_backend into read and write halfes.
Safekeeper needs this for bidirectional streams. To this end, encapsulate
reading-writing postgres messages to framed.rs with split support without any
additional changes (relying on BufRead for reading and BytesMut out buffer for
writing).
- Use async postgres_backend throughout safekeeper (and in proxy auth link
part).
- In both safekeeper COPY streams, do read-write from the same thread/task with
select! for easier error handling.
- Tidy up finishing CopyBoth streams in safekeeper sending and receiving WAL
-- join split parts back catching errors from them before returning.
Initially I hoped to do that read-write without split at all, through polling
IO:
https://github.com/neondatabase/neon/pull/3522
However that turned out to be more complicated than I initially expected
due to 1) borrow checking and 2) anon Future types. 1) required Rc<Refcell<...>>
which is Send construct just to satisfy the checker; 2) can be workaround with
transmute. But this is so messy that I decided to leave split.
To untie cyclic dependency between sync and async versions of postgres_backend,
copy QueryError and some logging/error routines to postgres_backend.rs. This is
temporal glue to make commits smaller, sync version will be dropped by the
upcoming commit completely.
