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Fix sqlalchemy for postgres Unix sockets #761

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merged 10 commits into from
Nov 11, 2021
Merged

Fix sqlalchemy for postgres Unix sockets #761

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b03b44f
Fix sqlalchemy for postgres unix sockets
mattoberle Oct 19, 2021
610ee1e
Update CHANGELOG
mattoberle Oct 19, 2021
7103650
Merge branch 'main' into bugfix/sqlalchemy/unix-sockets
mattoberle Oct 19, 2021
48fd20e
Conditionally set net.transport for psql tcp/unix
mattoberle Oct 19, 2021
37ef73f
Use .value properties of enums
mattoberle Oct 19, 2021
68329b8
Merge branch 'main' into bugfix/sqlalchemy/unix-sockets
srikanthccv Oct 19, 2021
8538e80
Improve postgresql attribute detection from cursor
mattoberle Oct 20, 2021
c4e9be1
Fix formatting
mattoberle Oct 20, 2021
f906142
Merge branch 'main' into bugfix/sqlalchemy/unix-sockets
owais Nov 11, 2021
911305f
Merge branch 'main' into bugfix/sqlalchemy/unix-sockets
ocelotl Nov 11, 2021
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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Expand Up @@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0

## [Unreleased](https:/open-telemetry/opentelemetry-python/compare/v1.6.1-0.25b1...HEAD)

- `opentelemetry-instrumentation-sqlalchemy` Fix PostgreSQL instrumentation for Unix sockets
([#761](https:/open-telemetry/opentelemetry-python-contrib/pull/761))

### Changed

- `opentelemetry-sdk-extension-aws` & `opentelemetry-propagator-aws` Release AWS Python SDK Extension as 2.0.1 and AWS Propagator as 1.0.1
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12 changes: 10 additions & 2 deletions ...lemetry-instrumentation-sqlalchemy/src/opentelemetry/instrumentation/sqlalchemy/engine.py
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Expand Up @@ -16,7 +16,7 @@

from opentelemetry import trace
from opentelemetry.instrumentation.sqlalchemy.version import __version__
from opentelemetry.semconv.trace import SpanAttributes
from opentelemetry.semconv.trace import NetTransportValues, SpanAttributes
from opentelemetry.trace.status import Status, StatusCode


Expand Down Expand Up @@ -163,5 +163,13 @@ def _get_attributes_from_cursor(vendor, cursor, attrs):
data = parse_dsn(dsn)
attrs[SpanAttributes.DB_NAME] = data.get("dbname")
attrs[SpanAttributes.NET_PEER_NAME] = data.get("host")
attrs[SpanAttributes.NET_PEER_PORT] = int(data.get("port"))
if data.get("port"):
attrs[SpanAttributes.NET_PEER_PORT] = int(data["port"])
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If it is a unix socket path we can add different span attributes

opentelemetry-python-contrib/instrumentation/opentelemetry-instrumentation-redis/src/opentelemetry/instrumentation/redis/util.py

Lines 44 to 47 in fbb677a

attributes[SpanAttributes.NET_PEER_NAME] = conn_kwargs.get("path", "")
attributes[
SpanAttributes.NET_TRANSPORT
] = NetTransportValues.UNIX.value
.

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In this case the host attribute will be the path of the socket (which aligns with the way psql takes it as a parameter).
I am open to differentiating it though if NET_PEER_NAME is not an accurate representation in that context.

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@mattoberle mattoberle Oct 19, 2021 •
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It looks like NET_PEER_NAME should be the path to the socket:

If net.transport is "unix" or "pipe", the absolute path to the file representing it should be used as net.peer.name (net.host.name doesn't make sense in that context).

If we are setting NET_PEER_TRANSPORT anywhere it should be unix.
With the values we are setting now I think this should be okay, unless I'm missing a spot where other net.* values get set.

Edit: Sorry, misread! I think we are good on NET_PEER_NAME but you are right, the transport could be set as well.

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Makes sense. Let's add NET_PEER_TRANSPORT conditionally when connecting via unix socket.

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Is absence of port guaranteed to be a unix socket? could it be something else?

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@mattoberle mattoberle Oct 19, 2021 •
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@owais that's a great point.

It looks like the TypeError could apply to non-socket cases too.

from psycopg2.extensions import parse_dsn
from sqlalchemy import create_engine

engine = create_engine('postgresql://postgres@localhost/postgres')
conn = engine.raw_connection()
cur = conn.cursor()

cur.connection.dsn  # 'host=localhost user=postgres dbname=postgres
parse_dsn(cur.connection.dsn)  # {'user': 'postgres', 'dbname': 'postgres', 'host': 'localhost'}

However, there is cur.connection.info which provides:

cur.connection.info.port  # 5432
cur.connection.info.host  # 'localhost'

When connecting to a socket it provides:

cur.connection.info.port  # 5432
cur.connection.info.host  # '/var/run/postgresql/'

psycopg2 makes the assumption that every socket is named .s.PGSQL.{port}, meaning it only stores the absolute path of the socket directory. Mirroring that assumption here seems risky.

The info object seems like the safer bet since it's always provides certain values.
If you initialize a SQLAlchemy engine with engine = create_engine('postgresql://') the .dsn attribute will be an empty string.

I think at the very least the presence of a filesystem path in info.host is a clue we are using sockets... but I'll dig around the psycopg2 source a bit to see if I can find any better guarantees.

Edit: That being said, it seems like there is a bug present now that people will encounter if they aren't setting an explicit port (ie. relying on the default). The other function that sets attributes simply omits attributes that aren't present. Worth splitting the work into a bugfix and something that improves the attributes?

Edit 2: Mirroring the .s.PGSQL.{port} convention to construct the absolute path seems fine actually, that's a convention enforced by PostgreSQL itself. And since socket support isn't available on Windows a simple check for '/' at the start of the host should be enough to determine whether we are using a socket or not.

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Makes sense. Checking if the host starts with unix://, unix:/// or / makes more sense to me than checking for absence of port.

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@mattoberle mattoberle Oct 20, 2021 •
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I pushed up a change that implements the NET_TRANSPORT logic for sockets, although I found there is unreachable code.

I wrote a quick test locally.
The _get_attributes_from_cursor function is only called if host is not in the sqlalchemy URL.
This is the case for all unix socket connections (for postgres).

On the other hand, host is always present when connecting via TCP (it's a requirement, the default if omitted is unix socket).
The code that derives attributes from the URL depends on explicit args, so TCP connections will never get their net.transport (and won't get things like net.peer.port if using defaults).

We'd have to inspect the cursor for every vendor to get any information not inside the URL.
In the commit I just pushed up we are doing that for postgresql, but I feel like with this much divergent logic the test suite would basically need access to every supported SQLAlchemy engine.

Revisiting the original scope of this PR:

There is a bug when using sockets for postgres specifically because of unreachable (in tests) vendor-specific code.
I think the initial commit b03b44f addresses the bug without losing anything useful / introducing anything dangerous-- maybe enhancing the attribute recognition is better suited for a bigger PR?

    def test_netransport_attributes_from_cursor_unix_minimal_args(self):
        engine = create_engine("postgresql://")
        ...
        self.assertEqual(spans[0].attributes['net.peer.name'], '/var/run/postgresql/.s.PGSQL.5432')
        self.assertEqual(spans[0].attributes['net.transport'], 'unix')

    def test_netransport_attributes_from_cursor_unix_explicit_args(self):
        engine = create_engine("postgresql://postgres@:5432/postgres?host=/var/run/postgresql")
        ...
        self.assertEqual(spans[0].attributes['net.peer.name'], '/var/run/postgresql/.s.PGSQL.5432')
        self.assertEqual(spans[0].attributes['net.transport'], 'unix')

    def test_netransport_attributes_from_cursor_tcp_minimal_args(self):
        engine = create_engine("postgresql://postgres:postgres@localhost")
        ...
        self.assertEqual(spans[0].attributes['net.peer.name'], 'localhost')
        # self.assertEqual(spans[0].attributes['net.transport'], 'tcp')
        # self.assertEqual(spans[0].attributes['net.peer.port'], 5432)

    def test_netransport_attributes_from_cursor_tcp_explicit_args(self):
        engine = create_engine("postgresql://postgres:postgres@localhost:5432/postgres")
        ...
        self.assertEqual(spans[0].attributes['net.peer.name'], 'localhost')
        # self.assertEqual(spans[0].attributes['net.transport'], 'tcp')
        self.assertEqual(spans[0].attributes['net.peer.port'], 5432)

attrs[
SpanAttributes.NET_TRANSPORT
] = NetTransportValues.IP_TCP.value
else:
attrs[
SpanAttributes.NET_TRANSPORT
] = NetTransportValues.UNIX.value
return attrs