#
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# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you under the Apache License, Version 2.0 (the
# "License"); you may not use this file except in compliance
# with the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
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# software distributed under the License is distributed on an
# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
# KIND, either express or implied. See the License for the
# specific language governing permissions and limitations
# under the License.
"""SSH Remote Job Trigger for deferrable execution."""
from __future__ import annotations
import asyncio
from collections.abc import AsyncIterator
from typing import Any, Literal
import tenacity
from airflow.providers.ssh.hooks.ssh import SSHHookAsync
from airflow.providers.ssh.utils.remote_job import (
build_posix_completion_check_command,
build_posix_file_size_command,
build_posix_log_tail_command,
build_windows_completion_check_command,
build_windows_file_size_command,
build_windows_log_tail_command,
)
from airflow.triggers.base import BaseTrigger, TriggerEvent
[docs]
class SSHRemoteJobTrigger(BaseTrigger):
"""
Trigger that monitors a remote SSH job and streams logs.
This trigger polls the remote host to check job completion status
and reads log output incrementally.
:param ssh_conn_id: SSH connection ID from Airflow Connections
:param remote_host: Optional override for the remote host
:param job_id: Unique identifier for the remote job
:param job_dir: Remote directory containing job artifacts
:param log_file: Path to the log file on the remote host
:param exit_code_file: Path to the exit code file on the remote host
:param remote_os: Operating system of the remote host ('posix' or 'windows')
:param poll_interval: Seconds between polling attempts
:param log_chunk_size: Maximum bytes to read per poll
:param log_offset: Current byte offset in the log file
"""
def __init__(
self,
ssh_conn_id: str,
remote_host: str | None,
job_id: str,
job_dir: str,
log_file: str,
exit_code_file: str,
remote_os: Literal["posix", "windows"],
poll_interval: int = 5,
log_chunk_size: int = 65536,
log_offset: int = 0,
command_timeout: float = 30.0,
) -> None:
super().__init__()
[docs]
self.ssh_conn_id = ssh_conn_id
[docs]
self.remote_host = remote_host
[docs]
self.log_file = log_file
[docs]
self.exit_code_file = exit_code_file
[docs]
self.remote_os = remote_os
[docs]
self.poll_interval = poll_interval
[docs]
self.log_chunk_size = log_chunk_size
[docs]
self.log_offset = log_offset
[docs]
self.command_timeout = command_timeout
[docs]
def serialize(self) -> tuple[str, dict[str, Any]]:
"""Serialize the trigger for storage."""
return (
"airflow.providers.ssh.triggers.ssh_remote_job.SSHRemoteJobTrigger",
{
"ssh_conn_id": self.ssh_conn_id,
"remote_host": self.remote_host,
"job_id": self.job_id,
"job_dir": self.job_dir,
"log_file": self.log_file,
"exit_code_file": self.exit_code_file,
"remote_os": self.remote_os,
"poll_interval": self.poll_interval,
"log_chunk_size": self.log_chunk_size,
"log_offset": self.log_offset,
"command_timeout": self.command_timeout,
},
)
def _get_hook(self) -> SSHHookAsync:
"""Create the async SSH hook."""
return SSHHookAsync(
ssh_conn_id=self.ssh_conn_id,
host=self.remote_host,
)
@tenacity.retry(
stop=tenacity.stop_after_attempt(3),
wait=tenacity.wait_exponential(multiplier=1, min=1, max=10),
retry=tenacity.retry_if_exception_type((OSError, TimeoutError, ConnectionError)),
reraise=True,
)
async def _check_completion(self, hook: SSHHookAsync) -> int | None:
"""
Check if the remote job has completed.
Retries transient network errors up to 3 times with exponential backoff.
:return: Exit code if completed, None if still running
"""
if self.remote_os == "posix":
cmd = build_posix_completion_check_command(self.exit_code_file)
else:
cmd = build_windows_completion_check_command(self.exit_code_file)
try:
_, stdout, _ = await hook.run_command(cmd, timeout=self.command_timeout)
stdout = stdout.strip()
if stdout and stdout.isdigit():
return int(stdout)
except (OSError, TimeoutError, ConnectionError) as e:
self.log.warning("Transient error checking completion (will retry): %s", e)
raise
except Exception as e:
self.log.warning("Error checking completion status: %s", e)
return None
@tenacity.retry(
stop=tenacity.stop_after_attempt(3),
wait=tenacity.wait_exponential(multiplier=1, min=1, max=10),
retry=tenacity.retry_if_exception_type((OSError, TimeoutError, ConnectionError)),
reraise=True,
)
async def _get_log_size(self, hook: SSHHookAsync) -> int:
"""
Get the current size of the log file in bytes.
Retries transient network errors up to 3 times with exponential backoff.
"""
if self.remote_os == "posix":
cmd = build_posix_file_size_command(self.log_file)
else:
cmd = build_windows_file_size_command(self.log_file)
try:
_, stdout, _ = await hook.run_command(cmd, timeout=self.command_timeout)
stdout = stdout.strip()
if stdout and stdout.isdigit():
return int(stdout)
except (OSError, TimeoutError, ConnectionError) as e:
self.log.warning("Transient error getting log size (will retry): %s", e)
raise
except Exception as e:
self.log.warning("Error getting log file size: %s", e)
return 0
@tenacity.retry(
stop=tenacity.stop_after_attempt(3),
wait=tenacity.wait_exponential(multiplier=1, min=1, max=10),
retry=tenacity.retry_if_exception_type((OSError, TimeoutError, ConnectionError)),
reraise=True,
)
async def _read_log_chunk(self, hook: SSHHookAsync) -> tuple[str, int]:
"""
Read a chunk of logs from the current offset.
Retries transient network errors up to 3 times with exponential backoff.
:return: Tuple of (log_chunk, new_offset)
"""
file_size = await self._get_log_size(hook)
if file_size <= self.log_offset:
return "", self.log_offset
bytes_available = file_size - self.log_offset
bytes_to_read = min(bytes_available, self.log_chunk_size)
if self.remote_os == "posix":
cmd = build_posix_log_tail_command(self.log_file, self.log_offset, bytes_to_read)
else:
cmd = build_windows_log_tail_command(self.log_file, self.log_offset, bytes_to_read)
try:
exit_code, stdout, _ = await hook.run_command(cmd, timeout=self.command_timeout)
# Advance offset by bytes requested, not decoded string length
new_offset = self.log_offset + bytes_to_read if stdout else self.log_offset
return stdout, new_offset
except (OSError, TimeoutError, ConnectionError) as e:
self.log.warning("Transient error reading logs (will retry): %s", e)
raise
except Exception as e:
self.log.warning("Error reading log chunk: %s", e)
return "", self.log_offset
[docs]
async def run(self) -> AsyncIterator[TriggerEvent]:
"""
Poll the remote job status and yield events with log chunks.
This method runs in a loop, checking the job status and reading
logs at each poll interval. It yields a TriggerEvent each time
with the current status and any new log output.
"""
hook = self._get_hook()
while True:
try:
exit_code = await self._check_completion(hook)
log_chunk, new_offset = await self._read_log_chunk(hook)
base_event = {
"job_id": self.job_id,
"job_dir": self.job_dir,
"log_file": self.log_file,
"exit_code_file": self.exit_code_file,
"remote_os": self.remote_os,
}
if exit_code is not None:
yield TriggerEvent(
{
**base_event,
"status": "success" if exit_code == 0 else "failed",
"done": True,
"exit_code": exit_code,
"log_chunk": log_chunk,
"log_offset": new_offset,
"message": f"Job completed with exit code {exit_code}",
}
)
return
self.log_offset = new_offset
if log_chunk:
self.log.info("%s", log_chunk.rstrip())
await asyncio.sleep(self.poll_interval)
except Exception as e:
self.log.exception("Error in SSH remote job trigger")
yield TriggerEvent(
{
"job_id": self.job_id,
"job_dir": self.job_dir,
"log_file": self.log_file,
"exit_code_file": self.exit_code_file,
"remote_os": self.remote_os,
"status": "error",
"done": True,
"exit_code": None,
"log_chunk": "",
"log_offset": self.log_offset,
"message": f"Trigger error: {e}",
}
)
return