IPC Transports & Protocols#

The litestar_vite.ipc package provides cross-platform inter-process communication transports, data structures, and circuit breakers connecting Litestar to frontend SSR workers and the Vite dev server.

Transports & Protocols#

Inter-Process Communication (IPC) transports and resilience utilities for SSR and Fragments.

class litestar_vite.ipc.BaseIPCTransport[source]#

Bases: Protocol

Protocol defining the asynchronous IPC transport contract.

async start() → None[source]#: Start or initialize the IPC transport.

async close() → None[source]#: Gracefully shut down the IPC transport and release all resources.

async send_request(payload: dict[str, Any], timeout: float = 10.0) → dict[str, Any][source]#

Send a JSON payload and return the response.

Parameters:

payload¶ – Request dictionary payload.
timeout¶ – Maximum duration in seconds to wait for a response.

Returns:

Decoded response payload dictionary from the worker.

property is_running: bool#: Return True if the transport is running and ready to handle requests.

__init__(*args, **kwargs)#

exception litestar_vite.ipc.CircuitBreakerOpenError[source]#

Bases: IPCError

Raised when an IPC request is attempted while the circuit breaker is open.

__init__(*args, **kwargs)#

classmethod __new__(*args, **kwargs)#

add_note()#: Exception.add_note(note) – add a note to the exception

with_traceback()#: Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

class litestar_vite.ipc.CircuitState[source]#

Bases: str, Enum

Lifecycle states of the SSR circuit breaker.

__new__(value)#

encode(encoding='utf-8', errors='strict')#

Encode the string using the codec registered for encoding.

encoding: The encoding in which to encode the string.
errors: The error handling scheme to use for encoding errors. The default is ‘strict’ meaning that encoding errors raise a UnicodeEncodeError. Other possible values are ‘ignore’, ‘replace’ and ‘xmlcharrefreplace’ as well as any other name registered with codecs.register_error that can handle UnicodeEncodeErrors.

replace(old, new, count=-1, /)#

Return a copy with all occurrences of substring old replaced by new.

count
Maximum number of occurrences to replace. -1 (the default value) means replace all occurrences.

If the optional argument count is given, only the first count occurrences are replaced.

split(sep=None, maxsplit=-1)#

Return a list of the substrings in the string, using sep as the separator string.

sep
The separator used to split the string.

When set to None (the default value), will split on any whitespace character (including n r t f and spaces) and will discard empty strings from the result.

maxsplit
Maximum number of splits. -1 (the default value) means no limit.

Splitting starts at the front of the string and works to the end.

Note, str.split() is mainly useful for data that has been intentionally delimited. With natural text that includes punctuation, consider using the regular expression module.

rsplit(sep=None, maxsplit=-1)#

Return a list of the substrings in the string, using sep as the separator string.

sep
The separator used to split the string.

When set to None (the default value), will split on any whitespace character (including n r t f and spaces) and will discard empty strings from the result.

maxsplit
Maximum number of splits. -1 (the default value) means no limit.

Splitting starts at the end of the string and works to the front.

join(iterable, /)#

Concatenate any number of strings.

The string whose method is called is inserted in between each given string. The result is returned as a new string.

Example: ‘.’.join([‘ab’, ‘pq’, ‘rs’]) -> ‘ab.pq.rs’

capitalize()#

Return a capitalized version of the string.

More specifically, make the first character have upper case and the rest lower case.

casefold()#: Return a version of the string suitable for caseless comparisons.

title()#

Return a version of the string where each word is titlecased.

More specifically, words start with uppercased characters and all remaining cased characters have lower case.

center(width, fillchar=' ', /)#

Return a centered string of length width.

Padding is done using the specified fill character (default is a space).

count(sub[, start[, end]]) → int#: Return the number of non-overlapping occurrences of substring sub in string S[start:end]. Optional arguments start and end are interpreted as in slice notation.

expandtabs(tabsize=8)#

Return a copy where all tab characters are expanded using spaces.

If tabsize is not given, a tab size of 8 characters is assumed.

find(sub[, start[, end]]) → int#

Return the lowest index in S where substring sub is found, such that sub is contained within S[start:end]. Optional arguments start and end are interpreted as in slice notation.

Return -1 on failure.

partition(sep, /)#

Partition the string into three parts using the given separator.

This will search for the separator in the string. If the separator is found, returns a 3-tuple containing the part before the separator, the separator itself, and the part after it.

If the separator is not found, returns a 3-tuple containing the original string and two empty strings.

index(sub[, start[, end]]) → int#

Return the lowest index in S where substring sub is found, such that sub is contained within S[start:end]. Optional arguments start and end are interpreted as in slice notation.

Raises ValueError when the substring is not found.

ljust(width, fillchar=' ', /)#

Return a left-justified string of length width.

Padding is done using the specified fill character (default is a space).

lower()#: Return a copy of the string converted to lowercase.

lstrip(chars=None, /)#

Return a copy of the string with leading whitespace removed.

If chars is given and not None, remove characters in chars instead.

rfind(sub[, start[, end]]) → int#

Return the highest index in S where substring sub is found, such that sub is contained within S[start:end]. Optional arguments start and end are interpreted as in slice notation.

Return -1 on failure.

rindex(sub[, start[, end]]) → int#

Return the highest index in S where substring sub is found, such that sub is contained within S[start:end]. Optional arguments start and end are interpreted as in slice notation.

Raises ValueError when the substring is not found.

rjust(width, fillchar=' ', /)#

Return a right-justified string of length width.

Padding is done using the specified fill character (default is a space).

rstrip(chars=None, /)#

Return a copy of the string with trailing whitespace removed.

If chars is given and not None, remove characters in chars instead.

rpartition(sep, /)#

Partition the string into three parts using the given separator.

This will search for the separator in the string, starting at the end. If the separator is found, returns a 3-tuple containing the part before the separator, the separator itself, and the part after it.

If the separator is not found, returns a 3-tuple containing two empty strings and the original string.

splitlines(keepends=False)#

Return a list of the lines in the string, breaking at line boundaries.

Line breaks are not included in the resulting list unless keepends is given and true.

strip(chars=None, /)#

Return a copy of the string with leading and trailing whitespace removed.

If chars is given and not None, remove characters in chars instead.

swapcase()#: Convert uppercase characters to lowercase and lowercase characters to uppercase.

translate(table, /)#

Replace each character in the string using the given translation table.

table
Translation table, which must be a mapping of Unicode ordinals to Unicode ordinals, strings, or None.

The table must implement lookup/indexing via __getitem__, for instance a dictionary or list. If this operation raises LookupError, the character is left untouched. Characters mapped to None are deleted.

upper()#: Return a copy of the string converted to uppercase.

startswith(prefix[, start[, end]]) → bool#: Return True if S starts with the specified prefix, False otherwise. With optional start, test S beginning at that position. With optional end, stop comparing S at that position. prefix can also be a tuple of strings to try.

endswith(suffix[, start[, end]]) → bool#: Return True if S ends with the specified suffix, False otherwise. With optional start, test S beginning at that position. With optional end, stop comparing S at that position. suffix can also be a tuple of strings to try.

removeprefix(prefix, /)#

Return a str with the given prefix string removed if present.

If the string starts with the prefix string, return string[len(prefix):]. Otherwise, return a copy of the original string.

removesuffix(suffix, /)#

Return a str with the given suffix string removed if present.

If the string ends with the suffix string and that suffix is not empty, return string[:-len(suffix)]. Otherwise, return a copy of the original string.

isascii()#

Return True if all characters in the string are ASCII, False otherwise.

ASCII characters have code points in the range U+0000-U+007F. Empty string is ASCII too.

islower()#

Return True if the string is a lowercase string, False otherwise.

A string is lowercase if all cased characters in the string are lowercase and there is at least one cased character in the string.

isupper()#

Return True if the string is an uppercase string, False otherwise.

A string is uppercase if all cased characters in the string are uppercase and there is at least one cased character in the string.

istitle()#

Return True if the string is a title-cased string, False otherwise.

In a title-cased string, upper- and title-case characters may only follow uncased characters and lowercase characters only cased ones.

isspace()#

Return True if the string is a whitespace string, False otherwise.

A string is whitespace if all characters in the string are whitespace and there is at least one character in the string.

isdecimal()#

Return True if the string is a decimal string, False otherwise.

A string is a decimal string if all characters in the string are decimal and there is at least one character in the string.

isdigit()#

Return True if the string is a digit string, False otherwise.

A string is a digit string if all characters in the string are digits and there is at least one character in the string.

isnumeric()#

Return True if the string is a numeric string, False otherwise.

A string is numeric if all characters in the string are numeric and there is at least one character in the string.

isalpha()#

Return True if the string is an alphabetic string, False otherwise.

A string is alphabetic if all characters in the string are alphabetic and there is at least one character in the string.

isalnum()#

Return True if the string is an alpha-numeric string, False otherwise.

A string is alpha-numeric if all characters in the string are alpha-numeric and there is at least one character in the string.

isidentifier()#

Return True if the string is a valid Python identifier, False otherwise.

Call keyword.iskeyword(s) to test whether string s is a reserved identifier, such as “def” or “class”.

isprintable()#

Return True if all characters in the string are printable, False otherwise.

A character is printable if repr() may use it in its output.

zfill(width, /)#

Pad a numeric string with zeros on the left, to fill a field of the given width.

The string is never truncated.

format(*args, **kwargs) → str#: Return a formatted version of S, using substitutions from args and kwargs. The substitutions are identified by braces (‘{’ and ‘}’).

format_map(mapping) → str#: Return a formatted version of S, using substitutions from mapping. The substitutions are identified by braces (‘{’ and ‘}’).

static maketrans()#

Return a translation table usable for str.translate().

If there is only one argument, it must be a dictionary mapping Unicode ordinals (integers) or characters to Unicode ordinals, strings or None. Character keys will be then converted to ordinals. If there are two arguments, they must be strings of equal length, and in the resulting dictionary, each character in x will be mapped to the character at the same position in y. If there is a third argument, it must be a string, whose characters will be mapped to None in the result.

__dir__()#: Returns public methods and other interesting attributes.

__init__(*args, **kwds)#

exception litestar_vite.ipc.IPCError[source]#

Bases: Exception

Base exception for all IPC errors.

__init__(*args, **kwargs)#

classmethod __new__(*args, **kwargs)#

add_note()#: Exception.add_note(note) – add a note to the exception

with_traceback()#: Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

class litestar_vite.ipc.IPCRequest[source]#

Bases: object

Structured representation of an outbound IPC request payload.

to_dict() → dict[str, Any][source]#

Convert the request into a JSON-serializable dictionary.

Returns:: Dictionary payload adhering to the RPC framing contract.

__init__(id: int, method: str, params: dict[str, Any] | None = None) → None#

class litestar_vite.ipc.IPCResponse[source]#

Bases: object

Structured representation of an inbound IPC response payload.

__init__(id: int, result: Any = None, error: str | None = None) → None#

exception litestar_vite.ipc.IPCTimeoutError[source]#

Bases: IPCError

Raised when an IPC request exceeds the configured timeout threshold.

__init__(*args, **kwargs)#

classmethod __new__(*args, **kwargs)#

add_note()#: Exception.add_note(note) – add a note to the exception

with_traceback()#: Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

exception litestar_vite.ipc.IPCWorkerCrashError[source]#

Bases: IPCError

Raised when an IPC child worker terminates unexpectedly.

__init__(*args, **kwargs)#

classmethod __new__(*args, **kwargs)#

add_note()#: Exception.add_note(note) – add a note to the exception

with_traceback()#: Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

class litestar_vite.ipc.SSRCircuitBreaker[source]#

Bases: object

Three-state circuit breaker pattern for SSR worker stability.

__init__(failure_threshold: int = 3, cooldown: float = 30.0, reset_timeout: float | None = None) → None[source]#

Initialize the circuit breaker.

Parameters:

failure_threshold¶ – Number of consecutive failures before opening the circuit.
cooldown¶ – Time in seconds to wait in OPEN state before transitioning to HALF_OPEN.
reset_timeout¶ – Optional alias for cooldown duration in seconds.

property state: CircuitState#

Return the current circuit state, evaluating cooldown if currently OPEN.

Returns:: The effective CircuitState.

property failure_count: int#

Return the current consecutive failure tally.

Returns:: Failure count integer.

property failure_threshold: int#

Return the threshold of failures required to open the circuit.

Returns:: Failure threshold integer.

property cooldown: float#

Return the configured cooldown period in seconds.

Returns:: Cooldown duration in seconds.

property reset_timeout: float#

Return the configured reset timeout in seconds.

Returns:: Reset timeout duration in seconds.

can_execute() → bool[source]#

Determine whether an outbound request is permitted through the breaker.

Returns:: True if request is allowed, False if breaker is open.

allow_request() → bool[source]#

Return whether an outbound request is permitted through the circuit breaker.

Returns:: True if request is allowed, False if breaker is open.

record_success() → None[source]#: Record a successful execution, resetting failures and closing the circuit.

record_failure(exc: BaseException | None = None) → None[source]#

Record an execution failure, potentially tripping the circuit to OPEN.

Parameters:: exc¶ – Optional exception that caused the failure.

reset() → None[source]#: Manually reset the circuit breaker to closed state.

async __aenter__() → Self[source]#

Enter protected execution block or raise CircuitBreakerOpenError.

Returns:: Active circuit breaker instance.
Raises:: CircuitBreakerOpenError – When the circuit is open and refusing traffic.

async __aexit__(exc_type: type[BaseException] | None, exc_val: BaseException | None, exc_tb: TracebackType | None) → None[source]#

Exit protected block, updating circuit state based on whether an error occurred.

Parameters:

exc_type¶ – Exception type if raised during block.
exc_val¶ – Exception instance if raised.
exc_tb¶ – Traceback object if raised.

class litestar_vite.ipc.StdioIPCTransport[source]#

Bases: BaseIPCTransport

Asynchronous process transport communicating across stdin and stdout using NDJSON.

__init__(command: list[str] | None = None, cwd: Path | str | None = None, env: dict[str, str] | None = None, max_restarts: int = 3) → None[source]#

Initialize the Stdio subprocess transport.

Parameters:

command¶ – Command array for starting the worker process. Defaults to node ssr.js.
cwd¶ – Optional working directory for the worker subprocess.
env¶ – Optional environment dictionary override for the worker.
max_restarts¶ – Maximum number of automatic restarts upon worker crash.

property command: list[str]#: Return the worker command list.

property cwd: Path | None#: Return the configured working directory for the worker process.

property is_running: bool#

Return True if the transport is running and ready to handle requests.

Returns:: Boolean indicating process health and ready state.

async start() → None[source]#: Spawn the background worker process and launch asynchronous I/O readers.

async send_request(payload: dict[str, Any], timeout: float = 10.0) → dict[str, Any][source]#

Send an NDJSON request to the worker and await the correlated response.

Parameters:

payload¶ – Request dictionary payload.
timeout¶ – Maximum time in seconds to await response.

Returns:

Worker response dictionary.

Raises:

IPCTimeoutError – When response is not received within timeout.
IPCWorkerCrashError – When child worker exits unexpectedly.
IPCError – When worker reports an execution failure.

async close() → None[source]#: Gracefully terminate worker subprocess and release reader tasks.

class litestar_vite.ipc.TCPStreamIPCTransport[source]#

Bases: BaseIPCTransport

Send development SSR RPC requests through a pooled HTTP client.

__init__(host: str = '127.0.0.1', port: int = 5173, path: str = '/__litestar_ssr__', *, scheme: str = 'http') → None[source]#: Configure the Vite SSR endpoint, including HTTPS when enabled.

property host: str#: Return the target hostname or IP address.

property port: int#: Return the target TCP port.

property path: str#: Return the configured HTTP endpoint path.

property scheme: str#: Return the endpoint protocol.

property is_running: bool#: Return True because connections are established lazily on the next request.

async start() → None[source]#: Initialize the client connection pool if needed.

async close() → None[source]#: Release pooled connections.

async send_request(payload: dict[str, Any], timeout: float = 10.0) → dict[str, Any][source]#

Send an RPC request within a total deadline and validate its response.

Raises:

IPCTimeoutError – The request exceeded its total deadline.
IPCError – The connection failed or the server returned an invalid response.

Transport Overview#

litestar-vite includes two transports implementing BaseIPCTransport:

StdioIPCTransport: Production subprocess worker communicating over standard I/O pipes (stdin/stdout) with newline-delimited JSON framing. Supported on Linux, macOS, and Windows. Terminates the worker automatically when stdin closes.
TCPStreamIPCTransport: Pooled httpx2 HTTP transport used in development mode to dispatch SSR and fragment render requests to the running Vite dev server’s /__litestar_ssr__ endpoint.