Flow — Project task flow manager.

This module defines the FlowManager class.

class admit.FlowManager.FlowManager(connmap=None, bdpmap=None, depsmap=None, varimap=None, tasklevs=None, tasks=None)

Manages the flow of data products between ADMIT tasks.

The flow manager maintains the tree of ADMIT tasks (ATs) constituting a data flow. Tasks communicate through basic data products (BDPs) that flow between tasks, which combine and transform them into new BDPs according to their function. This class implements the bookkeeping to track task connections and inter-dependencies. A central concept is the task connection 4-tuple, (si, sp, di, dp), connecting a source task (ID si) output BDP (port sp) to a destination task (ID di) input BDP (port dp). The primary concern of the flow manager is to organize and maintain this connection information to permit efficient execution and modification of data flows.

The flow manager includes limited functionality supporting self-modifying variadic flows (variflows). In a variflow, at least one AT produces a variable number of outputs, whether from instance to instance or between runs of the same instance. This presents a problem for defining the sub-flow emanating from a variadic AT, as every concrete flow must assume a fixed number of outputs from each AT to define the connection map. To support variflows, the flow manager will automatically clone or prune (disable) sub-flows attached to the variadic output ports of an AT, each time the AT is executed, according to the actual number of BDPs present. When additional parallel sub-flows are needed, the sub-flow(s) attached to the first variadic output port is cloned and connected to the new, extra outputs. (If the port already has any ATs attached to it, the existing sub-flow(s) are enabled but no cloning is performed.) If fewer sub-flows are needed, the excess tasks are simply disabled (i.e., not removed).

Parameters:

connmap : triple-nested dictionary of 4-tuples, optional

Initial value of the _connmap attribute (defaults to an empty dictionary).

bdpmap : dictionary of list of 2-tuples, optional

Initial value of the _bdpmap attribute (defaults to an empty dictionary).

depsmap : dictionary of sets, optional

Initial value of the _depsmap attribute (defaults to an empty dictionary).

varimap : double-nested dictionary of list of sets, optional

Initial value of the _varimap attribute (defaults to an empty dictionary).

tasklevs : dictionary of int, optional

Initial value of the _tasklevs attribute (defaults to an empty dictionary).

tasks : dictionary of task references, optional

Initial value of the _tasks attribute (defaults to an empty dictionary).

Notes

All internal state is kept up to date by add() and remove() so that it is valid at all times. Hence _connmap, _depsmap, etc. should never be modified by any other methods, either inside or outside of FlowManager (the leading underscore emphasizes this intent).

Attributes

_connmap	(triple-nested dictionary of 4-tuples) Organizes connection 4-tuples in a 3-level dictionary hierarchy; _connmap[si][di][dp] is a connection 4-tuple (si, sp, di, dp) connecting source task ID si, BDP output port sp, to destination task di, input dp.
_bdpmap	(dictionary of list of 2-tuples) Relates BDP outputs from source tasks with the BDP inputs to connected destination tasks; _bdpmap[di] is a list of 2-tuples (si, sp), one for each BDP input port, describing the source of the corresponding BDP.
_depsmap	(dictionary of sets) Maintains the task dependency levels needed by the run() method; _depsmap[level] is the set of task IDs residing at the dependency level. Lower level tasks must execute prior to higher level tasks to satisfy dependency requirements; tasks at the same level may be executed in any order (even concurrently).
_varimap	(double-nested dictionary of list of sets) Tracks variadic sub-flows and their controlling (variadic) root task; _varimap[si][sp] is a list of sub-flow task IDs, each stored as a set (one per sub-flow), emanating from task ID si, (variadic) output port sp.
_tasklevs	(dictionary of int) Maintains task dependency information in a complementary (inverse) manner to _depsmap; _tasklevels[id] is the dependency level for task id.
_tasks	(dictionary of task references) Holds references to all ADMIT tasks in the flow, keyed by task id; _tasks[id] is an ADMIT task reference.
_aliases	(2-tuple of dictionary of task aliases) Reserved alias registry, keyed by alias base name (index 0) or AT type (index 1). For index 0, the value is an integer count of aliases created with that base name; for index 1, it is the number of default aliases created for ATs of that type. In both cases, the duplicate aliases are appended with ‘@N’ for some integer N. Not present in XML.
_taskid	(int) Task ID counter, used to ensure unqiue task IDs within the flow. Not present in XML.

Methods

add(a[, stuples, dtuples])	Appends or inserts an AT into the task flow.
clone(id[, flow, idmap])	Clones the flow emanating from a given root task (included).
connectInputs()	Connects input BDPs to all tasks in the flow.
diagram(dotfile)	Generates dot (graphviz) diagram for the current flow.
downstream(id[, leaf])	Determines the ATs downstream of a task (includes itself).
dryrun()	Performs a dry run.
find(isMatch)	Finds ATs in the flow matching a criterion.
findTwin(tid, flow0, twins)	Attempts to find corresponding task in another flow.
inFlow(a[, stuples])	Determines whether a compatible task exists in the flow.
mergeTasks(summary, flow0, summary0, twins, ...)	Merges task settings from another flow.
remove(id[, keepRoot, delFiles])	Removes an AT and its downstream tasks.
replace(id, a[, stuples])	Replaces one task with another, removing the original.
run([dryrun])	Executes the flow, but only tasks that are out of date.
sameLineage(tid, tid0, flow0, twins, match)	Determines whether two tasks in different flows have identical ancestry.
script(py[, proj, tcube])	Generates a Python script recreating the current flow.
show()	Displays formatted internal FlowManager state.
showsetkey([outfile])	Display keysettings for all tasks, meant to be used to
stale(id[, direct])	Sets the stale flag of an AT and its downstream ATs.
verify()	Verifies the internal state of the FlowManager.

add(a, stuples=None, dtuples=None)

Appends or inserts an AT into the task flow.

Appending a task creates a new leaf—a task whose BDP outputs (if any) are not connected to any tasks; in this case, dtuples can be omitted. Insertion implies that one or more of the tasks’s outputs feeds back into the flow, in which case dtuples will be non-empty.

Parameters:

a : AT

ADMIT task to append/insert into the flow.

stuples : list of 2-tuples, optional

List of source connection 2-tuples, one per BDP input port. For example, [(si0,sp0), (si1,sp1)] if the task requires two BDP inputs, the first (input port 0) from task si0, BDP output sp0 and the second (input port 1) from task si1, BDP output sp1. Defaults to None (no upstream tasks).

dtuples : list of 4-tuples, optional

List of destination connection 4-tuples (si, sp, di, dp). The number of connections varies but will be zero for leaf (i.e., appended) tasks. The source task ID in these tuples must match the input task ID a.id, as it is the source for all dtuples connections. For example, [(1, 0, 2, 1), (1, 0, 3, 2)] if this task (id #1) disseminates its BDP output (port 0) to two downstream task inputs (#2 port 1 and #3 port 2). Defaults to None (no downstream tasks).

Returns:

int

Input task ID on success, else -1 (error detected).

See also

remove, replace

Notes

Usually all but the root task(s) will have a non-empty stuples list.

As a convenience, in the stuples and dtuples arguments the task alias may be used in place of the integer task ID. Also, for the stuples argument (only), a destination port of zero may be omitted (implied); i.e., (si, 0) may be replaced with si (or the alias name).

clone(id, flow=None, idmap=None)

Clones the flow emanating from a given root task (included).

Creates an independent, parallel sub-flow duplicating the action of the original. If flow is None, the sub-flow emanating from task id (inclusive) is duplicated. Otherwise, the sub-flow defined by flow = (fm, tid), where fm is a FlowManager instance and task tid (contained in fm) is the root of the sub-flow, is duplicated and spliced into the current flow, using task id as its root instead—i.e., task tid is identified with id and the tasks following tid are cloned and appended to id. In the latter case, task id is not duplicated; the new sub-flow is merely appended to it.

Parameters:

id : int

Task ID of the existing sub-flow root task.

flow : 2-tuple, optional

Tuple (fm, tid) describing an external sub-flow; fm is a FlowManager object and tid the ID of a task within it.

idmap : dict of int key-values, optional

Dictionary mapping root task IDs in flow to corresponding tasks in self.

Returns:

int

Task ID of the new (possibly cloned) root task.

Notes

If an external flow is provided that is not autonomous (i.e., one or more of its ATs receives inputs from ATs outside the sub-flow), the idmap argument is required and must map task IDs from flow to self for all ATs outside the sub-flow. This informs the method how to identify parent tasks between flows.

connectInputs()

Connects input BDPs to all tasks in the flow.

Connections are made regardless of whether tasks are out of date or disabled. Missing inputs are ignored. This method also updates the stale flag on each task.

Parameters:None Returns:None

diagram(dotfile)

Generates dot (graphviz) diagram for the current flow.

Parameters:

dotfile : str

Output dot file name.

Returns:

None

downstream(id, leaf=None)

Determines the ATs downstream of a task (includes itself).

The downstream tasks constitute the sub-flow emanating from the specified root task (also considered part of the sub-flow).

Parameters:

id : int

Root task ID.

leaf : set of int, optional

Initial set of leaf task IDs.

Returns:

set

Set of AT task IDs (including the root, id) on success, else an empty list if recursion is detected.

Notes

Recursion through task id is detected. This is used by add() to prevent the creation of cyclic flows.

dryrun()

Performs a dry run.

Dry runs provide a summary of which tasks are in the flow, which are stale (out-of-date), and the order in which they will be executed in a live run.

Returns:None

find(isMatch)

Finds ATs in the flow matching a criterion.

Applies the function isMatch to all ATs in the flow, in proper dependency order, accumulating matching ATs in a list (the return value). Downstream ATs are guaranteed to follow their predecessors in this list. Often isMatch may be conveniently expressed as a lambda function.

Parameters:

isMatch : bool functor(AT)

Function object taking one AT as input and returning a Boolean.

Returns:

list of ATs

ATs testing True using isMatch.

Notes

Tasks at the same dependency level are scanned in an unspecified order. (Such tasks are all independent of each other.)

Examples

To find all ATs with ID less than 100 in flow fm:

>>> fm.find(lambda at: at.id() < 100)

findTwin(tid, flow0, twins)

Attempts to find corresponding task in another flow.

For tasks to correspond they must be of identical types with identical lineage. The latter means that the two tasks have identical parents (the same number of inputs connected to the same ports on tasks of identical type), grandparents, etc.

Parameters:

tid : int

Task ID in current flow.

flow0 : FlowManager

Flow in which to search for matching task.

twins : dict of ints

Mapping of previously matched task IDs in flow0 (keys) to corresponding IDs in the current flow (values).

Returns:

int or None

Valid flow0 task ID on success, else None.

inFlow(a, stuples=None)

Determines whether a compatible task exists in the flow.

A task is compatible with another if: 1. It has the identical concrete type. 2. It has the same task ID. 3. It has identical source connections (if supplied).

Parameters:

a : ADMIT task

Task reference.

stuples : list of 2-tuples, optional

List of source connection 2-tuples, one per BDP input port (default None bypasses the connection check).

Returns:

True if a compatible task exists in the flow, else False.

See also

add

mergeTasks(summary, flow0, summary0, twins, final)

Merges task settings from another flow.

Compares the tasks in flow0 to self; tasks of the same type, at the same dependency level and with equivalent BDP input trees, are identified and relevant settings transferred into the current flow. Any task in the current flow which cannot be matched with a flow0 task according to these criteria is passed unaltered. Each task in flow0 may be merged with at most one task in the current flow.

Parameters:

summary : SummaryData

Summary data for current flow.

flow0 : FlowManager

Flow from which to merge task stale settings.

summary0 : SummaryData

Original summary data for flow0.

twins : dict of ints

Task IDs of all known pairs of identified (merged) tasks.

final : bool

Whether this will be the last call to this method for the current flow. If so, any unattached variflow branches will be merged.

Returns:

None

Notes

This is a low-level method normally called only by Admit.mergeFlow().

In support of incremental flow construction, it is permissible to merge a flow multiple times; individual tasks will be merged at most once.

remove(id, keepRoot=False, delFiles=True)

Removes an AT and its downstream tasks.

Deletes an entire sub-flow starting from the specified root task.

Parameters:

id : int

Task ID of root AT to be removed.

keepRoot : bool, optional

Whether to preserve the root AT, id, and remove only its descendents.

delFiles : bool, optional

Whether to delete BDP data when removing tasks.

Returns:

None

See also

add, replace

Notes

This method does not remove any variflow-related metadata as this would disrupt the flow management performed by veriflows themselves. User removal of tasks within variadic flows is only supported via editing and re-running of script files.

replace(id, a, stuples=None)

Replaces one task with another, removing the original.

The replacement task must have the same output signature (i.e, produce the same types/number of output BDPs)—otherwise the existing task could not be removed—but stuples may be specified if the inputs differ.

Parameters:

id : int

Task ID of AT to be removed.

a : AT

Task to insert into the flow.

stuples : list of 2-tuples, optional

Source connection 2-tuples (si, sp) for a. The special default value None indicates that the existing task’s sources should be reused verbatim.

Returns:

None

See also

add, remove

run(dryrun=False)

Executes the flow, but only tasks that are out of date.

Runs all stale, enabled tasks in the correct order, accounting for their inter-dependencies. This will reduce to a no-op for tasks whose outputs are up-to-date (not dependent on stale tasks). The (global) project summary is updated on-the-fly as tasks are executed and must contain a valid Summary object on entry.

Parameters:

dryrun : bool, optional

Whether to perform a dry run (else a live run); defaults to False.

Returns:

None

sameLineage(tid, tid0, flow0, twins, match)

Determines whether two tasks in different flows have identical ancestry.

Ancestry is determined by the type and number of parents, the associated port connections, and likewise for all grandparents, etc.

Parameters:

tid : int

Task ID in current flow.

tid0 : int

Task ID in flow0.

flow0 : FlowManager

Flow in which to search for matching task.

twins : dict of ints

Mapping of previously matched task IDs in flow0 (keys) to corresponding IDs in the current flow (values).

match : int (or None)

Current best-match task ID in flow0 known to have lineage compatible with tid.

Returns:

bool

Whether tid0 task has lineage compatible with tid and is the better-matching task (compared to match).

Notes

• Fix stale setting when parent keywords have changed between flows, even though each task is individually up to date.

script(py, proj='p', tcube=None)

Generates a Python script recreating the current flow.

Parameters:

py : file

Open, writable Python file object.

proj : str, optional

Project variable name; defaults to ‘p’.

tcube : int, optional

Task ID of Ingest_AT to set input file=cubefile; defaults to None.

Returns:

None

Notes

This is a low-level method normally called only by Admit.script().

show()

Displays formatted internal FlowManager state.

Pretty-prints the current contents of the instance to the screen (standard output).

Returns:None

showsetkey(outfile=None)

Display keysettings for all tasks, meant to be used to write a template file for rerunning an admit

stale(id, direct=True)

Sets the stale flag of an AT and its downstream ATs.

Stale tasks will be re-run upon execution of the flow, updating their output BDPs in the process; tasks not so marked are skipped to minimize running time.

Parameters:

id : int

Root task ID.

direct : bool, optional

Whether to mark only direct descendants stale (else the entire sub-flow); defaults to True.

Returns:

None

verify()

Verifies the internal state of the FlowManager.

Verification searches for internal inconsistencies in the flow bookkeeping, which to improve runtime efficiency is partially redundant.

Returns:

bool

True if the FlowManager state is valid, else False.