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core/transaction: generate DOT graph of dependency cycle for easier debugging

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This commit is contained in:
Michal Sekletar 2024-11-29 17:11:24 +01:00
parent 66146f21c0
commit d11e70d92f
1 changed files with 25 additions and 1 deletions
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26
src/core/transaction.c
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@ -366,8 +366,12 @@ static int transaction_verify_order_one(Transaction *tr, Job *j, Job *from, unsi
/* Have we seen this before? */
if (j->generation == generation) {
Job *k, *delete = NULL;
Job *k, *prev = NULL, *delete = NULL;
_cleanup_free_ char **array = NULL, *unit_ids = NULL;
_cleanup_free_ char *dot = NULL;
if (!strextend(&dot, "digraph {"))
log_oom();
/* If the marker is NULL we have been here already and decided the job was loop-free from
* here. Hence shortcut things and return right-away. */
@ -382,6 +386,15 @@ static int transaction_verify_order_one(Transaction *tr, Job *j, Job *from, unsi
/* For logging below */
if (strv_push_pair(&array, k->unit->id, (char*) job_type_to_string(k->type)) < 0)
log_oom();
/* Add edge to the graph when we already have part of it. */
else if (dot) {
r = strextendf(&dot, "\"%s\" -> \"%s\";", k->unit->id, prev ? prev->unit->id : j->unit->id);
if (r < 0) {
log_oom();
/* Dot output is not essential so let's get rid of it in case we ran into OOM. */
dot = mfree(dot);
}
}
/* Mark every unit along the cycle */
k->unit->was_on_dependency_cycle = true;
@ -393,8 +406,13 @@ static int transaction_verify_order_one(Transaction *tr, Job *j, Job *from, unsi
/* Check if this in fact was the beginning of the cycle */
if (k == j)
break;
prev = k;
}
if (dot && !strextend(&dot, "}"))
log_oom();
unit_ids = merge_unit_ids(j->manager->unit_log_field, array); /* ignore error */
STRV_FOREACH_PAIR(unit_id, job_type, array)
@ -406,6 +424,12 @@ static int transaction_verify_order_one(Transaction *tr, Job *j, Job *from, unsi
*unit_id, *job_type),
"%s", strna(unit_ids));
if (dot && IN_SET(log_get_target(), LOG_TARGET_AUTO, LOG_TARGET_JOURNAL, LOG_TARGET_JOURNAL_OR_KMSG)) {
log_struct(LOG_WARNING,
LOG_UNIT_MESSAGE(j->unit, "Ordering cycle generated, see TRANSACTION_CYCLE= for details. Note that each arc represents Before= dependency."),
"TRANSACTION_CYCLE=%s", dot);
}
if (delete) {
const char *status;
/* logging for j not k here to provide a consistent narrative */