1SPANK(8) Slurm Component SPANK(8)
2
6 SPANK - Slurm Plug-in Architecture for Node and job (K)control
7
10 This manual briefly describes the capabilities of the Slurm Plug-in Ar‐
11 chitecture for Node and job Kontrol (SPANK) as well as the SPANK con‐
12 figuration file: (By default: plugstack.conf.)
13 SPANK provides a very generic interface for stackable plug-ins which
15 may be used to dynamically modify the job launch code in Slurm. SPANK
16 plugins may be built without access to Slurm source code. They need
17 only be compiled against Slurm's spank.h header file, added to the
18 SPANK config file plugstack.conf, and they will be loaded at runtime
19 during the next job launch. Thus, the SPANK infrastructure provides ad‐
20 ministrators and other developers a low cost, low effort ability to dy‐
21 namically modify the runtime behavior of Slurm job launch.
22 NOTE: All SPANK plugins should be recompiled when upgrading Slurm to a
24 new major release. The SPANK API is not guaranteed to be ABI compatible
25 between major releases. Any SPANK plugin linking to any of the Slurm
26 libraries should be carefully checked as the Slurm APIs and headers can
27 change between major releases.
28
30 SPANK plugins are loaded in up to five separate contexts during a Slurm
31 job. Briefly, the five contexts are:
32 local In local context, the plugin is loaded by srun. (i.e. the "lo‐
35 cal" part of a parallel job).
36 remote In remote context, the plugin is loaded by slurmstepd. (i.e.
38 the "remote" part of a parallel job).
39 allocator
41 In allocator context, the plugin is loaded in one of the job
42 allocation utilities salloc, sbatch or scrontab.
43 slurmd In slurmd context, the plugin is loaded in the slurmd daemon
45 itself. Note: Plugins loaded in slurmd context persist for the
46 entire time slurmd is running, so if configuration is changed
47 or plugins are updated, slurmd must be restarted for the
48 changes to take effect.
49 job_script
51 In the job_script context, plugins are loaded in the context of
52 the job prolog or epilog. Note: Plugins are loaded in
53 job_script context on each run on the job prolog or epilog, in
54 a separate address space from plugins in slurmd context. This
55 means there is no state shared between this context and other
56 contexts, or even between one call to slurm_spank_job_prolog or
57 slurm_spank_job_epilog and subsequent calls.
58 In local context, only the init, exit, init_post_opt, and lo‐
60 cal_user_init functions are called. In allocator context, only the
61 init, exit, and init_post_opt functions are called. Similarly, in
62 slurmd context, only the init and slurmd_exit callbacks are active, and
63 in the job_script context, only the job_prolog and job_epilog callbacks
64 are used. Plugins may query the context in which they are running with
65 the spank_context and spank_remote functions defined in
66 <slurm/spank.h>.
67 SPANK plugins may be called from multiple points during the Slurm job
69 launch. A plugin may define the following functions:
70 slurm_spank_init
73 Called just after plugins are loaded. In remote context, this is just
74 after job step is initialized. This function is called before any
75 plugin option processing.
76 slurm_spank_job_prolog
78 Called at the same time as the job prolog. If this function returns a
79 non-zero value and the SPANK plugin that contains it is required in
80 the plugstack.conf, the node that this is run on will be drained.
81 slurm_spank_init_post_opt
83 Called at the same point as slurm_spank_init, but after all user op‐
84 tions to the plugin have been processed. The reason that the init and
85 init_post_opt callbacks are separated is so that plugins can process
86 system-wide options specified in plugstack.conf in the init callback,
87 then process user options, and finally take some action in
88 slurm_spank_init_post_opt if necessary. In the case of a heteroge‐
89 neous job, slurm_spank_init is invoked once per job component.
90 slurm_spank_local_user_init
92 Called in local (srun) context only after all options have been pro‐
93 cessed. This is called after the job ID and step IDs are available.
94 This happens in srun after the allocation is made, but before tasks
95 are launched.
96 slurm_spank_user_init
98 Called after privileges are temporarily dropped. (remote context
99 only)
100 slurm_spank_task_init_privileged
102 Called for each task just after fork, but before all elevated privi‐
103 leges are dropped. (remote context only)
104 slurm_spank_task_init
106 Called for each task just before execve (2). If you are restricing
107 memory with cgroups, memory allocated here will be in the job's
108 cgroup. (remote context only)
109 slurm_spank_task_post_fork
111 Called for each task from parent process after fork (2) is complete.
112 Due to the fact that slurmd does not exec any tasks until all tasks
113 have completed fork (2), this call is guaranteed to run before the
114 user task is executed. (remote context only)
115 slurm_spank_task_exit
117 Called for each task as its exit status is collected by Slurm. (re‐
118 mote context only)
119 slurm_spank_exit
121 Called once just before slurmstepd exits in remote context. In local
122 context, called before srun exits.
123 slurm_spank_job_epilog
125 Called at the same time as the job epilog. If this function returns a
126 non-zero value and the SPANK plugin that contains it is required in
127 the plugstack.conf, the node that this is run on will be drained.
128 slurm_spank_slurmd_exit
130 Called in slurmd when the daemon is shut down.
131 All of these functions have the same prototype, for example:
133 int slurm_spank_init (spank_t spank, int ac, char *argv[])
134 Where spank is the SPANK handle which must be passed back to Slurm when
137 the plugin calls functions like spank_get_item and spank_getenv. Con‐
138 figured arguments (See CONFIGURATION below) are passed in the argument
139 vector argv with argument count ac.
140 SPANK plugins can query the current list of supported slurm_spank sym‐
142 bols to determine if the current version supports a given plugin hook.
143 This may be useful because the list of plugin symbols may grow in the
144 future. The query is done using the spank_symbol_supported function,
145 which has the following prototype:
146 int spank_symbol_supported (const char *sym);
147 The return value is 1 if the symbol is supported, 0 if not.
150 SPANK plugins do not have direct access to internally defined Slurm
152 data structures. Instead, information about the currently executing job
153 is obtained via the spank_get_item function call.
154 spank_err_t spank_get_item (spank_t spank, spank_item_t item, ...);
155 The spank_get_item call must be passed the current SPANK handle as well
157 as the item requested, which is defined by the passed spank_item_t. A
158 variable number of pointer arguments are also passed, depending on
159 which item was requested by the plugin. A list of the valid values for
160 item is kept in the spank.h header file. Some examples are:
161 S_JOB_UID
164 User id for running job. (uid_t *) is third arg of spank_get_item
165 S_JOB_STEPID
167 Job step id for running job. (uint32_t *) is third arg of
168 spank_get_item.
169 S_TASK_EXIT_STATUS
171 Exit status for exited task. Only valid from slurm_spank_task_exit.
172 (int *) is third arg of spank_get_item.
173 S_JOB_ARGV
175 Complete job command line. Third and fourth args to spank_get_item
176 are (int *, char ***).
177 See spank.h for more details.
179 SPANK functions in the local and allocator environment should use the
181 getenv, setenv, and unsetenv functions to view and modify the job's en‐
182 vironment. SPANK functions in the remote environment should use the
183 spank_getenv, spank_setenv, and spank_unsetenv functions to view and
184 modify the job's environment. spank_getenv searches the job's environ‐
185 ment for the environment variable var and copies the current value into
186 a buffer buf of length len. spank_setenv allows a SPANK plugin to set
187 or overwrite a variable in the job's environment, and spank_unsetenv
188 unsets an environment variable in the job's environment. The prototypes
189 are:
190 spank_err_t spank_getenv (spank_t spank, const char *var,
191 char *buf, int len);
192 spank_err_t spank_setenv (spank_t spank, const char *var,
193 const char *val, int overwrite);
194 spank_err_t spank_unsetenv (spank_t spank, const char *var);
195 These are only necessary in remote context since modifications of the
198 standard process environment using setenv (3), getenv (3), and unsetenv
199 (3) may be used in local context.
200 Functions are also available from within the SPANK plugins to establish
202 environment variables to be exported to the Slurm PrologSlurmctld, Pro‐
203 log, Epilog and EpilogSlurmctld programs (the so-called job control en‐
204 vironment). The name of environment variables established by these
205 calls will be prepended with the string SPANK_ in order to avoid any
206 security implications of arbitrary environment variable control. (After
207 all, the job control scripts do run as root or the Slurm user.).
208 These functions are available from local context only.
210 spank_err_t spank_job_control_getenv(spank_t spank, const char *var,
211 char *buf, int len);
212 spank_err_t spank_job_control_setenv(spank_t spank, const char *var,
213 const char *val, int overwrite);
214 spank_err_t spank_job_control_unsetenv(spank_t spank, const char *var);
215 See spank.h for more information.
218 Many of the described SPANK functions available to plugins return er‐
220 rors via the spank_err_t error type. On success, the return value will
221 be set to ESPANK_SUCCESS, while on failure, the return value will be
222 set to one of many error values defined in slurm/spank.h. The SPANK in‐
223 terface provides a simple function
224 const char * spank_strerror(spank_err_t err);
225 which may be used to translate a spank_err_t value into its string rep‐
226 resentation.
227 The slurm_spank_log function can be used to print messages back to the
230 user at an error level. This is to keep users from having to rely on
231 the slurm_error function, which can be confusing because it prepends
232 "error:" to every message.
233
236 SPANK plugins also have an interface through which they may define and
237 implement extra job options. These options are made available to the
238 user through Slurm commands such as srun(1), salloc(1), and sbatch(1).
239 If the option is specified by the user, its value is forwarded and reg‐
240 istered with the plugin in slurmd when the job is run. In this way,
241 SPANK plugins may dynamically provide new options and functionality to
242 Slurm.
243 Each option registered by a plugin to Slurm takes the form of a struct
245 spank_option which is declared in <slurm/spank.h> as
246 struct spank_option {
247 char * name;
248 char * arginfo;
249 char * usage;
250 int has_arg;
251 int val;
252 spank_opt_cb_f cb;
253 };
254 Where
256 name is the name of the option. Its length is limited to SPANK_OP‐
259 TION_MAXLEN defined in <slurm/spank.h>.
260 arginfo
262 is a description of the argument to the option, if the option
263 does take an argument.
264 usage is a short description of the option suitable for --help output.
266 has_arg
268 0 if option takes no argument, 1 if option takes an argument,
269 and 2 if the option takes an optional argument. (See getopt_long
270 (3)).
271 val A plugin-local value to return to the option callback function.
273 cb A callback function that is invoked when the plugin option is
275 registered with Slurm. spank_opt_cb_f is typedef'd in
276 <slurm/spank.h> as
277 typedef int (*spank_opt_cb_f) (int val, const char *optarg,
279 int remote);
280 Where val is the value of the val field in the spank_option
281 struct, optarg is the supplied argument if applicable, and re‐
282 mote is 0 if the function is being called from the "local" host
283 (e.g. host where srun or sbatch/salloc are invoked) or 1 from
284 the "remote" host (host where slurmd/slurmstepd run) but only
285 executed by slurmstepd (remote context) if the option was regis‐
286 tered for such context.
287 Plugin options may be registered with Slurm using the spank_option_reg‐
289 ister function. This function is only valid when called from the
290 plugin's slurm_spank_init handler, and registers one option at a time.
291 The prototype is
292 spank_err_t spank_option_register (spank_t sp,
293 struct spank_option *opt);
294 This function will return ESPANK_SUCCESS on successful registration of
295 an option, or ESPANK_BAD_ARG for errors including invalid spank_t han‐
296 dle, or when the function is not called from the slurm_spank_init func‐
297 tion. All options need to be registered from all contexts in which they
298 will be used. For instance, if an option is only used in local (srun)
299 and remote (slurmd) contexts, then spank_option_register should only be
300 called from within those contexts. For example:
301 if (spank_context() != S_CTX_ALLOCATOR)
302 spank_option_register (sp, opt);
303 If, however, the option is used in all contexts, the spank_option_reg‐
304 ister needs to be called everywhere.
305 In addition to spank_option_register, plugins may also export options
307 to Slurm by defining a table of struct spank_option with the symbol
308 name spank_options. This method, however, is not supported for use with
309 sbatch and salloc (allocator context), thus the use of spank_op‐
310 tion_register is preferred. When using the spank_options table, the fi‐
311 nal element in the array must be filled with zeros. A SPANK_OPTIONS_TA‐
312 BLE_END macro is provided in <slurm/spank.h> for this purpose.
313 When an option is provided by the user on the local side, either by
315 command line options or by environment variables, Slurm will immedi‐
316 ately invoke the option's callback with remote=0. This is meant for the
317 plugin to do local sanity checking of the option before the value is
318 sent to the remote side during job launch. If the argument the user
319 specified is invalid, the plugin should issue an error and issue a
320 non-zero return code from the callback. The plugin should be able to
321 handle cases where the spank option is set multiple times through envi‐
322 ronment variables and command line options. Environment variables are
323 processed before command line options.
324 On the remote side, options and their arguments are registered just af‐
326 ter SPANK plugins are loaded and before the spank_init handler is
327 called. This allows plugins to modify behavior of all plugin function‐
328 ality based on the value of user-provided options.
329 As an alternative to use of an option callback and global variable,
331 plugins can use the spank_option_getopt option to check for supplied
332 options after option processing. This function has the prototype:
333 spank_err_t spank_option_getopt(spank_t sp,
334 struct spank_option *opt, char **optargp);
335 This function returns ESPANK_SUCCESS if the option defined in the
336 struct spank_option opt has been used by the user. If optargp is
337 non-NULL then it is set to any option argument passed (if the option
338 takes an argument). The use of this method is required to process op‐
339 tions in job_script context (slurm_spank_job_prolog and
340 slurm_spank_job_epilog). This function is valid in the following con‐
341 texts: slurm_spank_job_prolog, slurm_spank_local_user_init,
342 slurm_spank_user_init, slurm_spank_task_init_privileged,
343 slurm_spank_task_init, slurm_spank_task_exit, and slurm_spank_job_epi‐
344 log.
345
348 The default SPANK plug-in stack configuration file is plugstack.conf in
349 the same directory as slurm.conf(5), though this may be changed via the
350 Slurm config parameter PlugStackConfig. Normally the plugstack.conf
351 file should be identical on all nodes of the cluster. The config file
352 lists SPANK plugins, one per line, along with whether the plugin is re‐
353 quired or optional, and any global arguments that are to be passed to
354 the plugin for runtime configuration. Comments are preceded with '#'
355 and extend to the end of the line. If the configuration file is miss‐
356 ing or empty, it will simply be ignored.
357 NOTE: The SPANK plugins need to be installed on the machines that exe‐
359 cute slurmd (compute nodes) as well as on the machines that execute job
360 allocation utilities such as salloc, sbatch, etc (login nodes).
361 The format of each non-comment line in the configuration file is:
363 required/optional plugin arguments
364 For example:
365 optional /usr/lib/slurm/test.so
366 Tells slurmd to load the plugin test.so passing no arguments. If a
367 SPANK plugin is required, then failure of any of the plugin's functions
368 will cause slurmd, or the job allocator command to terminate the job,
369 while optional plugins only cause a warning.
370 If a fully-qualified path is not specified for a plugin, then the cur‐
372 rently configured PluginDir in slurm.conf(5) is searched.
373 SPANK plugins are stackable, meaning that more than one plugin may be
375 placed into the config file. The plugins will simply be called in or‐
376 der, one after the other, and appropriate action taken on failure given
377 that state of the plugin's optional flag.
378 Additional config files or directories of config files may be included
380 in plugstack.conf with the include keyword. The include keyword must
381 appear on its own line, and takes a glob as its parameter, so multiple
382 files may be included from one include line. For example, the following
383 syntax will load all config files in the /etc/slurm/plugstack.conf.d
384 directory, in local collation order:
385 include /etc/slurm/plugstack.conf.d/*
386 which might be considered a more flexible method for building up a
387 spank plugin stack.
388 The SPANK config file is re-read on each job launch, so editing the
390 config file will not affect running jobs. However care should be taken
391 so that a partially edited config file is not read by a launching job.
392
395 When SPANK plugin results in a non-zero result, the following changes
396 will result:
397 ┌──────┬────────────────────────────────┬─────────┬────────┬───────────┬────────┐
400 │Command│Function │Context │Exitcode │Drains Node │Fails job│
401 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
402 │srun │slurm_spank_init │local │1 │no │ yes │
403 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
404 │srun │slurm_spank_init_post_opt │local │1 │no │ yes │
405 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
406 │srun │slurm_spank_local_user_init │local │1 │no │ no │
407 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
408 │srun │slurm_spank_user_init │remote │0 │no │ no │
409 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
410 │srun │slurm_spank_task_init_privileged │remote │1 │no │ yes │
411 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
412 │srun │slurm_spank_task_post_fork │remote │0 │no │ no │
413 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
414 │srun │slurm_spank_task_init │remote │1 │no │ yes │
415 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
416 │srun │slurm_spank_task_exit │remote │0 │no │ no │
417 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
418 │srun │slurm_spank_exit │local │0 │no │ yes │
419 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
420 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
421 │salloc │slurm_spank_init │allocator │1 │no │ yes │
422 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
423 │salloc │slurm_spank_init_post_opt │allocator │1 │no │ yes │
424 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
425 │salloc │slurm_spank_init │local │1 │no │ yes │
426 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
427 │salloc │slurm_spank_init_post_opt │local │1 │no │ yes │
428 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
429 │salloc │slurm_spank_local_user_init │local │1 │no │ yes │
430 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
431 │salloc │slurm_spank_user_init │remote │0 │no │ no │
432 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
433 │salloc │slurm_spank_task_init_privileged │remote │1 │no │ yes │
434 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
435 │salloc │slurm_spank_task_post_fork │remote │0 │no │ no │
436 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
437 │salloc │slurm_spank_task_init │remote │1 │no │ yes │
438 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
439 │salloc │slurm_spank_task_exit │remote │0 │no │ no │
440 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
441 │salloc │slurm_spank_exit │local │0 │no │ yes │
442 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
443 │salloc │slurm_spank_exit │allocator │0 │no │ yes │
444 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
445 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
446 │sbatch │slurm_spank_init │allocator │1 │no │ yes │
447 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
448 │sbatch │slurm_spank_init_post_opt │allocator │1 │no │ yes │
449 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
450 │sbatch │slurm_spank_init │local │1 │no │ yes │
451 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
452 │sbatch │slurm_spank_init_post_opt │local │1 │no │ yes │
453 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
454 │sbatch │slurm_spank_local_user_init │local │1 │no │ yes │
455 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
456 │sbatch │slurm_spank_user_init │remote │0 │yes │ no │
457 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
458 │sbatch │slurm_spank_task_init_privileged │remote │1 │no │ yes │
459 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
460 │sbatch │slurm_spank_task_post_fork │remote │0 │yes │ no │
461 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
462 │sbatch │slurm_spank_task_init │remote │1 │no │ yes │
463 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
464 │sbatch │slurm_spank_task_exit │remote │0 │no │ no │
465 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
466 │sbatch │slurm_spank_exit │local │0 │no │ no │
467 ├──────┼────────────────────────────────┼─────────┼────────┼───────────┼────────┤
468 │sbatch │slurm_spank_exit │allocator │0 │no │ no │
469 └──────┴────────────────────────────────┴─────────┴────────┴───────────┴────────┘
470 NOTE: The behavior for ProctrackType=proctrack/pgid may result in time‐
471 outs for slurm_spank_task_post_fork with remote context on failure.
472
475 Portions copyright (C) 2010-2022 SchedMD LLC. Copyright (C) 2006 The
476 Regents of the University of California. Produced at Lawrence Liver‐
477 more National Laboratory (cf, DISCLAIMER). CODE-OCEC-09-009. All
478 rights reserved.
479 This file is part of Slurm, a resource management program. For de‐
481 tails, see <https://slurm.schedmd.com/>.
482 Slurm is free software; you can redistribute it and/or modify it under
484 the terms of the GNU General Public License as published by the Free
485 Software Foundation; either version 2 of the License, or (at your op‐
486 tion) any later version.
487 Slurm is distributed in the hope that it will be useful, but WITHOUT
489 ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
490 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
491 for more details.
492
494 /etc/slurm/slurm.conf - Slurm configuration file.
495 /etc/slurm/plugstack.conf - SPANK configuration file.
496 /usr/include/slurm/spank.h - SPANK header file.
497
499 srun(1), slurm.conf(5)
500July 2022 Slurm Component SPANK(8)